Ring expansion reaction of formyl[2.2.1]bicyclic carbinols with primary amines

ORGN 826

Te-Fang Yang, tfyang@cyut.edu.tw, Li-Hsun Chen, and Li-Da Kao. Department of Applied Chemistry, Chaoyang University of Technology, 168, Gifeng E. Road, Wufong, 413, Taichung, Taiwan, Wufong, Taiwan
In the last decade, organic chemists have paid much attention to the ring expansion of [2.2.1]bicyclic carbinols due to its potential application to the preparation of precursors of natural products. Herein, we report that camphor- and camphene-derived formyl[2.2.1]bicyclic carbinols reacted with primary alkyl/aryl amines (RNH2: R = Me, Et, Ph, Bn, etc.) to form the corresponding imino[2.2.1]bicyclic carbinols in dichloromethane at room temperature. After the imono[2.2.1]bicyclic carbinols were refluxed in toluene, the [3.2.1]bicyclic α-amino ketones were produced. Especially, the reaction of formyl borneol with aniline and para-substituted anilines in dichloromethane gave directly the [3.2.1]bicyclic products without heating. It is noteworthy that the ring expansion reaction turned out to be one-pot, stereoselective and regioselective. A mechanism of the reaction is to be illustrated.