A survey of enoldiazo nucleophilicity in selective C-C bond forming reactions for the synthesis of natural product-like frameworks

Acid-catalyzed oxidative cross-coupling of acridans with silyl diazoenolates and a Rh-catalyzed rearrangement: two-step synthesis of γ-(9-acridanylidene)-β-keto esters

A MsOH-catalyzed oxidative cross-coupling of acridans and silyl diazoenolates and a Rh2(OAc)4-catalyzed rearrangement of the resultant diazo products are described. The reactions provide various γ-(9-acridanylidene)-β-keto esters in good yields, which bear an active α-methylene unit for further functionalization.

Catalytic Divergent [3+3]- and [3+2]-Cycloaddition by Discrimination Between Diazo Compounds

Highly selective divergent cycloaddition reactions of enoldiazo compounds and α-diazocarboximides catalyzed by copper(I) or dirhodium(II) have been developed. With tetrakis(acetonitrile)copper(I) tetrafluoroborate as the catalyst epoxypyrrolo[1,2-a]azepine derivatives were prepared in good yields and excellent diastereoselectivities through the first reported [3+3]-cycloaddition of a carbonyl ylide. Use of Rh2 (pfb)4 or Rh2 (esp)2 directs the reactants to regioselective [3+2]-cycloaddition generating cyclopenta[2,3]pyrrolo[2,1-b]oxazoles with good yields and excellent diastereoselectivities.

Cycloaddition reactions of enoldiazo compounds

Enoldiazo esters and amides have proven to be versatile reagents for cycloaddition reactions that allow highly efficient construction of various carbocycles and heterocycles. Their versatility is exemplified by (1) [2+n]-cycloadditions (n = 3, 4) by the enol silyl ether units of enoldiazo compounds with retention of the diazo functionality to furnish α-cyclic-α-diazo compounds that are themselves subject to further transformations of the diazo functional group; (2) [3+n]-cycloadditions (n = 1-5) by metallo-enolcarbenes formed by catalytic dinitrogen extrusion from enoldiazo compounds; (3) [2+n]-cycloadditions (n = 3, 4) by donor-acceptor cyclopropenes generated in situ from enoldiazo compounds that produce cyclopropane-fused ring systems. The role of dirhodium(ii) and the emergence of copper(i) catalysts are described, as are the different outcomes of reactions initiated with these catalysts. This comprehensive review on cycloaddition reactions of enoldiazo compounds, with emphasis on methodology development, mechanistic insight, and catalyst-controlled chemodivergence, aims to provide inspiration for future discoveries in the field and to catalyze the application of enoldiazo reagents by the wider synthetic community.

Functionalizing the γ-Position of α-Diazo-β-ketoesters

Although α-diazo-β-ketoesters are synthetically versatile intermediates, methodology for introducing this functionality into complex molecules is still limited, most frequently involving a carboxylic acid precursor, which is then activated and transformed into a β-ketoester, with the diazo group being subsequently added with a diazo transfer reagent. While introducing this highly functional moiety in a convergent one step process would be ideal, such an objective is limited by the relatively few studies which address functionalization of the α-diazo-β-ketoester at the γ-position. In the present investigation, we evaluate strategies, both new and established, for functionalizing α-diazo-β-ketoesters, particularly with regard to generating compounds prospectively useful in the synthesis of C1-substituted carbapenems. We report the first δ-aldehydo-α-diazo-β-ketoester as well as a method for its oxidation to the corresponding methyl ester, and the formation of a new substituted pyrazole under basic conditions.

An efficient route to highly enantioenriched tetrahydroazulenes and β-tetralones by desymmetrization reactions of δ,δ-diaryldiazoaceto-acetates

A highly stereoselective desymmetrization reaction of δ,δ-diaryl-α-diazo-β-ketoesters catalyzed by chiral dirhodium carboxylates forms aromatic cycloaddition products in up to 97% ee.

Synthesis of chiral cyclobutanes via rhodium/diene-catalyzed asymmetric 1,4-addition: a dramatic ligand effect on the diastereoselectivity

A highly diastereo- and enantioselective rhodium-catalyzed arylation of cyclobutene-1-carboxylate esters for the efficient synthesis of chiral cyclobutanes has been developed.