71886-64-1

Upstream product

• 1861-01-4 ethylbenzene-1,1-d2 
• 98-86-2 acetophenone 
• 3101-96-0 1-deuterio-1-phenylethanol 
• 876-27-7 4-chlorophenyl acetate 
• 108-22-5 Isopropenyl acetate 
• 98-85-1 1-Phenylethanol 
• 71886-69-6 1-²H-1-phenylethyl hydrogen phthalate 
• 3592-47-0 Benzaldehyde-d 
• 544-97-8 dimethyl zinc(II) 
• 41203-27-4 1-chloro-1-deuterio-1-phenylethane 
• 1517-69-7 (R)-1-phenylethanol 
• 1445-91-6 (S)-1-phenylethanol 
• 108-05-4 vinyl acetate 
• 115976-33-5 1-phenyl (O,1-⁽²⁾H₂)ethanol 

Downstream Products

• 101219-70-9 C₈H₈⁽²⁾HCl 
• 3101-96-0 1-deuterio-1-phenylethanol 
• 98-85-1 1-Phenylethanol 
• 98-86-2 acetophenone 
• 68566-80-3 (S)-(+)-1-phenylethane-1-d₁ 
• 71698-86-7 (R)-(-)-1-deuterioethylbenzene 
• 1517-69-7 (R)-1-phenylethanol 
• 71886-65-2 1-deuterio-(R)-(+)-1-phenylethanol 
• 41203-27-4 1-chloro-1-deuterio-1-phenylethane 

Relevant academic research and scientific papers

Abiotic reduction of ketones with silanes catalysed by carbonic anhydrase through an enzymatic zinc hydride

Enzymatic reactions through mononuclear metal hydrides are unknown in nature, despite the prevalence of such intermediates in the reactions of synthetic transition-metal catalysts. If metalloenzymes could react through abiotic intermediates like these, then the scope of enzyme-catalysed reactions would expand. Here we show that zinc-containing carbonic anhydrase enzymes catalyse hydride transfers from silanes to ketones with high enantioselectivity. We report mechanistic data providing strong evidence that the process involves a mononuclear zinc hydride. This work shows that abiotic silanes can act as reducing equivalents in an enzyme-catalysed process and that monomeric hydrides of electropositive metals, which are typically unstable in protic environments, can be catalytic intermediates in enzymatic processes. Overall, this work bridges a gap between the types of transformation in molecular catalysis and biocatalysis. [Figure not available: see fulltext.]

Cationic NHC-Phosphine Iridium Complexes: Highly Active Catalysts for Base-Free Hydrogenation of Ketones

Novel bidentate N-heterocyclic carbene-phosphine iridium complexes have been synthesized and evaluated in the hydrogenation of ketones. Reported catalytic systems require base additives and, if excluded, need elevated temperature or high pressure of hydrogen gas to achieve satisfactory reactivity. The developed catalysts showed extremely high reactivity and good enantioselectivity under base-free and mild conditions. In the presence of 1 mol % catalyst under 1 bar hydrogen pressure at room temperature, hydrogenation was complete in 30 minutes giving up to 96 % ee. Again, this high reactivity was achieved in additive-free conditions. Mechanistic experiments demonstrated that balloon pressure of hydrogen was sufficient to form the activate species by reducing and eliminating the 1,5-cyclooctadiene ligand. The pre-activated catalyst was able to hydrogenate acetophenone with 89 % conversion in 5 min.

Synthetic scope of Ru(OH)x/Al2O3-catalyzed hydrogen-transfer reactions: An application to reduction of allylic alcohols by a sequential process of isomerization/meerwein-ponndorf-verley-iype reduction

Reduction of allylic alcohols can be promoted efficiently by the supported ruthenium catalyst Ru(OH)x/Al2O3. Various allylic alcohols were converted to saturated alcohols in excellent yields by using 2-propanol without any additives. This Ru(OHx/Al 2O3-catalyzed reduction of a dienol proceeds only at the allylic double bond to afford the corresponding enol, and chemoselective isomerization and reduction can be realized under similar conditions. The catalysis is truly heterogeneous and the high catalytic performance can be maintained during at least three recycles of the Ru(OH)x/Al 2O3 catalyst. The transformation of allylic alcohols to saturated alcohols consists of three sequential reactions: oxidation of allylic alcohols to α,β-un-saturated carbonyl compounds; reduction of α,β-unsaturated carbonyl compounds to saturated carbonyl compounds; and reduction of saturated carbonyl compounds to saturated alcohols.

