- Manganese-catalyzed homogeneous hydrogenation of ketones and conjugate reduction of α,β-unsaturated carboxylic acid derivatives: A chemoselective, robust, and phosphine-free in situ-protocol
-
We communicate a user-friendly and glove-box-free catalytic protocol for the manganese-catalyzed hydrogenation of ketones and conjugated C[dbnd]C[sbnd]bonds of esters and nitriles. The respective catalyst is readily assembled in situ from the privileged [Mn(CO)5Br] precursor and cheap 2-picolylamine. The catalytic transformations were performed in the presence of t-BuOK whereby the corresponding hydrogenation products were obtained in good to excellent yields. The described system offers a brisk and atom-efficient access to both secondary alcohols and saturated esters avoiding the use of oxygen-sensitive and expensive phosphine-based ligands.
- Topf, Christoph,Vielhaber, Thomas
-
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- BiCl3-Facilitated removal of methoxymethyl-ether/ester derivatives and DFT study of -O-C-O- bond cleavage
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A simple method for the cleavage of methoxymethyl (MOM)-ether and ester derivatives using bismuth trichloride (BiCl3) is described. The alkyl, alkenyl, alkynyl, benzyl and anthracene MOM ether derivatives, as well as MOM esters of both aliphatic and aromatic carboxylic acids, were deprotected in good yields. To better understand the molecular roles of BiCl3and water for MOM cleavage, two possible binding pathways were investigated using the density functional theory (DFT) method. The theoretical results indicate the differential initial binding site preferences of phenolic and alcoholic MOM substrates to the Bi atom and suggest that water plays a key role in facilitating the cleavage of the MOM group.
- Pacherille, Angela,Tuga, Beza,Hallooman, Dhanashree,Dos Reis, Isaac,Vermette, Mélodie,Issack, Bilkiss B.,Rhyman, Lydia,Ramasami, Ponnadurai,Sunasee, Rajesh
-
supporting information
p. 7109 - 7116
(2021/05/03)
-
- A Practical and Stereoselective In Situ NHC-Cobalt Catalytic System for Hydrogenation of Ketones and Aldehydes
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Homogeneous catalytic hydrogenation of carbonyl groups is a synthetically useful and widely applied organic transformation. Sustainable chemistry goals require replacing conventional noble transition metal catalysts for hydrogenation by earth-abundant base metals. Herein, we report how a practical in situ catalytic system generated by easily available pincer NHC precursors, CoCl2, and a base enabled efficient and high-yielding hydrogenation of a broad range of ketones and aldehydes (over 50 examples and a maximum turnover number [TON] of 2,610). This is the first example of NHC-Co-catalyzed hydrogenation of C=O bonds using flexible pincer NHC ligands consisting of a N-H substructure. Diastereodivergent hydrogenation of substituted cyclohexanone derivatives was also realized by fine-tuning of the steric bulk of pincer NHC ligands. Additionally, a bis(NHCs)-Co complex was successfully isolated and fully characterized, and it exhibits excellent catalytic activity that equals that of the in-situ-formed catalytic system. Catalytic hydrogenation is a powerful tool for the reduction of organic compounds in both fine and bulk chemical industries. To improve sustainability, more ecofriendly, inexpensive, and earth-abundant base metals should be employed to replace the precious metals that currently dominate the development of hydrogenation catalysts. However, the majority of the base-metal catalysts that have been reported involve expensive, complex, and often air- and moisture-sensitive phosphine ligands, impeding their widespread application. From a mixture of the stable CoCl2, imidazole salts, and a base, our newly developed catalytic system that formed easily in situ enables efficient and stereoselective hydrogenation of C=O bonds. We anticipate that this easily accessible catalytic system will create opportunities for the design of practical base-metal hydrogenation catalysts. A practical in situ catalytic system generated by a mixture of easily available pincer NHC precursors, CoCl2, and a base enabled highly efficient hydrogenation of a broad range of ketones and aldehydes (over 50 examples and up to a turnover number [TON] of 2,610). Diastereodivergent hydrogenation of substituted cyclohexanone derivatives was also realized in high selectivities. Moreover, the preparation of a well-defined bis(NHCs)-Co complex via this pincer NHC ligand consisting of a N-H substructure was successful, and it exhibits equally excellent catalytic activity for the hydrogenation of C=O bonds.
