title: 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 ofBr2 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.
authors.affiliation: Centre for Synthesis and Chemical Biology, School of Chemistry and Chemical Biology, University College Dublin, Dublin 4, Ireland.
authors.forename: Johannes E M N
authors.initials: JE
authors.lastname: Klein
authors.forename: Helge
authors.initials: H
authors.lastname: Müller-Bunz
authors.forename: Paul
authors.initials: P
authors.lastname: Evans