Carbonyl isocyanates

Pyrolysis approaches can also be used to prepare substituted isocyanates which caimot be prepared using other methods. For example, A[,A[(A[ -trichlorocyanuric acid [87-90-1] thermally dissociates to yield chloroisocyanate [13858-09-8] and carbonyl diisocyanate [6498-10-8]. The carbonyl isocyanate is unstable and polymerizes (8,94). Table 3 Hsts specialty isocyanates. 

The reaction of diazoazoles and isocyanates leading to azolo-tetra-zinones of type 258 (Scheme 75) can be regarded as a [7 -l- 2]cycloaddition of the diazoazoles to the electron-deficient hetero double-bond of the isocyanates (pathway a) or, alternatively, as a two-step reaction involving [3 -I- 2]cycloaddition of the diazoazoles to the isocyanates, leading to the spirostructure 259 and subsequent [l,5]acyl shift (pathway b). An additional two-step mechanism (pathway c) could involve nucleophilic attack by the azole ring nitrogen on the carbonyl isocyanate to give a zwitterionic intermediate that collapses to the [7 + 2]cycloadduct 258. 

There is considerable discrepancy in the literature regarding the structures of the cycloadducts derived from carbonyl isocyanates and carbodiimides. For example, Arbuzov and Zobova " claim that a cycloadduct, mp 132-138 °C (dec.), derived from diphenylcar-bodiimide and phenylcarbonyl isocyanate at 0 °C has a diazetidinedione structure. Based on our findings an oxazetidine structure is indicated. 

The formation of tosyl chloride was shown to proceed through phosgenation of PTSI itself, thus affording chloro-carbonyl isocyanate which polymerizes. 

Dichloromethylenebenzamide could also be reacted with 2-aminoisoquinoline to give the angularly fused 2-phenyl-4-oxotriazino[2,l-a]isoquinoline derivative in poor yield <76CB118>. Ethoxy-carbonyl isocyanate with 2-(substituted amino)pyridines (131) gave 1-substituted betaines (133) via allophanates (132) (Scheme 9) <76CB366I>. 

Condensation of the 7V-imidazolyl ribofuranosylamine (18) with aryloxy-carbonyl isocyanates gave the corresponding ribofuranosyl-imidazo[l,2-a] 1,3,5-triazenes (19) (Scheme 3). Likewise 3-hypoxanthosine (20) had been obtained by reaction of 2,3-0-isopropylidene-D-ribofuranose with 5-amino-4-carbamoyl-... 

See, for example V. Jonas and G. Frenking, Chent. Phys. Lett., 177, 175 (1991). On the Crucial Importance of Polarization Functions for the Calculation of Molecules with Third-Row Elements The Conformation of Chloro Carbonyl Isocyanate C1C(0)NC0 and the Equilibrium of 1,2-Dithioglyoxal with its Cyclic Isomer 1,2-Dithiete. 

The synthesis and reactions of carbonyl isocyanate, isothiocyanate and di-isothiocyanate have been reported. 

Cheap and convenient syntheses of carbonyl di-isothiocyanate (304) and of carbonyl isocyanate isothiocyanate (305) have been reported. " Their reactions with water, H2S, HCl, and various nucleophiles lead to a variety of thiadiazine derivatives. 

In the reaction of l,l, 3,3 -tetraphenyl-2,2 diitnidazolinylidene 31 with carbonyl isocyanates the stable dipole 32 is obtained, which reacts with phenyl isocyanate to give tetraazaspiro-[4,4]nonanes 33" . 

In contrast, reaction of diazomethane with phenyl carbonyl isocyanate affords an oxa-zolone derivative formed via a [4+2] cycloaddition sequence . Diazomethane reacts with arenesulfonyl isocyanates to give 1,2,3-oxathiazole derivatives. The reaction of phenyl isocyanate with photochemically generated diphenylcarbene gives 2,2-diphenylindoxyl. ... 

Phenyl carbonyl isocyanates react with isonitriles to give 5-iminooxazolidinones 54 via a [4+2] cycloaddition... 

The [2+2] cycloaddition reaction of isocyanates proceeds better with olefins having electron donating groups attached to the double bond system. Examples include vinyl ethers, enamines, ketene acetals, tetraalkoxy- or tetraalkylaminooleflns. The more reactive sulfonyl and carbonyl isocyanates undergo cycloaddition reactions with vinyl ethers especially well. For example, the reaction of vinyl ethers with p-toluenesulfonyl isocyanate affords the [2+2] cycloadducts in a stereospecific reaction... 

Chlorosulfonyl isocyanate reacts similarly with dimethyl sulfoxide. Also, carbonyl isocyanates undergo an exchange reaction with dialkyl sulfoxides to give the corresponding sulfilimines . In contrast, dimethyl-oxo-sulfonium-methylid 170 reacts with isocyanates to give linear adducts 171 °. 

Also, aliphatic isocyanates react with chlorocarbonyl isocyanate to give the [4+2] cycloadducts. The reaction of carbonyl isocyanates with silylketenes affords unstable [4+2]... 

In contrast, aliphatic and aromatic carbonyl isocyanates react with 2-vinylpyridine to give 2-acyl-l-oxo-2,3-dihydro-l/f-pyrido[l,2c]pyrimidines 486... 

Cabon-carbon double- and triple-bond-containing substrates sometimes react with double bond-containing isocyanates to undergo the Diels-Alder reaction. For example, phenyl-carbonyl isocyanate reacts with ethoxyacetylene to give the [4+2] cycloadduct 491. ... 

Norbornadiene reacts similarly. Morpholinocyclohexene also reacts with phenylthio-carbonyl isocyanate to give [4+2] cycloadducts Likewise, dihydropyrane reacts with p-chlorophenylthiocarbonyl isocyanate to give the [4+2] cycloadduct. 

Several liganded metal complexes react with carbonyl isocyanates to give metallacycles, in which the carbonyl group adjacent to the isocyanate group participates in the bonding. For example, reaction of Pd(bipyridine)-(dibenzylindeneacetone) with phenylcarbonyl... 

Cycloadditions The [4+2] cycloaddition reactions of carbodiimides with phenyl-carbonyl isocyanate, phenylcarbonyl isothiocyanate and thiocarbamoyl isothiocyanate have been discussed above. In the dimerization reactions the functional carbodiimides react as both the diene and the dienophile. Unsaturated carbodiimides, generated in situ, can be trapped with N=N bond- or C=N bond-containing substrates. 

Trimethylsilylketene reacts similarly with carbonyl isocyanates to give [4+2] cycloadducts, which undergo a Diels-Alder reaction with acetylenes or enamines to give 2-pyridones. A theoretical study of the reaction of silylketenes with carbonyl isocyanates and subsequent Diels-Alder reaction with ynamines was conducted recently. ... 

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