Alcoholysis, acid-catalyzed

In this connection it is interesting that the steric course of the acid-catalyzed alcoholysis of the optically active (-)-( S)-A -diisopropyl-p-toluenesulfinamide 253 depends on the structure of the alcohol used. The results so far obtained are listed in Table 2 (246). 

Chiral titanium complexes with a, a, a, a -tetraaryl-l,3-dioxolane-4,5-dimethanol (TADDOL) ligands are versatile auxiliaries in the Lewis acid catalyzed alcoholysis of racemic 4-(arylmethyl)-2-phenyl-5(477)-oxazolones 234, providing the corresponding enantiomerically enriched N-protected amino acid esters 235 (Scheme 7.73). The enantioselectivity of the reaction is dependent on the solvent, temperature, and chiral ligand. Selected examples of the alcoholysis of saturated 5(477)-oxazolones are shown in Table 7.21 (Fig. 7.23). 

The alcoholysis of sulfites such as dimethyl sulfite offers a convenient method for the preparation of high-boiling dialkyl sulfites [33]. Earlier, Voos and Blanke [8a] reported that dimethyl sulfite is converted to diethyl sulfite in 44 % yield. The reaction was shown to be acid-catalyzed and failed when barium carbonate was present. However, a patent refers to the use of lithium hydride in the transalcoholysis of 2,2-(4,4 -dihydroxyphenyl)propane with diphenyl sulfite or di-o-cresyl sulfite [32]. Recently Mehrotra and Mathur [34] reported that the alcoholysis reaction proceeds in the absence of catalysts. Their results are summarized in Eqs. (21)—(23) and Table VII. Tertiary butanol did not... 

The alcoholysis reaction involves the acid-catalyzed exchange of an ethoxy group for a methoxy group on various ethoxysilanes. The progress of the reaction was followed by measuring the disappearance of the ethoxysilane vs. an internal standard (mesitylene). Response factors for each of the ethoxysilanes... 

The kinetics of the acid catalyzed alcoholysis of alkoxysilanes was studied. The influence of attaching a para-substituted phenyl group to the silicon was explored. 

Summary Compared with the fiequently investigated alkoxysilane hydrolysis the reverse silanol aleoholysis has been investigated at model silanols of type XMe2SiOH. The equilibrium constants are within the order of 0.1. The reaction rate of the acid-catalyzed silanol alcoholysis decreases with increasing electronegativity of the substituents X at Si, whereas the base-catalyzed reaction is accelerated. Various alcohols ROH affect the reaction rates preferably by the sterical influence of R. The acid-catalyzed silanol alcoholysis is slighly more affected by substituents X as the reverse alkoxysilane hydrolysis. 

The acid-catalyzed silanol alcoholysis, in dioxane with HCl as catalyst and a 20-fold excess of alcohol, has been investigated measuring the decrease of silanol concentration corresponding to Eq. 4. 

Table 1. Equilibrium constants K, rate constants and ki, for the acid and base-catalyzed alcoholysis of XMe2 iOH and rate constants k for the acid-catalyzed hydrolysis of XMezSiOR...

Hydrolysis or alcoholysis is certainly one of the typical ring-opening reactions of an oxirane ring (Scheme 2). Transition state effects in acid-catalyzed ring openings have been examined <2004JOC5204>. A number of catalysts... 

When an unsymmetrical secondary alcohol is formed, depending on which carbon-oxygen bond is cleaved. With propylene oxide, for example, a base-catalyzed reaction favors the formation of the secondary alcohol almost exclusively, whereas, a non-catalytic or acid-catalyzed alcoholysis yields a mixture of the isomeric ethers. However, the reactions of other a-epoxides, such as 3,4-epoxy-l-butene, 3,4-epoxy-l-chloropropane (epichlorohydrin), 3,4-epoxy-l-propanol (glycidol), and styrene oxide, are more complicated with respect to which isomer is favored. ... 

