4352-42-5Relevant academic research and scientific papers
Mild and Selective Rhodium-Catalyzed Transfer Hydrogenation of Functionalized Arenes
Wang, Yuhan,Chang, Zhiqian,Hu, Yan,Lin, Xiao,Dou, Xiaowei
supporting information, p. 1910 - 1914 (2021/03/08)
Diboron-mediated rhodium-catalyzed transfer hydrogenation of functionalized arenes is reported. In addition to good functional group tolerance, the reaction features operational simplicity and controllable chemoselectivity. The general applicability of this procedure is demonstrated by the selective hydrogenation of a range of arenes, including functionalized benzenes, biphenyls, and polyaromatics.
Selective Hydrogenation and Hydrodeoxygenation of Aromatic Ketones to Cyclohexane Derivatives Using a Rh&at;SILP Catalyst
Bordet, Alexis,Emondts, Meike,Leitner, Walter,Moos, Gilles
supporting information, p. 11977 - 11983 (2020/06/02)
Rhodium nanoparticles immobilized on an acid-free triphenylphosphonium-based supported ionic liquid phase (Rh&at;SILP(Ph3-P-NTf2)) enabled the selective hydrogenation and hydrodeoxygenation of aromatic ketones. The flexible molecular approach used to assemble the individual catalyst components (SiO2, ionic liquid, nanoparticles) led to outstanding catalytic properties. In particular, intimate contact between the nanoparticles and the phosphonium ionic liquid is required for the deoxygenation reactivity. The Rh&at;SILP(Ph3-P-NTf2) catalyst was active for the hydrodeoxygenation of benzylic ketones under mild conditions, and the product distribution for non-benzylic ketones was controlled with high selectivity between the hydrogenated (alcohol) and hydrodeoxygenated (alkane) products by adjusting the reaction temperature. The versatile Rh&at;SILP(Ph3-P-NTf2) catalyst opens the way to the production of a wide range of high-value cyclohexane derivatives by the hydrogenation and/or hydrodeoxygenation of Friedel–Crafts acylation products and lignin-derived aromatic ketones.
A novel lipase enzyme panel exhibiting superior activity and selectivity over lipase B from Candida antarctica for the kinetic resolution of secondary alcohols
O'Neill, Maeve,Beecher, Denis,Mangan, David,Rowan, Andrew S.,Monte, Agnieszka,Sroka, Stefan,Modregger, Jan,Hundle, Bhupinder,Moody, Thomas S.
experimental part, p. 583 - 586 (2012/08/13)
A novel, commercially available lipase enzyme panel performing kinetic bioresolutions of a number of secondary alcohols is reported. The secondary alcohols that have been chosen are known from the literature to be particularly challenging substrates to resolve. Following initial screening, four co-solvents were investigated for each lead enzyme in an effort to assess their tolerance to common organic solvents. The superiority of these novel enzymes over lipase B from Candida antarctica (CALB) has been demonstrated.
Borenium ion catalyzed hydroboration of alkenes with N-heterocyclic carbene-boranes
Prokofjevs, Aleksandrs,Boussonniere, Anne,Li, Linfeng,Bonin, Helene,Lacote, Emmanuel,Curran, Dennis P.,Vedejs, Edwin
supporting information; experimental part, p. 12281 - 12288 (2012/09/22)
Treatment of alkenes such as 3-hexene, 3-octene, and 1-cyclohexyl-1-butene with the N-heterocyclic carbene (NHC)-derived borane 2 and catalytic HNTf 2 (Tf = trifluoromethanesulfonyl (CF3SO2)) effects hydroboration at room temperature. With 3-hexene, surprisingly facile migration of the boron atom from C(3) of the hexyl group to C(2) was observed over a time scale of minutes to hours. Oxidative workup gave a mixture of alcohols containing 2-hexanol as the major product. A similar preference for the C(2) alcohol was observed after oxidative workup of the 3-octene and 1-cyclohexyl-1-butene hydroborations. NHC-borenium cations (or functional equivalents) are postulated as the species that accomplish the hydroborations, and the C(2) selective migrations are attributed to the four-center interconversion of borenium cations with cationic NHC-borane-olefin π-complexes.
Study of the enantioselectivity of the CAL-B-catalysed transesterification of α-substituted α-propylmethanols and α-substituted benzyl alcohols
Garcia-Urdiales, Eduardo,Rebolledo, Francisca,Gotor, Vicente
, p. 3047 - 3052 (2007/10/03)
A study of the enantioselectivity exhibited by the lipase B from Candida antarctica in the transesterification of different α-substituted α-propylmethanols with vinyl acetate is shown. The best results are obtained when the large-sized (L) substituent of the alcohol is either a phenyl group or more especially a cyclohexyl group, although the reaction rates are lower than when linear or slightly branched groups are present. It is also found that ramification at the β-position of the L substituent has a deleterious effect on both lipase activity and enantioselectivity. Moreover, some α-substituted benzyl alcohols bearing medium-sized (M) substituents larger than an ethyl and smaller than a propyl group are resolved by means of this methodology with moderate-good enantioselectivities (E=46-57) and similar reaction rates.
