Reduction and stereochemical studies through n.m.r. and X-ray techniques of indolo[2,1-b]quinazolines

Abstract

Indolo[2,1-b]quinazoline-6,12-dione (1) has been reduced by various methods and the stereochemistry of the products [e.g. 6-acetoxy-5a,6-dihydroindolo[2,1-b]quinazolin-12(5H)-one (10b) and 6-acetoxy-5-acetyl-5,5a,6,12-tetrahydroindolo[2,1-b]quinazoline (30b)] has been studied by n.m.r. spectroscopic methods. The detailed structure of the acetylated products, obtained from compound (1) by reduction with NaBH₄, [(10b)], and LiAlH₄, [(30b) and 1-(2-acetamidobenzyl)-3-acetoxyindole (34)], have been determined by X-ray crystallography.

Reduction of the dione (1) with hypophosphorus acid yielded the 6,6′-coupled dimeric product (40) which readily underwent dehydrogenation to the violet compound (41).