123166-03-0Relevant academic research and scientific papers
Enantioselective ring opening of epoxides with silicon tetrachloride in the presence of a chiral lewis base: Mechanism studies
Denmark, Scott E.,Barsanti, Paul A.,Beutner, Gregory L.,Wilson, Tyler W.
, p. 566 - 582 (2007)
The enantioselective ring opening of meso-epoxides (from both cyclic and acyclic olefins) with silicon tetrachloride under catalysis by chiral phosphoramides affords enantiomerically enriched chlorohydrins in excellent yields. Experiments designed to eluc
Electro-mediated PhotoRedox Catalysis for Selective C(sp3)–O Cleavages of Phosphinated Alcohols to Carbanions
Barham, Joshua P.,K?nig, Burkhard,Karl, Tobias A.,Reiter, Sebastian,Tian, Xianhai,Yakubov, Shahboz,de Vivie-Riedle, Regina
supporting information, p. 20817 - 20825 (2021/08/18)
We report a novel example of electro-mediated photoredox catalysis (e-PRC) in the reductive cleavage of C(sp3)?O bonds of phosphinated alcohols to alkyl carbanions. As well as deoxygenations, olefinations are reported which are E-selective and can be made Z-selective in a tandem reduction/photosensitization process where both steps are photoelectrochemically promoted. Spectroscopy, computation, and catalyst structural variations reveal that our new naphthalene monoimide-type catalyst allows for an intimate dispersive precomplexation of its radical anion form with the phosphinate substrate, facilitating a reactivity-determining C(sp3)?O cleavage. Surprisingly and in contrast to previously reported photoexcited radical anion chemistries, our conditions tolerate aryl chlorides/bromides and do not give rise to Birch-type reductions.
Enantioselective Ring Opening of meso-Epoxides with Silicon Tetrachloride Catalyzed by Pyridine N-Oxides Fused with the Bicyclo[3.3.1]nonane Framework
Neni?kis, Algirdas,Ston?ius, Sigitas
supporting information, p. 6359 - 6369 (2015/10/06)
The synthesis of new chiral Lewis basic organocatalysts that contain pyridine N-oxide moieties fused with the bicyclo[3.3.1]nonane framework is reported. The obtained pyridine N-oxides were employed as catalysts in the enantioselective ring opening of meso-epoxides with silicon tetrachloride. Derivative 1b endowed with two 2,4-diaryl-substituted pyridine N-oxide moieties proved to be a particularly effective catalyst for desymmetrization of norbornene oxide 16i to furnish Wagner-Meerwein rearrangement product 20i in unprecedented 96 % ee. Difunctional congener 3, which is striped of the 4-aryl substituents, exhibited moderate to high levels of asymmetric induction (47-88 % ee) with alicyclic epoxide substrates. Chiral Lewis basic catalysts with pyridine N-oxide moieties fused with a bicyclo[3.3.1]nonane framework were used in the enantioselective ring opening of meso-epoxides. 2,4-Diaryl-substituted N-oxide exhibited excellent asymmetric induction with norbornene oxide (96 % ee), whereas less-substituted congener was most effective with alicyclic epoxide substrates (47-88 % ee).
Conformationally rigid chiral bicyclic skeleton-tethered bipyridine N,N'-dioxide as organocatalyst: Asymmetric ring opening of meso-epoxides
Gnanamani, Elumalai,Someshwar, Nagamalla,Sanjeevi, Jayakumar,Ramanathan, Chinnasamy Ramaraj
supporting information, p. 2219 - 2223 (2014/07/21)
The conformationally rigid chiral bicyclic skeleton tethered bipyridine NN'-dioxide (-)-9 has been designed, synthesized and examined as an organocatalyst in the enantioselective ring opening of meso-epoxides using tetrachlorosilane (SiCl4). The catalyst (-)-9 is found to exhibit good enantioselectivity for substituted cis-stilbene epoxides; whereas, the saturated cyclic meso-epoxides display a moderate enantioselectivity. At -30 °C in chloroform, the catalyst (-)-9 with 0.5 mol % loading generated the chlorohydrins in up to 97 % yield with up to 93 % ee. The possible creation of transient axial chiral environment around hypervalent silicon species due to the presence of conformationally rigid chiral bicyclic skeleton tethered bipyridine N,N'-dioxide may be responsible for such enantioselectivity observed in the desymmetrization of meso-epoxides.
