Acidic alcoholysis

The benzotriazolyl derivative of acrolein acetal, compound 882, is lithiated, treated with chlorodiphenylphosphine, and the obtained intermediate is oxidized with hydrogen peroxide to phosphine oxide 883 (Scheme 145). The relatively acidic proton in derivative 883 is easily removed by a base, and the obtained anion adds to a carbonyl group of aldehyde or ketone. Subsequent rearrangement and elimination of the phosphorane group generates diene 884. For the derivatives of aldehydes (884, R2 = H), (E)-(E) stereoselectivity of the elimination is observed. Acidic alcoholysis of dienes 884 affords esters of P,y-unsaturated carboxylic acids 885 < 1997JOC4131>. 

The reaction of phosphonic acid chloride (254) with (S)-proline ethyl ester afforded a mixture of diasteromeric amides (255) in high diastereoselectivity. The diastereomers (255) can easily be purified by chromatography. The chiral, practically optical pure organophosphorus compound (256) was obtained from purified (255) by acid alcoholysis. 

Scheme 3 Intramolecular acid alcoholysis of P-lactams leading to y-lactones...

Tethered diacid 18 was as easily prepared as 8 was (Scheme 6).10 Knoevenagel adduct 20 was deprotonated with NaH and then alkylated with dibromide 9 to give 21 in 59% yield. Alkylation of diethyl malonate with 21 gave 22 in 85% yield, and ozonolysis of 22 and acidic alcoholysis delivered 18 in 88% yield. 

Chemical processes for the production of RH As and RHA alkyl esters are composed of two steps (9,22) (Fig. 1). First, PHA is synthesized in natural or recombinant bacteria and then purified. Cells containing PHA can also be used. Second, purified PHA (or cells containing PHA) is depolymer-ized by acidic alcoholysis using sulfuric acid or hydrochloric acid as an acidic catalyst to produce RHA alkylesters. Subsequent saponification of the purified RHA alkylesters yields corresponding RHAs. 

A few 6- and 8-cyanopurines have been prepared and undergo characteristic nitrile addition reactions rather readily. Thus, alkaline hydrolysis produces carboxamides, then carboxylic acids, alcoholysis leads to imidates, ammonolysis to amidines, hydrazinolysis to amidhydrazines, hydroxylamine to amidoximes, and hydrogen sulfide to thioamides. Acid hydrolysis tends to give the decarboxylated acid derivative. Reduction either by sodium-ethanol or, preferably, by catalytic hydrogenation affords aminoalkylpurines and addition of Grignard reagents produces, in the first place, acylpurines. As with aldehydes, most of the compounds examined have been relatively non-polar derivatives. Table 28 lists some reactions and relevant literature. 

The various ways in which esters of cellulose and phosphorous adds can be synthesized are esterification cellulose with free acids alcoholysis, with cellulose, of the esters and amides of phosphoric adds and esterification with mixed anhydrides df phosphoric adds and carboxylic adds. 

Acylation of the bis-enamines (196) by acid chlorides followed by acidic alcoholysis leads to a wide variety of yields (highest in the absence of an a-H in the chloride) of 6-keto-esters (197) in an alternative to the direct Claisen method. The intermediate acylated enamines can also be converted into 6-keto-amides 185... 

Reactions of the nitrile group(s) In general, these reactions start with a nucleophilic attack at the C atom of the nitrile group. Thus 10 reacted with its anion in basic media to yield the dimerization product 2-amino-1,1,3-tricyanopropene . Thiolysis with H2S gave cyanothioacetamide. Acidic alcoholysis in an neutral solvent produced dialkyl propanediimidate dihydrohalides Metal-catalyzed reactions of 10 with methyl acetoacetate and other j5-dicarbonyls have been reported. ... 

The production of such enantiopure compounds, possessing a market value higher than that of the polymer itself, via chemical methods is complex and not economical. Classic PHA depolymerization methods via acidic alcoholysis after the... 

Reactions of Both Functional Groups. Hydrolysis of acrylonitrile catalyzed by hydrochloric acid yields 3-chloropropionic acid. Alcoholysis and chlorination occur simultaneously in the presence of sulfuric acid. Similarly, alcoholysis and hydrochlorination also occur. Addition of both ammonia and hydrogen produces both trimethylenediamine and propylamine. Treatment of acrylonitrile... 

Chemical depolymerisation of P(3HB) to generate methyl esters of (R)-3HB have been performed by acidic alcoholysis using sulfuric acid [244] and hydrochloric acid [245], whereby the latter method proved to be more effective. 

Recently, PHA are also gaining much attention as a source of enantiomerically pure compounds although this possibility was realised almost a decade ago [231,232], Due to the specificity of the PHA synthase, biosynthesised PHA only contain the (R)-isomers of 3-hydroxyacids. Close to 150 different monomer constituents of PHA have been identified to date and therefore various enantiomerically pure compounds can theoretically be obtained by depolymerising the polymers. The depolymerisation can be performed either by chemical or biological methods. Chemical depolymerisation of P[3HB] to generate methyl esters of (R)-3HB have been performed by acidic alcoholysis using sulfuric acid [232] and hydrochloric acid [233], whereby the latter method proved to be more effective. 

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