Chemoselective Reduction Of Aldehydes Research Articles

Zn-Catalyzed Regioselective and Chemoselective Reduction of Aldehydes, Ketones and Imines.

An operationally convenient Zn-catalyzed synthesis of alcohols by the reduction of aldehydes, ketones, and α,β-unsaturated aldehydes/ketones is reported. It is a rare example of using mild and sustainable HBpin as a reductant for catalytic reduction of carbonyl compounds in the absence of acid or base as hydrolysis reagent. The reaction is upscalable and proceeds in high selectivity without the formation of boronate ester by-products, and tolerates sensitive functionalities, such as iodo, bromo, chloro, fluoro, nitro, trifluoromethyl, aminomethyl, alkynyl, and amide. The Zn(OAc)2/HBpin combination has been also proved to be chemoselective for the C=N reduction of imine analogs.

Catalytic Hydroboration of Aldehydes, Ketones, and Alkenes Using Potassium Carbonate: A Small Key to Big Transformation

An efficient transition-metal-free protocol for the hydroboration of aldehydes and ketones (reduction) was developed. The hydroboration of a wide range of aldehydes and ketones with pinacolborane (HBpin) under the K2CO3 catalyst has been studied. The reaction system is practical and reliable and proceeds under extremely mild and operationally simple conditions. No prior preparation of the complex metal catalyst was required, and hydroboration occurred stoichiometrically. Further, the chemoselective reduction of aldehydes over ketones was carried out. Moreover, we demonstrated the use of K2CO3 as an efficient catalyst for the hydroboration of alkenes. The operational simplicity, inexpensive and transition-metal-free catalyst, and the applicability to gram-scale synthesis strengthen its potential applications for hydroboration (reduction) at an industrial scale.

Chemoselective reduction of aldehydes via a combination of NaBH4 and acetylacetone

A bench-stable combination of NaBH4–acetylacetone was developed for the efficient chemoselective reduction of aldehydes in the presence of ketones.

Green Approach for the Domino Reduction/Reductive Amination of Nitroarenes and Chemoselective Reduction of Aldehydes Using Fe/aq. Citric Acid/Montmorillonite K10

AbstractWe have developed a new and mild method for the direct one‐pot reduction/reductive amination of nitroarenes with arylaldehydes using Fe/aq citric acid/montmorillonite K10 catalytic system under ambient conditions. This catalyst has excellent functional group compatibility and the reaction provides rapid access to a diverse range of secondary amines. Under the conditions, aromatic aldehydes are selectively reduced to benzyl alcohols in the presence of ketones. A concise and efficient approach to the synthesis of diverse range of 1,2‐disubstituted benzimidazoles has also been accomplished for the first time from 1,2‐dinitrobenzene and aromatic aldehydes using the above catalytic system. The method involves the domino nitro reduction/cyclization/reduction cascade.

Lewis Base Catalyzed Intramolecular Reduction of Salicylaldehydes by Pinacol‐Derived Chlorohydrosilane

A newly developed stable chlorohydrosilane derived from pinacol is herein described. This was successfully used in the reduction of salicylaldehydes in reasonable to excellent yields (51–97 %). The ability of the hydrosilane to react as a reducing agent is increased upon the in situ formation of a trialkoxyhydrosilane and activation with a Lewis base, as further indicated by density functional theory studies. 1,3‐Dimethyl‐3,4,5,6‐tetrahydro‐2(1H)‐pyrimidinone (DMPU) was identified to be a suitable catalyst for this metal‐free reduction, promoting the regio‐ and chemoselective reduction of aldehydes in ortho‐position to phenols, despite the presence of vicinal ketones. The performance of pinacol‐derived chlorohydrosilane in the reduction of salicylaldehydes was further observed to be superior to that of well‐established commercially available chlorohydrosilanes.

