Cycloaddition reactions of enoldiazo compounds

Abstract

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.

Traditional and New methods for the Preparation of Diazocarbonyl Compounds

“…Another example of the versatility of enol diazoacetates can also be seen in cycloaddition reactions (Cheng et al 2017). These compounds can react in different cycloaddition pathways to construct several carbocycles and heterocycles (Jadhav et al 2012, Xu et al 2013, Cheng et al 2015, Deng et al 2016.…”

Catalytic asymmetric cycloaddition reactions of enoldiazo compounds

“…Recently the transition metal catalyzed vinylcarbene approach to cycloaddition has shown considerable promise for highly chemo-, regio-, and enantio-selective cycloaddition reactions. Examples of [3+4]-, 9 [3+3]-, [10][11][12][13][14] [3+2]-, [14][15][16][17][18][19][20] and even a [3+1]- 21 and [3+5]- 22 cycloaddition reactions have been reported using dipolar metallo-vinylcarbenes, generally in high yields with low catalyst loadings. The transformations of silyl-protected enoldiazo compounds (Scheme 2) involve initial nucleophilic attachment to the electrophilic vinylogous position of the metallo-vinylcarbene followed by electrophilic addition to the original carbenic center with displacement of the catalyst.…”

“…High stereocontrol has been achieved with silyl-protected enoldiazo-acetates, -acetamides, -ketones, and -sulfones in most of these cycloaddition reactions, and also with styryldiazoacetates in [3+2]cycloaddition reactions. Our earlier review of cycloaddition reactions involving silylprotected enoldiazo compounds 12 reported the breadth of these transformations mainly with diazoacetates and with dirhodium catalysts. This report documents the extensive growth in these reactions since 2016, their mechanistic implications for future expansion, and the applicability of chiral copper catalysts to compliment and improve previously documented performance with chiral dirhodium catalysts.…”

Triarylborane‐Catalyzed Alkenylation Reactions of Aryl Esters with Diazo Compounds

“…Diazo compounds have found a multitude of applications in synthetic chemistry and are versatile intermediates that can rapidly functionalize organic compounds in a single step. [1,2] In particular, diazo compounds and N-tosylhydrazones (diazo precursors) have attracted much attention as carbonyl equivalents in the construction of carbon-carbon double bonds. [3] Transition metal catalysts, such as palladium, are typically used in reactions with diazo compounds to synthesize C = C bonds.…”