Highly diastereoselective and enantioselective preparation of homoallylic amines:: Application for the synthesis of β-amino acids and γ-lactams

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 B-11 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 beta-methyl or beta-alkoxy homoallylic amines in very high diastereoselectivity and enantioselectivity are reported herein. Crotylbofation 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 P-amino acids in two steps has been described. Additionally, a procedure for the preparation of chiral delta-amino alcohols and gamma-lactams from nitriles is also reported.