Efficient and Convenient Reduction of Organic Carbonyl Compounds to their Corresponding Alcohols by Zn(BH4)2/Charcoal in THF

Zn(BH4)2 (0.5-1.5 mmol) in the presence of charcoal (1 mmol) reduces a variety of organic carbonyl compounds such as aldehydes, ketones, acyloins, α-diketones and α,β-unsaturated carbonyl compounds to their corresponding alcohols. Reduction reactions were carried out in THF at room temperature in high to excellent yields. The chemoselective reduction of aldehydes over ketones was successfully accomplished with this reducing system. In addition, regioselectivity and exclusive 1,2-reduction of conjugated carbonyl compounds to their corresponding allylic alcohols was also performed in in high to excellent yields with this reducing system.

Zinc‐Mediated Efficient and Selective Reduction of Carbonyl Compounds

We herein describe for the first time that an optimized combination of Zn and NH4Cl can be used for the selective reduction of aldehydes and ketones to the corresponding alcohols. The aldehyde and keto groups are selectively reduced in the presence of azide, cyano, epoxy, ester, and carbon–carbon double‐bond functional groups. A broad functional‐group compatibility, chemoselective reduction of aldehydes in the presence of ketones, and selective reduction of isatins at the C3 carbonyl group are the highlights of the present method.

Poly(vinylpyrrolidone)-Grafted Silica as Polymeric Cosolvent Catalyst for Chemoselective Reduction of Aldehydes and Ketones to Alcohols

Poly(vinylpyrrolidone)-grafted silica as a polymeric cosolvent catalyst was prepared. This heterogeneous catalyst is used for the chemoselective conversion of various aliphatic, aromatic and heterocyclic aldehydes and ketones to their corresponding alcohols with sodium borohydride in high yields and short reaction times. This catalytic system reduces α, β-unsaturated aldehydes to produce allyl alcohols as an important synthetic precursors. The catalyst can be reused several times without any considerable decrease in its activity.

Chemoselective Reduction of Aldehydes with Pd-Nanoparticles

Key words chemoselectivity - reduction - aldehydes - alcohols - palladium catalysis

ChemInform Abstract: Natural Deep Eutectic Salt Promoted Regioselective Reduction of Epoxides and Carbonyl Compounds.

AbstractA 1:2 mixture of cholin chloride and urea acts as both reaction media and green catalyst for the regio‐ and chemoselective reduction of aldehydes, ketones, and epoxides with NaBH4 in the presence of other reducible functional groups.

ChemInform Abstract: Chemoselective Reduction of Aldehydes with Zinc Borohydride in Tetrahydrofuran.

Abstract A variety of structurally different aldehydes undergo chemoselectire reduction over ketones with zinc borohydride in tetrahydrofuran at −10°C to the corresponding alcohols.

ChemInform Abstract: Solvent-Mediated Chemoselective Reduction of Aldehydes by Using Tributyltin Hydride in Methanol, Aqueous Organic Solvents, or Water: An Environmentally Benign Process.

Abstract Aldehydes are reduced chemoselectively by using tributyltin hydride in methanol, aqueous organic solvents, or water to provide the corresponding alcohols in high yields. No additional catalyst is required.

Chemoselective reduction of aldehydes by ruthenium trichloride and resin-bound formates

A simple, chemoselective transfer hydrogenation of aryl aldehydes with the aid of Amberlite® resin formate (ARF), a stable H-donor, in the presence of catalytic ruthenium trichloride is described. Aromatic aldehydes and 1,2-diketones are reduced efficiently and selectively, while aryl ketones remain unchanged. Several other potentially reducible groups attached to the aromatic moiety are unaffected.

ChemInform Abstract: Novel Chemoselective Reduction of Aldehydes in the Presence of Other Carbonyl Moieties with Thiourea Dioxide.

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Chemoselective Reduction of Aldehydes over Ketones with Sodium Tris(hexafluoroisopropoxy)borohydride

Chemoselective reduction of aldehydes in the presence of ketones was achieved using sodium tris(hexafluoroisopropoxy)borohydride which can be stored as a THF solution.

