A disubstituted alkene lacking an aromatic substituent, 3-octen-2-one (1r), smoothly underwent the hydrogenation to give 2r in 56% yield. We assessed whether the cis or trans configuration of the double bond had an influence on the reaction outcome: both diethyl fumarate and diethyl maleate underwent the hydrogenation to give diethyl succinate 2s in 90% yield in both cases. 2-Cyclohexenone 1b was successfully hydrogenated to give the product in 90% yield within 5 h. Allylic alcohol 1t and the terminal alkenes estragole and eugenol gave the corresponding products 2t-2v in high yields of 80, 87 and 83%, respectively. In contrast, when eugenol was protected with a benzyl group, the yield decreased significantly, possibly due to the decreased solubility of the starting material in the reaction solvent (2w, 26% yield). Based on the observation that the substrate solubility had a significant effect on the reaction outcome, we carried out further solvent screening using 1w as a model substrate (see Table ). The best results were observed with a saturated solution of n-BuOH, one of the greenest solvents (in H2SO4, 0.25 M aq.), and 2w was obtained in a high 77% yield (Scheme 7). We then reexamined the reactions of substrates 1g, 1i, and 1j in n-butanol, and significantly better yields of 59, 72, and 82%, respectively, were obtained (Scheme 7). The hydrogenation of trisubstituted alkenes proved to be more challenging; diethyl mesaconate was hydrogenated to give 2x in 37% yield. The same method was used for the direct hydrogenation of alkynes into saturated derivatives; N-(3-butynyl)phthalimide gave 2y in 43% yield. The limitations of the method can be seen in the Supporting Information (Scheme S2).