- Zhong, Rui,Wei, Zeyuan,Zhang, Wei,Liu, Shun,Liu, Qiang
-
supporting information
p. 1552 - 1566
(2019/06/14)
-
- Cerium-free Luche reduction directed by rehydrated alumina
-
A 1,2-regioselective reduction of α,β-unsaturated ketones to their corresponding allylic alcohols is accomplished with NaBH4 in the presence of acidic activated alumina rehydrated to the Brockmann II grade by adding 3 % w/w water. The substrate scope includes eight ketones reduced in high regio- and diastereoselectivity to their corresponding allylic alcohols. This is the first example of the strategy of systematically tuning the surface chemistry of alumina via partial rehydration in order to modulate selectivity in a reaction. Alumina is an appealing alternative to the common Luche reduction additive, CeCl3, from the perspective of cost and procedural simplicity.
- Jones-Mensah, Ebenezer,Nickerson, Leslie A.,Deobald, Jackson L.,Knox, Hailey J.,Ertel, Alyssa B.,Magolan, Jakob
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p. 3748 - 3753
(2016/06/06)
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- Eco-friendly stereoselective reduction of α,β-unsaturated carbonyl compounds by Er(OTf)3/NaBH4 in 2-MeTHF
-
An operationally simple and environmentally benign catalytic procedure has been developed to selectively reduce different α,β-unsaturated ketones. The corresponding allylic alcohols are obtained with high chemo- and diastereoselectivity using Er(OTf)3 and NaBH4 in 2-MeTHF. This protocol reduces the amount of catalyst and NaBH4 needed, compared to classical procedures and the stages of extraction/purification are carried out in aqueous solutions avoiding the use of toxic solvents. Taking into account that Er(OTf)3 can be considered even less toxic than table salt and the 'greenness' of 2-MeTHF as a solvent, the system Er(OTf)3/2-MeTHF can be proposed as a cheap, efficient, and environmentally sustainable reduction system for the synthesis of allylic alcohols.
- Nardi, Monica,Sindona, Giovanni,Costanzo, Paola,Oliverio, Manuela,Procopio, Antonio
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p. 1132 - 1135
(2015/02/19)
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- Nickel-Catalyzed Regioselective Reductive Cross-Coupling of Aryl Halides with Polysubstituted Allyl Halides in the Presence of Imidazolium Salts
-
The nickel-catalyzed direct reductive cross-coupling of aryl halides with readily accessible polysubstituted allyl halides provides an efficient method for preparing diverse allylated arenes under mild conditions. Both allyl bromides and allyl chlorides are compatible with the transformation.
- Zhang, Zhan,Xu, Lijun,Chen, Zhengkai,Liu, Zhubo,Miao, Maozhong,Song, Jinyu,Ren, Hongjun
-
supporting information
p. 2784 - 2788
(2015/12/18)
-
- Chemoselective reduction of carbonyl compounds to alcohols with co-doped ammonia borane
-
Chemoselective reduction of various carbonyl compounds to alcohols with Co-doped ammonia borane was investigated in the present work. It was observed that Co-doped ammonia borane exhibited much better performance than ammonia borane. The Co-based catalysts could be reused up to four times with a slight decrease in activity. Thus, a mild and efficient method for chemoselective reduction of carbonyl compounds with Co-doped ammonia borane was established. The Co-doped ammonia borane sample was characterized by electron paramagnetic resonance. Electron paramagnetic resonance characterization revealed that Co element in a partially reduced state.
- Huang, Pengmian,Tang, Wenjuan,Tan, Guishan,Zeng, Wenbin,Li, Yuanjian,Zhang, Qinghua,Chen
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p. 8248 - 8250
(2015/02/02)
-
- Hydrogenation of aldehydes and ketones to corresponding alcohols with methylamine borane in neat water
-
GRAPHICAL ABSTRACT Chemoselective hydrogenation of various aldehydes and ketones with methylamine borane (MeAB) in neat water was investigated. MeAB is suitable for green organic reactions, for MeAB is a nontoxic, environmentally benign, and easily handled reagent. Aldehydes were selectively and rapidly hydrogenated in excellent yields (86-97%) for 30 min, but hydrogenation of aromatic ketones needed over 20 h at room temperature because of their poor water solubility and steric hindrance. Thus we investigated polyethylene glycol (PEG400) and acidic cation-exchange D072 resin as catalysts to accelerate the hydrogenation reaction of aromatic ketones and achieved excellent yields within several hours. PEG 400 and D072 resin are both suitable for green organic reactions. The D072 resin was reused up to four times without any significance loss in activity.