A Novel Addition-Rearrangement of O-(1-Benzotriazolylaklyl)oximes with Organolithium Reagents. Convenient Non-oxidative Conversions of Aldehydes into Amides
Katritzky, Alan R.,Jiang, Jinlong,Greenhill, John V.,Steel, Peter J.
, p. 3055 - 3060 (2007/10/02)
Condensation of an aldehyde, an oxime and benzotriazole gives an O-(1-benzotriazolylalkyl)oxime which undergoes an addition-rearrangement on treatment with an organolithium reagent.This reaction provides a novel non-oxidative method for the transformation of aldehydes into amides which has afforded several new N-monosubstituted amides with crowded structures.Grignard reactions of the O-(1-benzotriazolylalkyl)oximes give alcohols as the major products.
Selective Reductions. 45. Asymmetric Reduction of Prochiral Ketones by Iso-2-methyl, Iso-2-ethyl-, and apopinocampheyl>-tert-butylchloroboranes. Evidence for a Major Influence of the Steric Requirements of the 2-Substituent on the Efficiency of Asymmetric Redu.
Brown, Herbert C.,Ramachandran, P. Veeraraghavan
, p. 4504 - 4511 (2007/10/02)
The asymmetric reduction of prochiral aliphatic ketones with chiral organylboranes has not yet given desirable results although considerable success has been achieved for the reduction of prochiral aralkyl and related ketones.We have now developed more efficient chiral reducing agents for aliphatic ketones following a strategy based on a tentative hypothesis that the steric requirements of the substituent at the 2-position of apopinene may be a major factor in achieving successful asymmetric reduction.The adduct of nopol benzyl ether and tert-butylchloroborane was prepared and characterized.This compound reduces prochiral ketones to the product alcohols in very high enantiomeric excess.For example, 3-methyl-2-butanone is reduced, in THF, 0.5 M, at room temperature, to the R alcohol in 89percent ee.Cyclohexyl methyl ketone is reduced to the alcohol in 96percent ee.Cyclohexyl ethyl ketone, cyclohexyl n-propyl ketone, and cyclopentyl methyl ketone are all reduced to the corresponding R alcohols in 85percent, 83percent, and 81percent ee, respectively. 2-Cyclohexen-1-one is reduced to (S)-2-cyclohexen-1-ol in 88percent ee.Finally, 2-octanone is converted to (R)-2-octanol in 40percent ee.Unfortunately, these reductions are very slow, requiring 2 to 14 days, or more.The slowness of the reaction is attributed to the coordination of the ether oxygen to the boron atom.The higher optical yields achieved over those realized previously with the related isopinocampheyl-tert-butylchloroborane are attributed to the greater steric requirement of the (benzyloxy)ethyl group as compared to the methyl group of the α-pinene unit.On this basis, the corresponding derivative, (iso-2-ethylapopinocampheyl)-tert-butylchloroborane was synthesized in the hope that the rates would be higher, because of the absence of a coordinating ether linkage, while the optical yields would be comparable, because of the larger steric requirements of the 2-ethyl substituent.Indeed, the rates are considerably faster and the enantiomeric excesses achieved are almost comparable. 3-Methyl-2-butanone is reduced, in THF, 0.5 M, at room temperature, in 16 h to an alcohol of 84percent ee.Cyclohexyl methyl ketone, cyclohexyl ethyl ketone, cyclohexyl n-propyl ketone, and cyclopentyl methyl ketone are all reduced to the corresponding R alcohols in 90percent, 73percent, 73percent, and 72percent ee, respectively. 2-Octanone is reduced to (R)-2-octanol in 33percent ee.For comparison, the reductions of the same ketones with Ipc-t-BuBCl at room temperature and Ipc2BCl at -25 deg C were carried out. dIpc-t-BuBCl reduces (25 deg C) 3-methyl-2-butanone, cyclohexyl methyl ketone, cyclohexyl ethyl ketone, cyclohexyl n-propyl ketone, and cyclopentyl methyl ketone to the corresponding S alcohols in 37percent, 48percent, 53percent, 50percent, and 26percent ee, respectively, whereas dIpc2BCl reduces (-25 deg C) the same ketones to the corresponding S alcohols in 32percent, 26percent, 23percent, 38percent, and 45percent ee, respectively.This study supports the conclusion that the chiral outcome in reduction with reagents derived from pinanyl derivatives is influenced by the steric requirements of the group at position 2 of ap.
The Reaction of the Highly Functionalized Copper Reagents RCu(CN)ZnI.BF3 with Aldehydes
Yeh, Ming Chang P.,Knochel, Paul,Santa, Leroy E.
, p. 3887 - 3890 (2007/10/02)
The new copper reagent RCu(CN)ZnI2, which may contain important functional groups like the ester nitrile, enoate or imide group, react in the presence of BF3.OEt2 with aldehydes to afford polyfunctional secondary alcohols in googd yields (68-93percent).
