Copper-Mediated Synthesis of Substituted 2-Aryl-N-benzylbenzimidazoles and 2-Arylbenzoxazoles via C–H Functionalization/C–N/C–O Bond Formation
摘要:
An efficient method for the transformation of N-benzyl bisarylhydrazones and bisaryloxime ethers to functionalized 2-aryl-N-benzylbenzimidazoles and 2-arylbenzoxazoles is described. The protocol involves a copper(II)-mediated cascade C-H functionalization/C-N/C-O bond formation under neutral conditions. Substrates having either electron-donating or -withdrawing substituents undergo the cyclization to afford the target heterocycles at moderate temperature.
The reductive singleelectrontransfer (SET) umpolung amination of aldehyde-derived hydrazones has been developed through visible-light-promoted photoredox catalysis. The ideal transformation of hydrazones into the corresponding hydrazonamide through selective carbon–hydrogen (C–H) bond functionalization represents one of the most step- and atom-economical methods. This SET umpolung strategy features
One-pot synthesis of 5-sulfonamidopyrazole from terminal alkynes, sulfonyl azides and hydrozones
作者:Yao Li、Deng Hong、Yuanxun Zhu、Ping Lu、Yanguang Wang
DOI:10.1016/j.tet.2011.08.067
日期:2011.10
5-Sulfonamidopyrazoles were efficiently synthesized from terminal alkynes, sulfonylazides and hydrozones. The sequential reaction involves a copper-catalyzed three-component reaction, a Lewis acid-catalyzed electrocyclic reaction and a dehydrogenation.
Mn(III)-mediated phosphinoylation of aldehyde hydrazones: Direct “one-pot” synthesis of α-iminophosphine oxides from aldehydes
作者:Xue-Wei Bian、Ling Zhang、Adedamola Shoberu、Jian-Ping Zou
DOI:10.1016/j.tet.2021.132053
日期:2021.4
A “one-pot” strategy for the straightforward Mn(III)-mediated phosphinoylation of aldehyde hydrazones with diphenylphosphine oxide to furnish α-iminophosphine oxides is described. This mild and practical method allows the direct use of aldehydes as substrates in one pot to generate the hydrazones, which are then engaged “in situ” by the phosphorus reagent in the presence of Mn(OAc)3 oxidant. Thus,
novel efficient tandem reaction of hydrazones and α-bromo ketones is reported for the preparation of 1,3,5-trisubstituted pyrazoles by visible light catalysis. In this system, the monosubstituted hydrazones show wonderful reaction activity with alkyl radicals, generated from α-bromo ketones. A radical addition followed by intramolecular cyclization affords the important pyrazole skeleton in good to
cycloaddition of nitrile imines with 3-alkenyl-oxindoles was catalyzed by a new chiral Mg(ClO4)2 complex of an N,N′-dioxide ligand. The reaction is so far the sole catalytic synthesis of spiro-pyrazoline-oxindole derivatives. A wide variety of substrates were explored to obtain good yields (up to 98%) and excellent enantioselectivities (up to 99%). This cycloaddition expands the scope of propargyl anion type 1