A Highly diastereoselective synthesis of (1R)-(+)-camphor-based chiral allenes and their asymmetric hydroboration-oxidation reactions

Shang-Cheng Hung; Yen-Fang Wen; Jia-Wen Chang; Chun-Chen Liao; Biing-Jiun Uang

doi:10.1021/jo016201i

A Highly diastereoselective synthesis of (1R)-(+)-camphor-based chiral allenes and their asymmetric hydroboration-oxidation reactions

J Org Chem. 2002 Feb 22;67(4):1308-13. doi: 10.1021/jo016201i.

Authors

Shang-Cheng Hung¹, Yen-Fang Wen, Jia-Wen Chang, Chun-Chen Liao, Biing-Jiun Uang

Affiliation

¹ Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan 300, Republic of China.

PMID: 11846679
DOI: 10.1021/jo016201i

Abstract

Synthesis of camphor derived chiral allenes and their hydroboration-oxidation reactions are described. Reaction of (1R)-(+)-camphor with alkynyllithium followed by the reduction of the resulted propargyl alcohol derivatives using AlH3 furnished chiral allenes 2a-g in excellent yields with high diastereoselectivity. Reduction of the propargyl alcohols with aluminum hydride proceeded through selective intermolecular anti-addition of hydride ion. The stereochemistry of the chiral allenes 2 was assigned based on lanthanide shift studies and chemical correlations. Diastereoselectivity was observed in the hydroboration-oxidation of 2 which produced a mixture of (E,R) and (E,S) stereoisomers in a ratio of 6:1 to 18:1.