共查询到20条相似文献,搜索用时 31 毫秒
1.
A zirconium borohydride piperazine complex (Ppyz)Zr(BH4)2Cl2, obtained by the reaction of an ethereal solution of ZrCl4 and LiBH4 with piperazine is a stable, selective and efficient reducing agent. (Ppyz)Zr(BH4)2Cl2 reduces aldehydes, ketones, silylethers, α,β-unsaturated carbonyl compounds and esters. The reactions were performed in diethyl ether at room temperature or under reflux, and the yields of the corresponding alcohols were excellent. The selective reduction of aldehydes in the presence of ketones and complete regioselectivity in the reduction of α,β-unsaturated carbonyl groups were observed. 相似文献
2.
Cédric Balan Roxana Pop Virginie Comte Didier Poinsot Virginie Ratovelomanana‐Vidal Pierre Le Gendre 《应用有机金属化学》2014,28(7):517-522
The influence of hydrogen pressure on the hydrosilylation of ketones catalyzed by [((S)‐SYNPHOS)Rh(nbd)]OTf has been studied. We have notably demonstrated that hydrogen significantly affected the outcome of the reaction while not being consumed as stoichiometric reducing agent. In THF, diethyl ether or toluene, the hydrogen pressure exceedingly accelerated the hydrosilylation reaction and preserved or even improved the enantioselectivity of the process. In CH2Cl2, the rhodium catalyst also showed generally higher catalytic activity under hydrogen pressure. Most serendipitously, several ketones were found to give products of absolute opposite configuration upon performing the hydrosilylation under argon atmosphere or under hydrogen pressure. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
3.
New active-iron based reducing system for carbonyl compounds and imines. Stereoselective reduction of cyclic ketones 总被引:1,自引:0,他引:1
The reaction of different carbonyl compounds and imines with a mixture of iron(II) chloride tetrahydrate, an excess of lithium powder, and a catalytic amount of 4,4′-di-tert-butylbiphenyl (DTBB, 5 mol%) in THF at room temperature, led to the formation of the corresponding alcohols and amines, respectively. The process was also applied to the transformation of α,β-unsaturated carbonyl compounds into the corresponding saturated alcohols. The new reducing system exhibited good to excellent diastereoselectivity toward the reduction of different monocyclic and polycyclic ketones. 相似文献
4.
The action of Raney nickel on substituted 3-cyano-2-methylthiopyridines was studied. Under conditions of catalytic hydrogenation,
the reaction yields a mixture containing the aminosulfide resulting from reduction of the nitrile group with retention of
the methylthio group, the nitrile resulting from elimination of the methylthio group, and the amine resulting from both reduction
of the nitrile group and elimination of the methylthio group. Treatment of 3-cyano-2-methylthiopyridines with a large amount
of Raney nickel under desulfurization conditions induces simultaneous elimination of the methylthio group and reduction of
the nitrile group to the aminomethyl group. When reductive desulfurization is carried out in methanol or THF, primary amines
are formed, while the reactions in isopropyl or ethyl alcohol give secondary or tertiary amines, which are formed upon alkylation
of the amino group with alcohols.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2497–2500, November, 2005. 相似文献
5.
The electrophilic α-alkylation of ketones with alcohols is accomplished by a hydrogen autotransfer process catalyzed by RuCl2(DMSO)4. The reaction can produce either simple alkylated ketones or α,β-unsaturated ketones just by choosing the appropriate starting ketones (methyl ketones or bicyclic methylenic ketones, respectively), as well as quinolines (by using 2-aminobenzyl alcohol derivatives) or the corresponding alcohol derivatives by the addition of an extra equivalent of the initial alcohol. In the last case, after the above alkylation process reduction of the carbonyl compound takes place. A mechanistic study seems to indicate that the process goes through the oxidation of the alcohols with ruthenium (after a previous deprotonation) to yield the corresponding aldehyde and a ruthenium hydride intermediate. In turn, the aldehyde suffers a classical aldol reaction with the starting ketone to form the corresponding α,β-unsaturated ketone, which finally is reduced through a Michael-type addition by the aforementioned ruthenium hydride intermediate. 相似文献
6.
