THE EFFECT OF LIGANDS, SOLVENT AND TEMPERATURE ON THE REACTIONS OF ALLYLTIN(IV) COMPOUNDS WITH SINGLET OXYGEN

The reaction of singlet oxygen with a variety of allyltin compounds CH2 = CHCH2SnR3 (R3 = Me3, Bu3, allyl3, (cyclo-C6H11)3, Ph3, allylBu2, Bu2Cl, Bu2OAc, allylCl2, allylCl2bipy) has been investigated, and the allylperoxytin compounds, 3-stannylallyl hydroperoxides, and 4-stannyl-1,2-dioxolanes which result from M-ene, H-ene and cycloaddition processes, respectively, have been identified by NMR spectroscopy. As the tin centre becomes more electropositive, as indicated by the C-13 NMR shift of the allylic CH2 group, the proportion of the M-ene reaction increases, and when delta-CH2 is above about 23.7, the allylperoxytin compound is the only product. An exception to this rule is tetrallytin, delta-CH2 16.13, which similarly shows only the M-ene reaction. This is tentatively ascribed to the special effect of hyperconjugation between the C-Sn sigma-bond and the remaining pi-systems. A polar solvent favours the M-ene reaction. The cycloaddition reaction is favoured by low temperature, and at -70-degrees-C in a non-polar solvent it may become the major route. Diallylmercury and allylmercury chloride react with singlet oxygen to show only the M-ene reaction, but also undergo extensive photosensitized decomposition. With 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD), allylmercury chloride shows only the M-ene reaction.