Reduction Of Cyclic Ketones Research Articles

ChemInform Abstract: Selective Reduction of Organic Compounds with Al‐Trifluoromethanesulfonyldiisobutylalane. Comparison of Its Reactivity with Al‐Methanesulfonyldiisobutylalane.

AbstractDiisobutylaluminum triflate shows higher reactivity and diastereoselectivity in the reduction of cyclic ketones (I) and (IV) compared to diisobutylaluminum mesylate.

Monascus kaoliang CBS 302.78 immobilized in tailor-made agars as catalyst for reduction of ketones: On the quest for a green biocatalyst

After a hierarchical screening Monascus kaoliang CBS 302.78 was selected due to its high activity in the reduction of cyclic ketones. Several tailor made agars and agaroses were used in the immobilization of the fungus. The best-immobilized biocatalyst was obtained after immobilization in low methoxylated agar (A27/03) at 2.5% (w/v). The biocatalyst shape was optimized as microplates (1.27 cm × 1.27 cm × 0.31 cm). The observable modulus for external mass transfer, Ω ⋘ 1, indicates the absence of external mass transfer phenomena. The internal effectiveness factor η < 1 and the high value of the Thiele module ( ϕ > 3), indicates that there is an intra-particle mass transfer restriction according to the Weisz criteria. As consequence, the kinetics of the reduction of ketones follows a formal first order kinetic model. The catalysts deactivation follows a simple exponential decay expression. Due to the renewal characteristics of the agar, the biocatalysts can be considered as green catalysts.

Diplogelasinospora grovesii IMI 171018, a New Whole Cell Biocatalyst for the Stereoselective Reduction of Ketones.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Diplogelasinospora grovesii IMI 171018, a new whole cell biocatalyst for the stereoselective reduction of ketones

A screening of 416 strains (71 bacterial strains, 45 actinomycetes, 59 yeast, 60 basidiomycetes, 33 marine fungi and 148 filamentous fungi) has been performed to look for microorganisms that display reductase activity in the absence of oxidase activity. A new microorganism, Diplogelasinospora grovesii IMI 171018 (a nonpathogen strain), was isolated and showed very high activity and stereoselectivity in the reduction of cyclic ketones. The fungus was selected due to its selectivity towards monocyclic and bicyclic ketones and its easy culture conditions, which allow an easy scale-up. D. grovesii is more active in the reduction of conventional ketones than S. cerevisiae type II (from Sigma) and can work in the presence of high ketone concentrations (<60 mM). Comparative molecular fields analysis (CoMFA) has been applied in order to explain the steric and electronic properties of the carbonylic compound to be substrate for the microbial alcohol reductase. The CoMFA model is highly predictive ( q 2=0.549) and can be used to explain and to predict the structure of ketones that can or cannot be reduced by this microorganism.

Reaction of Lithium (2,3‐Dimethyl‐2‐butyl)‐t‐butoxyborohydride with Selected Organic Compounds Containing Representative Functional Groups.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Reaction of Lithium (2,3-Dimethyl-2-butyl)-t-butoxyborohydride with Selected Organic Compounds Containing Representative Functional Groups

The general reducing charagteristics of a newly synthesized reducing agent, lithium(2.3-dimethyl-2-butyl)-<TEX>${\iota}$</TEX>-butoxyborohydride (Li <TEX>$Thx'BuOB_2$</TEX>, 1), in tetrahydrofuran (THF) toward selected organic compounds containing representative fundtional groups under practical has been examined. The reagent revealed an interesting and unique reducing characteristics. Especially, the stereoselectivity in the reduction of cyclic ketones was extraordinary. Thus, the introduction of bulky alkyl and alkoxy groups into the parent borohydride affonds a high stereoselectivity. In general, the reducing power of the reagent is somewhere between the dialiylborohydride and the parent borohydride. This permits the reagent to be a reagent of choice for selecitive reduction of organic compounds with an improved selectivity.

Palladium-catalyzed reduction of ketones with nBu 2SnH 2

Whereas the Pd(PPh 3) 4-catalyzed reduction of ketones with n Bu 3SnH does not proceed at all, the use of n Bu 2SnH 2, instead of n Bu 3SnH, leads to the efficient reduction of a variety of ketones in the presence of a catalytic amount of Pd(PPh 3) 4 under mild conditions, providing the corresponding alcohols in good yields. The stereoselectivity in the reduction of cyclic ketones is also investigated by using this Pd(PPh 3) 4/ n Bu 2SnH 2 reduction system.

