Phenylcarbonyl isocyanate

The reaction of phenylcarbonyl isocyanate with carbodiimides at low temperatures affords oxazetidine imines 214 by addition across the OO bond of the isocyanate group. 

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. 

Tsuge and Sakai obtain [2+4] cycloadducts 216 when the reaction of arylcarbonyl isocyanates with carbodiimides is conducted in refluxing benzene. Fom phenylcarbonyl isocyanate andN-phenyl-N -2-methylphenylcarbodiimide mixtures of [2+4] cycloadducts... 

Cycloaddition Reactions. In [2+2] cycloaddition reactions with car-bodiimides sometimes [2+4] cycloadducts are produced as coproducts. Examples include the reaction of phenylcarbonyl isocyanate, phenylcarbonyl isothiocyanate and thiocarbamoyl isothiocyanate with carbodiimides to give [2+4] cycloadducts, discussed in Section 5.3.1. In the current section, mainly [2+4] cycloaddition of carbodiimides as dienophile with dienes derived from oxoketenes, generated in situ or masked oxoketenes, especially 2,3-diones investigated by Kollenz and his coworkers are discussed. 

However, heating of phenylcarbonyl isocyanate in the presence of a phospholene oxide catalyst gives 2,6-diphenyl-4-benzoylimino-l,3,5-oxadiazine20. ... 

Across carbon multiple bonds The reaction of acetylenes with phenylcarbonyl isocyanate affords the expected [2+2] cycloadduct 56 . However, the assigned structure is in doubt because MNDO results suggest that it is impossible to prepare the unsaturated )8-lactams by [2+2] cycloaddition of acetylenes with acyl isocyanates . In other acetylene reactions with isocyanates the [2+2] cycloadducts are only postulated as intermediates. 

Two equivalents of the isocyanate react with cyanotrimethylsilane at 50 °C to give a flve-membered ring [2+2+1] cycloadduct. Af,Af -disubstituted 5-trimethyl-silyliminoimidazolidinediones are obtained in the reaction of aryl- or arenesulfonyl isocyanates with trimethylsilyl cyanide. In the reaction with arenesulfonyl isocyanates the initially formed insertion products can also be isolated. The reaction of trimethylsilylamldes with phenylcarbonyl isocyanate also affords the insertion product. 

Epoxides react with isocyanates at elevated temperatures to give 2-oxazolidinones 347 . A similar reaction is observed with phenylcarbonyl isocyanate. The reaction is catalyzed by palladium (o)-triisopropyl phosphite catalysts, lithium salt-phosphine adducts, aluminum trichloride or calcium ethoxide. The reaction can formally be regarded as interception of the thermally generated 1,3-dipolar intermediates, and it was shown that the reaction does not occur, unless the catalyst initiates ring opening... 

On heating of the cycloadduct with phenyl isocyanate an exchange reaction across the C=N bond is observed with formation of isopropyl isocyanate. A similar reaction is observed when di-t-butyldiaziridinone 386 is treated with phenylcarbonyl isocyanate to... 

Thiirans react with phenylcarbonyl isocyanate to give both cyclic [3-1-2] adducts 393 and linear adducts 394". ... 

The cyclodimerization of isocyanates attached to an a-carbonyl, a-thiocarbonyl or a-imidoyl group proceeds via a [4+2] cycloaddition sequence. For example, treatment of phenylcarbonyl isocyanate with a catalytic amount of triehtylamine at 50 °C gives rise to the formation of the cyclodimer 469" . 

Dimethylketene reacts with phenylcarbonyl isocyanate to give a [4+2] cycloadduct . Phenylthiocarbonyl isocyanate adds across the C=0 bond of aromatic ketenes or the C=N bond of aromatic ketenimines to give [4+2] cycloadducts iV-Alkyltrichlorovinylketenimine reacts with trichlorocarbonyl isocyanate to give the [4+2] cycloadduct 507 resulting from addition across the ketenimine C=C bond. ... 

Phosphacumulenylidene derivatives, such as 510, react with phenylcarbonyl isocyanate... 

Cyclic aldo- and ketonitrones react similarly with phenyl isothiocyanateHowever, substituted phenyl isothiocyanates react with 5,5-dimethyl-l-pyrroline-l-oxide to give cycloadducts derived from addition across the C=N bond as well as the C=S bond of the isothiocyanates. The C=S cycloadducts are unstable and undergo further transformations . The [3+2] cycloaddition reaction of 3,3,5,5-tetramethylpyrroline-l-oxide with aryl- and phenylcarbonyl isocyanates also occurs exclusively by addition across the C=S bond . ... 

Some aziridines, such as 366, react with aryl isocyanates" or phenylcarbonyl iso-... 

Also, [3+2] cycloadducts are obtained in the reaction of alkyl azides with phenylcarbonyl or ethoxycarbonyl isocyanates . ... 

Acylketenes, generated in the thermolysis of 4-oxo-l,3-dioxine derivatives, react with phenylcarbonyl-, methoxycarbonyl-, or phenoxycarbonyl isocyanates by a [4+2] cycloaddition reaction to give 2,4-dioxo-l,3- oxazines. ... 

The C=N bond in 3-phenyl-2i/-azirines reacts with phenylcarbonyl or phenylthiocarbonyl isocyanate to give the [4+2] cycloadduct 516 . 

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. 

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