An aminoisoflavone — salicyloylindole ring transformation

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.