164850-19-5Relevant academic research and scientific papers
Enantioselective Radical Cyclization for Construction of 5-Membered Ring Structures by Metalloradical C-H Alkylation
Wang, Yong,Wen, Xin,Cui, Xin,Zhang, X. Peter
supporting information, p. 4792 - 4796 (2018/04/17)
Radical cyclization represents a powerful strategy for construction of ring structures. Traditional radical cyclization, which is based on radical addition as the key step, necessitates the use of unsaturated substrates. Guided by the concept of metalloradical catalysis, a different mode of radical cyclization that can employ saturated C-H substrates is demonstrated through the development of a Co(II)-based system for catalytic activation of aliphatic diazo compounds for enantioselective radical alkylation of various C(sp3)-H bonds. It allows for efficient construction of chiral pyrrolidines and other valuable 5-membered cyclic compounds. This alternative strategy of radical cyclization provides a new retrosynthetic paradigm to prepare five-membered cyclic molecules from readily available open-chain aldehydes through the union of C-H and C=O elements for C-C bond formation.
Br?nsted Acid-Catalyzed Intramolecular Nucleophilic Substitution of the Hydroxyl Group in Stereogenic Alcohols with Chirality Transfer
Bunrit, Anon,Dahlstrand, Christian,Olsson, Sandra K.,Srifa, Pemikar,Huang, Genping,Orthaber, Andreas,Sj?berg, Per J. R.,Biswas, Srijit,Himo, Fahmi,Samec, Joseph S. M.
supporting information, p. 4646 - 4649 (2015/04/27)
The hydroxyl group of enantioenriched benzyl, propargyl, allyl, and alkyl alcohols has been intramolecularly displaced by uncharged O-, N-, and S-centered nucleophiles to yield enantioenriched tetrahydrofuran, pyrrolidine, and tetrahydrothiophene derivatives with phosphinic acid catalysis. The five-membered heterocyclic products are generated in good to excellent yields, with high degree of chirality transfer, and water as the only side-product. Racemization experiments show that phosphinic acid does not promote SN1 reactivity. Density functional theory calculations corroborate a reaction pathway where the phosphinic acid operates as a bifunctional catalyst in the intramolecular substitution reaction. In this mechanism, the acidic proton of the phosphinic acid protonates the hydroxyl group, enhancing the leaving group ability. Simultaneously, the oxo group of phosphinic acid operates as a base abstracting the nucleophilic proton and thus enhancing the nucleophilicity. This reaction will open up new atom efficient techniques that enable alcohols to be used as nucleofuges in substitution reactions in the future.
Methods for the synthesis of chiral sulfur heterocycles and their application in the asymmetric Baylis-Hillman reactions
Periasamy, Mariappan,Gurubrahamam, Ramani,Muthukumaragopal, Gopal P.
, p. 568 - 574 (2013/06/27)
Enantiomerically pure (2S,6S)-2,6-diphenyltetrahydro-2H-thiopyran, (2S)-2-phenyltetrahydro thiophene, and (2S)-2-phenyltetrahydro-2H-thiopyran were prepared in 70-72% yields and with 86-99% ee via cyclization of the corresponding dimesylate in an SN2 cyclization reaction using sodium sulfide nonahydrate. The results on the application of various chiral sulfides in asymmetric Baylis-Hillman reactions are also described.
Phosphorothioic acids and related compounds as surrogates for H 2S-synthesis of chiral tetrahydrothiophenes
Robertson, Forest J.,Wu, Jimmy
, p. 2775 - 2780 (2012/03/22)
The convenient preparation of chiral tetrahydrothiophenes (THTs) in high enantiopurity via phosphorothioic acids and related compounds is reported. We consider these to be safer alternatives to the use of H2S which is a highly toxic gas. Each o
