Photolysis of Tertiary Amines in the Presence of CO2: The Paths to Formic Acid, α-Amino Acids, and 1,2-Diamines

The photolysis of triethylamine (1a) in the presence of carbon dioxide leads to the hydrogenation of CO2 the alpha-C-C coupling of 1a, and the CO2 insertion into the alpha-C-H sigma-bond of amine 1a. This reaction is proposed to proceed through the radical ion pair [R3N center dot+center dot CO2 center dot-] generated by the photoionization of amine la and the electron capture by CO2. The presence of lithium tetrafluoroborate in the reaction medium promotes the efficient and stereoselective alpha-C-C coupling of la by enhancing the production of alpha-dialkylamino radicals and the isomerization of N,N,N',N'-tetraethylbutane-2,3-diamine (4a).