Biocatalytic deuterium- and hydrogen-transfer using over-expressed ADH-'A': Enhanced stereoselectivity and 2H-labeled chiral alcohols

Employing the over-expressed highly organic solvent tolerant alcohol dehydrogenase ADH-'A' from Rhodococcus ruber DSM 44541, versatile building blocks, which were not accessible by the wild type catalyst, were obtained in > 99% e.e.; furthermore, employing d8-2-propanol as deuterium source, stereoselective biocatalytic deuterium transfer was made feasible to furnish enantiopure deuterium labeled sec-alcohols on a preparative scale employing a single enzyme. The Royal Society of Chemistry 2006.

Synthetic scope and mechanistic studies of Ru(OH)x/Al 2O3-catalyzed heterogeneous hydrogen-transfer reactions

Three kinds of hydrogen-transfer reactions, namely racemization of chiral secondary alcohols, reduction of carbonyl compounds to alcohols using 2-propanol as a hydrogen donor, and isomerization of allylic alcohols to saturated ketones, are efficiently promoted by the easily prepared and inexpensive supported ruthenium catalyst Ru(OH)x/Al2O 3. A wide variety of substrates, such as aromatic, aliphatic, and heterocyclic alcohols or carbonyl compounds, can be converted into the desired products, under anaerobic conditions, in moderate to excellent yields and without the need for additives such as bases. A larger scale, solvent-free reaction is also demonstrated: the isomerization of 1-octen-3-ol with a substrate/catalyst ratio of 20000/1 shows a very high turnover frequency (TOF) of 18400 h 1, with a turnover number (TON) that reaches 17200. The catalysis for these reactions is intrinsically heterogeneous in nature, and the Ru(OH)x/Al2O3 recovered after the reactions can be reused without appreciable loss of catalytic performance. The reaction mechanism of the present Ru(OH)x/Al2O 3-catalyzed hydrogentransfer reactions were examined with monodeuterated substrates. After the racemization of (S)-1-deuterio-1-phenylethanol in the presence of acetophenone was complete, the deuterium content at the α-position of the corresponding racemic alcohol was 91%, whereas no deuterium was incorporated into the α-position during the race mization of (S)-1-phenylethanol-OD. These results show that direct carbon-to-carbon hydrogen transfer occurs via a metal monohydride for the racemization of chiral secondary alcohols and reduction of carbonyl compounds to alcohols. For the isomerization, the α-deuterium of 3-deuterio-1-octen-3-ol was selectively relocated at the β-position of the corresponding ketones (99% D at the β-position), suggesting the involvement of a 1,4-addition of ruthenium monohydride species to the α,β-unsaturated ketone intermediate. The ruthenium monohydride species and the α,β-unsaturated ketone would be formed through alcoholate formation/β-elimination. Kinetic studies and kinetic isotope effects show that the Ru - H bond cleavage (hydride transfer) is included in the rate-determining step.

Enantioselective reduction of aromatic and aliphatic ketones catalyzed by ruthenium complexes attached to β-cyclodextrin

Water-soluble chiral Ru complexes with a β-cyclodextrin unit have been shown to catalyze the reduction of aliphatic ketones (see scheme) with up to 97% ee and in good to excellent yields in the presence of sodium formate. The β-cyclodextrin unit is an essential component of the catalyst. It contributes to the unprecedented levels of enantioselectivity observed through the preorganization of the substrates in the hydrophobic cavity.

