Nitroalkenes copper-catalyzed

In 1993, Alexakis et al. reported the first copper-catalyzed asymmetric conjugate addition of diethylzinc to 2-cyclohexenone using phosphorous ligand 28 (32% ee).36 An important breakthrough was achieved by Feringa et al. with chiral phosphoramidite (S,R,R)-29 (Figure 1), which showed excellent selectivity (over 98% ee) for the addition of 2-cyclohexenone.37 Since then, efficient protocols for the conversion of both cyclic and acyclic enones, as well as lactones and nitroalkenes, have been developed featuring excellent stereocontrol. 

Nitroalkenes have also been employed in the copper-catalyzed asymmetric... 

Ligand 4, which is highly effective for the 1,4-addition of diethylzinc to 2-cyclohexen-l-one, shows relatively wide scope with respect to the p-substituent in the copper-catalyzed asymmetric 1,4-addition of diethylzinc to acyclic nitroalkenes... 

Copper-Catalyzed Reaction with Nitroalkenes by Using External Chiral Ligands... 

CuOTf-catalyzed synthesis of polysubstituted pyrroles from a-diazoketones, nitroalkenes, and amines was reported by Lu, Wang, and coworkers. The corresponding polysubstituted pyrroles could be obtained in moderate yields using air as the oxidant. This cascade process of the polysubstituted pyrrole formation involves an NH insertion of carbene, a copper-catalyzed oxidative dehydrogenation of amine, and a [3+2] cycloaddition of azomethine ylide [21] (Scheme 8.9). 

In 2010, Wang s group reported a copper-catalyzed three-component reaction of a-diazoketones 122 with amines 123 and nitroalkenes 124 under aerobic conditions (Scheme 5.86) [87], The cascade reaction follows a sequence of an N—H insertion, a copper-catalyzed oxidative dehydrogenation of amine, a [3+2] cycloaddition, and finally, an elimination of HNOj/dehydrogenation, affording a variety of polysubsti-tuted pyrroles 125. 

The copper(I)-catalyzed addition of Grignard reagents to P-(alkylthio)-a,p-unsaturated esters is the preferred protocol for substitution of the alkylthio substituent, e.g. (310 - 311),21 while potassium enolates add to a-ketoketene dithioacetals, e.g. (312 — 313), without dialkylation (Scheme 96).218b,c Further, Hanessian reports an expedient synthesis of penam (315) via intramolecular cyclization of the (3-lactam nitroalkene (314), but loss of the methylthio moiety does not occur spontaneously (Scheme 97).219... 

Bernadi and Scolastico, and later Evans in a more effective manner, indicated that the enantioselective addition reaction using silyl enol ethers can be catalyzed by Lewis acidic copper(II) cation complexes derived from bisoxazolines [38-40]. In the presence of the copper complex (S,S)-14 (10 mol %), silyl enol ethers derived from thioesters add to alkylidenemalonates or 2-alkenoyloxazo-lidone in high ees (Scheme 12). Bernadi, Scolastico, and Seebach employed a titanium complex derived from TADDOL for the addition of silyl enol ethers to nitroalkenes or 2-cyclopentenone [41-43], although these are stoichiometric reactions. 

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