The carbonyl-carbonyl olefination reaction promoted by (over)stoichiometric amounts of titanium and metal reductants, which is known as the McMurry reaction, represents an attractive strategy for the formation of carbon-carbon double bonds. However, the one-step direct coupling of two carbonyl groups in a catalytic fashion remains challenging and less explored. Herein, we report a Mo-catalyzed intramolecular carbonyl-carbonyl olefination reaction for the syntheses of heterocycles from the carbonyl or 1,2-dicarbonyl compounds. By utilizing the commercially available molybdenum catalyst, various substituted indoles, benzofurans, and benzothiophene were obtained in up to 98% yield. The synthetic utility of the method is further demonstrated by gram-scale syntheses and derivatization of several bioactive molecules. Preliminary mechanistic studies suggest that Mo-carbene species is presumably involved in the reaction. Moreover, this strategy could be further applied to the syntheses of valuable 2-pyrone, coumarins and their derivatives through the direct intermolecular deoxygenative cross coupling of readily available salicylic aldehydes or 1,3-dicarbonyl compounds with ɑ-ketoesters.

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