Self-Activation and 1,8-Stereoinduction in a Boronate-substituted Dienophile

Abstract The [4+2] cycloaddition of ORTHO-boronoanilide dienophile 4 with cyclopentadiene was found to proceed faster than both its PARA isomer 8 and the unsubstituted derivative 6, thereby confirming that self-activation by internal coordination is operative in the case of 4. Chiral boronic esters derivatives 9 and 10 provided a small level of remote 1,8-stereoinduction. These results show that dialkoxyboronic esters can operate as weak, internal Lewis acids and activate carbonyl-containing functionalities in cycloaddition reactions.