Asymmetric alkyldifluoroboranes and their use in secondary amine synthesis.
[reaction: see text] Asymmetric diol boronic esters with potassium bifluoride form the corresponding alkyltrifluoroborate and free diol under mild conditions. Defluoridation with tetrachlorosilane produces an alkyldifluoroborane intermediate. This conversion of relatively unreactive boronic esters to derivatives that are strong Lewis acids opens new synthetic opportunities, as illustrated by the preparation of (R)-2-phenylpyrrolidine in 98% ee from a pinanediol or 1,2-dicyclohexyl-1,2-ethanediol boronic ester via potassium (2-phenyl-4-azidobutyl)trifluoroborate.
Matteson
Donald S
DS
Department of Chemistry, P.O. Box 644630, Washington State University, Pullman, Washington 99164-4630, USA. dmatteson@wsu.edu
Kim
Gyung Youn
GY
D000588:Amines / Q000138:chemical synthesis*; D001880:Boranes / Q000737:chemistry*; D003500:Cyclization; D005459:Fluorides / Q000737:chemistry
D000588:Amines; D001880:Boranes; D005459:Fluorides