- Duan, Yifan,Bai, Ruijiao,Tian, Jun,Chen, Ligong,Yan, Xilong
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p. 2555 - 2564
(2014/08/05)
-
- Selective reduction of organic compounds with Al- trifluoromethanesulfonyldiisobutylalane. Comparison of its reactivity with Al-methanesulfonyldiisobutylalane
-
The new MPV type reagent, Al-trifluoromethanesulfonyldiisobutylalane (DIBAO3SCF3), has been prepared and its reducing characteristics in the reduction of selected organic compounds containing representative functional groups have been examined, and compared its reactivity with that of Al-methanesulfonyldiisobutylalane (DIBAO3SCH 3) in order to understand the fluorine-substituent effect on its reactivity. In general, the reactivity of DIBAO3SCF3 appears to be much higher than that of DIBAO3SCH3, apparently due to the acidity increase by the electron-withdrawing fluorine-substituent. The reagent reduced aldehydes and ketones readily, but showed a perfect selectivity in the reduction of α,β-unsaturated aldehydes and ketones to produce the corresponding allylic alcohols in an absolutely 100% purity. In addition, the reagent achieved the regioselective cleavage of phenyl-or/and alkyl-substituted epoxides to the less substituted alcohols in a perfect regioselectivity. Moreover, the reagent also showed an high stereoselectivity in the reduction of substituted cycloalkanones to produce the thermodynamically more stable alcohol epimers exclusively.
- Cha, Jin Soon
-
experimental part
p. 219 - 224
(2011/11/06)
-
- Reductive coupling of carbonyl compounds promoted by cobalt or titanium nanoparticles
-
The reaction of a series of aldehydes and ketones with readily prepared cobalt or titanium nanoparticles, under mild reaction conditions, led to the obtention of different reductive dimerization products depending on the nature of the transition metal used. Cobalt nanoparticles (CoNPs) allowed the selective transformation of the starting carbonyl compounds into vicinal diols, whereas the reaction promoted by titanium nanoparticles (TiNPs) led to the formation of the corresponding alkenes. In this last case, the use of trimethylsilyl chloride (TMSCl) as additive, at 0 °C, also allowed the obtention of vicinal diols after acidic aqueous work-up. ARKAT-USA, Inc.
- Nador, Fabiana,Mascaro, Evangelina,Castro, Melisa,Vitale, Cristian,Radivoy, Gabriel
-
experimental part
p. 312 - 326
(2011/06/17)
-
- Selective reduction of organic compounds with Al- methanesulfonyldiisobutylalane
-
The new MPV type reagent, Al-methanesulfonyldiisobutylalane (DIBAO 3SCH3), has been prepared and its reducing characteristics in the reduction of selected organic compounds containing representative functional groups have been examined in order to find out a new reducing system with high selectivity in organic synthesis. In general, the reagent is extremely mild, showing only reactivity toward aldehydes, ketones and epoxides. The reagent exhibits a unique reducing applicability in organic synthesis. Thus, the reagent can achieve a clean 1,2-reduction of α,β-unsaturated aldehydes and ketones to produce the corresponding allylic alcohols in 100% purity. In addition, the reagent shows an excellent regioselectivity in the ring-opening reaction of epoxides. Finally, DIBAO3SCH3 shows a high stereo-selectivity in the reduction of cyclic ketones to produce the thermodynamically more stable epimers exclusively.
- Cha, Jin Soon,Noh, Minyeong
-
experimental part
p. 840 - 844
(2010/10/21)
-
- Asymmetric hydrogenation of heteroaromatic ketones and cyclic and acyclic enones mediated by Cu(I)-chiral diphosphine catalysts
-
Copper(I)-catalyzed asymmetric hydrogenation of heteroaromatic ketones, cyclic and acyclic enones is reported. The choice of the chiral diphosphine ligand highly influenced enantiose-lectivity as well as chemoselectivity. Highly enantioselective hydrogenation of ortho-substituted heteroaromatic ketones was achieved using BDPP as the ligand. In the 1,2-selective hydrogenation of acylic enone, SEGPHOS gave higher enantioselectivity than BDPP. On the other hand, the bulky ligand DTBM-SEGPHOS had a 1,4-selective nature, leading to the first highly 1,4-selective and enantioselective hydrogenation of cyclic enones.
- Shimizu, Hideo,Nagano, Takuto,Sayo, Noboru,Saito, Takao,Ohshima, Takashi,Mashima, Kazushi
-
scheme or table
p. 3143 - 3146
(2010/03/24)
-
- Bis(imino)pyridine iron complexes for aldehyde and ketone hydrosilylation
-
(Chemical Equation Presented) Bis(imino)pyridine iron dinitrogen and dialkyl complexes are well-defined precatalysts for the chemo- and regioselective reduction of aldehydes and ketones. Efficient carbonyl hydrosilylation is observed at low (0.1-1.0 mol %) catalyst loadings and with 2 equiv of either PhSiH3 or Ph2SiH2, representing one of the most active iron-catalyzed carbonyl reductions reported to date.
