The all‐cis stereoisomers of tetrasubstituted azetidine‐2‐carboxylic acids and derivatives that possess three chiral centers have been prepared in high yield and stereocontrol from silyl‐protected Z‐γ‐substituted enoldiazoacetates and imido‐sulfur ylides by asymmetric [3+1]‐cycloaddition using chiral sabox copper(I) catalysis followed by Pd/C catalytic hydrogenation. Hydrogenation of the chiral p‐methoxybenzyl azetine‐2‐carboxylates occurs with both hydrogen addition to the C=C bond and hydrogenolysis of the ester.

The all-cis stereoisomers of tetrasubstituted azetidine-2-carboxylic acids and derivatives that possess three chiral centers have been prepared in high yield and stereocontrol from silyl-protected Z-g-substituted enoldiazoacetates and imido-sulfur ylides by asymmetric [3+ +1]-cycloaddition using chiral sabox copper(I) catalysis followed by Pd/C catalytic hydrogenation. Hydrogenation of the chiral p-methoxybenzyl azetine-2-carboxylates occurs with both hydrogen addition to the C = Cbond and hydrogenolysis of the ester.

1,2,3-Trisubstituted donor-acceptor cyclopropenes (DACPs) generatedi ns itu from enoldiazo compounds react with nucleophilest of orm a-substituted succinic acid derivatives in high yields. Initial dirhodium(II)c arboxylate catalysis rapidly converts enoldiazo-acetates or-acetamides to DACPs that undergo catalyst-free Favorskii ring openingw ith amines, and also with anilines,a lcohols, and thiols, when facilitated by catalytic amounts of 4-dimethylaminopyridine (DMAP). This methodology providese asy access to mixed esters and amides of monosubstituted succinic acids, including derivatives of naturallyo ccurring compounds.I ta lso affords dihydrazide, dihydroxamic acid, and diamide derivatives, as well as a-substituted tetrahydropyridazine-3,6diones in high yields. Attempts to generate optically enriched DACPs were not successful because their populations having the R and S configurations formedw ithachiral dirhodiumcatalystare quite similar, and the loss of enantiocontrol likely originates from the DACP ring forming step which is reversible with its intermediate metal carbene. Scheme1.Nucleophilic retro-Claisen and Favorskii-type ring opening of strained ring systems.