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The addition of isocyanides to esters (III) generates a reactive intermediate which is trapped by 6-quinolinol.

A simple one-pot synthesis of functionalized 4-hydroxyquinoline derivatives is presented which as the advantage of neutral conditions.

The three-component one-pot reaction of pyridin-2(1H)-one or isoquinolin-1(2H)-one (I), isocyanides (II), and activated acetylenes (III) yields 1-azabuta-1,3-dienes of type (IV).

2,6-Dimethylphenyl isocyanide reacts with benzoyl isothiocyanate in a clean one-pot reaction to afford a sterically congested ten-membered ring containing the S–S–S moiety in nearly quantitative yield. Dynamic effects are observed in the 1H nuclear magnetic resonance (NMR) spectrum of this compound for the restricted rotation around two of the Ar–N single bonds.

An effective route to novel 2,6‐dioxohexahydropyrimidines is described. This involves reaction of alkyl isocyanides and dialkyl acetylenedicarboxylates in the presence of N,N′‐dimethylurea in 1M aq. glucose.

Benzoyl isothiocyanate reacts with dialkyl acetylenedicarboxylates in the presence of triphenylphosphine in a mechanistically novel reaction to afford highly substituted dialkyl 2-(benzoylimino)-5-phenyl-4H-[1,3]dithiolo[4,5-b]pyrrole-4,6-dicarboxylates with double insertion of the isothiocyanate. The reaction proceeds via a carbon to nitrogen migration of an alkoxycarbonyl group.

Alkyl isocyanides react with 2-hydroxybenzaldehyde or 2-hydroxy-5-nitrobenzaldehyde to afford N -alkyl-2-aryl-2-oxoacetamides and N 2 , N 4 -dialkyl-2-aryl-4 H -1,3-benzodioxine-2,4-dicarboxamides in nearly 1:1 ratios. Treatment of 2,6-dimethylphenyl isocyanide with 2-hydroxy-5-nitrobenzaldehyde affords only the 2-oxoacetamide derivative.

The regioselective reaction of N1-benzyl-N2-(4-nitrophenyl)ethanediamide with dialkyl acetylenedicarboxylates or alkyl propiolates in the presence of triphenylphosphine leads to dialkyl 4-benzylamino-1-(4-nitrophenyl)-5-oxo-2,5-dihydro-1H-pyrrole-2,3-dicarboxylates or alkyl 4-benzylamino-1-(4-nitrophenyl)-2-oxo-5-pyrrolidinecarboxylates in good yields.

The 1:1 adduct produced in the reaction between tert-butyl isocyanide and dialkyl acetylenedicarboxylates was trapped by alkyl 2-fluoro-anilino-2-oxo-acetates or ethyl 2-oxo-2-(trifluoromethylanilino)-acetate to produce functionalised ketenimines in good yields. Dynamic NMR effects were observed in the 1H NMR spectra of these compounds as a result of restricted rotation around the single bond linking the aryl group to the ketenimine system. The free energy of activation (ΔG≠) for this process is 64.9–66.5 kJ mol−1.

Alkyl cinnamates are formed in fairly good yields from the reaction of dialkyl acetylenedicarboxylates and 3-hydroxy-4-methoxybenzaldehyde in the presence of triphenylphosphine.

Addition of 1-naphthol, 2-naphthol or 3-hydroxybenzaldehyde to tert-butyl propiolate in the presence of triphenylphosphine leads to tert-butyl 2-arylacrylates and tert-butyl 3-aryloxypropenoates in nearly 1:1 ratio. When phenol, 3-hydroxy-4-methoxybenzaldehyde, 8-hydroxyquinoline or 7-hydroxycoumarin was employed as OH-acid, only alkyl 3-aryloxypropenoates were obtained.

The regioselective reactions of N 1 -alkyl- N 2 -(4-nitrophenyl)ethanediamide with dialkyl acetylenedicarboxylates in the presence of tert -butyl isocyanide lead to dialkyl 2-{[2-(alkylamino)-2-oxoacetyl]-4-nitroanilino}-3-[( tert -butylimino)methylene]succinates in good yields.

The reaction of dibenzoylacetylene and enaminocarbonyl compounds leads to 3-alkylidene-2,3-dihydro-1H-pyrrol-2-ol derivatives in nearly quantitative yields. The reaction of this heterocyclic system with alcohols in the presence of a catalytic amount of HCl produces highly functionalized pyrroles in good yields.

The reactions of dibenzoylacetylene with cyclic enaminocarbonyls in the THF–H 2 O system lead to 3-alkylidene-1,2,3,5,6,7-hexahydro-4 H -indol-4-one derivatives in high yields.

Alkyl 2-(2-fluoro-anilino)-2-oxo-acetates or ethyl 2-oxo-2-(trifluoromethylanilino)-acetate undergo a multistep reaction with dialkyl acetylenedicarboxylates in the presence of triphenylphosphine to produce dialkyl 1-(2-fluorophenyl)-4-alkoxy-5-oxo-2,5-dihydro1H-pyrrole-2,3-dicarboxylates or dialkyl 4-ethoxy-5-oxo-1-[2-(trifluoromethyl)-phenyl]-2,5-dihydro-1H-pyrrole-2,3-dicarboxylates in good yields. Dynamic NMR study of dimethyl 4-ethoxy-5-oxo-1-[2-(trifluoromethyl)-phenyl]-2,5-dihydro-1H-pyrrole-2,3-dicarboxylate shows a fairly high energy barrier (ΔG ≠ = 60.9 kJ mol - 1 ) for rotation around the N-aryl single bond, which leads to an observable atropisomerism.

The 1:1 reactive intermediates produced in the reaction between alkyl isocyanides and dialkyl acetylenedicarboxylates were trapped with N-aryl-2,2,2-trichloroacetamides. When the aryl group was 1-naphthyl, two products were obtained in nearly 2:1 ratio.

Alkyl isocyanides react with dialkyl acetylendicarboxylates in the presence of CH-acids such as cyclopentane-1,3-dione, cyclohexane-1,3-dione, or 5,5-dimethylcyclohexane-1,3-dione to afford highly functionalized 4H-pyrans in fairly high yields. In the case of reaction between dimethyl acetylenedicarboxylate and 5,5-dimethylcyclohexane-1,3-dione in the presence of cyclohexyl isocyanide or benzyl isocyanide tetrahydro-cyclopenta[b]pyran derivatives were isolated in addition to the 4H-pyran system. The free energy barrier (96.9 kJ mol−1) for restricted rotation around the polarized double bond of the enaminone moiety in dimethyl 2-[cyclohexylamino-(4,4-dimethyl-2,6-dioxocyclohexylidene)methyl]but-2-enedioate was determined by dynamic NMR spectroscopy.

The reactive intermediate generated by the addition of alkyl isocyanides to dimethyl acetylenedicarboxylate was trapped by phenols such as resorcinol, catechol, hydroquinone, pyrogallol, 2,4-dihydroxybenzaldehyde, or 8-hydroxyquinoline to produce highly functionalized 4H-chromenes in fairly good yields.