DESILYLATION BY ETHER CLEAVAGE

The electron-transfer-sensitized photolysis of substituted phenyl-(trimethylsilyl)methyl ethers was studied. N-Methylquinolinium perchlorate, p-tolyltropylium perchlorate and 9,10-dicyanoanthracene were used as electron acceptors. The main reaction of the stabilization of the radical cation of the ether (the intermediate formed by single electron transfer to the singlet-excited acceptor) is CO bond cleavage. With 9,10-dicyano-anthracene as acceptor 100% phenol is formed. The competing CSi bond cleavage is a minor reaction in the case of the quinolinium salt. This leads to addition of the ether fragment and the acceptor. The photoexcited tropylium salt does not induce any reaction of the added ether. The quantum efficiencies of ether cleavage are relatively high and depend on the donor capacity of the substituent in the phenyl ring. This is explained by competition between back electron transfer and bond cleavage in the radical pair formed. Electron paramagnetic resonance (EPR) was used to detect the intermediate radicals and flash photolysis to detect the anion radicals. © 1990.