Abstract Photochemical reactions of caffeine with several aliphatic aldehydes are performed. In the reactions with ethanal, propanal and butanal stable 8-acyl-8, 9-dihydrocaffeines 2 and 3 together with unreduced 8-acylcaffeines 4 and 8-(α-hydroxyalkyl) caffeines 6 are produced. Under similar conditions, the reactions of 2-methylpropanal, 2-methylbutanal and 2, 2-dimethylbutanal resulted in the formation of the corresponding 8-alkylcaffeines 7.
