The photooxygenation of benzyl, heteroarylmethyl and allyl sulfides

S. M. BONESI, R. TORRIANI, M. MELLA, A. ALBINI

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY

Wiley-VCH verlag

Lugar: Wienheim; Año: 1999 p. 1723 - 1728

1434-193X

The photosensitised oxidation of benzyl ethyl sulfides in and the 3-cyclohexenyl sulfide give the corresponding aprotic solvents (benzene or acetonitrile) gives the ketone (the latter in a low yield), but the a-methylbenzyl corresponding aldehydes under mild conditions. This is a sulfide gives the sulfoxide as the main product. The rate for general reaction which applies to benzyl derivatives singlet oxygen quenching and for chemical reaction have containing either electron-donating or electron-withdrawing been measured for representative benzyl sulfides. The substituents and furthermore to hetero analogues such as 2- reaction is discussed in the frame of the currently accepted pyridinylmethyl sulfide (not to the 3-indolylmethyl sulfide, mechanism for sulfide photooxygenation. The key step for since reaction at the heterocycle moiety competes) as well as oxidative C–S bond cleavage appears to be hydrogen to allyl sulfides. In a protic solvent (methanol) these sulfides transfer from the activated a position in the first formed give the sulfoxides instead (except for the nitrobenzyl intermediate, the persulfoxide. This reaction is inhibited in derivatives, where the aldehyde remains the major product). methanol where the persulfoxide is hydrogen-bonded. Among the a-substituted sulfides tested, the a-phenylbenzyla-methylbenzyl corresponding aldehydes under mild conditions. This is a sulfide gives the sulfoxide as the main product. The rate for general reaction which applies to benzyl derivatives singlet oxygen quenching and for chemical reaction have containing either electron-donating or electron-withdrawing been measured for representative benzyl sulfides. The substituents and furthermore to hetero analogues such as 2- reaction is discussed in the frame of the currently accepted pyridinylmethyl sulfide (not to the 3-indolylmethyl sulfide, mechanism for sulfide photooxygenation. The key step for since reaction at the heterocycle moiety competes) as well as oxidative C–S bond cleavage appears to be hydrogen to allyl sulfides. In a protic solvent (methanol) these sulfides transfer from the activated a position in the first formed give the sulfoxides instead (except for the nitrobenzyl intermediate, the persulfoxide. This reaction is inhibited in derivatives, where the aldehyde remains the major product). methanol where the persulfoxide is hydrogen-bonded. Among the a-substituted sulfides tested, the a-phenylbenzyla position in the first formed give the sulfoxides instead (except for the nitrobenzyl intermediate, the persulfoxide. This reaction is inhibited in derivatives, where the aldehyde remains the major product). methanol where the persulfoxide is hydrogen-bonded. Among the a-substituted sulfides tested, the a-phenylbenzyla-substituted sulfides tested, the a-phenylbenzyl