Alcohol direct oxidative esterification

Because of the problems with disposal of the bisulfate waste and the handling of HCN, much research has been devoted to alternative processes. The new processes range from using new feedstocks such as isobutylene / t-butyl alcohol, ethylene, isobutane or methylacetylene to techniques for recycling the HCN and / or ammonium bisulfate279 28°. In 1998 Asahi replaced 60,000 tonnes per year of MMA capacity based on direct oxidation of isobutylene with a new process that also starts with isobutylene. However the new direct oxidative esterification (DOE) process makes MMA by the simultaneous oxidation and esterification of methacrolein, which eliminates the intermediate production of methacrylic acid298. 

Esters are very useful chemical intermediates, in terms of atom economy and versatility, and can be helpful in further transformations. Esterification is one of the fundamental transformations in organic synthesis and is widely used in laboratories and industry [1]. Oxidative esterification of aldehydes with alcohols is an attractive method for the synthesis of esters because aldehydes are readily available raw materials on a commercial scale. Although several facile and selective esterification reactions have been reported [2], the development of a catalytic method for the direct oxidative esterification of aldehydes with alcohols under mild and neutral conditions in the presence of molecular oxygen as the terminal oxidant is highly desirable from both economic and environmental aspects. 

Figure 13.6 Life cycle of polyfmethyl methacrylate) (PMMA)-containing products. MMA, Methyl methacrylate ACH, acetone cyanohydrin method TBA-DO, tertiary butyl alcohol (isobutylene) direct oxidation method TBA-DOE, tertiary butyl alcohol (isobutylene) direct oxidative esterification method C2, ethylene method TR, thermal recovery MR, material recycling. Modified from Kikuchi Y, Hirao M, Ookubo T Sasaki A. Design of recycling system for polyfmethyl methacrylate) (PMMA). Part 1 recycling scenario analysis. Int J Life Cycle Assess 20i4 i9(i) 120—9.

Direct oxidative esterification of alcohols (Fig. 5.21) can be viewed as an example ofa catalytic cycle with seven steps. 

Fig. 5.21 Catalytic cycle for direct oxidative esterification of alcohols. (Reproduced from S. Tang,J. Yuan, C. Liu, A. Lei, Dalton Trans. 43 (2014) 13460—13470. Copyright 2014 Royal Society of Chemistry).

Some acrylates are still produced by a modified Reppe process that involves the reaction of acetylene, the appropriate alcohol (in the case of butyl acrylate, butyl alcohol is used), and carbon monoxide in the presence of an acid. The process is continuous and a small amount of acrylates is made this way. The most economical method of acrylate production is that of the direct oxidation of propylene to acrylic acid, followed by esterification. 

In contrast to the oxidative deavage of the C10-C11-moiety, hydroboration followed by oxidation furnishes Cll-functionalized quinine and quinidine derivatives. As an illustration, only transformations in the quinidine series are shown (cf. Scheme 12.14). Cll-aldehyde 58 was obtained either upon direct oxidation of the borane species with PCC/Si02 or via an improved stepwise procedure including (i) oxidation with Me3NO-2 H20 to yield the terminal alcohol 57 and (ii) subsequent Dess-Martin oxidation [35], Oxidation and esterification of alcohol 57 using Jones reagent and MeOH/HCl gave the Cl 1-ester 59, which is a suitable precursor for the synthesis of cinchona alkaloid macrocycles (Scheme 12.15) [38],... 

The oxidation of aldehydes to carboxylic acids has been most extensively investigated with horse liver alcohol dehydrogenases (65-67, 69, 73). There are two distinct reactions the direct oxidation of aldehydes as their hydrated gem-diol form [reaction (9)] and the oxidation of hemiacetals to esters [oxidative esterification, reaction (10)]. 

