Efficient and general synthesis of 5-(alkoxycarbonyl)methylene-3-oxazolines by palladium-catalyzed oxidative carbonylation of prop-2-ynylamides.
A variety of prop-2-ynylamides have been carbonylated under oxidative conditions to give oxazolines, oxazolines with chelating groups, and bisoxazolines bearing an (alkoxycarbonyl)methylene chain at the 5 position in good yields. The cyclization-alkoxycarbonylation process was carried out in alcoholic media at 50-70 degrees C and under 24 bar pressure of 3:1 carbon monoxide/air in the presence of catalytic amounts of 10% Pd/C or PdI2 in conjunction with KI. Cyclization occurred by anti attack of an oxygen function on the palladium-coordinated triple bond, followed by stereospecific alkoxycarbonylation, strictly resulting in E-stereochemistry. The structures of representative oxazolines and bisoxazolines have been determined by X-ray diffraction analysis.
Bacchi
Alessia
A
Dipartimento di Chimica Generale, Analitica e Chimica Fisica, Università di Parma, Parco Area delle Scienze 17, 43100 Parma, Italy.
Costa
Mirco
M
Gabriele
Bartolo
B
Pelizzi
Giancarlo
G
Salerno
Giuseppe
G