저자는 재정 지원을 위해 도이치 Forschungsgemeinschaft, 바이엘 제약 AG, Chemtura의하여 Organometallics GmbH의 카멘, 바이엘 서비스 GmbH, BASF AG 및 사졸 GmbH에 감사드립니다.

1. 티타늄 (IV) 급의 -butoxide/Triethylchlorosilane 용액의 조제 <ol><li> 티탄 (IV) 급 - 부톡 사이드 (1 mmol)의 건조 디클로로 메탄 10 ㎖에 400 mg의 (400 μL)을 녹이고. RT에서이 용액에 150 밀리그램 (170 μL) triethylchlorosilane (1 밀리몰)를 추가합니다. 이 디클로로 메탄 용액을 1 ㎖ 0.1 밀리몰 티탄을 포함 (IV) 급 - 부톡 사이드 및 0.1 밀리몰 triethylchlorosilane. </li></ol> 2. 테트라 페닐 -1,2 - 에탄 디올의 피나 콜 반응 (1) 2 Ethylbutyraldehyde 함께 <ol><li> 테트라 페닐 -1,2 - 에탄 디올 (1, 1 밀리몰) 및 3 ㎖의 건조 디클로로 메탄에 새로 증류 ethylbutyraldehyde -2 - (3 밀리몰)의 (300) MG (370 μL) 중 366 mg의 해결. </li><li> 별도로 준비 티타늄의 0.5 ML을 추가합니다 (IV) 급 -butoxide/triethylchlorosilane 솔루션 (0.05 mmol)을 첨가 하였다. </li><li> 밀봉 된 반응 관에 RT에서 생성 된 혼합물을 교반 하였다. </li><li> 확인 합니실리카겔 TLC 플레이트 상 (60 F254) - (1분의 9 헥산 / 아세톤을 용리액) RM 반응물을 박층 크로마토 그래피에 의해 완성된다. 반응 종료는 테트라 페닐 -1,2 - 에탄 디올 (1)는 더 이상 (~ 12 시간)을 검출 할 수없는 시점에 도달한다. 상품의 RF-값은 0.3 (14)이다. </li><li> 디클로로 메탄 50 ㎖로 생성 된 반응 혼합물을 희석. </li><li> 분별 깔때기에 염화 암모늄 수용액과 탄산 수​​소 나트륨 포화 용액 20 ㎖로 연속적으로 희석 된 반응 혼합물을 씻는다. </li><li> 분액 깔때기로 유기층을 분리. </li><li> 건조 황산 마그네슘 교반 유기층 건조시켰다. </li><li> 플루트를 불 ㄴ 종이 필터에 의해 현탁액을 여과하고 여과 액을 수집합니다. </li><li> 회전 증발기 (10 ~ 30 mmHg로)를 사용하여 40 ° C에서 진공 여과 액에서 디클로로 메탄을 제거합니다. 용매의 증발은 20 분을 필요로 할 것이다. </li><li> 잔류 물을 정제1,2 - 디올 2F 280 mg의 취득 헥산 / 아세톤의 구배 (19시 1분부터 아래 16시 4분 예정)로 실리카 겔 컬럼 (0.035-0.070 mm, ACROS)를 통한 플래쉬 칼럼 크로마토 그래피에 의하여 (0.99 밀리몰). </li><li> 등을 CDCl3 용매를 사용하여 1 H 핵 자기 공명 분광법 (NMR)에 의해 1,2 - 디올 2F의 신원을 확인한다. 