Asymmetric Propargylboration of Aldimines and Ketimines with the Borabicyclo[3.3.2]decanes: Novel Entries to Allenyl Carbinamines, Amino Acids, and Their α-Methyl Counterparts

Abstract

Available in either enantiomerically pure form through quantitative Grignard procedures from air-stable crystalline complexes (1, 3), the B-γ-TMS propargylic derivatives of the 10-TMS- (2) and 10-phenyl-9-borabicyclo[3.3.2]decanes (4) provide highly selective entries to 2°-allenyl carbinamines (8, 60-85%, 78-99% ee) and their 3° counterparts (13, 62-82%, 95-99% ee) through their additions to aldimines and ketimines, respectively. The absolute configurations of these amines were obtained from the known amino acid derivatives 16eR and 19dR through the ozonolysis of 8eR and 13dR and from the single-crystal X-ray structure of 14fR.