The photoreaction of (5R)-5-menthyloxyfuran-2[5H]-one (1) into the adduct 2 in the presence of N-methylpyrrolidine (MeP) and several ketones in acetonitrile was investigated by time resolved absorption spectroscopy. The transient properties and the quenching rate constants of the ketone/1/MeP system are described for benzophenone, 4,4'-dimethoxybenzophenone, xanthone, acetophenone and methoxyacetophenone and compared with those where MeP is replaced by triethylamine. (C) 2003 Elsevier B.V. All rights reserved.