다음과 같이 300 MHz의 NMR 분광계를 들어, 디올의 1 H NMR 스펙트럼은 : δ = 0.78 (t, 3H, J = 7.4 Hz에서), 0.87 (t, 3H, J = 7.3 Hz에서), 1.18-1.40 (m , 4H), 1.75-1.81 (m, 1H), 1.91 (S, 1H, OH), 3.12 (S, 1H, OH), 4.68 (d, 1H, J = 1.2 Hz에서), 7.19-7.37 (m, 6H ), 7.44-7.46 (m, 2H), 7.61-7.63 (m, 2H). </li></ol> 3. 테트라 페닐 -1,2 - 에탄 디올의 피나 콜 반응 (1) 디 에틸 케톤 <ol><li> 테트라 페닐 -1,2 - 에탄 디올 (1, 1 mmol) 및 3에 345 mg의 다이 에틸 케톤 (423 μL) (4 밀리몰)의 366 mg의 해결건조 디클로로 메탄 ML. </li><li> 별도로 준비 티타늄 (IV) 급 -butoxide/triethylchloro-silane 솔루션 (0.1 mmol)을 1 ㎖를 추가합니다. </li><li> 밀봉 된 반응 관에 RT에서 생성 된 혼합물을 교반 하였다. </li><li> 실리카겔 TLC 플레이트 (60 F254)에 : (헥산 / 아세톤 9:1 리제) 반응이 얇은 층 크로마토 그래피에 의해 완료 확인합니다. 테트라 페닐 -1,2 - 에탄 디올 (1) (~ 12 시간)을 검출 할 수 없을 때, 반응의 단부는, 시간에 도달한다. 제품의는 Rf 0.3 14입니다. </li><li> 디클로로 메탄 50 ㎖로 생성 된 반응 혼합물을 희석. </li><li> 분별 깔때기에 염화 암모늄 수용액 및 탄산나트륨 포화 용액 20 ㎖로 연속적으로 희석 된 반응 혼합물을 씻는다. </li><li> 분액 깔때기로 유기층을 분리. </li><li> 건조 황산 마그네슘 교반 유기층 건조시켰다. </li><li> 플루트를 불 ㄴ 종이 FIL하여 현탁액을 여과터 및 여과 액을 수집합니다. </li><li> 회전 증발기 (10 ~ 30 mmHg로)를 사용하여 40 ° C에서 진공 디클로로 메탄을 제거합니다. 휘발성 성분의 증발이 30 분을 필요로 할 것이다. </li><li> 일 250 mg의 취득 (19:1에서부터 16:4까지 내려 가고), 헥산 / 아세톤의 구배로 실리카 겔 컬럼 (0.035-0.070 mm, ACROS)를 통해 플래시 칼럼 크로마토 그래피에 의해 잔류 물을 정제하여, 2 - 디올 4F (0.93 밀리몰). </li><li> 등을 CDCl3 용매를 사용하여 1 H 핵 자기 공명 분광법 (NMR)에 의해 상품의 ID를 확인한다. 다음과 같이 300 MHz의 NMR 분광계를 들어, 디올 4F의 1 H NMR 스펙트럼은 : δ = 0.92 (t, 6H, J = 7.6 Hz에서), 1.78 (m, 4H), 2.03 (S, 1H, OH), 2.83 (S, 1H, OH), 7.26-7.35 (m, 6H), 7.69-7.71 (m, 4H). </li></ol>