Reduction of Aliphatic and Aromatic Cyclic Ketones to sec-Alcohols by Aqueous Titanium Trichloride/Ammonia System. Steric Course and Mechanistic Implications

In contrast to the dissolved metal and metal hydride reductions, the reduction of cyclic ketones by the aqueous TiCl3/NH3 system favours the formation of the less thermodynamically stable axial alcohol. The ammonium ion formed in situ is essential for the reduction to proceed because it behaves as a mild Brønsted acid in basic medium and favours the protonation of the intermediate ketyl. The corresponding α-hydroxy radical is then rapidly reduced under conditions where the first electron transfer to the substrate takes place. We suggest that the stereoselectivity is determined by the second reduction step, which occurs through the less hindered transition state, regardless of whether the radical to be reduced is thermodynamically favoured or not.

Reduction of Aliphatic and Aromatic Cyclic Ketones tosec-Alcohols by Aqueous Titanium Trichloride/Ammonia System. Steric Course and Mechanistic Implications

In contrast to the dissolved metal and metal hydride reductions, the reduction of cyclic ketones by the aqueous TiCl3/NH3 system favours the formation of the less thermodynamically stable axial alcohol. The ammonium ion formed in situ is essential for the reduction to proceed because it behaves as a mild Bronsted acid in basic medium and favours the protonation of the intermediate ketyl. The corresponding α-hydroxy radical is then rapidly reduced under conditions where the first electron transfer to the substrate takes place. We suggest that the stereoselectivity is determined by the second reduction step, which occurs through the less hindered transition state, regardless of whether the radical to be reduced is thermodynamically favoured or not.

ChemInform Abstract: Reexamination of Aluminum Hydride as a Stereoselective Reducing Agent for Reduction of Cyclic Ketones to Thermodynamically More Stable Alcohols.

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Reduction of ketones with polydibenzo-18-crown-6-borohydride

Polydibenzo-18-crown-6-(P-DB-18-C-6), a condensation polymer of dibenzo-18-crown-6 and formaldehyde has ben used as support for borohydride ions in the reduction of few cyclic and acyclic ketones. The reagent has been found to be more stereoselective than dibenzo-18-crown-6-borohydride in the reduction of cyclic ketones. 4- t -butylcyclohexanone has been converted exclusively (100%) to trans -4- t -butylcyclohexanol.

ChemInform Abstract: Preparation of Potassium 9‐Alkyl‐9‐boratabicyclo(3.3.1)nonanes and Their Stereoselectivity in the Reduction of Cyclic Ketones.

AbstractTreatment of the 9‐substituted 9‐borabicyclo(3,3,1)nonanes (I) with potassium hydride yields the potassium salts (II) which are employed in the reduction of norcamphor, camphor, and several cyclohexanones.

Preparation of Potassium 9-Alkyl-9-bortabicyclo[3.3.1]nonanes and Their Stereoselectivity in the Reduction of Cyclic Ketones

Preparation des composes du titre a partir des alkyl-9 bora-9 bicyclo [3.3.1] nonanes et d'hydrure de potassium. La reduction de cyclohexanones substituees, du camphre et de la norbornanone-2 en alcools correspondants est etudiee

Stereoselectivity in the Reduction of Cyclic Ketones with Sodium Borohydride. Effect of the Ratio of the Components of a Mixed Solvent of Tetrahydrofuran and Methanol

Abstract Reduction of relatively conformationally rigid cyclic ketones with sodium borohydride was examined in a mixed solvent of tetrahydrofuran(THF) and methanol(MeOH) with varying the ratio of the components. The highest stereoselectivities of the reductions were observed in the mixed solvent, and not in each individual solvent.

Ir(COD)(PPh 3) 2] +: A hydrogen transfer catalyst precursor for reduction of ketones as active as alcohol dehydrogenase enzyme

Reduction of cyclic ketones via hydrogen transfer reaction is catalyzed by iridium complexes with an activity comparable to that of horse liver alcohol dehydrogenase.

Lithium Methylborohydride. A New Stereoselective Reducing Agent for Reduction of Cyclic Ketones

Abstract Although in the past decade considerable efforts have been devoted to the development of the hindered trialkylborohydrides which allow conversion of cyclic and bicyclic ketones into the thermodynamically less stable alcohols in excellent stereoselectivity,1 there are few reports in the literature on the use of monoalkylborohydride reducing agents.2 As part of our research program directed toward the development of new hydride reducing agents, we have recently reported the reducing properties of lithium n-butylborohydride.3 This paper describes useful synthetic potential of lithium methylborohydride for highly stereoselective reductions of cyclic ketones.

Stereoselective electrochemical reduction of cyclic ketones

The electrochemical reduction of 4-t-butylcyclohexanone and dihydroisophorone has been studied at controlled potential and current density and it has been found that at relatively small cathodic potentials, in the presence of acetic acid, the equatorial (stable) and axial (less stable) alcohols are formed in approximately equal amounts.