Recent advances in transition-metal-catalyzed carbene insertion to C–H bonds

Abstract

This review summarizes the recent advance in transition-metal-catalyzed carbene insertion to C–H bonds, forming diverse C–C bonds.

Catalyst-dependent chemoselective insertion of diazoalkanes into the N–H/C–H/O–H/C–O bonds of 2-hydroxybenzothiazoles

“…The corresponding Rh 2 (OAc) 4 -catalyzed species is known to react with diazoalkanes proceeding via a Rh-carbenoid intermediate. 3 The direct reaction of diazomethane with 2-hydroxybenzothiazole affords the major product of O -alkylation. According to the mechanism of a Darzens-type epoxidation 19 and Roskamp reaction 20 of diazoesters with carbonyls, we speculated that the reaction with the less abundant benzo[ d ]thiazol-2(3 H )-one tautomer generates an epoxide intermediate with ring-opening to give the insertion of diazomethane into the C–O bond (Scheme 5).…”

“…2 The ability of transition metals to activate diazoalkanes via metal-carbenoids is well established. 3 For example, Bi's group developed and showed that AgOTf and Sc(OTf) 3 adjust the chemoselective insertion of diazo compounds into the C–C or C–H bonds of 1,3-dicarbonyl compounds. 4 In 2018, Sun and co-workers reported the Rh-catalyzed regioselective N 2 -alkylation of benzotriazoles with diazoalkanes/enynones.…”

Photocatalytic Deoxygenative Alkylation of C(sp3)−H Bonds Using Sulfonylhydrazones

“…However, lowering the catalyst loading of 4-Cl2-BP from 20 to 10 mol% resulted in lower yields (Table 1A, Entry 7). Also the electronic properties of the aryl sulfonyl group of the hydrazone were investigated: while the commonly used tosyl (Ar2) and mesityl (Ar4) variants resulted in lower yields (Table 1A, Entries 8 and 10), 58 the presence of a more electron-withdrawing ring completely shuts down the reaction (Table 1A, Entry 9). Of particular note is the practical one-pot protocol in which the hydrazone is generated in situ from 4-(trifluoromethyl)benzaldehyde (70% yield, Table 1A, Entry 11).…”

Visible-Light-Mediated Formal Carbene Insertion Reaction: Enantioselective Synthesis of 1,4-Dicarbonyl Compounds Containing All-Carbon Quaternary Stereocenter

“…The carbene species can participate in a variety of chemical transformations, such as cyclopropanation reactions, Wolff rearrangement reactions, or X–H (X = O, S, C, N, Si, B, etc.) bond insertion reactions . Generally, transition metal catalysts are required for these reactions; however, transition metal catalysts are difficult to recover and expensive, which is not conducive to practical applications.…”