Enantioselective Intermolecular C–H Functionalization of Allylic and Benzylic sp³ C–H Bonds Using N-Sulfonyl-1,2,3-triazoles

Abstract

The enantioselective intermolecular sp3 C–H functionalization at allylic and benzylic positions was achieved using rhodium-catalyzed reactions with 4-phenyl-N-methanesulfonyl-1,2,3-triazole. The optimum dirhodium tetracarboxylate catalyst for these reactions was Rh2(S-NTTL)4. The rhodium-bound α-imino carbene intermediates preferentially reacted with tertiary over primary C–H bonds in good yields and moderate levels of enantioselectivity (66-82% ee). This work demonstrates that N-sulfonyltriazoles can be applied to the effective C–H functionalization at sp3 C–H bonds of substrates containing additional functionality.

Bimetallic Rhodium(II)/Indium(III) Relay Catalysis for Tandem Insertion/Asymmetric Claisen Rearrangement

“…Nevertheless, the catalytic enantioselective version of this tandem process remains elusive. This is in sharp contrast with chiral Rh II catalyst‐mediated highly enantioselective cyclopropanation,– C−H insertion,, and formal [3+2] cycloaddition, of 1,2,3‐triazoles. Mechanistically, as described by Miura, Murakami and co‐workers, O ‐insertion of allyl alcohol derivatives to Rh II ‐bound imino carbene intermediates I furnishes zwitterionic intermediate II .…”

Catalytic Asymmetric Intermolecular Allylic Functionalization of Unactivated Internal Alkenes

“…77–79 Around the same time as Müller’s initial report of an acceptor/acceptor-substituted carbenoid for moderately enantioselective allylic C–H alkylations, Davies began to explore this mode of C–H functionalization with donor/acceptor stabilized carbenoids. 80–85 These reports on the Rh 2 (DOSP) 4 -catalyzed decomposition of aryldiazoacetates have become one of the most selective methods for C(sp 3 )–H functionalization.…”

Selective Functionalization of Aromatic C(sp2)−H Bonds in the Presence of Benzylic C(sp3)−H Bonds by Electron‐Deficient Carbenoids Generated from 4‐Acyl‐1‐Sulfonyl‐1,2,3‐Triazoles

“…Davies et al. reported that the reaction of 4‐phenyltriazole with 5 e , using Rh 2 ( S ‐NTTL) 4 as the catalyst, (1.0 mol %) gave the C(sp 3 )−H insertion product (24 %, 72 % ee ) and a [3+2] cycloadduct (10 %, 92 % ee ; Scheme a) . In contrast, when the reaction conditions A were applied to 4 a , the N ‐sulfonylenaminones 11 ae and 12 ae were obtained in 69 and 19 % yields, respectively (Scheme b).…”