- Tondreau, Aaron M.,Lobkovsky, Emil,Chirik, Paul J.
-
supporting information; experimental part
p. 2789 - 2792
(2009/05/27)
-
- Synthesis of chiral odoriferous oxy-derivatives of 1,5,5- trimethylcyclohexene
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Ten racemic and ten enantiomeric pairs of odoriferous compounds, mainly esters, were obtained from isophorone. The starting material, isophorone was reduced to racemic isophorol, which was resolved in pure enantiomers via the lipase catalyzed esterification. The next steps of syntheses, orthoacetic Claisen rearrangement, reduction of esters, esterification of alcohols or their oxidation were carried out with the racemic and enantiomerically enriched (above 98% ee) compounds. The propionates of isophorol (7, 7a, 7b) and 2-(1,5,5-trimethyl-2-cyclohexen-1-yl)ethanol (10, 10a, 10b) possess the most valuable odoriferous properties, useful for cosmetic and food industries.
- Winska,Wawrzenczyk
-
p. 1887 - 1897
(2008/09/18)
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- Use of achiral (diphosphine)RuCl2(diamine) precatalysts as a practical alternative to sodium borohydride for ketone reduction
-
Stoichiometric sodium borohydride is frequently used in the chemoselective reduction of ketones to racemic secondary alcohols. Catalytic homogeneous hydrogenation using (diphosphine)RuCl2(diamine) complexes provides a practical and economic alternative. A range of substrates were investigated and the optimum precatalyst identified in each case. Norcamphor was reduced with high diastereoselectivity using (Ph3P)2-RuCl 2(en); (E)-4-phenylbut-3-en-2-one was reduced with good chemoselectivity, and acetophenone was hydrogenated very efficiently using the same precatalyst. Isophorone and 3-dimethylaminopropiophenone were effectively hydrogenated using (dppf)RuCl2(en).
- De Koning, Pieter D.,Jackson, Mark,Lennon, Ian C.
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p. 1054 - 1058
(2012/12/23)
-
- Solvent-free reduction of aldehydes and ketones using solid acid-activated sodium borohydride
-
A simple and convenient procedure for the reduction of aldehydes and ketones with sodium borohydride activated by solid acids such as boric acid, benzoic acid, and p-toluenesulfonic acid monohydrate under solvent-free conditions is described.
- Cho, Byung Tae,Kang, Sang Kyu,Kim, Min Sung,Ryu, Soo Ryeon,An, Duk Keun
-
p. 8164 - 8168
(2007/10/03)
-
- A radical cyclisation based cyclopentenone annulation of allyl alcohols
-
A four-step cyclopentenone annulation reaction of allylic alcohols employing a 5-exo-trig radical cyclisation reaction of mixed allyl methyl ketals of bromoacetone as the key step is described. The annulated product 12b obtained from 2,3-dimethylcyclohexenol has been further elaborated into (±)-epibakkenolides employing a 5-exo-dig radical cylisation reaction based α-spiro-β-methylene-γ-butyrolactone annulation methodology.
- Srikrishna,Viswajanani,Sattigeri
-
p. 2975 - 2983
(2007/10/03)
-
- Chemoselective Hydrogen Transfer Reduction of Unsaturated Ketones to Allylic Alcohols with Solid Zr and Hf Catalysts
-
α,β-Unsaturated ketones were reduced to allylic alcohols with high chemo- and diastereoselectivity, using Zr and Hf compounds heterogenised on mesoporous molecular sieves.
- De Bruyn, Mario,De Vos, Dirk E.,Jacobs, Pierre A.
-
p. 1120 - 1125
(2007/10/03)
-
- A novel, efficient, and highly selective O-Bn bond cleavage reaction via a rare K-induced electron transfer process
-
A new, efficient and highly selective deprotective method of both benzyl and benzylidene groups for protection of monohydroxyl and dihydroxyl, respectively, has been developed by using the system K-t-BuNH2-t-BuOH-18-crown-6. This method is valu
- Shi, Lei,Wu, Jiong Xia,Fu, Min Zhang,Yong, Qiang Tu
-
p. 1505 - 1507
(2007/10/03)
-
- Reductions of α,β-unsaturated ketones by NaBH4 or NaBH4 + CoCl2: Selectivity control by water or by aqueous micellar solutions
-
Operationally simple and environmentally benign procedures have been developed to selectively reduce different α,β-unsaturated ketones, 4,4- dimethylcyclohex-2-ene-1-one (1), isophorone (2), benzylideneacetone (3), chalcone (4) by NaBH4 or by the system NaBH4 + COCl2. Alternative reaction media to the extensively used MeOH have been explored, and new procedures take advantage of the acceleration and chemoselectivity induced by water or by aqueous micellar solutions. It was possible to selectively and quantitatively afford pure products of 1,2 and of 1,4 reduction as well as the totally reduced compounds (yield and selectivity > 90%) by simple changes in the experimental conditions.
