REACTION OF A POLYMERIZATION-RESISTANT 1,2-DITHIOLANE WITH LITHIATED NITROGEN-HETEROCYCLES

Nitrogen-containing five-membered heterocycles, N-methylpyrrole 2, N-m ethylpyrazole 4, N-methylimidazole 6, 4-methylthiazole 11, N-methylind ole 14, benzothiazole 16, N-methylbenzimidazole 18, and benzoxazole 20 were lithiated with BuLi and LDA in THF and reacted with the polymeri zation-resistant 1,2-dithiolane 1. All of the corresponding lithiohete rocycles cleaved the S-S bond of the 1,2-dithiolane 1 to give the ring -opened products in line with the carbanion mechanism proposed for the enzyme-reductive acylations of lipoic acid. The ring-opened products 8, 9, 13, 22, and 23 were isolated in good yields and high purity. The ring-opened products from benzothiazole and N-methylbenzimidazole wer e decomposed by the action of excess lithioheterocycles. The lithioben zoxazole was less reactive than the other lithioheterocycles. (C) 1998 John Wiley & Sons, Inc.