Abstract o-Di-isobutenyl-benzene (4) on irradiation in hexane with a low-pressure mercury lamp gives 4 photoproducts in an overall yield of 24%. Three of these products were identified as 4, 4, 6, 6-tetramethyl-benzobicyclo [3.1. 0] hex-2-ene (5, main product, 14%), 1.1-dimethyl-2-isopropenyl-indane (6, 8%) and 1-isopropenyl-2, 2-dimethyl-indane (10, 2%). 6 is also formed by irradiation of 5 in hexane.
