Divergent Oxidative Rearrangements in Solution and in a Zeolite:Distal vs Proximal Bond Cleavage of Methylenecyclopropanes

摘要

Irradiation of 9,10-dicyanoanthracene(DCA)or p-chloranil in the presence of E-1-benzylidene-2-phenylcyclopropane(E-5)in CH_2Cl_2 causes E-5 to undergo methylenecyclopropane rearrangement.An adduct,Z-7,between DCA and 5 firmly supports the involvement of a bifunctional trimethylenemethane radical cation.In contrast,incorporation of E-5 into HZSM-5 produces trans,trans-1,4-diphenyl-1,3-butadiene radical cation sequestered in the HZSM-5 interior,tt-8~(centre dot+)@ HZSM-5,identified by ESR and diffuse reflectance spectroscopy.In addition,low yields of tt-8,its cis,trans-isomer(ct-8),and 1-phenyl-1,2-dihydronaphthalene(9)were isolated from the supernatant solution.The sharp contrast between the photoinduced electron-transfer reaction with photosensitizers in solution and the spontaneous reaction with redox-active acidic zeolite offers the prospect of further zeolite-induced regiodivergent reactions in a range of additional substrates.