Additive and Vinylogous Pummerer Reactions of Amido Sulfoxides and Their Use in the Preparation of Nitrogen Containing Heterocycles
摘要:
The alpha-thiocarbocation generated from the Pummerer re action of N-methyl-N-phenyl-2-[2-(toluene-4-sulfinyl)phenyl]acetamide undergoes Friedel-Crafts reaction at the gamma-carbon with the tethered aromatic ring. Reductive removal of the phenylthio group from the resulting product using Raney nickel occurs in high yield, and the overall reaction represents a new method for the synthesis of a variety of 3-phenyl-substituted oxindoles. Treatment of the related N-benzyl-N-alkyl amido sulfoxide system with trifluoroacetic anhydride affords tetrahydroisoquinolone derivatives. The product distribution encountered coincides with the rotamer population of the starting amide. When the N-benzyl-N-methyl amide is used, only the normal Pummerer product is formed. In this case, the thionium ion is generated in the wrong conformation for pi-cyclization to occur. The corresponding N-tert-butyl amido system, however, exists in a geometric orientation which places the benzylic group in the crucial conformation necessary for pi-cyclization, and consequently, the reaction proceeds smoothly. Related cyclization reactions occur in good yield with the corresponding furanyl and cyclohexenyl N-tert-butyl amido sulfoxides. The additive Pummerer reaction of 3-phenylsulfinyl-N-benzyl-N-tert-butylacrylamide gave products derived from both 5- and 6-exo trig cyclizations. Intramolecular electrophilic aromatic substitution via six-membered ring closure ultimately afforded a dihydropyridone. The competitive process involving ipso attack of the aromatic ring on the thionium ion generates a spiro cyclohexadienyl cation that undergoes fragmentation of the adjacent a-bond. The resulting acyl iminium ion is converted to N-tert-butyl-2-phenyl-3-phenylsulfinylacrylamide upon aqueous workup. Only cyclizations leading to five-membered rings occur with the corresponding indolyl and alkenyl N-tert-butyl amido sulfoxides.
Reductive Transformations of Carbonyl Compounds Catalyzed by Rhodium Supported on a Carbon Matrix by using Carbon Monoxide as a Deoxygenative Agent
作者:Niyaz Z. Yagafarov、Dmitry L. Usanov、Alexey P. Moskovets、Nikolai D. Kagramanov、Victor I. Maleev、Denis Chusov
DOI:10.1002/cctc.201500493
日期:2015.9.1
An efficient method for the rhodium on carbon matrix catalyzed preparation of secondary and tertiary amines, cyanoesters, and nitriles through the reductive amination/alkylation of carbonyl compounds was developed, including a convenient procedure for the tandem formal reductive addition of acetonitrile to aldehydes. The catalyst could be reused, and at least three consecutive reaction cycles were
Reported here is an asymmetric CH functionalization approach to β‐lactams using readily accessible chloroacetamide substrates. Important aspects of this transformation are challenging C(sp3)C(sp3) and strain‐building reductive eliminations to for the four‐membered ring. In general, the β‐lactams are formed in excellent yields and enantioselectivities using a bulky taddolphosphoramidite ligand in combination
Activation of Hydrogen and Hydrogenation Catalysis by a Borenium Cation
作者:Jeffrey M. Farrell、Jillian A. Hatnean、Douglas W. Stephan
DOI:10.1021/ja307995f
日期:2012.9.26
The readily prepared borenium salt [(IiPr(2))(BC(8)H(14))][B(C(6)F(5))(4)] (2) [IiPr(2) = C(3)H(2)(NiPr)(2)] is shown to activate H(2) heterolytically in the presence of tBu(3)P. Compound 2 also acts as a catalyst for the metal-free hydrogenation of imines and enamines at room temperature.
[EN] BORENIUM FRUSTRATED LEWIS PAIR CATALYSTS<br/>[FR] CATALYSEURS DE BORÉNIUM À BASE DE PAIRES FRUSTRÉES DE LEWIS
申请人:STEPHAN CONSULTING CORP
公开号:WO2013177708A1
公开(公告)日:2013-12-05
A process for the catalytic hydrogenation of a variety of organic substrates using frustrated Lewis pair catalysts comprising a borenium complex is described. The frustrated Lewis pair catalysts described can also be used in a variety of chemical transformations of organic molecules.
作者:Jillian A. Hatnean、Jordan W. Thomson、Preston A. Chase、Douglas W. Stephan
DOI:10.1039/c3cc47889k
日期:——
Di-isobutylaluminum hydride and tri-iso-butylaluminum (DIBAL 1, TIBAL 2) are shown to be efficient hydrogenation catalysts for a variety of imines at 100 °C and 100 atm of H2, operating via a hydroalumination/hydrogenolysis mechanism.