An Interesting Regioselectivity of Palladation for Bromoindole Derivatives: A Convenient One-Step Synthesis of 4-Bromodehydrotryptophan Derivatives

Abstract

N'-Protected-N-tosyl-4- or 5-bromodehydrotryptophan (3) was obtained by the regioselective vinylation of N-tosyl-4- or 5-bromoindole (1) with N-protected dehydroalanine methyl ester (2) by the use of stoichiometric amount of PdCl 2 . On the other hand, the same reaction of 4-bromoindole (1b) under catalytic conditions gave the 4-vinylated product (4)