synthesis-purification-iodoaziridines-involving-quantitative

Synthesis and Purification of Iodoaziridines Involving Quantitative Selection of the Optimal Stationary Phase for Chromatography

The highly diastereoselective preparation of cis-N-Ts-iodoaziridines through reaction of diiodomethyllithium with N-Ts aldimines is described. ...

Imperial College London

The first preparation of iodoaziridines is described. The addition of diiodomethyllithium to N-Boc-imines affords these novel aziridines in high yields. The reaction proceeds in one-pot via a highly diastereoselective cyclisation of an amino gem-diiodide intermediate.

Highly cis-selective synthesis of iodo-aziridines using diiodomethyllithium and in situ generated N-Boc-imines.

A series of novel, highly substituted N-PMP aziridines have been accessed in high yields by palladium-catalyzed cross-coupling of intact aziridines. The cross-coupling employed aryl bromides and tertiary organometallic aziridines, generated from sulfinylaziridines by sulfinyl-magnesium exchange and transmetalation to the aziridinylzinc with zinc chloride. A wide range of electron-rich and electron-poor aryl bromides were utilized to afford the functionalized aziridine products as single diastereoisomers with retention of configuration at the reacting center. Assessment of the reaction kinetics showed zero-order in both the aziridine species and the aryl bromide. This indicated that the rate-determining step was reductive elimination from the palladium(II) species bearing both the aziridine and aryl groups to form the hindered C-C bond. The intermediate aziridinylzinc species underwent a progressive, background degradation that led to a plateau in yield and afforded reduced yields in substrates with ortho-substituted aryl groups, which are less reactive due to the additional steric demands.

Palladium-catalyzed cross-coupling of aziridinylmetal species, generated by sulfinyl-magnesium exchange, with aryl bromides: reaction optimization, scope, and kinetic investigations.

The preparation of C-iodo-N-Ts-aziridines with excellent cis-diastereoselectivity has been achieved in high yields by the addition of diiodomethyllithium to N-tosylimines and N-tosylimine-HSO2Tol adducts. This addition-cyclization protocol successfully provided a wide range of cis-iodoaziridines, including the first examples of alkyl-substituted iodoaziridines, with the reaction tolerating both aryl imines and alkyl imines. An ortho-chlorophenyl imine afforded a β-amino gem-diiodide under the optimized reaction conditions due to a postulated coordinated intermediate preventing cyclization. An effective protocol to assess the stability of the sensitive iodoaziridine functional group to chromatography was also developed. As a result of the judicious choice of stationary phase, the iodoaziridines could be purified by column chromatography; the use of deactivated basic alumina (activity IV) afforded high yield and purity. Rearrangements of electron-rich aryl-iodoaziridines have been promoted, selectively affording either novel α-iodo-N-Ts-imines or α-iodo-aldehydes in high yield.

Synthesis of cis-C-iodo-N-tosyl-aziridines using diiodomethyllithium: reaction optimization, product scope and stability, and a protocol for selection of stationary phase for chromatography.

Lithium-iodine exchange on alkyl- or aryl-substituted N-tosyliodoaziridines afforded unstabilized aziridinyllithiums, which were subsequently trapped at low temperatures with a range of carbon and heteroatom electrophiles affording cis-substituted aziridines exclusively. When using isocyanates as electrophiles, access to aziridine carboxamides or 1,3,5-trisubstituted hydantoins can be selected by control of reaction temperature.

Tom Boultwood

Department of Chemistry

Imperial College London

Synthesis and Purification of Iodoaziridines Involving Quantitative Selection of the Optimal Stationary Phase for Chromatography

Tom Boultwood

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department of Chemistry

Imperial College London

Synthesis and Purification of Iodoaziridines Involving Quantitative Selection of the Optimal Stationary Phase for Chromatography

Department of Chemistry