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Highly Enantio- and Diastereoselective Synthesis of 1,2,3-Trisubstituted Cyclopropanes from α,β-Unsaturated Amides and Stabilized Sulfur Ylides Catalyzed by a Chiral Copper(I) Complex

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posted on 03.09.2021, 12:37 authored by Santosh K. Pagire, Naoya Kumagai, Masakatsu Shibasaki
The stereoselective preparation of 1,2,3-substituted cyclopropanes from α,β-unsaturated carbonyl compounds in the carboxylic acid oxidation state through Michael addition-initiated ring-closure reactions is a significant challenge in organic synthesis. Herein, the previously elusive catalytic asymmetric cyclopropanation of α,β-unsaturated amides with stabilized sulfur ylides has been efficiently accomplished utilizing a chiral Cu­(I) complex. This Lewis acid catalytic system effectively converts a wide range of electron-deficient alkenes into the corresponding 1,2,3-trisubstituted cyclopropanes under mild reaction conditions in good to excellent yields with both high to excellent enantio- and diastereoselectivities. The resulting enantiomerically enriched cyclopropane amides can be readily diversified into promising synthetic intermediates such as β-aminocyclopropanecarboxylic acids with the facile recovery of the 7-azaindoline auxiliary without influencing the optical purity of the cyclopropane unit, which highlights the synthetic efficacy of this catalytic approach.