We report on the synthesis of 1,2,4-triazoles substituted with 2 or 3 aminoacid side chains, using silver benzoate as a key reagent for the cyclization step. A complete study of the optical purity retention during the synthetic process leading to these compounds is described. In addition an improved work-up after the addition-cyclization step was also established leading to better yields and metal-free
Efficient Alkyl Ether Synthesis via Palladium-Catalyzed, Picolinamide-Directed Alkoxylation of Unactivated C(sp<sup>3</sup>)–H and C(sp<sup>2</sup>)–H Bonds at Remote Positions
作者:Shu-Yu Zhang、Gang He、Yingsheng Zhao、Kiwan Wright、William A. Nack、Gong Chen
DOI:10.1021/ja3023972
日期:2012.5.2
functionalization of unactivatedsp(3)- and sp(2)-hybridized C-H bonds. In the Pd(OAc)(2)-catalyzed, PhI(OAc)(2)-mediated reaction system, picolinamide-protected amine substrates undergo facile alkoxylation at the γ or δ positions with a range of alcohols, including t-BuOH, to give alkoxylated products. This method features a relatively broad substrate scope for amines and alcohols, inexpensive reagents
we report an efficient protocol for the C(sp2)–H carbonylation of amino acid derivatives based on an inexpensive cobalt(II) salt catalyst. Carbonylation was accomplished using picolinamide as a tracelessdirectinggroup, CO (1 atm) as the carbonyl source, and Co(dpm)2 as the catalyst. A broad range of phenylalanine derivatives bearing diverse functional groups were tolerated. Moreover, the method can
Improved Protocol for Indoline Synthesis via Palladium-Catalyzed Intramolecular C(sp<sup>2</sup>)–H Amination
作者:Gang He、Chengxi Lu、Yingsheng Zhao、William A. Nack、Gong Chen
DOI:10.1021/ol301352v
日期:2012.6.15
An efficient method has been developed for the synthesis of indoline compounds from picolinamide (PA)-protected β-arylethylamine substrates viapalladium-catalyzed intramolecular amination of ortho-C(sp2)–H bonds. These reactions feature high efficiency, low catalyst loadings, mild operating conditions, and the use of inexpensive reagents.
Diastereoselective assembly of pentanuclear circular helicates
作者:Oliver R. Clegg、Rebecca V. Fennessy、Lindsay P. Harding、Craig. R. Rice、T. Riis-Johannessen、Nicholas C. Fletcher
DOI:10.1039/c1dt11414j
日期:——
separated by a 1,3-phenylene spacer unit with Zn2+ ions results in a pentanuclearcircularhelicate [Zn5(L)5]10+ and this structure persists in both the solid and solution state. The formation of this high nuclearity species is governed by unfavourable steric interactions between the phenyl units which destabilize the simple linear helicate. Incorporation of enantiopure units within the ligand strand controls