100937-76-6Relevant articles and documents
3-benzyloxy-tetrahydropyrane, preparation method thereof and preparation method of single-configured tetrahydropyrane-3-cyclitol
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Paragraph 0055; 0056; 0057; 0058; 0065-0067; 0077-0083, (2017/10/27)
The invention relates to 3-benzyloxy-tetrahydropyrane, a preparation method thereof and a preparation method of single-configured tetrahydropyrane-3-cyclitol, and belongs to the technical field of medicines. The 3-benzyloxy-tetrahydropyrane has a structur
Regio- and enantioselective cyclization of epoxy alcohols catalyzed by a [Co(III)(salen)] complex
Wu, Michael H.,Hansen, Karl B.,Jacobsen, Eric N.
, p. 2012 - 2014 (2007/10/03)
The intramolecular cyclization of epoxy alcohols was catalyzed with excellent regio- and enantiocontrol by a [Co(III)(salen)] complex. High endo selectivity was observed for the enantioselective cyclization of terminal epoxy alcohols [Eq. (a)], while the reaction of meso substrates produced novel cyclic and bicyclic ethers in good yields and high enatiopurity. TBME = tert-butyl methyl ether.
Chiral synthesis via organoboranes. XVI. Boroxazolidones derived from α-amino acids and borinic or boronic esters. A simple procedure for upgrading borinates and boronates to materials of high optical purity
Brown, Herbert C.,Gupta, Ashok K.
, p. 73 - 82 (2007/10/02)
The synthesis of boron heterocycles from borinic and boronic esters with α-amino acids was explored as a means of upgrading the optical purities of intermediates from asymmetric hydroboration.B-Methoxy-9-borabicyclononane, methyl dicyclohexylborinate and (+)- and (-)-methyl diisopinocampheylborinate react with various α-amino acids to form the corresponding crystalline chelates.Recrystallization of the chelates derived from methyl trans-2-phenylcyclopentylisopinocampheylborinate of 85percent ee with l-phenylalanine, methyl isopinocampheyl-exo-norbornylborinate of 83percent ee with l-proline and both optical isomers of methyl diisopinocampheylborinate of 92percent ee with l-proline yield the corresponding products with optical purities approaching 100percent ee.Dimethyl cyclopentylboronate, dimethyl exo-norbornylboronate and dimethyl isopinocampheylboronate upon treatment with iminodiacetic acid and N-methyliminodiacetic acid form the corresponding bicyclic boronates.Recrystallization of the chelate derived from diethyl 3-tetrahydropyranylboronate and iminodiacetic acid yields a product of essentially 100percent ee.Consequently formation of boroxazolidones of asymmetric hydroboration products provides one possible route to upgrade such products to materials of high optical purity.
Hydroboration. 82. Asymmetric Hydroboration of Representative Cis Disubstituted and Heterocyclic Olefins with Dicaranylboranes of High Enantiomeric Purity
Brown, Herbert C.,Prasad, J.V.N. Vara,Zaidlewicz, Marek
, p. 2911 - 2916 (2007/10/02)
Dicaranylboranes (2-dIcr2BH and 4-dIcr2BH) are prepared by the reaction of borane-methyl sulfide with (+)-2- and (+)-3-carene, respectively.The reagents readily hydroborate prochiral cis disubstituted olefins to yield the corresponding trialkylboranes, which, upon oxidation, give chiral alcohols of 77-93percent ee (2-dIcr2BH) and 36-75percent ee (4-dIcr2BH). 2-dIcr2BH and 4-dIcr2BH convert cis-alkenes into alcohols of the opposite absolute configurations.The trialkylborane hydroboration products, upon treatment with benzaldehyde, eliminate (+)-2- or (+)-3-carene, providing the corresponding benzyl boronates.Thus, the chiral auxiliary is recovered, and the alcohols can be obtained by oxidation of the benzyl boronates or alternatively by their hydrolysis and oxidation of the boronic acids.Trans disubstituted and trisubstituted olefins are hydroborated by both reagents with partial elimination of (+)-2- or (+)-3-carene and low asymmetric induction.On the other hand, the hydroboration-oxidation of five-membered ring heterocyclic olefins proceeds rapidly to give the corresponding chiral alcohols of 11-85percent ee.Convenient procedures for the preparation of high purity (+)-2- and (+)-3-carene are described.
Chiral Synthesis via Organoboranes. 6. Hydroboration. 74. Asymmetric Hydroboration of Representative Heterocyclic Olefins with Diisopinocamphenylborane. Synthesis of Heterocyclic Boronates and Heterocyclic Alcohols of Very High Enantiomeric Purity
Brown, Herbert C.,Prasad, J. V. N. Vara
, p. 2049 - 2054 (2007/10/02)
The hydroboration of representative heterocycles bearing an endocyclic double bond with diisopinocamphenylborane (Ipc2BH) was investigated systematically to establish the asymmetric induction achieved in the reaction.The hydroboration of 2,3- and 2,5-dihydrofurans, 1,4-epoxy-1,4-dihydronaphthalene, and 2,3-dihydrothiophene with Ipc2BH in THF at -25 deg C proceeded very cleanly to afford the corresponding trialkylboranes.These trialkylboranes readily eliminate α-piene on treatment with acetaldehyde to give the corresponding boronates, R*B(OR)2.Oxidation afforded in high yields the corresponding heterocyclic alcohols of 100percent ee.N-(Carbobenzyloxy)-3-pyrroline could not be hydroborated with Ipc2BH below 0 deg C.The oxidation of the intermediate trialkylborane gave N-(carbobenzyloxy)-3-pyrrolidinol in 89percent ee.Similarly, six-membered heterocyclic olefins, namely, 3,4-dihydropyran and 3,4-dihydrothiapyran, were hydroborated with Ipc2BH at 0 deg C in THF.The resulting trialkylboranes on treatment with acetaldehyde followed by oxidation yielded 3-hydroxytetrahydropyran and 3-hydroxytetrahydrothiapyran of 83percent and 66percent ee, respectively.N-(Carbobenzyloxy)-1,2,3,6-tetrahydropyridine, hydroborated with Ipc2BH at 0 deg C, followed by oxidation, afforded the corresponding 3- and 4-piperidinols in an 85:15 ratio.The asymmetric induction achieved during hydroboration was 70percent.The five-membered heterocyclic boronates of very high optical purity, highly versatile synthetic intermediates, were isolated both as the diethyl and the diethanolamine esters.
A Stereochemical Test for Ether-Oxygen Participation and Oxonium Ion Formation in thr Acetolysis of 3-Tetrahydropyranyl Brosylate
Dunkin, Ian R.,Paul, Alan J.,Suckling, Colin J.,Valente, Edward,Wood, Hamish C. S.
, p. 1323 - 1326 (2007/10/02)
Optically active tetrahydropyran-3-ol was obtained by the horse liver alcohol dehydrogenase (HLADH)-catalysed reduction of tetrahydropyran-3-one, and the corresponding brosylate was prepared.Acetolysis of the optically active brosylate gave racemic 3-tetrahydropyranyl acetate as well as varying amounts of racemic tetrahydropyran-3-ol.Within experimental error, the polarimetric rate of acetolysis was the same as the previously measured tetrimetric rate.The results provide no support for the intermediacy of a bicyclic oxonium ion in the acetolysis of 3-tetrahydropyranyl brosylate.