Alcohols catalyst

Manufacture and Uses. Acetoacetic esters are generally made from diketene and the corresponding alcohol as a solvent ia the presence of a catalyst. In the case of Hquid alcohols, manufacturiag is carried out by continuous reaction ia a tubular reactor with carefully adjusted feeds of diketene, alcohol, and catalyst, or alcohol—catalyst blend followed by continuous purification (Fig. 3). For soHd alcohols, an iaert solvent is used. Catalysts used iaclude strong acids, tertiary amines, salts such as sodium acetate [127-09-3], organophosphoms compounds, and organometaHic compounds (5). 

Aldehydes and Ketones. Esters are obtained readily by condensation of aldehydes in the presence of alcoholate catalysts such as aluminum... 

Hydration of Ethyl Ether. Using the same type of acid catalysts as in the hydration of ethylene to ethanol, ethyl ether can be hydrated to the alcohol. Catalysts that have been used for the hydration of ether include phosphoric acid (144), sulfuric acid (145,146), hydrochloric acid (147), metallic oxides (141,148,149) and sihcates (150). Sulfuric acid concentrations ranging from 5—25% at 200°C (144) to 63—70% at 110—135°C and 1.01—1.42 MPa (10—14 atm) (148) have been claimed. 

Since the addition of dialkylzinc reagents to aldehydes can be performed enantioselectively in the presence of a chiral amino alcohol catalyst, such as (-)-(1S,2/ )-Ar,A -dibutylnorephedrine (see Section 1.3.1.7.1.), this reaction is suitable for the kinetic resolution of racemic aldehydes127 and/or the enantioselective synthesis of optically active alcohols with two stereogenic centers starting from racemic aldehydes128 129. Thus, addition of diethylzinc to racemic 2-phenylpropanal in the presence of (-)-(lS,2/ )-Ar,W-dibutylnorephedrine gave a 75 25 mixture of the diastereomeric alcohols syn-4 and anti-4 with 65% ee and 93% ee, respectively, and 60% total yield. In the case of the syn-diastereomer, the (2.S, 3S)-enantiomer predominated, whereas with the twtf-diastereomer, the (2f ,3S)-enantiomer was formed preferentially. 

Entry Secondary alcohol Primary alcohol Catalyst (mol% Ir) Base Yield (%) ... 

Catalyst Alcohol Catalyst wt% Reaction time Yield (%) Reference... 

Alcohol Mole ratio of ethyl carbamate/ alcohol Catalyst Temp. (°C) Time (hr) Yield (%) M.p. (°C)... 

Enantioselective alkenylation was first reported by Oppolzer and Nadinov. Divinylzinc adds to aldehydes in the presence of the chiral diamino alcohol catalyst 37 with high enantioselectivity (>96% ) (equation 16)51. Alkenylzinc bromide adds to aldehydes in the presence of the lithium alkoxide of /V-methylephcdrinc (>98% )52. Ti-TADDOL is also an effective chiral catalyst in the addition of divinylzinc53. 

Mechanistic studies of asymmetric amplification using a chiral amino alcohol catalyst have continued to dale"1 151 155. In the case of the chiral titanium complex, the observed asymmetric amplification was influenced by the method of preparation of the catalyst153. Asymmetric amplification is also observed in the catalytic addition of diphenylzinc to ketones100. 

Highly stereospecific catalysts for the polymerization of these monomers were found quite naturally along two lines of search starting from the triethylaluminum-water and triethylaluminum-alcohol catalyst systems, which were known to be stereospecific polymerization catalysts for these monomers when we started the experiments on this subject. Development and interrelation of these catalysts in our research are shown in Scheme 1 (8). 

Organic halide Allylic alcohol Catalyst Reaction conditions Products % yield)... 

Figure 7. Lineweaver-Burk plots of amylose hydrolysis rates catalyzed by the random copolymer in the presence of poly(vinyl alcohol). [Catalyst] = 2.00 X 10 3N. [Poly(vinyl alcohol)] = (O) 0 ( ) 4.0 X 10 2M (A) 8.0 X 10 2M. Km and Kr calculated according to Equation 4 are 0.083 and 0.22 M, respectively.

Primary, secondary, and tertiary y-amino alcohols (27-30) have been used as chiral catalysts in the enantioselective addition of diethylzinc to aromatic aldehydes.109 The first evidence of the substituent-dependent enantioselectivity of 1,3-amino alcohol catalysts has been observed, and the phenomenon interpreted by using molecular modeling at the ab initio level. 

The transition state shown in Scheme 9.6 was also postulated by the Pete group [16], Both functional groups of the /(-amino alcohol catalyst play an important role in proton transfer by coordinating to the dienol. The resulting cyclic transition state is shown in Scheme 9.6. It is postulated that in this transition state abstraction of the hydroxyl proton from the dienol occurs in concert with protonation of the carbon in a-position by the hydroxyl group of the /(-amino alcohol. 

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