Mechanism of Homogeneously and Heterogeneously Catalysed Meerwein-Ponndorf-Verley-Oppenauer Reactions for the Racemisation of Secondary Alcohols

The mechanism of hydrogen transfer from alcohols to ketones, catalysed by lanthanide(III) isopropoxides or zeolite Beta has been studied. For the lanthanide catalysed reactions, (S)-1-phenyl-(1-2H 1)ethanol and acetophenone were used as case studies to determine the reaction pathway for the hydrogen transfer. Upon complete racemisation all deuterium was present at the 1-position, indicating that the reaction exclusively takes place via a carbon-to-carbon hydrogen transfer. Zeolite Beta with different Si/Al ratios was applied in the racemisation of (S)-1-phenylethanol. In this case the racemisation does not proceed via an oxidation/reduction pathway but via elimination of the hydroxy group and its readdition. This mechanism, however, is not characteristic for all racemisation reactions with zeolite Beta. When 4-tert-butyl cyclohexanone is reduced with this catalyst, a classical MPV reaction takes place exclusively. This demonstrates that zeolite Beta has a substrate dependent reaction pathway.

Mechanistic investigations of the palladium-catalyzed aerobic oxidative kinetic resolution of secondary alcohols using (-)-Sparteine

The mechanistic details of the Pd(II)/(-)-sparteine-catalyzed aerobic oxidative kinetic resolution of secondary alcohols were elucidated, and the origin of asymmetric induction was determined. Saturation kinetics were observed for rate dependence on [(-)-sparteine]. First-order rate dependencies were observed for both the Pd((-)-sparteine)Cl2 concentration and the alcohol concentration at high and low [(-)-sparteine]. The oxidation rate was inhibited by addition of (-)-sparteine HCl. At low [(-)-sparteine], Pd-alkoxide formation is proposed to be rate limiting, while at high [(-)-sparteine], β-hydride elimination is proposed to be rate determining. These conclusions are consistent with the measured kinetic isotope effect of kH/kD = 1.31 ± 0.04 and a Hammett ρ value of -1.41 ± 0.15 at high [(-)-sparteine]. Calculated activation parameters agree with the change in the rate-limiting step by increasing [(-)-sparteine] with ΔH? = 11.55 ± 0.65 kcal/ mol, ΔS? = -24.5 ± 2.0 eu at low [(-)-sparteine], and ΔH? = 20.25 ± 0.89 kcal/mol, ΔS? = -5.4 ± 2.7 eu at high [(-)-sparteine]. At high [(-)-sparteine], the selectivity is influenced by both a thermodynamic difference in the stability of the diastereomeric Pd-alkoxides formed and a kinetic β-hydride elimination to maximize asymmetric induction. At low [(-)-sparteine], the selectivity is influenced by kinetic deprotonation, resulting in lower krel values. A key, nonintuitive discovery is that (-)-sparteine plays a dual role in this oxidative kinetic resolution of secondary alcohols as a chiral ligand on palladium and as an exogenous chiral base.

Dual role of (-)-sparteine in the palladium-catalyzed aerobic oxidative kinetic resolution of secondary alcohols

The mechanistic details of the palladium-catalyzed aerobic oxidative kinetic resolution of secondary alcohols have been elucidated. (-)-Sparteine was found to have a dual role as a chiral ligand and an exogenous base. Saturation kinetics were observed for the dependence on (-)-sparteine concentration. A first-order dependence on [alcohol] and [catalyst] as well as inhibition by addition of (-)-sparteine HCl were observed. These results are consistent with rate-limiting deprotonation under low (-)-sparteine concentrations and rate-limiting β-hydride elimination using saturating (-)-sparteine concentrations. This conclusion is further supported by a kinetic isotope effect of 1.31 ± 0.04 under saturation. The enantioselectivity events are also controlled by addition of (-)-sparteine in which high concentrations afford a more selective kinetic resolution. Copyright

On the steric course of transmetallations on enantiomerically defined α-carbamoyloxy organolithiums

The steric courses of the transmetallations of the title organolithiums to the Sn(IV)-, Mg(II)-, Ce(III)-, Zn(II)-, and Cu(I)-species are described.