21367-12-4

Upstream product

• 1785-02-0 triphenyl isocyanurate 
• 103-71-9 phenyl isocyanate 
• 5593-70-4 titanium (IV) butoxide 
• 100-52-7 benzaldehyde 
• 1538-74-5 N-phenyl-carbamic acid butyl ester 

Downstream Products

• 1785-02-0 triphenyl isocyanurate 
• 1538-74-5 N-phenyl-carbamic acid butyl ester 
• 103-71-9 phenyl isocyanate 

Relevant academic research and scientific papers

Computational tools for mechanistic discrimination in the reductive and metathesis coupling reactions mediated by titanium(IV) isopropoxide

A theoretical study has been carried out at the B3LYP/LANL2DZ level to compare the reactivity of phenyl isocyanate and phenyl isothiocyanate towards titanium(IV) alkoxides. Isocyanates are shown to favour both mono insertion and double insertion reactions. Double insertion in a head-to-tail fashion is shown to be more exothermic than double insertion in a head-to-head fashion. The head-to-head double insertion leads to the metathesis product, a carbodiimide, after the extrusion of carbon dioxide. In the case of phenyl isothiocyanate, calculations favour the formation of only mono insertion products. Formation of a double insertion product is highly unfavourable. Further, these studies indicate that the reverse reaction involving the metathesis of N,N ′-diphenyl carbodiimide with carbon dioxide is likely to proceed more efficiently than the metathesis reaction with carbon disulphide. This is in excellent agreement with experimental results as metathesis with carbon disulphide fails to occur. In a second study, multilayer MM/QM calculations are carried out on intermediates generated from reduction of titanium(IV) alkoxides to investigate the effect of alkoxy bridging on the reactivity of multinuclear Ti species. Bimolecular coupling of imines initiated by Ti(III) species leads to a mixture of diastereomers and not diastereoselective coupling of the imine. However if the reaction is carried out by a trimeric biradical species, diastereoselective coupling of the imine is predicted. The presence of alkoxy bridges greatly favours the formation of the d,l (±) isomer, whereas the intermediate without alkoxy bridges favours the more stable meso isomer. As a bridged trimeric species, stabilized by bridging alkoxy groups, correctly explains the diastereoselective reaction, it is the most likely intermediate in the reaction.

Metathesis of carbon dioxide and phenyl isocyanate catalysed by group(IV) metal alkoxides: An experimental and computational study

The insertion reactions of zirconium(IV) n-butoxide and titanium(IV) n-butoxide with a heterocumulene like carbodiimide, carbon dioxide or phenyl isocyanate are compared. Both give an intermediate which carries out metathesis at elevated temperatures by inserting a second heterocumulene in a head-to-head fashion. The intermediate metallacycle extrudes a new heterocumulene, different from the two that have inserted leading to metathesis. As the reaction is reversible, catalytic metathesis is feasible. In stoichiometric reactions heterocumulene insertion, metathesis and metathesis cum insertion products are observed. However, catalytic amounts of the metal alkoxide primarily led to metathesis products. It is shown that zirconium alkoxides promote catalytic metathesis (isocyanates, carbon dioxide) more efficiently than the corresponding titanium alkoxide. The difference in the metathetic activity of these alkoxides has been explained by a computational study using model complexes Ti(OMe) 4 (1bTi) and Zr(OMe)4 (1bZr). The computation was carried out at the B3LYP/LANL2DZ level of theory. Indian Academy of Sciences.

Room temperature metathesis of aryl isocyanates and aromatic aldehydes catalyzed by group(IV) metal alkoxides: An experimental and computational study

Aromatic aldehydes and aryl isocyanates do not react at room temperature. However, we have shown for the first time that in the presence of catalytic amounts of group(IV) n-butoxide, they undergo metathesis at room temperature to produce imines with the extrusion of carbon dioxide. The mechanism of action has been investigated by a study of stoichiometric reactions. The insertion of aryl isocyanates into the metal n-butoxide occurs very rapidly. Reaction of the insertion product with the aldehyde is responsible for the metathesis. Among the n-butoxides of group(IV) metals, Ti(OnBu)4 (8aTi) was found to be more efficient than Zr(OnBu)4 (8aZr) and Hf(OnBu)4 (8aHf) in carrying out metathesis. The surprisingly large difference in the metathetic activity of these alkoxides has been probed computationally using model complexes Ti(OMe)4 (8bTi), Zr(OMe)4 (8bZr) and Hf(OMe)4 (8bHf) at the B3LYP/LANL2DZ level of theory. These studies indicate that the insertion product formed by Zr and Hf are extremely stable compared to that formed by Ti. This makes subsequent reaction of Zr and Hf complexes unfavorable.

Kinetics and Catalysis of Consecutive Isocyanate Reactions. Formation of Carbamates, Allophanates and Isocyanurates

Organic isocyanates (I) react with alcohols and phenols (HX) in a sequence of reactions to give carbamates, allophanates and isocyanurates.Rate and equilibrium constants of the individual steps have been determined.The partitioning of the reaction products predominantly depends on the I:HX ratio and the nature of the catalyst applied.At equimolar I:HX ratios, the carbamate is the dominating product in the absence and in the presence of catalysts like tin carboxylates and common tertiary amines including 1,4-diazabicyclooctane (DABCO).In these cases, the rate constant of carbamate formation (k1) is larger than those of allophanate and isocyanurate formation (k2 and k3).With catalysts such as aminals, aminoalcohols, amidines and carboxylate, phenolate and alkoxide anions, however, the isocyanurate is mainly formed.With these catalysts the ratio of rate constants is k1 2 ca. k3.For base catalysts, the k1:k2:k3 ratios depend on the mechanism of catalysis.Tertiary amines react in the alcohol-isocyanate reaction by a concerted termolecular mechanism, whereas the anionic catalysts react by a stepwise mechanism via alcoholate anions.In the reactions of the isocyanate with phenols, carbamates and allophanates, all base catalysts react by the step-wise anionic mechanism, but the anionic ones are more efficient because their conjugate acids form hydrogen-bonded homoassociate complexes in higher extend.At high I:HX ratios, the isocyanurate is the only final product formed via the carbamate and allophanate as detectable intermediates.The kinetics of cyclotrimerisation is mainly governed by the k1:k2:k3 ratios and the magnitude of the equilibrium constants K1, K2 and K3.The kinetic order with respect to isocyanate may vary from 1 to 3.