Phenyl isocyanate, reaction with

Figure 3.13 shows the reaction kinetics curves (conversion against time) of the phenyl isocyanate reaction with oligo-polyols having various percentages of primary hydroxyls. 

The cyclic carbamate (oxazoIidin-2-one) 313 is formed by the reaction of phenyl isocyanate (312) with vinyloxirane[I92]. Nitrogen serves as a nucleophile and attacks the carbon vicinal to the oxygen exclusively. The thermodynamically less stable Z-isomer 315 was obtained as a major product (10 I) by the reaction of 2-methoxy-l-naphthyI isocyanate (314) with a vinyloxir-... 

Phenyl isocyanate reacts with (82) to form (83) by ring enlargement (74JOC948). Reaction of oxaziridines with diphenylketene proceeds less obviously. Isolated products (84) and (85) contain only the R—N group of the starting material (69TL263). 

When the reaction is carried out at 120-140°, 2 moles of phenyl isocyanate react with one of the enamine (16) to give l,3-diphenyl-5,5-dimethyl-6-dimethylamino hydrouracil (159) (109). 

A 1,4-dipolar cycloaddition between tetrahydropyrido[l,2-a]pyrimidi-none 114 (R = Me) and 4-methyl-l, 2,4-triazoline-3,5-dione 666gave stable adduct 667 in acetonitrile or in acetic acid at room temperature for 1 hour (Scheme 44) (85CB4567). When ethyl cyanoformate was used as dienophile in boiling toluene for 20 hours, ethyl 3-methyl-4-oxo-6,7,8,9-tetrahydro-4//-pyrido[ 1,2-a]pyrimidine-2-carboxylate 669 was obtained (86CB1445). Pyrido[l,2-a]pyrimidine-2-carboxylate 669 was formed from the initial adduct 668 by elimination of phenyl isocyanate. Reaction of tetrahydropyr-ido[l,2-a]pyrimidinone 114 (R = Me) with l-(diethylamino)-l-propyne in... 

A special technique of trimerization has been described by Kogon 24, 25). Phenyl isocyanate reacts with ethyl alcohol to form a urethane (ethyl carbanilate). At 125° a substantial yield of ethyl a,7-diphenyl allophanate is observed as well as a small amount of phenyl isocyanate dimer. However, when A-methyhnorpholine (NMM) is added as a catalyst, the reaction is altered and the product is triphenylisocyanurate (isocyanate trimer) in high yield. The reaction sequence is believed to be ... 

In view of the fact that the methanol-phenyl isocyanate reaction is known to be an auto-catalytic reaction due to the weakly basic character of the phenylurethane formed, one would expect an upward drift of the second-order plot if the reaction were truly of the second order. This is apparently the case in n-butyl acetate and dioxane. The straight line plot in MEK and acetonitrile and the downward curvature found in toluene and nitrobenzene were taken to indicate an order greater than 2 with respect to the reactants. It appeared that the deviations from second-order kinetics toward higher order in the sequence toluene > nitrobenzene > acetonitrile > MEK > n-butyl acetate > dioxane increased with an increase in the hydrogen bonding capacity of the solvent. 

The reaction rate depends on the structure of the isocyanate and the reactant and also on the catalyst used. Primary hydroxyl groups have been shown to be more than three times faster in their reactions with phenyl isocyanate than with secondary hydroxyl groups. Additional rate studies with DBTDL, phenyl isocyanate, and a variety of primary and secondary alcohols are shown in Table 6.2.6. This confirmed the higher reaction rate with primary alcohols, but also showed that neighboring groups have an effect on the rate. 

Reaction of epoxides with isocyanates. Calcium ethoxide is the most efficient catalyst for the reaction of phenyl isocyanate (1) with the epoxide (2) to form the 2-oxazolidinone (3). ... 

The bis-ylide (4) underwent C-acylation with phenyl isocyanate, but with benzoyl chloride afforded the 0-acylation product as reported for other sulphonium ylides, In the latter reaction, the initially formed sulphonium salt apparently was cleaved by the chloride ion to afford the... 

The reaction was also carried out with functionally substituted phenyl isocyanates and with p-phenylene diisocyanate. The reaction of diethyltin dihydride with phenyl isocyanate affords a compound with two phenyl-formamido groups attached to one tin atom. 

Reductive carbonylation of nitro compounds is catalyzed by various Pd catalysts. Phenyl isocyanate (93) is produced by the PdCl2-catalyzed reductive carbonylation (deoxygenation) of nitrobenzene with CO, probably via nitrene formation. Extensive studies have been carried out to develop the phosgene-free commercial process for phenyl isocyanate production from nitroben-zene[76]. Effects of various additives such as phenanthroline have been stu-died[77-79]. The co-catalysts of montmorillonite-bipyridylpalladium acetate and Ru3(CO) 2 are used for the reductive carbonylation oLnitroarenes[80,81]. Extensive studies on the reaction in alcohol to form the A -phenylurethane 94 have also been carried out[82-87]. Reaction of nitrobenzene with CO in the presence of aniline affords diphenylurea (95)[88]. 

Amides result from the reaction of aromatic hydrocarbons with isocyanates, such as phenyl isocyanate [103-71-9], ia the presence of aluminum chloride. Phenyl isothiocyanate [103-72-0] similarly gives thioanilides (136). 

The hydroxyl number can be deterrnined in a number of ways such as acetylation, phthalation, reaction with phenyl isocyanate, and ir and nmr methods. An imidazole-catalyzed phthalation has been used to measure the hydroxyl number for a number of commercial polyether polyols and compared (favorably) to ASTM D2849 (uncatalyzed phthalation) (99). The uncatalyzed method requires two hours at 98°C compared to 15 minutes at the same temperature. 

Cyanuric acid readily dissolves in aqueous formaldehyde forming tris(hydroxymethyl)isocyanurate [10471-40-6] (THMIC) which can be isolated by evaporation (11). THMIC in turn reacts with acetic anhydride to yield tris(acetoxymethyl)isocyanurate [54635-07-3], either thionyl chloride or phosphoms pentachloride to give tris(chloromethyl)isocyanurate [63579-00-0], and phenyl isocyanate in pyridine to yield tris(A/-phenylcarbamoxymethyl) isocyanurate [21253-39-4] in 87% yield (65). Reaction of CA with paraformaldehyde and 2,6-dicyclohexylphenol yields... 

Substituted imidazoles can be acylated at the 2-position by acid chlorides in the presence of triethylamine. This reaction proceeds by proton loss on the (V-acylated intermediate (241). An analogous reaction with phenyl isocyanate gives (242), probably via a similar mechanism. Benzimidazoles react similarly, but pyrazoles do not (80AHC(27)24l) cf. Section 4.02.1.4.6). 

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