INDOLE-3-PYRUVIC ACID OXIME ETHERS AND THIENO ANALOGS BY HECK CYCLIZATION - APPLICATION TO THE SYNTHESIS OF THIA-TRYPTOPHANS

N-allylation of N-BOC substituted o-iodo anilines (14a-e) and thienoam ines (16,18,20) employing methyl or benzyl oxime ethers of ethyl (E)-2 -oxo-5-bromo-3-pentenoate 2a, followed by palladium-catalysed Heck cyc lisation yielded oxime ethers of Bz-substituted ethyl indole-3-pyruvat es (15a-f) and thienopyrroles (17,19,21-23). Attempted conversion of 2 a into the corresponding tosyl hydrazone or oxime resulted in formatio n of pyridazine (10) and oxazine (13) derivatives. The three possible isomers of thia-tryptophan were obtained as the ethyl esters from corr esponding methyl oxime ethers by reduction of the oxime double bond. C opyright (C) 1996 Elsevier Science Ltd