O. A. Linchenko

C→N migrations of the ethoxycarbonyl group in reactions of ortho-substituted aryl isocyanates with the 1,3-zwitterion derived from triisopropylphosphine and ethyl 2-cyanoacrylate

The reactions of meta—para-substituted aryl isocyanates with phosphorus-containing 1,3-zwitterions, which proceed with the C→N migration of the CO2Et group to form the corresponding carbamates, were extended to ortho-substituted aryl isocyanates. The influence of the steric and electronic effects of the ortho substituents in the aromatic rings of aryl isocyanates on the ease of this rearrangement is qualitatively considered.

C-N migration of allyl- and propargyloxycarbonyl groups

Reactions of triisopropylphosphine with allyl-and propargyl-2-cyanoacrylates give corresponding 1,3-zwitterions. Under the action of phenyl-or 1-naphthylisocyanates the zwitterions exert C-N migration of allyl-or propargyloxycarbonyl groups affording carbamates. Atropisomerism at room temperature was established for the carbamate formed from 1-naphthylisocyanate.

Formation of substituted pyrazolines in the reaction of C, N-diphenylnitrilimine with a zwitterion derived from triisopropylphosphine and ethyl 2-cyanoacrylate

The reaction of C,N-diphenylnitrilimine with a P-zwitterion derived from Pri3P and H2C=C(CN)CO2Et afforded the first representative of 2-pyrazolines containing the phosphonium group and products of the addition of nitrilimine to Pri3P and H2C=C(CN)CO2Et. The reaction of the P-zwitterion with C-4-nitrophenyl-N-phenylnitrilimine gave rise to a condensation product of one Pri3P molecule and two nitrilimine molecules. The three-dimensional structures of the compounds synthesized were established by X-ray diffraction analysis.

On the mechanism of C ⇄ N migration of alkoxycarbonyl groups in reactions of pyridinium ylides with isocyanates

New examples of reversible C ⇄ N migrations of alkoxycarbonyl groups, which occur in the reactions of pyridinium and 3-(diethylcarbamoyl)pyridinium ylides, viz., derivatives of dimethyl and diethyl malonates, with aryl isocyanates were studied. The mechanism of migration of the methoxycarbonyl group from the carbon atom to the nitrogen atom was considered on the basis of quantum-chemical calculations. The product of the primary attack of the isocyanate group by pyridinium ylide was established to be rearranged with low potential barriers to form carbamate without formation of cyclic intermediate compounds.

Novel reactions of arylmalonate carbanions. The reaction with phenyl isocyanate resulting in carbamates by 1,3-C→N migration of the ethoxycarbonyl group

The reactions of carbanions of diethyl phenyl and 4-nitrophenylmalonates with phenyl isocyanate occur with 1,3-C→N migration of the ethoxycarbonyl group to form the corresponding adducts. The introduction of NO2 groups into the benzene ring of arylmalonates inhibits the reaction.

Reactions of isocyanates with compounds containing active methylene groups in the presence of triethylamine

Compounds containing active methylene groups react with isocyanates of different structures in the presence of triethylamine to form functionally substituted amides.

Cyclizations in the reactions of isocyanates with compounds containing active methylene groups in the presence of triethylamine

Novel reactions of isocyanates with compounds containing active methylene groups in the presence of triethylamine are described. The reactions afford derivatives of pyrrolidine-2,3,5-trione and barbituric acid.