Efficient palladium(II) catalysis under air. Base-free oxidative heck reactions at room temperature or with microwave heating.
Scope and limitations of the base-free oxidative Heck reaction with arylboronic acids have been explored. Under our conditions, the dmphen-palladium(II)-catalyzed arylation proceeded with air or p-benzoquinone as reoxidants of palladium(0). We found that ambient temperature and mild aerobic conditions allow for the use of substrates sensitive to palladium(II)-catalyzed oxidation. Oxidative Heck couplings, employing different arylboronic acids, were smoothly and regioselectively conducted with both electron-rich and electron-poor olefins, providing high yields even with disubstituted butyl methacrylate, sensitive acrolein, and a vinylboronate ester. Controlled microwave processing was used to reduce reaction times from hours to minutes both in small scale and in 50 mmol scale batch processes.
Lindh
Jonas
J
Organic Pharmaceutical Chemistry, Department of Medicinal Chemistry, Uppsala Biomedical Center, Uppsala University, P.O. Box 574, SE-751 23 Uppsala, Sweden.
Enquist
Per-Anders
PA
Pilotti
Ake
A
Nilsson
Peter
P
Larhed
Mats
M
D000179:Acrylates / Q000737:chemistry*; D000332:Aerobiosis; D001555:Benzene Derivatives / Q000737:chemistry*; D001897:Boronic Acids / Q000737:chemistry*; D002384:Catalysis; D002625:Chemistry, Organic / Q000379:methods*; D006358:Hot Temperature; D008872:Microwaves; D010084:Oxidation-Reduction; D010165:Palladium / Q000737:chemistry*; D013696:Temperature
D000179:Acrylates; D001555:Benzene Derivatives; D001897:Boronic Acids; D010165:Palladium; C032490:n-butyl acrylate