Photoelectrochemical asymmetric dehydrogenative [2 + 2] cycloaddition between C–C single and double bonds via the activation of two C(sp3)–H bonds

Abstract

The efficient generation of high structural complexity, which correlates with the number of stereocentres, is an important objective in organic synthesis. Ideally, from a perspective of economy and sustainability, the conversion should include the direct functionalization of unactivated C(sp3)–H bonds. Here we introduce a methodology that enables the generation of complex cyclobutanes with up to four consecutive stereocentres, including all-carbon quaternary stereocentres, from a direct reaction of C–C single bonds with C=C double bonds. The asymmetric photoelectrocatalysis combines photocatalysis, electrochemical redox catalysis and asymmetric catalysis. It avoids the use of chemical oxidants, exhibits excellent enantioselectivity and diastereoselectivity, reveals high functional group compatibility, and also succeeds in the simultaneous conversion of two C(sp3)–H bonds into consecutive carbon stereocentres. This work demonstrates the power of combining electrochemistry with photochemistry and asymmetric catalysis to generate complex structures in an economic and sustainable fashion. Asymmetric catalytic photoelectrochemical reactions for the construction of complex compounds are underdeveloped. Now, merging photoelectrochemistry with asymmetric catalysis has enabled the dehydrogenative [2 + 2] photocycloaddition between alkyl ketones and alkenes affording enantioenriched cyclobutanes.