931-13-5Relevant articles and documents
A phosphonium ylide as a visible light organophotoredox catalyst
Toda, Yasunori,Tanaka, Katsumi,Matsuda, Riki,Sakamoto, Tomoyuki,Katsumi, Shiho,Shimizu, Masahiro,Ito, Fuyuki,Suga, Hiroyuki
supporting information, p. 3591 - 3594 (2021/04/14)
A phosphonium ylide-based visible light organophotoredox catalyst has been designed and successfully applied to halohydrin synthesis using trichloroacetonitrile and epoxides. An oxidative quenching cycle by the ylide catalyst was established, which was confirmed by experimental mechanistic studies.
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.
Enzymatic preparation of (1S,2R)- and (1R,2S)-stereoisomers of 2-halocycloalkanols
Kolodiazhna, Olga O.,Kolodiazhna, Anastasy O.,Kolodiazhnyi, Oleg I.
, p. 37 - 42 (2013/02/25)
The stereoisomers of cis-2-halocycloalkanols were resolved by a kinetically controlled transesterification with vinyl acetate in the presence of lipases in organic media. High enantioselectivities (ee >98%) and good isolated yields were obtained for all substrates using the appropriate lipase. Burkholderia cepacia lipase was the most efficient enzyme for the resolution of these substrates. The enantiomeric purities of the compounds were defined by derivatization with Mosher's acid and the absolute configurations were determined by chemical correlation.
Facile synthesis of chiral 1,2-chlorohydrins via the ring-opening of meso-epoxides catalyzed by chiral phosphine oxides
Kotani, Shunsuke,Furusho, Haruka,Sugiura, Masaharu,Nakajima, Makoto
, p. 3075 - 3081 (2013/03/28)
The facile synthesis of chiral 1,2-chlorohydrins via the enantioselective ring-opening of meso-epoxides with silicon tetrachloride in the presence of a chiral phosphine oxide was accomplished. The chiral 1,2-chlorohydrins were also obtained from the corresponding cis-alkenes in one-pot without significant loss in the selectivity, thereby permitting easy access to the 1,2-chlorohydrins from cis-alkenes with good yields and enantioselectivities.
Enantioselective epoxide ring opening catalyzed by bis(tetrahydroisoquinoline) N,N′-dioxides
Kadlcikova, Aneta,Vlasana, Klara,Kotora, Martin
experimental part, p. 415 - 422 (2011/12/21)
Four bis(tetrahydroisoquinoline) N,N′-dioxides were used as catalysts for the epoxide ring opening with tetrachlorosilane under various conditions. A strong solvent effect on asymmetric induction was observed for each of the used catalysts. The highest achieved asymmetric induction for the opening of meso-stilbene oxide was 69% ee. Regarding the cycloalkene oxides, 56% ee was obtained in the reaction with cyclooctene oxide.
Design, validation, and implementation of a rapid-injection NMR system
Denmark, Scott E.,Williams, Bruce J.,Eklov, Brian M.,Pham, Son M.,Beutner, Gregory L.
scheme or table, p. 5558 - 5572 (2010/11/18)
A Rapid Injection NMR (RINMR) apparatus has been designed and constructed to allow the observation of fast chemical reactions in real time by NMR spectroscopy. The instrument was designed to allow the rapid (2 s) injection and mixing of a metered volume
Allenes in asymmetric catalysis: Asymmetric ring opening of meso-epoxides catalyzed by allene-containing phosphine oxides
Pu, Xiaotao,Qi, Xiangbing,Ready, Joseph M.
supporting information; experimental part, p. 10364 - 10365 (2009/12/03)
(Chemical Equation Presented) Unsymmetrically substituted allenes (1,2-dienes) are inherently chiral and can be prepared in optically pure form. Nonetheless, to date the allene framework has not been incorporated into ligands for asymmetric catalysis. Since allenes project functionality differently than either tetrahedral carbon or chiral biaryls, they may create complementary chiral environments. This study demonstrates that optically active, C 2-symmetric allene-containing bisphosphine oxides can catalyze the addition of SiCl4 to meso-epoxides with high enantioselectivity. The epoxide opening likely involves generation of a Lewis acidic, cationic (bisphosphine oxide)SiCl3 complex. The fact that high asymmetric induction is observed suggests that allenes may represent a new platform for the development of ligands and catalysts for asymmetric synthesis.
Opening of epoxide rings catalyzed by niobium pentachloride
Constantino, Mauricio Gomes,Lacerda Jr., Valdemar,Invernize, Paulo Roberto,Filho, Luiz Carlos Da Silva,Da Silva, Gil Valdo Jose
, p. 3529 - 3539 (2008/03/13)
The behavior of several epoxides when treated with NbCl5 was studied. In general, the studied epoxides reacted rapidly with NbCl5, giving, in most cases, more than one product (chlorohydrins, products containing solvent residues, as well as rearrangement products). A detailed study was performed to verify the effects of the temperature (rt, 0°C, or -78°C) and of the NbCl5 molar concentration on the composition of the products, yield, and time required for the reactions. Copyright Taylor & Francis Group, LLC.
Asymmetric synthesis using organoboranes. Relative effectiveness of the B-Halobis(terpenyl)boranes for the enantioselective halogenative cleavage of representative meso-epoxides
Roy, Chandra D.,Brown, Herbert C.
, p. 835 - 842 (2008/03/12)
A comparative study of the relative effectiveness of various Ter 2BX, such as dEap2BX, lEap 2BX, 2-dIcr2BX, 4-dIcr 2BX, and lCleap2BX
