Using heterogeneous photocatalysis, the radical addition of tertiary amines with electron deficient
alkenes can be performed in high yields (up to 98%) and high facial diastereoselectivity. The photochemical
induced electron transfer process initiates the radical chain reaction and inorganic semiconductors
like TiO2 and ZnS were used. According to the proposed mechanism, the reaction takes place at the surface
of the semiconductor and the termination step results from an interfacial electron transfer from the conduction
band to the oxoallyl radical intermediate. Frequently, semiconductors are used for the mineralisation
of organic compounds in wastewater. However, in this case, they are used in organic synthesis. The process
can be performed in a convenient way and is particularly interesting from the ecological and economical
point of view. No previous functionalization of the tertiary amines is necessary for C − C bond formation.
Further on, the amines are used both as reactant and as solvent. The excess is recycled by distillation and the
inexpensive sensitiser can be easily removed by filtration. In this way, products of high interest for organic
synthesis are obtained by a diastereoselective radical reaction.