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저자는 더 경쟁 재정적 이익을 선언하지 않습니다.

반응 시간 및 높은 수율의 전반적인 감소는 전자가 풍부한 카르 보닐 화합물의 전개 (13, 표 2와 17, 표 1 항목 (19) 항목 3 비교)에 의해 관찰된다. 또한, 부피가 큰 치환기와 케톤의 반응에서 수율의 감소는 (11, 표 2와 항목 12)와 비교 비교 조건에서 관찰된다. 카르 보닐 화합물의 넓은 범위가이 신규 한 프로세스에 적용 ...

피나 콜 커플 링 반응은 대칭의 인접한 디올 (1,2 - 디올 pinacols)의 제조에 일반적으로 사용되는 일반적인 방법이다. 이 분야에서 포괄적 인 리뷰를 참조 히라 1, 터지과 조시 2, Ladipo 3, Gansäuer 및 Bluhm은 4를 참조하십시오. 그와 대조적으로, 단지 소수의보고가 대응하는 비대칭 1,2 - 디올 (티타늄 (IV) 클로라이드 / 망간 4.0, 사마륨 (II) 요오다 이드 06 마그네슘을 수득 크로스 피나 콜 커플 링 반응의 효율적인 구현을 참조 출판 / 트리메틸 클로로 실란 (II) (8), 지르코늄 / 주석 9 7, 바나듐, 이테르븀 및 10). 따라서, 분자간 상호 피나 커플 링 반응은 여전히​​, 유기 화학에서의 변형이 특히 촉매 실행 큰 과제로 남아. 크로스 커플 링 제품의 형성은 역학적으로 선호되지이며고전 피나 커플 링 조건 하에서. 비대칭 제품의 충분한 양을 얻기 위해 하나의 카르 보닐 화합물의 첨가가 가능 지연. 이 개념을 개발하는 몇 가지 예를 존재하지만, 그들은 몇 가지 특정 실험 조작에 기초하고 있으며, 따라서 일반화 할 수 없습니다. 또한, 이러한 변환 한 카르 보닐 화합물의 필수 과량 복잡한 생성물 혼합물 (11)의 분리 힘든 결과. 이러한 목적을위한 대안이 필요한 추가적인 시약 몰량 렌더링 한 반응물의 precomplexation 의해 표현된다. 리버시블 피나 반응의 다양한 예 12를 설명 하였다. 이들은 이러한 조건은 크로스 커플 링 제품 선택적 합성을위한 최적의 시작점 수도 고려 이어질. 저 가의 금속뿐만 아니라 이후 반응성 라디칼 종 반응계에서 동시에 형성된다, 비대칭 디올 적합한 카르 보닐 반응물의 존재하에 단독으로 형성 될 수있다. (포르타는 등. 생성하는 AIBN의 화학 양 론적 양의 추가 배치 (2,2 &#39;- 아조 - 비스 - 이소 부티로 니트릴)에 의해 비교 ​​피나 분열 이후의 커플 링을 설명하기 전에 우리가 아는 한 그런 방법은보고 된 바 없음 필요한 라디칼) 13. 여기 프로토콜은 비대칭 1,2 - 디올에 신속하고 운영 체제는 간단한 액세스를 제공하는 시각화됩니다. 비대칭 피나 제품 (&gt; 95 %) 우수한 수율 대부분 액세스 할 수 있습니다. 원하지 않는 대칭 피나 제품은 관찰되지 않습니다. 이 새로운 크로스 피나 방법론 retropinacol / 크로스 피나 결합 서열에 기초한다. 그것은 벤조 피나의 대표적인 반응 (1,1,2,2 - 테트라 페닐 -1,2 - 에탄 디올, 1) 2 ethylbutyraldehyde (알데히드 시리즈) 및 w와 의해 이하에 설명 될 것이다(케톤 시리즈) i 번째 디 에틸.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:363px;">1.2-Dichloromethane</td>
			<td style="width:179px;">Sigma-Aldrich</td>
			<td style="width:137px;">319929</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Titanium(IV)tert-butoxide</td>
			<td>VWR International</td>
			<td>200014-852</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">2-Ethylbutyraldehyde</td>
			<td>Sigma-Aldrich</td>
			<td>110094</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Benzopinacol</td>
			<td>Aldrich</td>
			<td>B9807</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Triethylchlorosilane</td>
			<td>Aldrich</td>
			<td>&#160;235067</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">hexane, certified ACS</td>
			<td>Fisher scientific</td>
			<td>H29220</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">acetone, certified ACS</td>
			<td>ACROS</td>
			<td>42324</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ammonium chloride</td>
			<td>ACROS</td>
			<td>19997</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sodium hydrogen carbonate</td>
			<td>ACROS</td>
			<td>12336</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Magnesium sulphate</td>
			<td>ACROS</td>
			<td>41348</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="26">
			<td height="26" style="height:26px;">silica gel 60 F254 TLC plates</td>
			<td>VWR International</td>
			<td>1,057,140,001</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">&#160;silica gel, 0.035-0.070 for flash-chromatography</td>
			<td>ACROS</td>
			<td>240360300</td>
			<td style="width:79px;"></td>
		</tr>
	</tbody>
</table>

retropinacol/cross-pinacol coupling reactions - a catalytic access to 1,2-unsymmetrical diols

비대칭 1,2 - 디올을 환원 피나 커플 링 공정에 의해 단단하게 접근 가능하다. 이러한 변화의 성공적인 실행은 명확한 인식과 두 개의 유사한 카르 보닐 화합물 (차 1,2 - 디올 → 보조 1,2 - 디올 또는 케톤 → 알데히드)의 엄격한 차별에 바인딩됩니다. 이 미세 조정은 여전히​​ 유기 화학자를위한 도전과 해결되지 않은 문제입니다. 가 이러한 변화의 성공적인 실행에 대한 몇 가지 보고서를 존재하지만 그들은 일반화 할 수 없습니다. 여기서 우리는 retropinacol / 크로스 피나 커플 시퀀스를 통해 진행하여 촉매 직접 피나 커플 프로세스를 설명한다. 따라서, 비대칭 치환 된 1,2 - 디올은 매우 온화한 조건 하에서 운영 체제는 간단한 성능에 의해 거의 양적 수율에 액세스 할 수 있습니다. 같은 주사기 펌프 기술 또는 반응물의 지연 추가 등의 인공 기술은 필요하지 않습니다. 우리가 설명하는 절차에 매우 빠른 액세스를 제공합니다크로스 피나 제품 (1,2 - 디올, 비시 디올). 거울상 이성질체의 성능 예를 들어,이 새로운 프로세스의 추가 확장, 비대칭 키랄 1,2 - 디올의 합성에 매우 유용한 도구를 제공 할 수 있습니다.