Yasuda M Hirata K Nishino M Yamamoto A Baba A 《Journal of the American Chemical Society》2002,124(45):13442-13447
The diastereoselective addition of gamma-substituted allylic nucleophiles to ketones has been accomplished to give tertiary homoallylic alcohols. The reaction of tributylcinnamyltin 1a with simple ketones 2 in the presence of stannous chloride (SnCl(2)) gave the tertiary homoallylic alcohols 3, which include the anti form (based on Ph and OH), with high diastereoselectivity. In the reaction course, transmetalation of tributylcinnamyltin 1a with SnCl(2) proceeds to form an active nucleophile which is tentatively considered to be a cinnamyltin(II) species. A cyclic transition state A is favorable because the chlorinated tin(II) center is highly capable of accepting ligands. The other diastereomers (syn form) 4 were obtained in the reaction of tributylcinnamyltin 1a with ketones 2 by the use of BF(3) x OEt(2) instead of SnCl(2). This reaction proceeds through an acyclic transition state in which BF(3) acts as a Lewis acid for activation of ketones. When 3-tributylstannylcyclohexene 1b or 3-tributylstannylcyclopentene 1c was used with SnCl(2), high diastereoselective formation of the corresponding homoallylic alcohols 6 which have the syn form (based on ring chain and OH) was observed. The selectivity was also explained by the cyclic transition state B. When tributylcrotyltin 1d or 1e was used, the stereochemistry of the products depends on the additives (SnCl(2) or BF(3) x OEt(2)), substituents of ketones, and reaction temperature. It is interesting that those additives compensate for each other in terms of diastereoselective alkylation. The alkylation of alpha-alkoxy, aryloxy, or hydroxyketones 16 was achieved in extremely high selectivity using an allylic tributyltin 1a-c/SnCl(2) system. The chelation by carbonyl and beta-oxygens provides a rigid transition state (E or F) for selective reactions. It is noted that the hydroxyketone can be used without protection in this reaction system. The relative stereochemistry of the produced tertiary homoallylic alcohols was determined on the basis of X-ray analyses. 相似文献
7.
Alkylation of hydrazinedicarboxylate (a Mitsunobu by-product) is not a notable problem in common Mitsunobu alkyl aryl etherification reactions. Good yields can be obtained with a wide range of solvents. However, this side reaction can cause yield reduction for the reactions of sterically hindered phenols and primary alcohols. To suppress the side reaction, solvent effect was investigated. It was found that hydrazinedicarboxylate is about five times less soluble in diethyl ether than in THF, and the yields are improved for ortho-substituted phenols of a wide range of steric hindrance using diethyl ether as the solvent instead of THF which is the more commonly used for Mitsunobu reactions. 相似文献
8.
S. A. Mitchenko A. N. Vdovichenko T. V. Bezbozhnaya L. M. Kapkan 《Theoretical and Experimental Chemistry》2005,41(3):203-206
A new catalytic reaction of the etherification of alcohols in the system ROH-PtCl
4
2−
has been observed. At 70 °C in the presence of catalytic amounts of chloride complexes of platinum(II) methanol gave dimethyl ether. Methyl tert-butyl ether and di-tert-butyl ether were formed analogously from a mixture of methanol and tert-butanol. In the reaction with ethanol the products were diethyl ether and a π-ethylene complex of platinum(II). It is suggested that the step-wise mechanism includes the oxidative addition of the alcohol with the intermediate formation of an alkyl complex of platinum(IV), the decomposition of which by reductive elimination under the influence of a second molecule of alcohol or an alkoxide anion gives an ether and regenerates the catalyst, a chloride complex of platinum(II).__________Translated from Teoreticheskaya i Eksperimental’naya Khimiya, Vol. 41, No. 3, pp. 190–193, May–June, 2005. 相似文献
9.
Substituted five-membered cyclic nitrones (pyrroline N-oxides) have been obtained in good to high yields from tertiary γ-nitro ketones and nitriles employing aluminium amalgam as a reducing agent in moist diethyl ether or THF. Attempts to obtain cyclic amino nitrones from α- or β-nitro nitriles failed and only the corresponding hydroxylamines have been isolated. Both nitrones and hydroxylamines have been used for synthesis of tertiary C-nitroso nitriles or ketones. 相似文献
10.
