Synthesis of adamantane derivatives—38: Synthesis of 1,3-bishoadamantane via ring-expansion of homoadamantan-2-one and homoadamant-4-en-2-one

The ring expansion of homoadamant-4-en-2-one (7) via the corresponding aminomethyl alcohol (9) gave 1,3-bishomoadamant-7-en-4-one (10) as the major product which was converted to 1,3-bishomoadamant-4-ene (14) and 1,3-bishomoadamanta-4,7-diene (16) via the alcohols 13 and 15. Catalytic hydrogenation of 14 and 16 afforded 1,3-bishomoadamantane (2). The ring expansion of homoadamantan-2-one (17) via the aminomethyl alcohol (19) afforded a 9:1 mixture of 1,3-bishomoadamantan-4-one (12) and 5-one (20). The same mixture was also obtained directly from 17 on treatment with diazomethane. The Wolff-Kishner reduction of 12 and 20 gave also 2.