Acetate Esters Ac

Acetates are generally cleaved under mildly basic conditions but they can be cleaved by acid-catalysed solvolysis (transesterification) as well however, in the 

Chfomobacterium loscosunf lipase or Mucor miehei lipase 91% 

Further examples of enzyme-mediated deprotections of ester derivatives will be discussed in Chapter 6. 

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SYNS ACETIC ACID, (METHYL-ONN-AZOXY)-METHYL ESTER CYCASIN ACETATE MAM AC MAM ACETATE METHYLAZOXYMETH.ANOL ACETATE METHYLAZOXYMETHYLESTER KYSEUNY OCTOVE (CZECH) (METHYL-ONN-AZOXY)METHANOL, ACETATE (ester)... 

R = H) in warm aqueous solution [79], and 2-O-acctylglyccrol (39 R = H, R = Ac) readily isomerizes to an equilibrium mixture consisting largely of the 1-acetate (39 R = Ac, R = H) in neutral or mildly alkaline solution [58], The use of the acetyl protecting group for alcoholic hydroxyl functions is widespread in glycoside (including nucleoside) synthesis [80], oxidation [81], phosphorylation [82], and other reactions. Acetate esters are most readily solvolyzed under basic conditions, but acid-catalyzed solvolysis has also been used [83]. Perhaps the most commonly used deacetylation procedures are ammonolysis with NHs/MeOH and methoxide ion catalyzed methanolysis. 

It yields an oxime meUiiig at 88 and a semicariiHiEone melting aC 124°. On reduction with sodium and alcolio], it vields the con espond-ing alcohol, dorcmol CijU -OH, which occurs in tlie oil in the form of its acetic ester. Doi emol has zhci following characters... 

The catalytic asymmetric aldol reaction of (3-ketoesters with acetals yielded chiral keto-acetal-esters. One such product was reduced to alcohol (-f)-63, which was converted into CSDP ester ( )-64. The ACs of these compounds were determined to be (2/f,3S,4S), respectively, by X-ray crystallography of ( )-64 based on the known AC of CSDP ester moiety. ... 

Acid anhydrides react with alcohols to form esters The reaction may be carried out in the presence of pyridine or it may be catalyzed by acids In the example shown only one acyl group of acetic anhydride becomes incorporated into the ester the other becomes the ac yl group of an acetic acid molecule... 

A number of other methods exist for the a halogenation of carboxylic acids or their derivatives.134 The acids or their chlorides or anhydrides can be a chlorinated by treatment with CuCl in polar inert solvents (e.g., sulfolane).135 Acyl halides can be a brominated or chlorinated by use of N-bromo- or N-chlorosuccinimide and HBr or HC1.136 The latter is an ionic, not a free-radical halogenation (see 4-2). Direct iodination of carboxylic acids has been achieved with L-Cu(II) acetate in HO Ac.137 Acyl chlorides can be a iodinated with L and a trace of HI.138 Carboxylic esters can be a halogenated by conversion to their enolate ions with lithium N-isopropylcyclohexylamide in THF and treatment of this solution at - 78° with I2138 or with a carbon tetrahalide.139 Carboxylic acids, esters, and amides have been a fluorinated at -78°C with F2 diluted in Ni.,4°... 

Cellulose Acetates or Acetyl Celluloses(AC) are esters of cellulose acetic acid, and are the most widely known org cellulose derivs they are used extensively in industry under a variety of trade names. Olsen et al(Ref 3) proposed that AC s be used as deterrents in priming compns, and PreckeI(Ref 8) patented their use as an inhibitor film on large-grain smokeless proplnts. There are also numerous applications of CA s in textiles plastics used in ordnance. The specification requirements for AC s used in proplnts are given in MIL-C-20301. See also Vol l,p A55-R under Acetyl Cellulose for addnl info on AC s... 