The vicinal functionalization of olefins: A facile route to the direct synthesis of β-chlorohydrins and β-chloroethers
Swamy, Peraka,Kumar, Macharla Arun,Reddy, Marri Mahender,Naresh, Mameda,Srujana, Kodumuri,Narender, Nama
, p. 26288 - 26294 (2014/07/08)
An efficient and environmentally benign protocol for the synthesis of vicinal chlorohydroxy and chloromethoxy derivatives in a highly regioselective manner from olefins using NH4Cl as a chlorine source and oxone as an oxidant in aqueous acetone and methanol is demonstrated. This methodology offers an additive and metal chloride free approach and is endowed with simple reaction conditions, high yields a broad substrate scope and good functional group tolerance. Moreover, the aromatic substrates with a terminal double bond exhibited merely Markovnikov selectivity, while the internal alkenes show exclusive regiocontrol and low to moderate diastereoselectivity.
Highly regio- and diastereoselective halohydroxylation of olefins: A facile synthesis of vicinal halohydrins
Zhang, Jinglei,Wang, Jie,Qiu, Zhuibai,Wang, Yang
experimental part, p. 6859 - 6867 (2011/10/02)
An efficient method for the synthesis of vicinal chlorohydrin or bromohydrin derivatives has been developed on the basis of direct halohydroxylation of various olefins with electrondonating or withdrawing substituent. The reactions were carried out under mild conditions in the presence of N-tosyl-l-threonine (NTsLT) as an acidic additive using chloramine T trihydrate, 1,3-dichloro-5,5-dimethylhydantoin (DCDMH) or N-bromoacetamide (AcNHBr) as the halogen source, respectively, affording the corresponding vicinal halohydrins in good to high yields with excellent regio- and stereoselectivities.
Chiral pyridine N-oxides derived from monoterpenes as organocatalysts for stereoselective reactions with allyltrichlorosilane and tetrachlorosilane
Chelucci, Giorgio,Baldino, Salvatore,Pinna, Gerard A.,Benaglia, Maurizio,Buffa, Laura,Guizzetti, Stefania
, p. 7574 - 7582 (2008/12/20)
The synthesis of enantiomerically pure C2-symmetric dipyridylmethane ligands and related N,N′-dioxides is reported. A procedure for the synthesis of a few new enantiomerically pure C2-symmetric pyridine N-oxides and the preparation of four pyridine N-oxides with oxygen and nitrogen atoms as further coordinating elements in the heterocycle framework is described. All compounds were prepared from naturally occurring monoterpenes. These new compounds were assessed as organocatalysts in two different reactions, namely the allylation of aldehydes with allyltrichlorosilane that afforded homoallylic alcohols in good yields and up to 85% ee and the stilbene oxide opening by the addition of tetrachlorosilane that gave chlorohydrin in quantitative yield and up to 70% ee.
Demonstration of a phosphazirconocene as a catalyst for the ring opening of epoxides with TMSCI
Wang, Li-Sheng,Hollis, T. Keith
, p. 2543 - 2545 (2007/10/03)
(Matrix presented) In this study, it was demonstrated for the first time that a phosphazirconocene catalyzes the ring opening of epoxides with TMSCI. This reactivity leads to a facile preparation of chlorohydrins. The late transition metal Fe analogue was found to catalyze the reaction at rates and stereoselectivity comparable to those of the Zr complex.
