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NameMr. Alafate Adili
Organization or InstitutionUniversity of Florida
TopicOrganic Chemistry
Title

Catalytic Enantioselective Diasterodivergent Oxa-Pictet−Spengler Reactions

Author(s)

Alafate Adili†, Bishwaprava Das†, Chenfei Zhao‡ and Daniel Seidel*†

Author Institution(s)

†University of Florida
‡University of California Berkeley

Abstract

An oxocarbenium ion can be generated under mild or weakly acidic conditions by using two cooperative catalysts, an amine HCl salt and bisthiourea.  The amine catalyst can generate an electrophilic iminium ion that can validate 1,2-attack by tryptophol.  Catalyst turnover is achieved by amine elimination with collateral formation of an oxocarbenium intermediate.  The bisthiourea catalyst in collaboration with the oxocarbenium intermediate via ion pair/anion binding can accelerate the reaction and enhance stereoselectivity.  By manoeuvring this new concept, our recent work is focused on direct enantioselective Oxa-Pictet−Spengler reactions of tryptophol with various aldehydes.  Introducing a substituent at the β position of tryptophol involves a diasterodivergent process which can afford both diastereomers of products in good yields and with excellent enantioselectivity.