Palladium-catalyzed carboxylative cyclization of propargylic amines with aryl iodides, CO2 and CO under ambient pressure.

A palladium-catalyzed four-component carboxylative cyclization comprising propargylic amines, aryl iodides, CO2 and CO was developed. By selecting Et3N and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as the base, respectively, both terminal and internal propargylic amines proceeded well facilitated by Pd(PPh3)2Cl2, affording the functionalized 2-oxazolones in moderate yields. This protocol enlarges the product diversity based on CO2 conversion and simultaneously provides a cooperative transformation route for both CO2 and CO.

Visible light-driven carbamoyloxylation of the α-C(sp3)-H bond of arylacetones via radical-initiated hydrogen atom transfer.

Photocatalytic synthesis has emerged as an efficient route to transform CO2 into functionalized organic carbamates by photocatalysis. Herein, a catalyst-free carbamoyloxylation of arylacetones with CO2 and amines under visible light was developed for the synthesis of O-ß-oxoalkyl carbamates in yields up to 93%. This protocol proceeded smoothly with the assistance of inexpensive carbon tetrabromide at room temperature under atmospheric CO2 pressure, leading to simultaneous construction of C-O and C-N bonds. Mechanism studies suggested the photoinduced hydrogen atom transfer (HAT) pathway followed by radical addition or single electron transfer (SET).