A Cs2CO3-catalyzed alkylation reaction of indoles with trifluoromethyl ketones was presented. Both alicyclic and aromatic trifluoromethyl ketones as well as various substituted indoles are compatible with the methodology. Good to excellent yields of the corresponding trifluoromethyl substituted tertiary alcohols 2,2,2-tritrifluoro-1-(1H-indol-3-yl)-ethan-1-ols were acquired as the sole products. 相似文献
11.
Alexander Kremsmair Henrik R. Wilke Matthias M. Simon Quirin Schmidt Konstantin Karaghiosoff Paul Knochel 《Chemical science》2021,13(1):44
A general preparation of enantiomerically and diastereomerically enriched secondary alkylmagnesium reagents was reported as well as their use for performing highly stereoselective transition-metal free electrophilic aminations leading to α-chiral amines in up to 97% ee. Thus, the reaction of t-BuLi (2.2 equiv.) with a mixture of chiral secondary alkyl iodides and the commercially available magnesium reagent Me3SiCH2MgCl in a 2 : 1 mixture of pentane and diethyl ether at up to −50 °C provided optically enriched secondary mixed alkylmagnesium species of the type alkyl(Me)CHMgCH2SiMe3 with high retention of configuration (up to 99% ee). The resulting enantiomerically enriched dialkylmagnesium reagents were trapped with electrophiles such as non-enolizable ketones, aldehydes, acid chlorides, isocyanates, chlorophosphines and O-benzoyl hydroxylamines providing α-chiral tertiary alcohols, ketones, amides, phosphines and tertiary amines in up to 89% yield (over three reaction steps) and up to 99% ee.We report a general method for the preparation of enantiomerically enriched secondary alkylmagnesium reagents, which undergo highly stereoselective transition-metal free electrophilic aminations, leading to α-chiral amines in up to 97% ee. 相似文献
12.
Propargylic bromides can be condensed with aldehydes and ketones in the presence of Hiyama's reagent (2CrCl3+LiAlH4 in THF) leading to α-allenic alcohols, to homopropargylic alcohols or to the mixture of both of them. The selectivity (or specificity) of this reaction depends on the substitution of the propargylic bromide, on the structure of the ketone, and on the presence of HMPT in the reaction mixture. In many cases, the α-allenic alcohol has been specifically or very selectively obtained. The mechanism of the reaction and the influence of the various parameters are discussed. 相似文献
13.
Marek Gliński 《Reaction Kinetics and Catalysis Letters》2009,97(2):275-279
The vapour phase reduction of various aliphatic ketones to the corresponding carbinols by propan-2-ol in the presence of MgO
as a catalyst has been studied. A strong decrease of the reactivity (from 86 to 0%) in the reduction of pentan-3-one and its
polymethyl derivatives with an increase of the bulkiness of both alkyl groups in the ketone has been observed. For ketones
with the general formula CH3-(CH2)n-CO-(CH2)8–n-CH3, where n = 0, 1, 2, 3 and 4, a shift of the carbonyl group to the middle of a molecule causes only a small decrease of the reactivity.
It has been stated that the observed changes in the reactivity of ketones are mainly caused by a steric hindrance around their
carbonyl groups. 相似文献
14.
The reaction of secondary alcohols 1 with chlorodimethylsilane (HSiMe(2)Cl) proceeded in the presence of a catalytic amount of GaCl(3)/diethyl tartrate to give the corresponding organic chlorides 3. In the catalytic cycle, the reaction of diethyl tartrate 4a with HSiMe(2)Cl 2 gives the chlorosilyl ether 5 with generation of H(2). Alcohol-exchange between the formed chlorosilyl ether 5 and the substrate alcohol 1 affords alkoxychlorosilane 6, which reacts with catalytic GaCl(3) to give the chlorinated product 3. The moderate Lewis acidity of GaCl(3) facilitates chlorination. Strong Lewis acids did not give product due to excessive affinity for the oxy-functionalities. Although tertiary alcohols were chlorinated by this system even in the absence of diethyl tartrate, certain alcohols that are less likely to give carbocationic species were effectively chlorinated using the GaCl(3)/diethyl tartrate system. 相似文献
15.
