Highly Enantioselective Copper—Bisoxazoline‐Catalyzed Allylic Oxidation of Cyclic Olefins with tert‐Butyl p‐Nitroperbenzoate.

Abstract

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Catalytic Enantioselective Transformations Involving C–H Bond Cleavage by Transition-Metal Complexes

“…The copper-catalyzed oxidation of allylic C(sp 3 )−H bonds with peresters (the Kharasch−Sosnovsky reaction) was the first allylic C(sp 3 )−H functionalization reaction to be conducted in an asymmetric fashion. Although this methodology has been covered in detail elsewhere 16,20,21 and is thus beyond the scope of this review, for comparative purposes we feel it worthwhile to mentioned that good levels of enantiocontrol have only been achieved using an excess of symmetrical cyclic olefins, 291 and as such, much attention has been devoted to the development of alternative protocols. 292 Initial attempts to conduct an acetoxylation of olefins 472 with chiral sulfoxide ligands, under palladium catalysis, proved to be ineffective due to the rapid π−σ−π equilibrium between the π-allyl−Pd intermediates 475 and 476, thus scrambling any chiral information that may be imparted during C−H cleavage.…”

Cobalt-Catalyzed Diastereo- and Enantioselective Allyl Addition to Aldehydes and α-Ketoesters through Allylic C–H Functionalization

“…More recently, enantioselective allylic C-H functionalization via allyl radicals through metal-catalyzed or photocatalyzed C-H bond cleavage has been revealed ( Figure 1a). [30][31][32][33][34][35][36] However, enantioselective transformations of nucleophilic allyl-metal intermediates directly produced from oxidative allylic C-H bond cleavage promoted by a single catalyst remained undeveloped. Herein, we report an unprecedented protocol for catalytic generation of nucleophilic allyl-Co complexes followed by diastereo-and enantioselective addition to aldehydes and a-ketoesters to furnish a variety of homoallylic alcohols that are otherwise di cult to access.…”