Reactions of o-quinones with some bis-phosphonium salts in the presence of lithium ethoxide

Abstract

Reactions of the 1,3-bis-phosphonium salts (2a–d) with phenanthrene-9,10-quinone (1) in the presence of lithium ethoxide gave the phenanthro derivatives (3), (4), (5), and (7) respectively, instead of the expected bis-Wittig reaction products. However, from the reaction of the salt (2c) the bis-Wittig product (6) was also obtained, but in very low yield. On the other hand, reactions of 1,6- and 1,5-bis-phosphonium salts (18) and (26) with o-quinones (1), (20), and (21) resulted in the formation of 9-(o-hydroxyaryl)phenanthrenes (22)–(24) and 1-(o-hydroxyaryl)acenaphthylenes (28) and (29). Reaction mechanisms involving initial Wittig reaction of one carbonyl group with one ylide group are proposed. Bromination of (22) and (28) and dehydrobromination of the bromo derivatives (33) and (35) produced gave the annelated furan derivatives (34) and (36) respectively.