Enantioselective Synthesis of Allenamides via Sulfimide [2,3]-Sigmatropic Rearrangement

Abstract

Chiral allenamides are prepared with high levels of enantiomeric purity by [2,3]-sigmatropic rearrangement of propargylic sulfimides. The required branched propargylic sulfides are prepared by an enantioselective organocatalytic aldehyde alpha-sulfenylation followed by Corey-Fuchs alkynylation.

Allenamides: A Powerful and Versatile Building Block in Organic Synthesis

“…Armstrong 34 later synthesized allenamides 50 in high yields via a [2,3]-sigmatropic rearrangement of propargyl sulfimides 49 , which were prepared in situ from propargyl sulfides 47 and amidation agent 48 (Scheme 19). Notably, optically enriched allenamides 50 [see a-d ] were also achieved with effective transfer of chirality information from enantiomerically enriched propargyl sulfimides 47 [see a–d ].…”

Catalyst‐Free Imidation of Allyl Sulfides with Chloramine‐T and Subsequent [2,3]‐Sigmatropic Rearrangement

“…[4] The iron-catalyzed imidation of sulfides with tert-butoxycarbonyl azide and [2,3]-sigmatropic rearrangement has been investigated by Bach [5] and van Vranken [6] respectively. Very recently, the synthesis of allenamides has been achieved by Armstrong [7] through this rearrangement by employing CbzNHOTf as the nitrene precursor.…”

A Simple Procedure for the Synthesis of β‐Hydroxyallenamides via Homoallenylation of Aldehydes

“…While significant efforts have been devoted toward the development of new methods to access chiral allenes, the asymmetric synthesis of allenamides has been limited to chirality transfer reactions of enantioenriched starting materials, which include allenyl halides, [23] propargyl amides, [24] propargyl sulfides, [25] propargyl phosphorimidates, [26] and esters. [27] Therefore, a strong demand remains for the development of asymmetric syntheses of enantiomerically enriched allenamides from prochiral starting materials.…”