Development of new catalytic systems for efficient use of carbon monoxide

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Development of efficient methods for the use of carbon monoxide is one of the most important subjects in the chemical industry. This project has been set up for this purpose focussing on the development of new catalytic system using elemental selenium rather than transition metals which have been frequently used for introduction of carbon monoxide into organic molecules. The results obtained in this project are summarized below.Selenium has been found to have an extremely high catalytic activity for carbonylation with carbon monoxide of a variety of organic molecules having protic hydrogen such as amines,alcohols,and thiols. Application of this reaction to diamines and aminoalcohols results in achievement of efficient methods for the syntheses of cyclic ureas and cyclic urethanes. A delailed study on the selenium catalyzed carbonylation of amines leading to urea derivatives has revealed that the reaction proceeds via carbamoselenoate and biscarbamoyl diselenide as the key intermediates. Such a high activity of selenium for the carbonylation may be based on the facile formation of carbonyl selenide (Se=C=O) from selenium and carbon monoxide, which reacts readily with nucleophiles in the reaction system. Several types of organoselenium compounds in which SeCO moiety is incorporated have been synthesized. Examination of synthetic utility of these compounds revealed that biscarbamoyl diselenides and Se-alkyl selenocarbonates can be used as carbamoylating and oxycarbonylating reagents, respectively. In addition to this selenium assisted carbonylation, a new method for homologation of esters and acetals by combined use of carbon monoxide, hydrosilanes and cobalt carbonyl has been developed, where carbon monoxide is incorporated as siloxymethyl group in the products.