P-Tolyl cyanate

It was shown earlier that (diphenylamine-p-tolylive-cyanate) urea (DTCU) may be used as antioxidant of thermo- and photooxidative destruction of AC. It was interesting to use DTCU for increasing antioxidative stability of PCA. With this purpose small amount of DTCU were introduced into e - caprolactam directly before its polycondensation, which was carried out according to well known methods [132]. Content of DTCU additives in polycondensation mixture was 0,5 - 3% from caprolactam mass. 

MeNHj CO, Me NCONMe Cyanic acid esters, PhOCN, p-Tolyl cyanate, 2,4-Di-methylphenyl -Isocyanates Phenyl isocyanate 2-Ethoxy-N-ethoxy-carbonyl-1,2-dihydro-quinoline Carbodiimides Diisopropyl-carbo-diimide, Dicyclohexyl-, Di-p-tolyl-Polyhexamethylene-carbodiimide N-Methyl-N,N -dicyclo-hexylcarbodiimidium iodide... 

Cyanation of iodoarenes with NaCN was catalyzed by [PdCl2(TPPMS)2] in the presence ofNaBH4 and ZnC in water/heptane, toluene or anisole biphasic systems (Scheme 9.11) [37]. Lipophilic catalysts prepared with P(p-tolyl)3 or PPhs showed negligible activities for the biphasic cyanation, due to the lack of CN in the organic phase. The reaction provided good to excellent yields of the respective benzonitriles with several substituted iodoarenes. 

An important class of compounds that can be prepared by this route is the 2-arylpropionitriles, precursors for the widely used anti-inflammatory 2-arylpro-panoic acids [3]. Of these, only naproxen [( SJ-2-(6-methoxynaphthyl)propanoic acid] is sold as an optically pure drug. Nugent and McKinney first reported efficient syntheses of racemic ibuprofen and naproxen via the Ni[P(0-p-tolyl)3]4-catalyzed hydro cyanation of the corresponding vinylarene precursors (Scheme 2)... 

Aq. K-cyanate treated with cyclohexylcarboxaldehyde and p-tolyl isonitrile in methanol, then n-dodecylamine hydrochloride added with stirring and icecooling, and the product isolated after 2 hrs. l-n-dodecyl-5-cyclohexyl-hydantoin 4-p-tolylimide. Y 1S%. F. e., also from azomethines, s. I. Ugi and K.Offermann, B. 97, 2276 (1964). 

Dinitrogen cleavage can also be achieved by addition of KH to [(ONO)V (thf)] (where ONO = 2,6-(3- Bu-5-Me-2-OC6H2CH2)2-4- Bu-(p-tolyl) NC6H4 ) (54) under an atmosphere of N2 to give the V(IV) nitrido dimer (55) that can be oxidized to the V(V) nitrido species (56) (Scheme 21). Compound 56 reacts readily with CO and isonitriles to form the cyanate (57) and carbodiimide (58) complexes, respectively. The cyanate species 57 releases KNCO on alkyne addition to form 59, which converts to 54, when dissolved in THF and thereby closing the cycle. 

The electronic properties of the ligand also affect this equilibrium constant. For example, the for dissociation of ttie phosphite P(0-o-tolyl)3 from the corresponding Ni[P(0R)3l complex is smaller ttian the Rp for dissociation of PPhj, despite the similar cone angles of the two ligands. This difference in equilibrium constants was ascribed to the ability of the phosphite ligand to stabilize ttie low oxidation state of Ni(0) by acting as a iT-acceptor. P(Oo-tolyl)3 is the ligand that was initially used in the commercial hydro-cyanation process. 

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