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Highly Diastereoselective and Enantioselective Preparation of Homoallylic Amines: Application for the Synthesis of β‐Amino Acids and γ‐Lactams
Author(s) -
Ramachandran P. Veeraraghavan,
Burghardt Thomas E.
Publication year - 2005
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200401295
Subject(s) - chemistry , reagent , enantioselective synthesis , methanol , aldimine , silylation , organic chemistry , alkoxy group , catalysis , alkyl
Abstract Reactions of N‐silyl‐ and N‐aluminoimines with B‐allyldiisopinocampheylborane in the presence of methanol, followed by oxidative workup furnished homoallylic amines in good yields and high ee . A 11 B NMR spectroscopy study revealed that the reactions do not proceed, even at room temperature, unless a molar equivalent of water or methanol is added. The first reagent‐controlled asymmetric crotylboration and alkoxyallylboration of aldimines furnishing β‐methyl or β‐alkoxy homoallylic amines in very high diastereoselectivity and enantioselectivity are reported herein. Crotylboration and alkoxyallylboration of imines proceed only with the “allyl”‐boron “ate” complexes, instead of the “allyl”‐dialkylboron reagents used with aldehydes. The addition of methanol is necessary for these reactions as well. Application of this methodology for the conversion of representative nitriles to β‐amino acids in two steps has been described. Additionally, a procedure for the preparation of chiral δ‐amino alcohols and γ‐lactams from nitriles is also reported.