- Aramini, Andrea,Brinchi, Lucia,Germani, Raimondo,Savelli, Gianfranco
-
p. 1793 - 1797
(2007/10/03)
-
- Highly regio- and stereoselective reductions of carbonyl compounds in aqueous glycosidic media
-
Highly regioselective reductions of α,β-unsaturated ketones to the corresponding allylic alcohols were performed in essentially quantitative yields in aqueous media containing either glycosidic surfactants or amphiphilic carbohydrates. Reductions of cyclohexanones and cyclohexenones lead under the same conditions, stereoselectively to reduced compounds bearing an equatorial alcohol function. Hydrophobic interactions between amphiphilic carbohydrates and lipophilic substrates were modelized and should account for the observed stereodifferentiation.
- Denis, Cecile,Laignel, Benoit,Plusquellec, Daniel,Le Marouille, Jean-Yves,Botrel, Alain
-
-
- Aminoborohydrides. 4. The Synthesis and Characterization of Lithium Aminoborohydrides: A New Class of Powerful, Selective, Air-Stable Reducing Agents
-
Lithium aminoborohydrides (LiABH3) are a new class of powerful yet selective reducing agents that reproduce, in air, virtually all of the transformations for which lithium aluminum hydrides is now used.LiABH3's can be readily prepared as solids or generated in situ, are nonpyrophoric, and liberate hydrogen only slowly with protic solvents above pH 4.LiABH3's can be handled in dry air as easily as sodium borohydride and retain their chemical activity for at least 6 month when stored under nitrogen or dry air at 25 deg C.LiABH3's can be synthesized from any primary or secondary amine, thus allowing control of the steric and electronic environment of these reagents.
- Fisher, Gary B.,Fuller, Joseph C.,Harrison, John,Alvarez, Salvador G.,Burkhardt, Elizabeth R.,et al.
-
p. 6378 - 6385
(2007/10/02)
-
- Organic reactions in a solid matrix-VII sodium on alumina: A convenient reagent for reduction of ketones, esters and oximes
-
Sodium dispersed on alumina is described and evaluated as a convenient off-the-shelf reagent (in a wax-coated form) for reduction of ketones, esters and oximes. While isopropanol is the preferred proton donor for the reduction of ketones and oximes, t-butanol is the alcohol of choice for the reduction of esters.
- Singh, Satendra,Dev, Sukh
-
p. 10959 - 10964
(2007/10/02)
-
- Diisopropoxytitanium(III) Tetrahydroborate: A Highly Useful Reagent for the Remarkably Selective 1,2-Reduction of α,β-Unsaturated Carbonyl Compounds
-
Diisopropoxytitanium(III) tetrahydroborate formed by the reaction of diisopropoxytitanium dichloride and benzyltriethylammonium borohydride (1:2) reacts with a variety of α,β-unsaturated carbonyl compounds in dichloromethane (-20 deg C) very readily to yield exclusively the corresponding allylic alcohols in excellent yields.
- Ravikumar, K. S.,Baskaran, Sundarababu,Chandrasekaran, Srinivasan
-
p. 5981 - 5982
(2007/10/02)
-
- Aminoborohydrides. 2. Regiospecific reductions of α,β-unsaturated carbonyl compounds with lithium pyrrolidinoborohydride. A facile conversion of α,β-unsaturated aldehydes and ketones to the corresponding allylic alcohols in high purity
-
Lithium aminoborohydrides (LiABH3), obtained by the reaction of n-BuLi with amine-boranes, are powerful reducing agents for the reduction α,β-unsaturated aldehydes and ketones to the corresponding allylic alcohols. Thus, lithium pyrrolidinoborohydride (LiPyrrBH3) and reduces cinnamaldehyde and cyclohexenone to give exclusively cinnamyl alcohol and 2-cyclohexen-1-ol respectively. This 1,2-reduction appears to be general and ester groups are tolerated. The yield of allylic alcohols from this procedure is essentially quantitative.
- Fuller, Joseph C.,Stangeland, Eric L.,Goralski, Christian T.,Singaram, Bakthan
-
p. 257 - 260
(2007/10/02)
-
- Pyrrolidines and allylic amines from radical-induced cleavage of aziridines
-
Cleavage of α-aziridinylalkyl radicals has been observed; the resulting aminyl radicals react with tributyltin hydride to form amines or clyclise onto appropriately sited alkenes to give pyrrolidines.
