Flash vacuum thermolysis (FVT) of 3-methylene-6-spirocyclohexa-1, 4-dienes (2) was investigated as a synthetic approach to small [n] paracyclophanes 1 (1a, n= 8; 1b, n= 7; 1c, n= 6). The method was found to be preparatively attractive for 1a (80% yield), less so for 1b (7% useful yield), and not at all for 1c which was too unstable to survive the conditions of its formation. Besides 1, p-alkylstyrenes (3) and 2-methylbenzocycloalkenes (4) were ...