Adducts from quinones and diazoalkanes. Part 9. The adduct from 2-methyl-1,4-napthoquinone and diazoethane and the derived secondary carbanion: regioisomerism in carbanion–quinone additions

Abstract

Diazoethane adds to 2-methyl-1,4-naphthoquinone giving mainly one regioisomeric pyrazoline (5a) as a mixture of epimers at position 3. The other regioisomer was detected and a related compound (7) was obtained from a similar reaction with diazomethane. The pyrazoline (5a) is transformed into the carbanion (3b) with base and thence into the butylenediquinone (9). Thermal decomposition affords 2-ethyl-3-methyl-1,4-naphthoquinone. Treatment with methanolic base and 2-methyl-1,4-naphthoquinone gives the fluorene derivative (11a) not the expected alcohol (12). Treatment with methanolic base and trimethyl-1,4-benzoquinone affords the expected xanthen derivative (16) but the congeneric fluorene alcohols differed regiospecifically from those observed in other series. One (14) has a cis-fused nucleus; the other is believed to be the trans-fused analogue (13), another departure from previous experience. On the other hand, the reaction with 2,5-dimethyl-1,4-benzoquinone leads to the cage tetraketone (17a) as expected.