- Dickinson, Julia M.,Murphy, John A.
-
p. 1317 - 1326
(2007/10/02)
-
- REDUCTION OF ISOPHORONE WITH SODIUM BOROHYDRIDE: CHANGE IN REGIOSELECTIVITY WITH HYDROTROPES
-
Preferential 1,4-reduction of isophorone by sodium borohydride occurs in the presence of hydrotropes such as polyalkylene glycols.An anomalous effect of temperature was also observed using sodium salicylate as hydrotrope.
- Laxman, Mahalaxmi,Sharma, Man Mohan
-
p. 111 - 117
(2007/10/02)
-
- Synthesis of (+/-)-4'-Hydroxy-γ-ionylideneacetic Acids, Fungal Biosynthetic Intermediates of Abscisic Acid
-
(+/-)-cis and (+/-)-trans-4'-Hydroxy-γ-ionylideneacetic acids (1a and 2a) were synthesized from (+/-)-cis- and (+/-)-trans-4'-acetoxy-γ-cyclocitrals (11a and 11b), respectively, which were obtained by -sigmatropic rearangement of the bromide (9a) prepared from isophorone.Racemic 1a was also synthesized from (+/-)-2,2-dimethyl-4-THPoxy-1-cyclohexanone (14) in 12 steps.
- Oritani, Takayuki,Yamamoto, Hiroshi,Yamashita, Kyohei
-
p. 125 - 130
(2007/10/02)
-
- SELECTIVE REDUCTION OF α,β-UNSATURATED KETONES WITH POTASSIUM TRIPHENYLBOROHYDRIDE
-
Potassium triphenylborohydride is an excellent 1,4-reducing agent for acyclic enones and β-unsubstituted cyclohexenones, and shows a greater tendency for 1,4-reduction than K-Selectride for β-substituted cyclohexenones and aromatic enones.
- Kim, Kwan Eung,Park, Soo Bong,Yoon, Nung Min
-
-
- Meerwein-Ponndorf-Verley-Type Reduction of Dicarbonyl Compounds to Hydroxy Carbonyl Compounds and α,β-Unsaturated Carbonyl Compounds to Allylic Alcohols Catalyzed by Zirconocene and Hafnocene Complexes
-
Group IVA metallocene complexes such as bis(η5-cyclopentadienyl)zirconium dihydrides, Cp2ZrH2 (1), and hafnium dihydrides, Cp2HfH2 (8), catalyze the chemoselective reduction of polycarbonyl compounds to hydroxy carbonyl compounds.For instance, the reduction of keto aldehydes 3-ketobutanal (2g) and 2-phenyl-2-ketoethanal (2h) proceeded selectively at aldehyde group to provide the corresponding hydroxy ketones 3g and 3h in 91percent and 93percent yields, respectively.Under similar conditions, however, cyclohexanediones were easily aromatized to benzenediols.On the other hand, 1 and 8 also catalyze the selective 1,2-reduction of various types of α,β-unsaturated carbonyl compounds, giving the corresponding allylic alcohols in good to excellent yields.Thus, steroidal dicarbonyl compounds, having an enone framework in their molecules Δ4-androstene-3,17-dione (11a) and Δ4-progestene-3,20-dione (11b) were reduced by 1 to 17-hydroxy-Δ4-androsten-3-one (12a) and 20-hydroxy-Δ4-progest-3-one (12b), which are essential human hormones, in 80percent and 67percent yields, respectively.
- Nakano, Tatsuya,Umano, Shigetoshi,Kino, Yoshio,Ishii, Yasutaka,Ogawa, Masaya
-
p. 3752 - 3757
(2007/10/02)
-
- Transmission of Substituent Effects through Unsaturated Systems. Part 6. Kinetics of Reduction of β-Substituted α, β-Unsaturated Ketones with Sodium Borohydride
-
The rate constants for addition of sodium borohydride to 3-substituted 5,5-dimethylcyclohex-2-enones (1), para-substituted 3-phenylcyclohexenones (2), and para-substituted acetophenones (3) have been determined in an alkaline solution (NaOH, 0.025 mol l-1) of water-dioxane (1:1 v/v) at 298 K.The conjugated cyclohexenone systems (1) and (2) undergo exclusive 1,2-reduction in these conditions to produce the corresponding allylic alcohols.The regioselectivity of reduction is discussed.The linear free energy relationships obtained between the rate constants and ?p or ?p+ confirm that these 3-substituted cyclohexenone structures are good models for the investigation of the substituent effects on the reactivity of ethylenic systems.Comparison of reaction constants for the three series leads to the conclusion that, as for borohydride reductions of acetophenone, the cyclohexenone reduction must have a late transition state in the final quarter of the reaction co-ordinate.
