56572-26-0Relevant articles and documents
Iron(III)/TEMPO-Catalyzed Synthesis of 2,5-Disubstituted 1,3,4-Oxadiazoles by Oxidative Cyclization under Mild Conditions
Zhang, Guofu,Yu, Yidong,Zhao, Yiyong,Xie, Xiaoqiang,Ding, Chengrong
supporting information, p. 1373 - 1377 (2017/06/27)
A simple and efficient cationic Fe(III)/TEMPO-catalyzed oxidative cyclization of aroyl hydrazones has been developed for the synthesis of 2,5-disubstituted 1,3,4-oxadiazole derivatives. The reaction offers a broad scope, good functional-group tolerance, and high yields under mild conditions in the presence of O 2.
Tin Powder-Promoted One-Pot Construction of α-Methylene-γ-lactams and Spirolactams from Aldehydes or Ketones, Acylhydrazines, and 2-(Bromomethyl)acrylate
Xu, Yanli,Huang, Danfeng,Wang, Ke-Hu,Ma, Junyan,Su, Yingpeng,Fu, Ying,Hu, Yulai
, p. 12224 - 12233 (2016/01/09)
A concise and efficient method for the synthesis of α-methylene-γ-lactams is developed from multicomponent one-pot reactions of aldehydes or ketones, hydrazides, and ethyl 2-(bromomethyl)acrylate promoted by tin powder. The reaction proceeds smoothly under mild reaction conditions without using any catalyst to give the corresponding products in high yields. α-Methylene-γ-spirolactams can also be prepared from cyclic ketones.
Mechanism and selectivity of N -triflylphosphoramide catalyzed (3+ + 2) Cycloaddition between hydrazones and alkenes
Hong, Xin,Küük, Hatice Bapinar,Maji, Modhu Sudan,Yang, Yun-Fang,Rueping, Magnus,Houk
supporting information, p. 13769 - 13780 (2015/02/05)
Bronsted acid catalyzed (3+ + 2) cycloadditions between hydrazones and alkenes provide a general approach to pyrazolidines. The acidity of the Bronsted acid is crucial for the catalytic efficiency: the less acidic phosphoric acids are ineffective, while highly acidic chiral N-triflylphosphoramides are very efficient and can promote highly enantioselective cycloadditions. The mechanism and origins of catalytic efficiencies and selectivities of these reactions have been explored with density functional theory (M06-2X) calculations. Protonation of hydrazones by N-triflylphosphoramide produces hydrazonium-phosphoramide anion complexes. These ion-pair complexes are very reactive in (3+ + 2) cycloadditions with alkenes, producing pyrazolidine products. Alternative 1,3-dipolar (3 + 2) cycloadditions with the analogous azomethine imines are much less favorable due to the endergonic isomerization of hydrazone to azomethine imine. With N-triflylphosphoramide catalyst, only a small distortion of the ion-pair complex is required to achieve its geometry in the (3+ + 2) cycloaddition transition state. In contrast, the weak phosphoric acid does not protonate the hydrazone, and only a hydrogen-bonded complex is formed. Larger distortion energy is required for the hydrogen-bonded complex to achieve the ion-pair geometry in the cycloaddition transition state, and a significant barrier is found. On the basis of this mechanism, we have explained the origins of enantioselectivities when a chiral N-triflylphosphoramide catalyst is employed. We also report the experimental studies that extend the substrate scope of alkenes to ethyl vinyl ethers and thioethers.
Studies on the synthesis of 2-alkyl-5-aryl-1,3,4-oxadiazolines from N-acylhydrazones
Marqués-López, Eugenia,Díez, Elena,Martín-Zamora, Eloísa,álvarez, Eleuterio,Fernández, Rosario,Lassaletta, José M.
supporting information; experimental part, p. 885 - 888 (2012/05/20)
Reaction of N-acylhydrazones with benzyloxyacetyl chloride in the presence of i-Pr2EtN affords new 1,3,4-oxadiazolines in excellent yields (72-95%), under mild reaction conditions and in short reaction times. The structures of the products were confirmed by single-crystal X-ray diffractometry. A plausible reaction mechanism is proposed. Georg Thieme Verlag Stuttgart · New York.
Asymmetric Br?nsted acid catalyzed cycloadditions-efficient enantioselective synthesis of pyrazolidines, pyrazolines, and 1,3-diamines from N-acyl hyrazones and alkenes
Rueping, Magnus,Maji, Modhu Sudan,Kü?ük, Hatice Ba?pínar,Atodiresei, Iuliana
supporting information, p. 12864 - 12868 (2013/02/22)
A general, metal-free, highly enantioselective Bronsted acid catalyzed [3+2] cycloaddition between hydrazones and alkenes has been developed that affords pyrazolidine derivatives (see scheme). The resulting optically active pyrazolidines can undergo many chemical transformations which allow, for example, the enantioselective synthesis of valuable pyrazolines and 1,3-diamines. Copyright
Indium-mediated catalytic enantioselective allylation of N -benzoylhydrazones using a protonated chiral amine
Kim, Sung Jun,Jang, Doo Ok
supporting information; experimental part, p. 12168 - 12169 (2010/10/03)
A catalytic enantioselective indium-mediated allylation of N-benzoylhydrazones in conjunction with a protonated chiral amine affording enantioenriched homoallylic amines with an extremely high level of enantioselectivity and chemical yield was developed.