An X ray examination of the product from the interaction of (2B,4fi,5S)-(-)-3,4-dimethyl-2-phenyl-1,3,2-oxazaphospholidine 2-oxide with an aryl Grignard reagent has demonstrated that ring opening occurs with retention of configuration at phosphorus in accord with Inch s work, but at variance with that of Koizumi, and also in stereochemical opposition to that displayed by acyclic analogues (Mislow). Acid catalyzed alcoholysis of the acyclic phosphinic amide... 

Hydrolysis of trimethylsilyl (TMS) ether [129,130] and alcoholysis of a tetrahy-dropyranyl (THP) [131,132] group have been also employed in acid-catalyzed conversion to PHOST (Fig. 24) (or novolac). Another acetal-protected PHOST, poly[4-(l-phenoxyethoxy)styrene], was prepared by radical polymerization of the corresponding monomer and also by chemical modification of PHOST [133]. This acetal polymer produces a phenolic polymer and phenol upon aci-dolysis (Fig. 24). 

Other reported chemical amplification resist polymers based on the acid-catalyzed deprotection of ether-protected groups include the hydrolysis of tri-methylsilyl (TMS) ether polymer and the alcoholysis of tetrapyranal (THP) -protected group polymer all of these lead to conversion to PHOST (see Scheme 1.2% ) ... 

In 1993, Taguchi and coworkers synthesized the dihydropyrones I3a-d from the fluorinated budding block, 2,4-diaIkoxy-l,l-difluoro-l,3-diene 12 using a Lewis acid-catalyzed hetero Diels-Alder reaction. Treatment of dihydropyrone I3a with TSOH/CH2CI2 followed by Luche reduction and alcoholysis gave the racemic 2,4-dideoxy-4,4-difluorosugars ( )-14a-b (Scheme 5.2). ... 

In this example, prior to water addition, alcoholysis causes the sol to consist primarily of TEOS in 4 equivalents of acetic acid. Thus the question becomes, why does TEOS gel much faster in acetic acid than in ethanol Figure 48.5 shows Si NMR spectra for the Si(OAc)4-ethanol system just described and for TEOS in 4 mol of acetic acid, both spectra taken 45 min after addition of 4 mol of 1 M HCl. No evidence is seen in the NMR spectra for substitution of ethoxide ligands by acetate in the TEOS-acetic acid system. The two spectra are similar. (Additionally, the gel times for the two systems are nearly identical.) Condensation has proceeded rapidly to give a distribution of condensed species typical of acid-catalyzed sols. H NMR spectra show rapid and nearly complete hydrolysis and the... 

Methyl esters of soya, rapeseed and palm oil fatty acids used as biodiesel (Chapters 7 and 8) are preferentially manufactured by transesterification." The acid catalyzed esterification and the alcoholysis of triacylglycerides apply also for the manufacture of higher alcohol monoesters as well as for fatty acid polyol esters. Due to their oily consistency and to their solubilizing properties fatty acid esters of low Mw alcohols are components in odorous substances like perfumes, and cosmetic and drug formulations such as ointments, creams or lotions. 

Cardoso, A. L., S. C. G. Neves M. J. da Silva (2009) Kinetic study of alcoholysis of the fatty acids catalyzed by tin chloride (II) An alternative catalyst for biodiesel production. Energy Fuels, 23,1718-1722,ISSN 0887-0624. 

The addition of a phosphite to an aldehyde giving a phosphonate is the most important reaction [40]. The reaction is catalyzed by acid and since the product is acidic, the reaction is autocatalytic. Furthermore, acids catalyze hydrolysis and alcoholysis and therefore the remedy proposed is continuous removal of the phosphonate over a basic resin (Amberlyst A-21). The examples in the patents illustrate that very stable systems can be obtained when the acidic decomposition products are removed continuously. 

Mbianda and co-workers reported the solvolysis of l-oxo-2,8-diphenyl-2,5,8-triaza-l A -phosphabicyclo[3.3.0]octane under base-promoted alcoholysis and acid-catalyzed alcoholysis. Scheme 8 shows the two different products of such solvolysis reactions [86]. 

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