- Geribaldi, Serge,Decouzon, Michele,Boyer, Bernard,Moreau, Claude
-
p. 1327 - 1330
(2007/10/02)
-
- Zinc-Modified Cyanoborohydride as a Selective Reducing Agent
-
Zinc-modified cyanoborohydride generated from sodium cyanoborohydride and zinc chloride in a 2:1 molar ratio is found to be a selective and versatile reducing agent.The reagent in diethyl ether reduces aldehydes, ketones and acid chlorides to the corresponding alcohols but does not reduce acid anhydrides, acids, esters and tertiary amides.The reagent in methanol is very useful for reduction of enamines, reductive amination of aldehydes and ketones, reductive methylation of amines, and deoxygenation of aldehydes and ketones.
- Kim, Sunggak,Oh, Chang Ho,Ko, Jae Suk,Ahn, Kyo Han,Kim, Yong Jin
-
p. 1927 - 1932
(2014/12/12)
-
- Ate Complex from Diisobutylaluminum Hydride and n-Butyllithium as a Powerful and Selective Reducing Agent for the Reduction of Selected Organic Compounds Containing Various Functional Groups
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The "ate" complex generated from diisobutylaluminum hydride and n-butyllithium in an equimolar ratio either in tetrahydrofuran-hexane or in toluene-hexane was reacted with a series of selected organic compounds containing various functional groups in order to explore the reducing properties and to determine the synthetic utility of the reagent.The reagent is very effective for selective 1,2-reduction of both acyclic and cyclic enones.The reagent in tetrahydrofuran-hexane gives slightly better 1,2-selectivity than in toluene-hexane in the reduction of some acyclic enones, whereas the reagent in toluene-hexane gives better 1,2-selectivity in the reduction of conjugated cyclohexenones.Esters and lactones are completely reduced to the corresponding alcohols at room temperature, whereas they are reduced to the corresponding alcohols and aldehydes at -78 deg C even with an excess amount of the reagent.Partial reduction of the esters and the lactones to the corresponding aldehydes has not been observed.Acid chlorides are rapidly reduced to the corresponding alcohols with an excess amount of the reagent at -78 deg C, whereas they are reduced to a mixture of the alcohol, the aldehyde, and the unreacted acid chloride with a stoichiometric amount of the reagent at -78 deg C.Acid anhydrides are rapidly and quantitatively reduced to an equimolar mixture of the acid and the alcohol at -78 deg C.Carboxylic acids and primary and secondary amides are inert to the reagent at room temperature and are recovered unchanged..Tertiary amides are cleanly reduced to the aldehydes with a stoichiometric amount of the reagent either at 0 deg C or at room temperature, whereas they are inert to the reagent at -78 deg C, which permits the selective reduction of other reducible functional groups in the presence of the tertiary amide group at the latter temperature.The reagent rapidly reduces simple primary alkyl, benzyl, and allyl bromides but slowly primary alkyl chlorides and secondary alkyl bromides.Tertiary alkyl and aryl halides are essentially inert to the reagent, whereas trityl bromide and vinyl bromide are reduced at a reasonable rate.Epoxides are cleanly reduced to the corresponding alcohols.The opening of the epoxide ring with this reagent proceeds with excellent isomeric purity, yielding the more highly substituted alcohol almost exclusively.Nitriles are resistant to reduction and are only slowly converted to the corresponding aldehydes at room temperature.Disulfides are rapidly and quantitatively reduced to the corresponding thiols.Sulfoxides and sulfones are inert to the reagent and are recovered unchanged.Selective reductions of an ester in the presence of other reducible groups such as a bromide, a tertiary amide, and a nitrile are achieved with the reagent at -78 deg C by using a modified procedure.Furthermore, the reagent is capable of reducing selectively a ketone in the presence of an ester.
