Generation and reactions of 2-(1-adamantyl)adamantene. Rearrangement to 3-(1-adamantyl)-4-protoadamantylidene

The S(N)1 methanolysis of (1-adamantyl)(3-noradamantyl)methyl heptafluorobutyrate at 100 degrees C yielded (1-adamantyl)-(3-noradamantyl)methyl methyl ether (17), 2-(l-adamantyl)-1-methoxyadamantane (18), and 4-(1-adamantyl)-3-methoxyprotoadamantane (19) in a 2:65:33 ratio. The methanolysis of (l-adamantyl)(3-noradamantyl)diazomethane (7) at 0 OC also yielded 17, 18, and 19 in a 4:33:63 ratio. On the other hand, the photolysis of 7 in 99: 1 (v/v) hexane-methanol gave 17, 18, 2-(l-adamantyl)-2-methoxyadamantane (25), and 2-(I-adamantyl)-2,4-didehydroadamantane (20) in a 30:9:36:25 ratio. Presence of triethylamine decreased the yields of ethers 17, 18, and 25, and increased the yield of 20 to 46%. The formation of a considerable amount of 17 and the absence of 19 in the photolysis products indicate the generation of (l-adamantyl)(3-noradamantyl)methylidene (8). The formation of 25 and 20 suggests that the generated carbene 8 rearranges to 2-(l-adamantyl)adamantene (3b) and then gives 3-(l-adamantyl)-4-protoadamantylildene by the subsequent retro-insertion. An attempt to isolate 3b in the photolysis of 7 in cyclohexane failed, and the sole isolated product was 20.