Issue 5, 2009

Studies concerning the electrophilic amino-alkene cyclisation for the synthesis of bicyclic amines

Abstract

The bromination of a series of cyclohexenyl substituted secondary amines 1a-i has been investigated using Br2, PHT and NBS. In the case of Br2 and NBS the secondary amines preferentially undergo N-bromination. In contrast, PHT cleanly affords the products of alkene dibromination. In the case of Br2 the N-bromo species then give the products of alkene dibromination, albeit less efficiently. On subsequent treatment with K2CO3 these dibromides form the corresponding hexahydroindoles 2a-h and octahydroquinoline 2i. The presence of an N-substituent bearing a stereogenic centre (1h and 1i) was studied and the products 2h and 2i were isolated with no diastereoselectivity. When NBS was used a novel cyclisation, forming bromo-substituted octahydroindoles 9a,b and d, was observed. In relation to this sequence it was shown that these products were not intermediates in the former Br2/PHT processes and that the reaction only proceeded in the presence of the succinimide by-product of N-bromination.

Graphical abstract: Studies concerning the electrophilic amino-alkene cyclisation for the synthesis of bicyclic amines

Supplementary files

Article information

Article type
Paper
Submitted
04 Nov 2008
Accepted
04 Dec 2008
First published
23 Jan 2009

Org. Biomol. Chem., 2009,7, 986-995

Studies concerning the electrophilic amino-alkene cyclisation for the synthesis of bicyclic amines

J. E. M. N. Klein, H. Müller-Bunz and P. Evans, Org. Biomol. Chem., 2009, 7, 986 DOI: 10.1039/B819610A

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