A Highly diastereoselective synthesis of (1R)-(+)-camphor-based chiral allenes and their asymmetric hydroboration-oxidation reactions.
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.
Hung
Shang-Cheng
SC
Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan 300, Republic of China.
Wen
Yen-Fang
YF
Chang
Jia-Wen
JW
Liao
Chun-Chen
CC
Uang
Biing-Jiun
BJ