[CONTRIBUTION h'o. 31 13 FROM THE GATES AND CRELLIN LABORATORIES ... PASADENA, CALIFORSIA] Thermal and Photosensitized Dimerizations of Cyclohexadiene ... JR.,'~ AND GEORGE S. HAMMOND RECEIVED JASUARY 20, 1964 ... Photosensitized dimerization of 1,3-cyclohexadiene gives 9OYc yields of trans-cis-t~ans-tricyclo[6.4.0.0*~~]- dodeca-3,ll-diene (3), the corresponding cis-cis-cis-isomer (4), and exo-dicyclohexadiene (2) in 3 : 1 : 1 ...