Abstract: A successful use of lithium dicyclohexylamine as a base in practical syntheses of 1,1-dimethyl-2-(1-naphthyl) cyclopropane (1) and 1,1-dimethyl-2-(9-phenanthryl) cyclopropane (2) from the corresponding ArCH,Cl and isobuterie was reported. Direct irradiation of (1) or (2) led to the corresponding 2-methyl-4-aryl-1-butene (major product), arylethylene and 2,3-dimethyl-2-butene. Euns with benzhydrol and benzopheno-ne present showed that both (1) and (2) quenched benzopinacolization and therefore demonstrated that triplet transfer to (1) or (2) was indeed occuring. Hence the reaction is singlet process. The lacking of vertical excited state stabilization due to aryl group revealed that the p orbitals of aryl ring did not participate the reaction transion. Thus, the rearrangement is likely to proceed via a Hiickel-like four electron cyclic array transion, which followed the “small K vs large K” generalization.