The presented work is devoted to isocyanate synthesis by the thermal decomposition of carbamates model. The work describes the existing isocyanate-obtaining processes and the main problems in the study of isocyanate synthesis by the thermal decomposition of carbamates, which can be solved using mathematical and computer models. Experiments with carbamates of various structures were carried out. After processing the experimental data, the activation energy and the pre-exponential factor for isocyanate synthesis by the thermal decomposition of carbamates were determined. Then, a mathematical model of the reactor for the thermal decomposition of carbamates using the COMSOL Multiphysics software was developed. For this model, computational experiments under different conditions were carried out. It was shown that the calculation results correspond to the experimental ones, so the suggested model can be used in the design of the equipment for isocyanate synthesis by the thermal decomposition of carbamates.

Venous thromboembolism including deep vein thrombosis and pulmonary embolism is an abundant and dangerous disease with significant relapse probability and mortality. In pursuit of an effective treatment, Bayer created Rivaroxaban, nowadays known under the brand name Xarelto, that was approved by the FDA in 2011. By 2022, the number of main indications for the drug has been increased 10-fold as well as the drug's prevalence in the field of thrombosis treatment. It is therefore apparent that with growing prescriptions new synthetic pathways are highly desirable, especially those utilizing inexpensive and safe reagents in environmentally benign protocols. The present work reviews the literature concerning Rivaroxaban preparation with an emphasis on the applicability of synthetic pathways on a large scale. Within the synthetic sequences, common intermediates are discussed in detail and relevant comparisons are made. Our main purpose is to provide an overview of the subject in its current state, paying attention to advances made and suggesting possible directions for further development.

The kinetic patterns of the reaction between dimethyl carbonate and anilines in the presence of a potassium methylate as a catalyst were studied. The mechanism of aminolysis was clarified, which includes the detachment of the proton from the amino group of aniline and the subsequent attack of the resulting anion on the carbonyl group of dimethyl carbonate. It is shown that when the reaction occurs in the dimethyl carbonate‐methanol 3:1 system, the process can be described as an irreversible first‐order reaction in the aniline though the target reaction is complicated by side interaction between potassium methylate and dimethyl carbonate. The rate constants of the target reaction with substituted anilines and of the side reaction in the temperature range of 70‐90°C were determined. It is shown that the influence of the substituent on the reaction rate is described by the Hammett equation, with the constant of the reaction series being positive and the best correlation being achieved for σ‐scale. The results obtained are consistent with the proposed mechanism of the reaction and are explained by the facilitation of the aniline deprotonation with increasing acceptor properties of the substituent. Effective activation energies for the reaction of various anilines with dimethyl carbonate are found.

Butyl isocyanate is widely distributed as a precursor for the production of a number of biologically active substances: fungicides, preservatives, insecticides, personal care products, etc. Nowadays, there are a number of methods for the preparation of isocyanates, which can be divided into liquid phase and gas phase. One of the perspective methods for the production of isocyanates is the thermolysis of carbamate and/or the actions of various reaction activating agents, accompanied by the elimination of alcohol, but this process is reversible, which greatly complicates its use in industry. The paper presents the results of studies of non-catalytic thermal decomposition of N-alkylcarbamates with the formation of alkylisocyanates on the example of butylisocyanate in the gas phase, flow reactor in a wide temperature range (200 to 450 °C). In addition, a series of experiments was carried out using a catalyst, dibutyltin dilaurate, in order to reduce the thermolysis temperature and increase the yield of the final product. To implement the isocyanate production process, an experimental laboratory setup, consisting of a gas flow meter (argon) regulator, a packed column (for heating) and a sorption solution tank, was developed and tested. The thermolysis of N-n-butylcarbamate was carried out in two variations: the preparation of an individual n-butylisocyanate and the passage of reaction products through a sorption solution linking the n-butyl isocyanate to N-n-butyl-N '-(1-phenylethyl)urea, which allows to estimate the yield of the target n-butylisocyanate without additional losses. The analysis of the obtained substances was carried out by high performance liquid chromatography with a UV detector (target product) and a mass detector (analysis of by-products). According to the results of research, a modification of the laboratory facility was proposed, as well as n-butylisocyanate was obtained with a yield of 49% on the basis of a new technique.

A carbamates (urethanes) are an organic compounds with the general formula R'R''NCOOR are esters of carbamic acid and its derivatives. Due to their biological activity, carbamates are common as pesticides, insecticides, herbicides, and are used as drugs. Polyurethanes are widely used in industry. The main method of synthesis is the interaction of isocyanates with the corresponding alcohols or phenols, it is also possible to use urea, isocyanic acid or other methods, including the use of in-situ formed isocyanate. In the literature, N-alkyl-O-methylcarbamate is synthesized by reacting amines with dimethylcarbonates with various catalysts. In view of the economic feasibility and difficulty of isolating the target product the overwhelming number of the described methods are hardly applicable for scaling and industrial synthesis. A study was conducted to develop a method of synthesis of O-methyl-N-alkylcarbamate, which will be able to scale and be introduced into production. The most promising synthesis methods described in the literature have been tested, and a new method for producing various carbamates has been developed. The model amines for the experiment were selected industrially important – n-butylamine and cyclohexylamine. The structure of the product was confirmed by 1H NMR spectra. A number of the described methods had a way out in practice several times below the literature data presented, and some target products could not be received. The best way to react with n-butylamine is to use water as a catalyst. The yield obtained according to this procedure for O-methyl-N-cyclohexylcarbamate was 53%, for O-methyl-N-n-butylcarbamate – 68%, so the method was expanded to obtain several O-methyl-N-alkylcarbamate.