Barbier–Negishi Coupling of Secondary Alkyl Bromides with Aryl and Alkenyl Triflates and Nonaflates
A mild and practical Barbier–Negishi coupling of secondary alkyl bromides with aryl and alkenyl triflates and nonaflates has been developed. This challenging reaction was enabled by the use of a very bulky imidazole-based phosphine ligand, which resulted in good yields as well as good chemo- and site selectivities for a broad range of substrates at room temperature and under non-aqueous conditions. This reaction was extended to primary alkyl bromides by using an analogous pyrazole-based ligand.
TRANSITION METAL-CATALYZED ALKYLATION OF C-H BONDS WITH ORGANOBORON REAGENTS
One aspect of the present invention relates to methods for functionalization of 2-arylpyridine and arylpyrazoles with organoboron reagents in the presence of a transition metal catalyst to furnish alkylated arylpyridines and arylpyrazoles via regioselective functionalization of sp2 -hybridized C-H bonds at a position ortho to the point of attachment of the pyridine or pyrazole ring to the aromatic nucleus, hi other embodiments, the present invention provides for alkylation of sp3-hybridized C-H bonds in alkylpyridines.
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Page/Page column 6; 62; 68
(2008/06/13)
Palladium-catalyzed alkylation of sp2 and sp3 C-H bonds with methylboroxine and alkylboronic acids: Two distinct C-H activation pathways
Palladium-catalyzed alkylations of sp2 and sp3 C-H bonds with either methylboroxine or alkylboronic acids were developed. Ag2O or AgCO3 is used as a crucial oxidant and promoter for the transmetalation step. Ether, ester, alcohol, and alkene functional groups are tolerated. A new C-H activation pathway differing from the cyclometalation process is elucidated using methylboroxine as the coupling partner. Copyright
Chen, Xiao,Goodhue, Charles E.,Yu, Jin-Quan
p. 12634 - 12635
(2008/02/05)
A Convenient Method for the Regioselective Synthesis of 4-Alkyl(aryl)pyridines Using Pyridinium Salts
RCu.BF3 reacted with 1-ethocycarbonylpyridinium chloride at the 4-position with almost complete regioselectivity (>99percent) to afford the corresponding 1,4-dihydropyridine derivatives in high yields (81-94percent).The dihydropyridines were oxidized by oxygen to give 4-alkyl(aryl)pyridines (38-68percent).Grignard reagents also reacted with 1-t-butyldimethylsilylpyridinium triflate with almost complete regioselectivity (>99percent) to afford the corresponding 1,4-dihydropyridines, which were easily oxidized to give 4-substituted pyridines in higher yields than above (58-70percent).
Akiba, Kin-ya,Iseki, Yuji,Wada, Makoto
p. 1994 - 1999
(2007/10/02)
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