Efficient synthesis of indoles using [3,3]-sigmatropic rearrangement of N-trifluoroacetyl enehydrazines

摘要

[3,3]-Sigmatropic rearrangement of N-triflluoroacetyl enehydrazines provides a novel method for the construction of indoles. N-Trifluoroacetyl enehydrazine having a cyclopentene ring smoothly underwent [3,3]-sign-tatropic rearrangement followed by cyclization to give indolines in excellent yield. On the other hand, both cyclohexenyl N-trifluoroacetyl enchydrazine and acyclic N-trifluoroacetyl enehydrazine gave indoles in good yield. Additionally, the substituent effect on the benzene ring was also studied. The rearrangement of N-trifluoroacetyl enchydrazines proceeded smoothly even Linder either aqueous or solvent-free conditions. (c) 2006 Elsevier Ltd. All rights reserved.