Lower photoreactivity of 3‐methyl‐3‐(4′‐biphenylyl)‐t‐butene

Direct and sensitized photolyses of 3‐methyl‐3‐(4′‐biphenylyl)‐1‐butene gave 1,1‐dimethyl‐2‐(4′‐biphenylyl)cyclopropane as primary product and 2‐methyl‐4‐(4′‐biphenylyl)‐1‐butene as secondary product with quantum yields of 7.6×10 −3 and 5.6×10 −3 , respectively. On direct photolysis, the triplet reactant rearranged with a quantum yield of 4.4×10 −3 and is more reactive than the singlet. The exceptionally low photoreactivity shows that the excitation energy is largely localized on the biphenylyl portion but can be delivered to the reaction center slowly.