As part of a medicinal chemistry program [16] directed toward discovering new muscarinic receptor ligands, a series of endo- and exo-2-alkyl-2-aza-bicyclo[2.2.1]heptan-5-ol (38 and 39) and endo- and exo-2-alkyl-2-aza-bicyclo[2.2.1]heptan-6-ol (40 and 41) esters have been synthesized from 2-alkyl-2-azabicyclo[2.2.1]heptan-5-enes (Scheme 2.4). Oxidation of the olefin and stereochemical manipulation of the secondary alcohols followed by esterification of the azanorbornene products provided the different isomers required for systematic investigation of the structure-activity relationships of this structural series. 

Esters. Most acryhc acid is used in the form of its methyl, ethyl, and butyl esters. Specialty monomeric esters with a hydroxyl, amino, or other functional group are used to provide adhesion, latent cross-linking capabihty, or different solubihty characteristics. The principal routes to esters are direct esterification with alcohols in the presence of a strong acid catalyst such as sulfuric acid, a soluble sulfonic acid, or sulfonic acid resins addition to alkylene oxides to give hydroxyalkyl acryhc esters and addition to the double bond of olefins in the presence of strong acid catalyst (19,20) to give ethyl or secondary alkyl acrylates. 

Ethyl benzoylformate has been prepared by the direct esterification of the acid 1 and by the action of oxides of nitrogen on an alcoholic suspension of indigo.2 The acid has been prepared by many different reactions but the most practical are the hydrolysis of benzoyl cyanide,3 the oxidation of acetophenone 4 and the oxidation of mandelic acid.5... 

A huge number of ester and carbonate derivatives of polynitroaliphatic alcohol have been synthesized driven by the search for new explosives and energetic plasticizers and oxidizers for propellant and explosive formulations. Most of these are derived from 2-fluoro-2,2-dinitroethanol and 2,2,2-trinitroethanol ° and have excellent oxygen balances. Some examples are illustrated above (168-174) but more comprehensive lists can be found in numerous reviews. " " Direct esterification of polynitroaliphatic alcohols with nitric acid, mixed acid, or acetic anhydride-nitric acid has been used as a route to mixed polynitroaliphatic-nitrate ester explosives. ... 

Support-bound, enantiomerically pure alcohols can be converted into phosphonates by Mitsunobu esterification, which results in complete inversion at the stereo-genic center. This strategy has been used to prepare peptidyl phosphonates on solid phase. These are interesting transition-state analogs with potential utility as peptidase inhibitors (Figure 11.3 [12,13]) or tyrosine phosphatase inhibitors [14]. Serine or threonine derivatives can be converted into phosphonates by direct phosphonylation with an activated monoalkyl phosphonate [15] or by treatment with phosphonamidites RP(OR)NR2 in the presence of tetrazole followed by oxidation [16]. 

The metatheis of acetates with the alkali alkoxides (method 5) can be used for the preparation of the methoxides and ethoxides of all three elements and is the only reaction leading to Hg(OR)2 [1623]. The trans-esterification of Zn(OMe)2 (method 6), according to [1121], can be carried out only in the presence of LiOR (forming soluble bimetallic complexes). The direct electrochemical synthesis on the anodic oxidation of metals in alcohols has been described for Zn(OEt)2 and a series of cadmium derivatives (Cd(OR)2 — obtained in the presence of such donor ligands as Dipy, Phen, and Dmso [98]) (method 2). 

The final oxidation step of the primary alcohol at C-l in L-Srb requires acetone protection, which is carried out in a standard textbook way in the presence of an excess of sulfuric acid. The oxidation at C-l has been accomplished in a number of ways [147] it seems that nowadays aerobic oxidation in the presence of palladium or platinum is preferred. Deprotection, requiring additional sulfuric acid, affords 2KLG, which is transformed into ASA via esterification and lac-tonization. Alternatively, the diacetone derivative of 2KLG can be converted directly into ASA by treatment with HC1 in an organic solvent. 

