Synthesis of N-allyl- and N-acyl-2-vinylindoline

Heating a mixture of (2R*,3R*)- and (2R*,3S*)-2-(1S*)-1-iodoethyl]-3,5-dimethyl-1-(2-nitrophenyl) sulfonyl]indolines with N-isopropylpiperidine in xylene resulted in (2S*,3R*)-3,5-dimethyl-1-(2-nitrophenyl) sulfonyl]-2-vinylindoline. The latter reacted with thiophenol to afford (2S*,3R*)-3,5-dimethyl-2-vinylindoline, whose reaction with allyl halides or acetyl bromide gave rise to N-allyl-, N-propenyl-, or N-acetyl derivatives. Nitration of 1-acetyl-3,5-dimethyl-2-vinylindoline yielded ortho-nitro derivative.