P. Hamel et al., Cyclization of 2-and 3-indolylthiobenzoic, phenylacetic and nicotinic acids and esters to novel indole-containing tetracyclic ring systems., J HETERO CH, 36(3), 1999, pp. 643-652
A series of 2- and 3-indolylthio benzoic, phenylacetic and nicotinic acids
or esters were cyclized under dehydrative conditions affording several tetr
acyclic indole-containing ketones, several of which constitute the first re
ported examples of novel ring systems, such as the [1]benzothiepino[2,3-b]
and [3,2-b]indole and the pyrido[3'2':5,6] and [3'4':5,6]thiopyrano[2,3-b]
and [3,2-b]indole as well as the [3'2':5,6] and [3'4':5,6][1,3]thiazino[3,2
-a]indole ring systems.