Selective Three-Component Coupling for CO 2 Chemical Fixation to Boron Guanidinato Compounds.

A selective three-component coupling was employed to fix carbon dioxide to boron guanidinato compounds. The one-pot reaction of carbon dioxide, carbodiimides, and borylamines (ArNH)BC8 H14 afforded the corresponding 1,2-adducts {R(H)N}C{N(Ar)}(NR)(CO2 )BC8 H14 . Alternatively, the reaction with p-MeOC6 H4 NC or 2,6-Me2 C6 H3 NC gave the corresponding isocyanide 1,1-adducts { i-PrHN}C{N(p-Me-C6 H4 )}(N i-Pr){CNAr}BC8 H14 . The molecular structures of products (2,6- i-Pr2 C6 H3 NH)BC8 H14 7, { i-Pr(H)N}C{N(p-MeC6 H4 )}(N i-Pr)(CO2 )BC8 H14 9, {Cy(H)N}C{N( p-MeC6 H4 )}(Cy)(CO2 )BC8 H14 13, and { i-PrHN}C{N( p-MeC6 H4 )}(N i-Pr){CNR″}BC8 H14 (R″ = p-MeOC6 H4 , 2,6-Me2 C6 H3 ) 14 and 15 were established by X-ray diffraction. Density functional theory calculations at the M05-2X level of theory revealed that CO2 fixation and formation of the corresponding adduct is exothermic and proceeds via a nonchelate boron guanidinato intermediate.