티탄 촉매량 우리 -1,2 - 디올 (4A) 1,1 - 디 페닐 - (1)의 형성을 관찰 (IV) 알콕사이드와 동시에 형성의 존재하에 테트라 페닐 -1,2 - 에탄 디올 (1)과 아세톤의 반응에서 벤조 페논 3 (반응식 1). 아세톤의 경쟁력 피나 결합에 의해 형성된 대응하는 대칭 1,2 - 디올은 검출되지 않았다. 그러나, 양적 전환을 구하는 것이 매우 길고 용인 반응 시간은 이러한 조건 하에서 ?...

Watch this Scientific Journal Video about Retropinacol/Cross-pinacol Coupling Reactions - A Catalytic Access to 1,2-Unsymmetrical Diols at JoVE.com

Retropinacol/Cross-pinacol Coupling Reactions - A Catalytic Access to 1,2-Unsymmetrical Diols

retropinacol / 크로스 피나 결합 메커니즘을 기반으로 비대칭 1,2 - 디올의 합성을위한 신규 계좌 설명한다. 때문에 기존의 크로스 피나 커플 링에 비해 반응 상당한 개선의 촉매 실행에 달성된다.

Retropinacol / 크로스 피나 커플 링 반응 - 1,2 - 비대칭 디올에 촉매 액세스

Unsymmetrical 1,2-diols are hardly accessible by reductive pinacol coupling processes. A successful execution of such a transformation is bound to a clear ...

retropinacolcross-pinacol-coupling-reactions-catalytic-access-to-12

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Alcohols and Phenols

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12.9K 조회수.  Humboldt University of Berlin.  retropinacol / 크로스 피나 결합 메커니즘을 기반으로 비대칭 1,2 - 디올의 합성을위한 신규 계좌 설명한다. 때문에 기존의 크로스 피나 커플 링에 비해 반응 상당한 개선의 촉매 실행에 달성된다. 

비디오: Retropinacol/Cross-pinacol Coupling Reactions - A Catalytic Access to 1,2-Unsymmetrical Diols

Mizoroki-Heck Cross-coupling Reactions Catalyzed by Dichloro{bis[1,1',1''-(phosphinetriyl)tripiperidine]}palladium Under Mild Reaction Conditions

Dichloro-bis(aminophosphine) complexes of palladium with the general formula of [(P{(NC5H10)3-n(C6H11)n})2Pd(Cl)2] (where n = 0-2), belong to a new family of easy accessible, very cheap, and air stable, but highly active and universally applicable C-C cross-coupling catalysts with an excellent functional group tolerance. Dichloro{bis[1,1',1''-(phosphinetriyl)tripiperidine]}palladium [(P(NC5H10)3)2Pd(Cl)2] (1), the least stable complex within this series towards protons; e.g. in the form of water, allows an eased nanoparticle formation and hence, proved to be the most active Heck catalyst within this series at 100 &#176;C and is a very rare example of an effective and versatile catalyst system that efficiently operates under mild reaction conditions. Rapid and complete catalyst degradation under work-up conditions into phosphonates, piperidinium salts and other, palladium-containing decomposition products assure an easy separation of the coupling products from catalyst and ligands. The facile, cheap, and rapid synthesis of 1,1',1"-(phosphinetriyl)tripiperidine and 1 respectively, the simple and convenient use as well as its excellent catalytic performance in the Heck reaction at 100 &#176;C make 1 to one of the most attractive and greenest Heck catalysts available.
We provide here the visualized protocols for the ligand and catalyst syntheses as well as the reaction protocol for Heck reactions performed at 10 mmol scale at 100 &#176;C and show that this catalyst is suitable for its use in organic syntheses.

Mizoroki-Heck Cross-coupling Reactions Catalyzed by Dichloro{bis[1,1',1''-phosphinetriyltripiperidine]}palladium Under Mild Reaction Conditions

Dichloro{bis[1,1',1''-(phosphinetriyl)tripiperidine]}palladium [(P(NC5H10)3)2Pd(Cl)2] (1) is an easy accessible, cheap, and air stable, but highly active Heck catalyst with an excellent functional group tolerance that efficiently operates under mild reaction conditions to give the coupling products in very high yields.

