The photo-assisted catalytic transfer hydrogenation and the catalytic hydrogenation of norbornadiene (1) and quadricyclane (II) over a photo-activated Rh cluster in 2-propanol in the presence of acetone was studied under comparative conditions. With the photo-assisted catalytic transfer hydrogenation, the hydrogen produced by dehydrogenation of 2-propanol is used very effectively for the addition to the reactants without evolving H-2. Norbornane (IV) and nortricyclene (V) are formed in parallel in the photo-assisted hydrogen transfer reaction of II. In the reaction of I, the acetone-sensitized isomerization of I to II occurs prior to hydrogenation in a concentration of 58 mmol/l of I. However, at a lower concentration, we observed a stepwise hydrogenation of I to IV via norbornene (III). The yield of III formed in the catalytic hydrogenation was larger than that in the photo-assisted catalytic transfer hydrogenation. Compound II was not observed in the catalytic hydrogenation of I, and the yield of V was less than 1%. Compound II behaves in catalytic hydrogenation similar to as in photo-assisted catalytic transfer hydrogenation. The hydrogenation paths of I and II in both the reactions are discussed on the basis of a reaction mechanism shown in Scheme 1. (C) 2003 Elsevier Science B.V. All rights reserved.