Transition-Metal-Free Cross-Coupling of Aryl Halides with Arylstannanes
Transition-metal-free LiCl-promoted cross-coupling reactions of tetraphenyltin, trichlorophenyl-, dichlorodiphenyl-, and chlorotriphenylstannanes with aryl halides in DMF provided access to biaryls in good to high yields. Up to four phenyl groups were transferred from the organostannanes substrates. The aryls bearing electron-withdrawing groups in either halides or organotin substrates gave coupling products in higher yields. The methodology has been applied for the efficient synthesis of ipriflavones.
He, Qing,Wang, Liwen,Liang, Yong,Zhang, Zunting,Wnuk, Stanislaw F.
p. 9422 - 9427
(2016/10/17)
Amine-catalyzed direct photoarylation of unactivated arenes
Constructing biaryls through direct aromatic C-H functionalization of unactivated arenes has become a popular topic in organic chemistry. Many efficient methods have been developed. In this Communication, a direct arylation of unactivated arenes with a broad range of aryl iodides is reported. This reaction proceeds through a new type of amine-catalyzed single electron transfer initiated radical coupling procedure to form biaryls in high yields under UV irradiation at room temperature. Only 20 mol% of TMEDA is used as the catalyst. No other additives are required for this transformation, thus avoiding the use of toxic transition metal catalysts, strong bases, or large amounts of other organic additives. This greener protocol provides a new strategy to achieve direct aromatic C-H functionalization and offers a new example of cost-effective and environmentally benign access to biaryls. Copyright
Fingerprints of singlet and triplet phenyl cations
The photolyses of seven phenyl cation precursors in acetonitrile in the presence of anisole resulted in four distinct product patterns. These patterns are due to the chemoselective and regioselective chemistry of various phenyl cation isomers. This spin-selective chemistry provides a tool with which to fingerprint the singlet/triplet nature of any phenyl cation. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
Slegt, Micha,Overkleeft, Hermen S.,Lodder, Gerrit
p. 5364 - 5375
(2008/03/14)
Formation Constants of Cyanohydrins of Substituted Acetylbiphenyls
The formation constants of cyanohydrins of 2'- and 3'-substituted 4-acetylbiphenyls have been determined at 30 deg C in 80percent dioxan-water (v/v).The 3'-substituted 4-acetylbiphenyls obey the Hammett equation giving a ρ-value of 0.52; 2'-substituted cyanohydrins do not obey the Hammett equation.The formation constants of 3'-substituted 4-acetylbiphenyls and their rate constants for the reduction by sodium borohydride reveal a linear relationship (r = 0.990).The influence of 2'-substituents reveals the existence of ?-electron steric effect.
Ananthakrishnanadar, P.,Kannan, N.
p. 74 - 75
(2007/10/02)
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