온화한 반응 조건 하에서 팔라듐 - 디클로로 {비스 [(phosphinetriyl) tripiperidine 1,1 &#39;, 1 &#39;&#39;]} 의해 촉매 Mizoroki-헥 크로스 커플 링 반응

Dichloro-bis(aminophosphine) complexes of palladium with the general formula of [(P{(NC5H10)3-n(C6H11)n})2Pd(Cl)2] (where n = 0-2), belong to a new family ...

연구

화학

Facile Preparation of (2Z,4E)-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate

Direct cross-coupling between two alkenes via vinylic C-H bond activation represents an efficient strategy for the synthesis of butadienes with high atomic and step economy. However, this functionality-directed cross-coupling reaction has not been developed, as there are still limited directing groups in practical use. In particular, a stoichiometric amount of oxidant is usually required, producing a large amount of waste. Due to our interest in novel 1,3-butadiene synthesis, we describe the ruthenium-catalyzed olefination of electron-deficient alkenes using allyl acetate and without external oxidant. The reaction of 2-phenyl acrylamide and allyl acetate was chosen as a model reaction, and the desired diene product was obtained in 80% isolated yield with good stereoselectivity (Z,E/Z,Z = 88:12) under optimal conditions: [Ru(p-cymene) Cl2]2 (3 mol %) and AgSbF6 (20 mol %) in DCE at 110 &#186;C for 16 h. With the optimized catalytic conditions in hand, representative &#945;- and/or &#946;-substituted acrylamides were investigated, and all reacted smoothly, regardless of aliphatic or aromatic groups. Also, differently N-substituted acrylamides have proven to be good substrates. Moreover, we examined the reactivity of different allyl derivatives, suggesting that the chelation of acetate oxygen to the metal is crucial for the catalytic process. Deuterium-labeled experiments were also conducted to investigate the reaction mechanism. Only Z-selective H/D exchanges on acrylamide were observed, indicating a reversible cyclometalation event. In addition, a kinetic isotope effect (KIE) of 3.2 was observed in the intermolecular isotopic study, suggesting that the olefinic C-H metalation step is probably involved in the rate-determining step.

Facile Preparation of 2Z,4E-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate

The ruthenium-catalyzed olefination of electron-deficient alkenes with allyl acetate is described here. By using aminocarbonyl as a directing group, this external oxidant-free protocol has high efficiency and good stereo- and regioselectivity, opening a novel synthetic route to (Z,E)-butadiene skeletons.

손쉬운 준비 (2<em&gt; Z</em&gt;, 4<em&gt; E</em&gt;) - 알렌 아세테이트를 이용한 전자 불충분 알켄의 합성에 의한 디에나 미이드

Direct cross-coupling between two alkenes via vinylic C-H bond activation represents an efficient strategy for the synthesis of butadienes with high ...

Versatile CO2 Transformations into Complex Products: A One-pot Two-step Strategy

CO2 transformations using a one-pot two-step method are presented herein. The purpose of the method is to give access to a variety of value-added products and notably to generate chiral carbon centers. The crucial first step consists in the selective double hydroboration of CO2 catalyzed by an iron hydride complex. The product obtained with this 4 e- reduction is a rare bis(boryl)acetal, compound 1, which is subjected in situ to three different reactions in a second step. The first reaction concerns a condensation reaction with (diisopropyl)phenylamine affording the corresponding imine 2. In the second and third reaction, intermediate 1 reacts with triazol-5-ylidene (Enders&#39; carbene) to afford compounds 3 or 4, depending on the reaction conditions. In both compounds, C-C bonds are formed, and chiral centers are generated from CO2 as the only source of carbon. Compound 4 exhibits two chiral centers obtained in a diastereoselective manner in a formose-type mechanism. We proved that the remaining boryl fragment plays a key role in this unprecedented stereocontrol. The interest of the method stands on the reactive and versatile nature of 1, giving rise to various complex molecules from a single intermediate. The complexity of a two-step method is compensated by the overall short reaction time (2 h for the larger reaction time), and mild reaction conditions (25 &#176;C to 80 &#176;C and 1 to 3 atm of CO2).

Versatile CO2 Transformations into Complex Products: A One-pot Two-step Strategy

CO2 transformations are conducted in a one-pot two-step procedure for the synthesis of complex molecules. The selective 4 e- reduction of CO2 with a hydroborane reductant affords a reactive and versatile bis(boryl)acetal intermediate which is subsequently involved in condensation reaction or carbene-mediated C-C coupling generation.

