100858-32-0Relevant articles and documents
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 (1986)
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.
Enantioselective reduction of heterocyclic ketones with low level of asymmetry using carrots
Machado, Naira Vieira,Omori, álvaro Takeo
, p. 475 - 480 (2021)
A whole spectrum of biocatalysts for asymmetric reduction of prochiral ketones is well known including the Daucus carota root. However, this type of reaction is still challenging when pro-chiral ketones present low level of asymmetry, like heterocyclic ketones. In this work, 4,5-dihydro-3(2H)-thiophenone (1), 2-methyltetrahydrofuran-3-one (2), N-Boc-3-pyrrolidinone (3), 1-Z-3-pyrrolidinone (4) and 1-benzyl-3-pyrrolidinone (5) were studied in order to obtain the respective enantioselective heterocyclic secondary alcohols. Except for 5, the corresponding alcohols were obtained in high values of conversion and with high selectivity. In order to circumvent the low isolated yield of the corresponding chiral alcohol from 2, we observed that the use of carrots in the absence of water is feasible. Addition of co-solvents was needed to the water-insoluble ketones 3 and 4. Comparatively, baker’s yeast was used for bio reductions of 1, 3 and 4. And in terms of conversion, selectivity and work-up, the use of carrots were a more efficient biocatalyst, as well as a viable method for obtaining 5-member heterocyclic secondary alcohols.
Ultrafast chiral separations for high throughput enantiopurity analysis
Barhate, Chandan L.,Joyce, Leo A.,Makarov, Alexey A.,Zawatzky, Kerstin,Bernardoni, Frank,Schafer, Wes A.,Armstrong, Daniel W.,Welch, Christopher J.,Regalado, Erik L.
supporting information, p. 509 - 512 (2017/01/13)
Recent developments in fast chromatographic enantioseparations now make high throughput analysis of enantiopurity on the order of a few seconds achievable. Nevertheless, routine chromatographic determinations of enantiopurity to support stereochemical investigations in pharmaceutical research and development, synthetic chemistry and bioanalysis are still typically performed on the 5-20 min timescale, with many practitioners believing that sub-minute enantioseparations are not representative of the molecules encountered in day to day research. In this study we develop ultrafast chromatographic enantioseparations for a variety of pharmaceutically-related drugs and intermediates, showing that sub-minute resolutions are now possible in the vast majority of cases by both supercritical fluid chromatography (SFC) and reversed phase liquid chromatography (RP-LC). Examples are provided illustrating how such methods can be routinely developed and used for ultrafast high throughput analysis to support enantioselective synthesis investigations.
Sulfonylcarbamate as a versatile and unique hydroxy-protecting group: A protecting group stable under severe conditions and labile under mild conditions
Manabe, Shino,Yamaguchi, Masanori,Ito, Yukishige
supporting information, p. 8332 - 8334 (2013/09/23)
The sulfonylcarbamate group is a unique hydroxyl protecting group. In contrast to typical acyl protecting groups, the sulfonylcarbamate group is stable under harsh basic conditions, while showing labile behavior under mild basic conditions. Its compatibility with other hydroxyl protecting groups and application to carbohydrate chemistry is demonstrated.
