Thermal Rearrangement of 3-Methylenespirododeca-1,4,9-triene and Spirododeca-1,4,9-trien-3-one

Article abstract of DOI:10.1021/jo00351a001

Introduction of a double bond into the seven-membered ring of 3-methylenespiro<5.6>dodeca-1,4-dien-3-one (1) or spiro<5.6>dodeca-1,4-diene (16) alters the thermal behavior of both compounds.Pyrolysis of 3-methylenespiro<5.6>dodeca-1,4,9-triene (5) affords the isomeric hydrocarbon cis,cis-2,5-dimethylene-7-vinylbicyclo<4.3.0>non-3-ene (11).Pyrolysis of the related ketone spiro<5.6>dodeca-1,4,9-trien-3-one (6) gives a mixture of cis,cis-5-methylene-9-vinylbicyclo<4.3.0>-3-nonen-2-one (21), cis,cis-5-methylene-7-vinylbicyclo<4.3.0>-3-nonen-2-one (22), and trans,trans-2,4,5a,6,8a,8b-hexahydroacenaphthylen-5(1H)-one (23).Mechanistic rationales for these reactions are presented.