Oxidation of primary alcohols in acid media is often accompanied by esterification. By the use of the proper proportions of reactants, fair yields of esters may be obtained directly from the alcohols e.g., -butyl n>butyrate (47%) by chromic acid oxidation of n-butyl alcohol. Aqueous acid chlorate solutions in the presence of vanadium pentoxide have been used for this purpose. ... 

Uses Modifier for PP, PVC, polyethylene, PS, and high-performance engineering resins antioxidant heat stabilizer UV stabilizer vise, depressant emulsifier in cosmetics emollient, skin protectant, film-former in skin care chemical intermediate for oxidation, ethoxylation, sulfation, amination, esterification coemulsifier and direct additive in coatings processing aid, lubricant, dispersant in plastics food-pkg. adhesives Trade Names Unilin 700 Alcohol... 

The PTT is aromatic polyester prepared by the melt polycondensation of 1,3-propanediol (1,3-PDO) with either TPA or dimethyl terephthalate (DMT). The PTT is synthesized by the transesterification of propanediol with dimethylene terephthalate or by the esterification of propane diol with TPA. The reaction is carried out in the presence of hot catalyst like titanimn butoxide (Ti(OBu) ) and dibutyl tin oxide (DBTO) at a temperature of 260°C. The important by-products of this reaction include acrolien and allyl alcohol (Chuah, 2001). Direct esterification of propane diol and TPA is considered as the least economic and industrial method. The reaction is carried out in the presence of a heel imder a pressure of 70-150 kPa at a temperature of 260°C. The heel is usually referred to the added PTT oligomers which act as a reaction mediiun and increase the solubility of TPA (Chuah, 2001). Recent studies by different groups show that the selection of the catalyst plays a major role on the reaction rate and PTT properties. Commonly used catalysts like titanium (Doerr et al., 1994), tin (Kurian and Liang, 2001 Fritz et al., 1969) and antimony (Karayannidis et al., 2003 Fitz et al., 2000) compounds have their own limitations. Titanimn-based catalysts are active but the PTT is discolored, antimony-based catalysts are toxic and only active in polycondensation while tin-based compounds have lower catalytic activity. Karayannidis and co-workers (2003) reported the use of stannous oetoate ([CHj(CH2)3CH(C2Hj)COO]jSn) as the catalyst for PTT synthesis but its catalytic activity is poor, resulting in a low molecular weight PTT which was confirmed... 

PTT is melt-polymerized by either the transesterification of PDO with DMT or by the direct esterification of PDO with TPA. The process is similar to the polymerization of PET but with several important differences. Since the reactivity of PDO is much lower than that of ethylene glycol, hot catalysts such as titanium butoxide (12) and dibutyl tin oxide (13), normally too fast for PET, are used to polymerize PTT. Melt polymerization is carried out between 250 and 275°C, about 40° C lower than that used for PET. PTT has different polymerization side reaction products. Instead of cyclic trimers, PTT produces cyclic dimers. It also gives off acrolein and allyl alcohol instead of acetaldehyde gaseous by-products. Acrolein requires special handling and disposal. 

Surface modifications of polymers is brought about by the introduction of alcohol functionality, e.g., poly(tetrafluoroethylene-co-hexafluoropropylene) on reduction with sodium naphthalide in THF results in an unsaturated modified surface layer, the thickness of which is controlled with reaction time and temperature. The air sensitive surface contains alcohols, ketones, aliphatic C-H bonds in addition to C=C and C C. The more alcoholic groups are introduced by hydroboration-oxidation, but the esterification leads to the formation of ester in lower yield. This reveals that the reactivity of OH group is similar to hindered alcohols. The reactivity of the surface can be enhanced by chain extension of secondary surface alcohols with ethylene oxide to form a surface containing primary alcohols groups separated from the polymer backbone by C-2 spacer. On the other hand, primary alcohols are directly introduced to the surface by reaction of the reduced layer with 9-BBN, followed by carbonylation and reduction [5]. 

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