Selectivity: a key to synthetic efficiency.

The efficient synthesis of organic compounds requires the development of processes with enhanced selectivity. Selectivity is categorized according to chemical reactivity (chemoselectivity), orientation (regioselectivity), and spatial arrangement (diastereoselectivity and enantioselectivity). Recent developments in reduction-oxidation methods and C-C bond forming reactions illustrate some solutions to problems of selectivity. The design of selectivity-inducing groups and the increased role of main group and transition metals in enhancing selectivity are especially noted.