다재다능한CO2를 복합 제품으로 전환: 원포트 2단계 전략

CO2 transformations using a one-pot two-step method are presented herein. The purpose of the method is to give access to a variety of value-added products ...

Organocatalysis

Source: Vy M. Dong and Faben Cruz, Department of Chemistry, University of California, Irvine, CA
This experiment will demonstrate the concept of organocatalysis by illustrating the proper setup of a reaction that utilizes enamine catalysis. Organocatalysis is a form of catalysis that uses substoichiometric amounts of small organic molecules to accelerate reactions. This type of catalysis is complementary to other forms of catalysis such as transition metal or biocatalysis. Transition metal catalysis involves transition metals as catalysts and biocatalysis uses enzymes as catalysts. Some advantages of organocatalysis include the low toxicity and cost of the organocatalysts in comparison to many metal catalysts. In addition, most organocatalysts are not sensitive to air and moisture, unlike metal catalysts. In contrast to enzymes found in living organisms, the small molecules that act as organocatalysts are typically easy to access. Furthermore, organocatalysis offers complementary and new reactivity not observed with other forms of catalysis.

Organocatalysis: Principles and Applications

오가노카타리시스

Source: Vy M. Dong and Faben Cruz, Department of Chemistry, University of California, Irvine, CA
This experiment will demonstrate the concept of ...

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유기 화학 II

Palladium-Catalyzed Cross Coupling

Source: Vy M. Dong and Faben Cruz, Department of Chemistry, University of California, Irvine, CA
This experiment will demonstrate the concept of a palladium-catalyzed cross coupling. The set-up of a typical Pd-catalyzed cross coupling reaction will be illustrated. Pd-catalyzed cross coupling reactions have had a profound effect on how synthetic chemists create molecules. These reactions have enabled chemists to construct bonds in new and more efficient ways. Such reactions have found widespread applications in the fine chemical and pharmaceutical industries. Pd-catalyzed cross coupling reactions add another tool to the chemist&#39;s toolbox for constructing carbon-carbon bonds, which are central to organic chemistry. The combination of the importance of making carbon-carbon bonds and the impact of Pd-catalyzed cross coupling have resulted in these reactions being the subject of the 2010 Nobel Prize in Chemistry. Ei-ichi Negishi, one of the recipients of the 2010 Nobel Prize in chemistry, explained in his Nobel lecture that one of his motivations for developing this chemistry was to develop &#34;widely applicable straightforward Lego-like methods for hooking up two different organic groups&#34;.

Palladium-Catalyzed Cross Coupling; Heck Coupling Reaction

팔라듐-촉매 크로스 커플링

Source: Vy M. Dong and Faben Cruz, Department of Chemistry, University of California, Irvine, CA
This experiment will demonstrate the concept of a ...

Preparation of Diols and Pinacol Rearrangement

Compounds bearing two hydroxyl groups are known as diols. When the hydroxyl groups are located on adjacent carbon atoms, the diols are called vicinal diols or glycols. Under acidic conditions, vicinal diols undergo a specific reaction called pinacol rearrangement.
The reaction begins with transferring a proton from the acid catalyst to one of the hydroxyl groups, producing an oxonium ion.
<img alt="Figure1" src="/files/ftp_upload/11928/Figure_1-11928.svg" style="text-align: center; height: 75px;" />
In the second step, the oxonium ion loses H2O, forming a tertiary carbocation intermediate.
<img alt="Figure2" src="/files/ftp_upload/11928/Figure_2-11928.svg" style="text-align: center; height: 75px;" />
In the following step, a methyl group migrates from one carbon to the adjacent carbon, producing a resonance-stabilized cation intermediate where carbon and oxygen have complete octets of valence electrons.
<img alt="Figure3" src="/files/ftp_upload/11928/Figure_3-11928.svg" style="text-align: center; height: 75px;" />
Finally, the subsequent proton transfer from the resonance-stabilized cation intermediate to the solvent water completes the reaction to give pinacolone.
<img alt="Figure4" src="/files/ftp_upload/11928/Figure_4-11928.svg" style="text-align: center; height: 75px;" />
Since the reaction causes an overall change in the carbon backbone, it is termed a rearrangement.

Pinacol Rearrangement of Vicinal Diols: Mechanism

Diols 및 Pinacol 재배열의 준비

Compounds bearing two hydroxyl groups are known as diols. When the hydroxyl groups are located on adjacent carbon atoms, the diols are called vicinal ...

