An aminoisoflavone — salicyloylindole ring transformation

Abstract

A series of 2'-nitroisoflavones 8-10, 15, 22, 27 and 28 was prepared via the (2-nitro-phenyl)-acetic acids 1, 13, 19 and 25. In order to obtain the corresponding 2'-aminoisoflavones the reduction of 8-10, 15, 22, 27 and 28 was undertaken. Surprisingly, new 3-salicyloylindoles instead of the expected 2'-aminoisoflavones were the main reduction products. In the following paper the preparation of the 2'-nitroisoflavones 8-10, 15, 22, 27 and 28 as well as the reduction experiments obtaining the 2'-aminoisoflavones 33 and 35 and the 3-salicyloylindoles 29-32, 34 and 36 will be described. Furthermore, a possible mechanism responsible for the formation of the 3-salicyloylindoles from 2'-nitroisoflavones under reductive conditions will be discussed.