Novel Chemoselective Reduction of Aldehydes in the Presence of Other Carbonyl Moieties with Thiourea Dioxide

Reduction of a variety of aldehydes in the presence of other carbonyl moieties to the corresponding alcohols occurs chemoselectively in high yields upon treatment with inexpensive reagent thiourea dioxide (TUDO) in aqueous alkali–ethanolic system for 2 h at 90 °C.

Copper, Silver, and Gold Complexes in Hydrosilylation Reactions

The reduction of diverse functional groups is an essential protocol in organic chemistry. Transition-metal catalysis has been successfully applied to the reduction of olefins, alkynes, and many carbonyl compounds via hydrogenation or hydrosilylation; the latter presenting several advantages over hydrogenation. Notably, hydrosilylation generally occurs under mild reaction conditions, and consequently over-reduced products are rarely detected. Moreover, the great majority of hydrosilanes employed in this reaction are easily handled, inexpensive, or both. A large number of multiple bonds can be involved in this context, and the hydrosilylation reaction can be regarded as a useful method for the synthesis of silicon-containing organic molecules or a convenient way of reducing organic compounds. Furthermore, the silyl group can also be retained as a protecting group, a strategy that can be of great usefulness in organic synthesis. Since the first Wilkinson's catalyst-mediated hydrosilylation of ketones in 1972, metals such as rhodium and iridium have attracted most of the attention in this area. A wide array of catalytic systems for hydrosilylation reactions is nowadays available, which has allowed for a great expansion of the synthetic scope of this transformation. After having been overlooked in the early years, group 11 metals (Cu, Ag, and Au), especially copper, have emerged as appealing alternatives for hydrosilylation. The use of a stabilized form of copper hydride, the hexameric [(Ph3P)CuH]6, by Stryker represented a breakthrough in copper-catalyzed reduction reactions. Nowadays, several copper-based catalytic systems compare well with a variety of reported rhodium-based catalysts, which generally suffer from the high cost of the catalyst. Tertiary phosphine ligands are the most widely used in these transformations. However, other families such as N-heterocyclic carbenes (NHCs) have shown promising activities. Compared with copper, little attention has been paid to silver- or gold-based catalysts. Silver salts have been considered inert towards hydrosilylation, and they are often employed as innocent anion exchange reagents for the in situ generation of cationic transition metal catalysts. Despite the rare reports available, they have already shown interesting reactivity profiles, for example, in the chemoselective reduction of aldehydes in the presence of ketones. Furthermore, 1,2-hydride delivery is favored over 1,4-reductions for alpha,beta-unsaturated carbonyl compounds, in contrast with most copper-based systems.

Ionene-Bound Borohydrides: Efficient, Selective, and Versatile Polymer-Supported Reducing Agents

Reduction of structurally different carbonyl compounds, such as aldehydes, ketones, α,β-unsaturated enals and enones, acid chlorides, and imines was accomplished efficiently using high capacity ionene based borohydride reagents. Aldehydes and imines were reduced to the corresponding alcohols and amines in excellent yields in methanol at ambient temperature while ketones and acid chlorides were reduced in iso-propanol and THF-MeOH at reflux. Chemoselective reduction of aldehydes over ketones was achieved successfully with these reagents. Complete regioselectivity was also observed in the reduction of α,β-unsaturated aldehydes and ketones.

Chemoselective reduction of aldehydes and ketones to alcohols using boron tri-isopropoxide, B(O-i-Pr)3 and boron tri-secondary butoxide, B(O-s-Bu)3 as catalysts

Chemoselective reduction of aldehydes and ketones to alcohols using boron tri-isopropoxide, B(O-i-Pr)3 and boron tri-secondary butoxide, B(O-s-Bu)3 as catalysts

Chemoselective Reduction of Aldehydes Using Decaborane in Aqueous Solution.

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