- Kim, Sunggak,Ahn, Kyo Han
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p. 1717 - 1724
(2007/10/02)
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- Aminoborohydrides as Reducing Agents. 1. Sodium (Dimethylamino)- and (tert-Butylamino)borohydrides as Selective Reducing Agents
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Replacement of a hydride in borohydride by an electron-donating alkylamino group greatly enhances the reducing ability of the resulting reagents.Thus, sodium (dimethylamino)- and (tert-butylamino)borohydrides (1, NaDMAB, and 2, NaTBAB, respectively) not only reduce aldehydes and ketones to alcohols but also are effective for the conversion of esters to alcohols and primary amides to amines in good to excellent yields.Tertiary amides are reduced to alcohols (i.e., N,N-dimethylamides) or amines (i.e.N,N-diisopropylamides) depending on the steric bulk of the alkyl substituents on nitrogen.However, secondary amides are not reduced by the reagents allowing selective conversion of primary and tertiary amides in the presence of secondary amides.Nitriles are attacked by the reagents but do not afford synthetically useful amounts of amine products.Aryl halides are slowly converted to arenes, but alkyl halides and epoxides undergo unusual reactions with the amino portion of the reagents.
- Hutchins, Robert O.,Learn, Keith,El-Telbany, Farag,Stercho, Yuriy P.
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p. 2438 - 2443
(2007/10/02)
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- Regioselectivity and Steric Course of Lewis Acid Promoted Ring Enlargement of Cyclohexadiene Complexes with Carbon Monoxide
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Treating the tricarbonyliron complexes 5 and 7 of substituted cyclohexadienes with AlCl3 yields complexes 6, 8, and 9 of seven-membered ring ketones, containing carbon monoxide inserted into one of the double bonds with high regioselectivity depending on the substitution pattern.The mechanism of this ring enlargement is discussed, and an X-ray analysis of 8e is carried out.
- Eilbracht, Peter,Jelitte, Ruediger,Walz, Leonhard
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p. 3473 - 3489
(2007/10/02)
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- SELECTIVE REDUCTIONS WITH SODIUM BOROHYDRIDE IN DIMETHYL SULPHOXIDE WITN ADDED METAL SALTS.
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Sodium borohydride in dimethyl sulphoxide in the presence of added metal salts selectively reduces aldehydes in the presence of ketones and converts α,β-unsaturated ketones to the corresponding unsaturated alcohols.
- Adams, Chitra
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p. 1349 - 1354
(2007/10/02)
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- SELECTIVITE DE LA REDUCTION DE CYCLOHEXEN-2 ONES PAR NBu4BH4 DANS DIVERS SOLVANTS ET PAR NaBH4 DANS DES CONDITIONS DE TRANSFERT DE PHASE
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The 2-cyclohexenone 1 and isophorone 2 reductions with NBu4BH4 in aprotic solvents lead to a highly preferential 1-4 attack; i.e. 85percent with 1 and 96percent with 2 in THF.These regioselectivities are nearly the same as those observed with LiBH4 in the presence of cryptand confirming thus the cation influence.This method which is inexpensive and easy to work up, seems to constitute a general way to reduction of α-enones to saturate alcohols while other reagents such as K(sec Bu)3BH are not able to reduce the carbon-carbon double bond of isophoron.Phase transfer catalysis conditions are not useful for selective reduction: large amounts of allylic alcohols are formed in liquid-liquid phase transfer conditions (60percent in toluene-water); a good regioselectivity is only obtained when a cryptand is used as a transfer agent in solid-liquid conditions.
- D'Incan, E.,Loupy, A.
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p. 1171 - 1180
(2007/10/02)
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- ALKYL METAL ASYMMETRIC REDUCTION. 11. THE REACTION OF α,β-UNSATURATED KETONES WITH β-BRANCHED TRIALKYLALUMINIUM COMPOUNDS.
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The reduction of a series of α,β-unsaturated ketones has been studied under various experimental conditions, by using β-branched trialkylalanes.Asymmetric induction phenomena are observed when optically active trialkylalanes are used.
- Giacomelli, Giampaolo,Caporuso, Anna Maria,Lardicci, Luciano
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p. 3663 - 3666
(2007/10/02)
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- THE INFLUENCE OF LITHIUM COMPLEXING AGENTS ON THE REGIOSELECTIVITY OF REDUCTIONS OF SUBSTITUTED 2-CYCLOHEXENONES BY LiAlH4 and LiBH4
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A reversal of regioselectivity of LiAlH4 or LiBH4 reduction of 2-cyclohexenone induced by addition of -cryptand to the reaction medium is accompanied by a rate decrease.In the absence of the cryptand, carbonyl attack predominates (C1:C3=86:14 with LiAlH4 in THF).In the presence of the cryptand, double bond attack is favoured (C1:C3=14:86).This effect is larger with LiAlH4 than with LiBH4.This trend is general in the case of five substituted 2-cyclohexenones.Using 12-crown-4 as a Li+ coordinator, a change in regioselectivity occurs but it is less pronunced than with the cryptand.
- Loupy, Andre,Seyden-Penne, Jacqueline
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p. 1937 - 1942
(2007/10/02)
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