Reduction of CO2 with Organoborons

Hydrocarboxylation of olefins with CO2 and H2 is attractive because it is a thermodynamically feasible and atom-economic transformation of CO2. However 

In this chapter, we have reviewed theoretical studies of selected transition metal-catalyzed transformation of CO2 (i) hydrogenation of CO2 with H2 (ii) coupling reactions of CO2 and epoxides (iii) reduction of CO2 with organoborons (iv) carboxylation of olefins with CO2 and (v) hydrocarboxylation of olefins with CO  

2) In transition metal-catalyzed coupling reactions of COj and epoxides, CO2 is activated by electron-rich M-O bonds. A lone pair of electrons associated with the M-O oxygen facihtates the CO2 activation. Mechanistically, ring opening of epoxides gives an electron-rich M-O bondfrom which CO2 insertion can be achieved. The final step is reductive elimination of carbonates to regenerate the catalyst. 

5) In transition metal-catalyzed hydrocarboxylation of olefins with CO2 and H2, CO2 is activated by M-ethyl bonds, which can be considered as electron-rich 

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In this chapter, we discuss theoretical studies of some selected transition metal-catalyzed reactions of carbon dioxide to illustrate how important concepts and insights can be derived as a result of these studies. These selected reactions include hydrogenation of CO2 with Hj, coupling reactions of COj and epoxides, reduction of CO2 with organoborons, carboxylation of olefins with COj, and hydrocarboxy-lation of olefins with CO2 and Hj. They are fundamentally important reactions of carbon dioxide and have been intensively investigated experimentally and theoretically. This chapter is not intended to be a comprehensive review. Instead, we discuss the above-mentioned selected examples that we believe to be representative and important in the area of homogeneous catalysis of COj by transition metals from our own perspective. 

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