A series of unsaturated carbonyls, quinones, and pyridinium salts have been effectively reduced to the corresponding saturated carbonyls, dihydroxybenzenes, and hydropyridines in moderate to high yields with tetrahydroxydiboron/water as a mild, convenient, and metal-free reduction system. Deuterium-labeling experiments have revealed this protocol to be an exclusive transfer hydrogenation process from
Tertiary α-cyanoamines served as the precusors of iminiumions in the presence of titanium tetrachloride. Various intramolecular nucleophiles, olefinic and acetylenic, were found to produce cyclized products. The influences of ring sizes and substitutions on the double bonds were also investigated.