Reactions of diethyl azulene-1,3-dicarboxylate derivatives and 1-azaazulene derivatives with Grignard reagents, and alkyl- and aryllithium

Abstract

Reactions of diethyl azulene-1,3-dicarboxylate (1) and diethyl 2-chloroazulene-1,3-dicarboxylate (11) with Grignard reagents, followed by dehydration with tetrachloro-1,2-benzoquinone, gave 2-, 4,- and 6-substituted addition–oxidation products. Grignards reagents have a tendency to react with 1 at the positions in the order of 2 > 4 > 6, while steric hindrance has a greater influence at the positions in order of 2 > 4 > 6. Reactions of 1 and 11 with phenyllithium and methyllithium gave similar results. On the other hand, on the reaction of diethyl 2-methoxyazulene-1,3-dicarboxylate (15), Grignard reagents attacked preferentially at the methoxy group, and 2-substituted products were obtained. Use of excess molar equivalents of Grignard reagents led to diaryl-substituted products. Reaction of 2-chloro-1-azaazulenes with Grignard reagents also gave similar addition–oxidation products, and reacted at the positions in the order 8 ≫ 4 > 6, whereas reaction of 2-methoxy-1-azaazulene with a Grignard reagent gave 1-azaazulen-2(1H)-one.