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Asymmetric Traceless Petasis Borono‐Mannich Reactions of Enals: Reductive Transposition of Allylic Diazenes
Author(s) -
Jiang Yao,
Thomson Regan J.,
Schaus Scott E.
Publication year - 2017
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201708784
Subject(s) - stereocenter , chemistry , mannich reaction , allylic rearrangement , transposition (logic) , combinatorial chemistry , enantiomer , organic chemistry , aryl , alkyl , catalysis , enantioselective synthesis , linguistics , philosophy
Abstract The traceless Petasis borono‐Mannich reaction of enals, sulfonylhydrazines, and allylboronates, catalyzed by chiral biphenols, results in an asymmetric reductive transposition of the in situ generated allylic diazene. Acyclic 1,4‐diene products bearing either alkyl‐ or aryl‐substituted benzylic stereocenters are afforded in excellent yields and enantiomeric ratios of up to 99:1. The use of crotylboronates in the reaction results in concomitant formation of two stereocenters in either a 1,4‐ syn or anti relationship from the corresponding E ‐ or Z ‐crotylboronate used in the reaction. The use of β‐monosubstituted enals in the asymmetric traceless Petasis borono‐Mannich reaction of crotylboronates installs tertiary methyl‐bearing stereocenters in good yields and high enantioselectivities.