The reactions of alkyllithiums with ketones and thioketones proceed in fundamentally different ways. Whereas alkyllithiums add to the carbonyl carbon of ketones to give tertiary alcohols, the reaction with thioketones proceeds to give secondary thiols by reduction of the CS group. Transition states for the addition and reduction reactions of acetone and thioacetone in ethereal solution have been located and the computed activation free energies are in agreement with the observed behavior of ketones and thioketones in reactions with alkyllithiums. 相似文献
16.
Liu L Wang R Kang YF Chen C Xu ZQ Zhou YF Ni M Cai HQ Gong MZ 《The Journal of organic chemistry》2005,70(3):1084-1086
The catalytic asymmetric addition of phenylacetylene to aromatic ketones is reported. The catalyst, generated from commercially available Cinchona alkaloids and industrially available triethylaluminum, gives the expected tertiary alcohols with good enantiomeric excess (70-89%) and yields (60-83%). No previous case has been reported successfully using triethylaluminum as a Lewis acid in the asymmetric alkynylation of carbonylic derivatives, and thus we provide a new method to obtain optically active tertiary propargyl alcohols. 相似文献
17.
Erwin Mayer 《Monatshefte für Chemie / Chemical Monthly》1971,102(4):940-945
Zusammenfassung Die Reaktionen von B2H6 mit CO zu H3BCO und mit PH3 zu H3BPH3 werden in Lösung durch Äther katalytisch beschleunigt. Die Bildungsgeschwindigkeit von H3BCO nimmt in der Reihenfolge Diäthyläther < Diglyme < Monoglyme < < Dimethyläther (mit der Basenstärke der Äther) zu. Unter optimalen Bedingungen werden die beiden Addukte mit fast quantitat. Ausb. gebildet (für H3BCO: – 45° in Monoglyme, 1 Atm. CO; für H3BPH3: – 60° in Diäthyläther). In Dimethyläther und Tetrahydrofuran werden durch eine Konkurrenzreaktion zunehmend Äther—Boran-Komplexe gebildet.
Ether catalyzed reaction of diborane with lewis bases; simplified preparation of carbonyl borane and phosphine borane
The reactions of B2H6 with CO to H3BCO and with PH3 to H3BPH3 in solution are accelerated catalytically by ethers. In the series diethyl ether < diglyme < monoglyme < dimethyl ether the rate of formation of H3BCO increases with the base strength of the ethers. Using optimized conditions both adducts are obtained with nearly quantitative yields (for H3BCO: – 45° in monoglyme, 1 atm. CO; for H3BPH3: – 60° in diethyl ether). In dimethyl ether and tetrahydrofurane ether—borane complexes are formed increasingly via a competitive reaction.相似文献
18.
《高等学校化学研究》1999,(2)
IntroductionAsamildreductant,sodiumborohydride(NaBH4)iswidelyusedinorganicsynthesistopreparealcoholsfromaldehydesandketones.C... 相似文献
19.
G. F. Chernenko E. E. Ivanova Yu. V. Gatilov I. Yu. Bagryanskaya É. N. Shmidt 《Chemistry of Natural Compounds》1993,28(6):568-575
The chemical composition of a petroleum ether extract of the bark of the Siberian spruce has been studied. Extracts included saturated aliphatic alcohols and C16-C24 acids — abietic, dehydroabietic, isopimaric, oleic, lineolic, and linolenic — alkyl ferulates, ketones, and alcohols of the serratene type, and also 4-stigmasten-3-one. Onoceradienedione and onoceradienediol — precursors of the serratene triterpenoids — and also a saturated vicinal diol — triacontane-10,11-diol — have been isolated from the extractive substances of conifer in the native form for the first time.Novosibirsk Institute of Organic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 654–662, November–December, 1992. 相似文献
20.
The reduction of a variety of carbonyl compounds was efficiently carried out with NaBH4/DOWEX(R)50WX4 system. The reactions were performed to give the corresponding alcohols derivatives in perfect yields in THF at room temperature. Reduction of acyloins and a‐diketones by this reducing system produced efficiently the corresponding vicinal diols. Also, the reduction of aldehydes over ketones has been accomplished successfully by this system. Regioselectivity of this system was also investigated with exclusive 1,2‐reduction of conjugated carbonyl compounds to their corresponding allylic alcohols in high to excellent yields. 相似文献