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The reactive intermediate generated by the addition of tert-butyl and 1,1,3,3-tetramethyl butyl isocyanide to dialkyl acetylenedicarboxylate was trapped by 7-hydroxycoumarin to produce highly functionalized 4H-chromenes in fairly good yields. When the reaction is performed with cyclohexyl isocyanide, 1-azabuta-1,3-dienes were obtained.

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.

An effective route to novel coumarines and 4H-chromenes is described. This involves the reaction of tert-butyl isocyanide and dialkyl acetylenedicarboxylates in the presence of 2-hydroxybenzaldehydes.

Alkyl-(aryl) isocyanides react with benzoyl isothiocyanate in the presence of dialkyl acetylenedicarboxylates or dibenzoylacetylene in one-pot to afford highly substituted 4,7-bis[alkyl(aryl)imino]-2-phenyl-3-oxa-6-thia-1-azaspiro[4.4]nona-1,8-dienes, with double insertion of the isocyanide, in 38–45% yields (based on the isocyanide).

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.

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 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 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.