유기화학

주요 용어 및 개념

Oxidation of Alkenes: Syn Dihydroxylation with Osmium Tetraoxide

Alkenes are converted to 1,2-diols or glycols through a process called dihydroxylation. It involves the addition of two hydroxyl groups across the double bond with two different stereochemical approaches, namely anti and syn. Dihydroxylation using osmium tetroxide progresses with syn stereochemistry.
<img alt="Figure1" src="/files/ftp_upload/11781/11781_PT_Figure_1.svg" style="text-align: center; height: 60px;" />
<h4>Syn Dihydroxylation Mechanism</h4>
The reaction comprises a two-step mechanism. It begins with the addition of osmium tetroxide across the alkene double bond in a concerted manner forming a five-membered cyclic osmate ester as an intermediate, which can be isolated and characterized. Osmium tetroxide is electrophilic in nature, serving as a strong oxidizing agent. It accepts an electron pair from the alkene &#960; bond undergoing a reduction from +VIII to +VI.
In the next step,&#160; the cyclic osmate ester reacts with a reducing agent like sodium bisulfite that cleaves the Os&#8211;O bond producing a cis-glycol with retention of the syn stereochemistry of the two newly formed C&#8211;O bonds.
<img alt="Figure2" src="/files/ftp_upload/11781/11781_PT_Figure_2.svg" style="text-align: center; height: 200px;" />
A major drawback of the method is the use of toxic and expensive osmium tetroxide. To overcome this, osmium tetroxide is often used as a catalyst along with the co-oxidants like N-methylmorpholine N-oxide (NMO) or tert-butyl hydroperoxide (TBHP). The co-oxidants reoxidize the osmium +VI species to +VIII, thereby regenerating osmium tetroxide for further oxidation of the remaining alkenes.
<h4>Stereochemical Outcome</h4>
As oxidation of alkenes using osmium tetroxide is a stereospecific syn addition process, the two oxygens of osmium tetroxide are simultaneously added to the same face of the alkene &#960; bond. Based on this, dihydroxylation of (E)-hex-3-ene produces a pair of enantiomers, while (Z)-hex-3-ene gives a meso compound.
<img alt="Figure3" src="/files/ftp_upload/11781/11781_PT_Figure_3.svg" style="text-align: center; height: 130px;" />
<h4>Sharpless Asymmetric Dihydroxylation</h4>
Interestingly, Karl Barry Sharpless developed an enantioselective method for syn dihydroxylation of alkenes, for which he was awarded the Nobel prize. This method is known as Sharpless asymmetric dihydroxylation that is carried out using osmium tetroxide, a stoichiometric amount of the co-oxidant, and a chiral amine ligand.&#160;
<img alt="Figure4" src="/files/ftp_upload/11781/11781_PT_Figure_4.svg" style="text-align: center; height: 60px;" />

알켄의 산화 : 오스뮴 테트라 옥사이드를 사용한 Syn Dihydroxylation

Alkenes are converted to 1,2-diols or glycols through a process called dihydroxylation. It involves the addition of two hydroxyl groups across the double ...

Reactions of Alkenes

Oxidation of Alkenes: Anti Dihydroxylation with Peroxy Acids

Diols are compounds with two hydroxyl groups. In addition to syn dihydroxylation, diols can also be synthesized through the process of anti dihydroxylation. The process involves treating an alkene with a peroxycarboxylic acid to form an epoxide. Epoxides are highly strained three-membered rings with oxygen and two carbons occupying the corners of an equilateral triangle. This step is followed by ring-opening of the epoxide in the presence of an aqueous acid to give a trans diol. Peroxycarboxylic acids are strong oxidizing agents and analogous to carboxylic acids. However, they have an extra oxygen atom between the carbonyl group and the hydrogen atom. Commonly used organic peracids include meta-chloroperoxybenzoic acid and peroxyacetic acid.
The mechanism begins with a concerted nucleophilic attack by the alkene &#960; bond on the electrophilic oxygen of the peroxy acid, breaking the oxygen&#8211;oxygen bond and forming a new carbon&#8211;oxygen double bond, leading to a cyclic transition state.
<img alt="Figure1" src="/files/ftp_upload/11783/11783_PT_Figure_1.svg" style="text-align: center; height: 100px;" />
The second step of the reaction involves an acid-catalyzed ring-opening of the epoxide to finally form a trans diol.
<img alt="Figure2" src="/files/ftp_upload/11783/11783_PT_Figure_2.svg" style="text-align: center; height: 120px;" />
Overall, the regiochemistry of the reaction is governed by a combination of steric and electronic factors. In epoxides with a primary and secondary carbon, steric factors dominate, favoring an attack at the less substituted carbon. With a tertiary carbon, electronic effects dominate, favoring attack at the more substituted carbon.