The situation is more complicated in the case of 5-bromohexopyranose derivatives, because products of both endo- and exo-elimination may be formed, and available evidence indicates that, with 5-bromo-/ -D-glucopyr-anose esters, base-catalyzed elimination favors the production of endo-alkenes following loss of axial hydrogen and bromine atoms. Alternatively, treatment with zinc-acetic acid gives, mainly, the products of exo-elimination.90 From the acetate 164 (R = Ac) and the benzoate 164 (R = Bz), the 4-enes (165, R = Ac, Bz) were both obtained in 65% yield following treatment with 1,5-diazabicyclo[5.4.0]undec-5-ene, whereas zinc - acetic acid afforded the 5-enes (166, R = Ac, Bz) in 59 and 67% yield. The isomeric endo products 167 (R = Ac, Bz) were isolated in 15 and 11% yield, and, from the... 

ABA ABS ABS-PC ABS-PVC ACM ACS AES AMMA AN APET APP ASA BR BS CA CAB CAP CN CP CPE CPET CPP CPVC CR CTA DAM DAP DMT ECTFE EEA EMA EMAA EMAC EMPP EnBA EP EPM ESI EVA(C) EVOH FEP HDI HDPE HIPS HMDI IPI LDPE LLDPE MBS Acrylonitrile-butadiene-acrylate Acrylonitrile-butadiene-styrene copolymer Acrylonitrile-butadiene-styrene-polycarbonate alloy Acrylonitrile-butadiene-styrene-poly(vinyl chloride) alloy Acrylic acid ester rubber Acrylonitrile-chlorinated pe-styrene Acrylonitrile-ethylene-propylene-styrene Acrylonitrile-methyl methacrylate Acrylonitrile Amorphous polyethylene terephthalate Atactic polypropylene Acrylic-styrene-acrylonitrile Butadiene rubber Butadiene styrene rubber Cellulose acetate Cellulose acetate-butyrate Cellulose acetate-propionate Cellulose nitrate Cellulose propionate Chlorinated polyethylene Crystalline polyethylene terephthalate Cast polypropylene Chlorinated polyvinyl chloride Chloroprene rubber Cellulose triacetate Diallyl maleate Diallyl phthalate Terephthalic acid, dimethyl ester Ethylene-chlorotrifluoroethylene copolymer Ethylene-ethyl acrylate Ethylene-methyl acrylate Ethylene methacrylic acid Ethylene-methyl acrylate copolymer Elastomer modified polypropylene Ethylene normal butyl acrylate Epoxy resin, also ethylene-propylene Ethylene-propylene rubber Ethylene-styrene copolymers Polyethylene-vinyl acetate Polyethylene-vinyl alcohol copolymers Fluorinated ethylene-propylene copolymers Hexamethylene diisocyanate High-density polyethylene High-impact polystyrene Diisocyanato dicyclohexylmethane Isophorone diisocyanate Low-density polyethylene Linear low-density polyethylene Methacrylate-butadiene-styrene... 

Activated chemiluminescence is observed from these secondary peroxy-esters as well. When the thermolysis of peroxyacetate [281 in benzene solution is carried out in the presence of a small amount of an easily oxidized substance the course of the reaction is changed. For example, addition of N,N-dimethyldihydrodibenzol[ac]phenazine (DMAC) to peroxyester [28] in benzene accelerates the rate of reaction and causes the generation of a modest yield of singlet excited DMAC. This is evidenced by the chemiluminescence emission spectrum which is identical to the fluorescence spectrum of DMAC obtained under similar conditions. Spectroscopic measurements indicate that the DMAC is not consumed in its reaction with peroxyester 28 even when the peroxyester is present in thirty-fold excess. The products of the reaction in the presence of DMAC remain acetophenone and acetic acid. These observations indicate that DMAC is a true catalyst for the reaction of peroxyacetate 28. The results of these experiments with DMAC, plotted according to (27) give k2 = 9.73 x 10-2 M-1 s-1. 

Many cellulose esters, such as cellulose nitrate, cellulose acetate, and mixed esters of cellulose acetate butyrate, have found popularity in commercial scale production. Many new esters continue to appear in the market. Traditionally, esterification is conducted on a heterogeneous system (topo-chemical reaction) however, homogeneous systems employing mixed organic solvents have recently been developed. For example, Ikeda et al. [17] demonstrated that homogeneous esterification and acetalization of cellulose in LiCF DM AC can be achieved. 

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