Copper-catalyzed C(sp3)-C(sp2) cross-coupling: Synthesis of 4-aryl-2-alkylamino-3-nitro-4h-chromenes
Inexpensive copper(II) acetate effectively catalyzes cross-coupling of electron-deficient as well as electron-rich arylboronic acids with 4-methylsulfanyl-2-alkylamino-3-nitro-4H-chromenes under near neutral conditions at room temp. to furnish a range of 4-aryl-4H-chromenes. This new strategy enabled substitution of the C(4)SMe group present on a sp3 hybridized carbon of the 4H-chromenes with aryl/heteroaryl groups. Mechanistic probing revealed that the CuI-CuIII cycle is involved in catalysis. One-pot sequential substitution of C(4)SMe followed by C(6)Br with aryl groups has been achieved through Cu(OAc)2 and Pd 2(dba)3 (Suzuki coupling) catalysis. Copyright
Rao, H. Surya Prakash,Rao, A. Veera Bhadra
p. 3646 - 3655
(2014/06/23)
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