Organocatalytic methods for chemoselective O-tert-butoxycarbonylation of phenols and their regeneration from the O-t-Boc derivatives.
Carbon tetrabromide (CBr4) catalyzes O-tert-butoxycarbonylation of functionalized phenols without any side reactions (bromination, addition of CBr3 to a double bond, and formation of symmetrical diaryl carbonates, cyclic carbonates, or carbonic-carbonic anhydrides). The parent phenols are regenerated from the O-t-Boc derivatives by the catalyst system CBr4-PPh3 without affecting other protecting groups (aryl alkyl ether, alkyl ester, and thioacetal) or competitive side reaction such as bromination, nitrene (from NO2) and alpha,alpha-dibromoolefine (with CHO/COMe) formation, and transesterification (with CO2Me/Et) taking place.
Chankeshwara
Sunay V
SV
Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research, Sector 67, S. A. S. Nagar 160 062, Punjab, India.
Chebolu
Rajesh
R
Chakraborti
Asit K
AK
D002384:Catalysis; D004951:Esterification; D005563:Formic Acid Esters / Q000737:chemistry*; D008722:Methods; D010636:Phenols / Q000737:chemistry*
D005563:Formic Acid Esters; D010636:Phenols; C000345:t-butyloxycarbonyl group