Mo^V Reagents in Organic Synthesis

Abstract

Abstract The use of Mo V reagents, and in particular MoCl 5 , in organic synthesis is surveyed. The oxidative treatment of aromatic substrates is the most common application. The unique properties of these reagents are due to their high oxidative power combined with exquisite Lewis acid properties. In several examples Mo V reagents outperform other common oxidative coupling reagents. C–C bond formation through inter‐ and intramolecular oxidative coupling can lead to selective formation of five‐ to eight‐membered ring systems. Mechanistic investigations of the courses of reactions involving Mo V reagents and aromatic substrates indicate that radical cations are initially formed, entering the oxidative coupling scenery. Mechanistic studies reveal that Scholl‐type conversion is unlikely. However, over‐oxidation of the product seems to be the rationale for the selective conversion. Reduction occurs during workup, through the action of the lower‐valency molybdenum salts present. This opens up the pathway to oxidative domino sequences. MoCl 5 has already been used in the key steps of the syntheses of several natural products or their analogues. In addition, MoCl 5 can serve in chlorination reactions and in stereoselective isomerization by template formation, and also as a precursor for alkyne trimerization.