Expedient Dual Co/Organophotoredox Catalyzed Stereoselective Synthesis of All-Carbon Quaternary Centers.

An efficient and attractive Co/organophotoredox dual catalysis protocol has been developed allowing the stereoselective access to a wide variety of syn-configured 1,3-diols featuring quaternary carbon centers. The synthesis of the target molecules is achieved under ambient reaction conditions using modular and accessible reagents, substituted vinyl cyclic carbonates and aldehydes, and in short reaction times. Mechanistic control experiments suggest that the stereoselectivity can be rationalized via a preferred Zimmerman-Traxler transition state comprising a Co(allyl) species and an activated aldehyde. This newly developed process thus expands the use of base metal catalysis in the construction of challenging quaternary carbon stereocenters.