Oxidation of Alkenes: Anti Dihydroxylation with Peroxycarboxylic Acids

알켄의 산화 : 과산화산을 사용한 안티 디하이드록실화

Diols are compounds with two hydroxyl groups. In addition to syn dihydroxylation, diols can also be synthesized through the process of anti ...

Vicinal Diols via Reductive Coupling of Aldehydes or Ketones: Pinacol Coupling Overview

Wilhelm Rudolph Fittig discovered the pinacol coupling reaction in 1859. It is a radical dimerization reaction and involves the reductive coupling of aldehydes or ketones in the presence of hydrocarbon solvent to yield vicinal diols.
<img alt="Figure1" src="/files/ftp_upload/12905/12905_PT_Figure_1.svg" style="text-align: center; height: 160px;" />
The radical reaction is initiated by a single electron transfer from metals like sodium and magnesium to a spin-paired molecule like aldehydes or ketones to generate a ketyl&#8212;a radical anion. The ketyl has a radical character on the carbon atom and a charge on the oxygen atom. Its resonance form has a&#160;radical positioned on the oxygen atom and a charge on the carbon atom.
The behavior of ketyl is greatly influenced by the solvent in which the reaction is carried out.
Protic solvents, like ethanol, protonate the ketyl. This is followed by a second electron transfer from metal to give an alkoxide anion. Further, the acidification of an alkoxide anion forms alcohol. Here, the metal dissolves with the reaction, acting as a source of free electrons.
In the presence of aprotic solvents, like benzene or ether, ketyl radical anions do not undergo protonation due to the absence of protons. This promotes ketyl dimerization and forms a part of the famous pinacol coupling reaction.
Interestingly, metals like magnesium, aluminum, or sodium, favor the reaction by forming covalent metal-oxygen bonds, which coordinate with several ketyl radicals, reacting rapidly to form a diol. Notably, the electrostatic repulsions between the negative charges of the ketyls do not hamper dimerization. In summary, protic solvents favor the formation of alcohol, while aprotic solvents favor vicinal diols.

알데히드 또는 케톤의 환원적 결합을 통한 주변 디올: Pinacol 결합 개요

Wilhelm Rudolph Fittig discovered the pinacol coupling reaction in 1859. It is a radical dimerization reaction and involves the reductive coupling of ...

Radical Chemistry

Alkenes via Reductive Coupling of Aldehydes or Ketones: McMurry Reaction

The radical dimerization of ketones or aldehydes gives vicinal diols through a pinacol coupling reaction. However, the behavior of titanium metals used for the reaction as a source of electrons is unusual. When the reaction is carried out in the presence of titanium, diols can be isolated at low temperatures. Else titanium further reacts with diols, forming alkenes through the McMurry reaction.
<img alt="Figure1" src="/files/ftp_upload/12907/12907_PT_Figure_1v2.svg" style="text-align: center; height: 80px;" />
The reaction is a two-step process. The mechanism is still under study, but for some reagent combinations, the first step is similar to the pinacol coupling reaction, involving a single electron transfer from titanium to the carbonyl group to form a ketyl, eventually forming a diol. The second step involves deoxygenation of the diol via binding on the surface of titanium metal particles or coordinating to titanium complexes to yield an alkene. The McMurry coupling reaction involving two same carbonyl compounds gives symmetrical alkenes.
The intramolecular McMurry reaction affords cycloalkenes with eight or more carbon atoms in the ring.

알데히드 또는 케톤의 환원적 결합을 통한 알켄: McMurry 반응

The radical dimerization of ketones or aldehydes gives vicinal diols through a pinacol coupling reaction. However, the behavior of titanium metals used ...

Retropinacol / 크로스 피나 커플 링 반응 - 1,2 - 비대칭 디올에 촉매 액세스

요약

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이 비디오의 챕터

온화한 반응 조건 하에서 팔라듐 - 디클로로 {비스 [(phosphinetriyl) tripiperidine 1,1 ', 1 '']} 의해 촉매 Mizoroki-헥 크로스 커플 링 반응

손쉬운 준비 (2

다재다능한_CO2를 복합 제품으로 전환: 원포트 2단계 전략