Diols cyclic acid anhydrides

This chapter covers the kinetic resolution of racemic alcohols by formation of esters and the kinetic resolution of racemic amines by formation of amides [1]. The desymmetrization of meso diols is discussed in Section 13.3. The acyl donors employed are usually either acid chlorides or acid anhydrides. In principle, acylation reactions of this type are equally suitable for resolving or desymmetrizing the acyl donor (e.g. a meso-anhydride or a prochiral ketene). Transformations of the latter type are discussed in Section 13.1, Desymmetrization and Kinetic Resolution of Cyclic Anhydrides, and Section 13.2, Additions to Prochiral Ketenes. 

Polyesters contain the ester group —COO— in the main chain. Many methods are suitable for their synthesis self-condensation of a,o>-hydroxy acids, ring-opening polymerization of lactones, the polycondensation of dicarboxylic acids with diols, transesterification, the polycondensation of diacyl chlorides with diols, polymerization of O-carboxy anhydrides of a- and jS-hydroxycarboxylic acids, and the copolymerization of acid anhydrides with cyclic ethers. The last reaction is commercially used in the curing of epoxides with anhydrides. 

Polycondensation of diols with derivatives of dicarboxylic acids (e.g., cyclic dicarboxylic acid anhydrides, dicarboxylic acid chlorides, or dicarboxylic acid... 

In 1970, it was disclosed that it is possible to achieve the conversion of dimethylformamide cyclic acetals, prepared in one step from vicinal diols, into alkenes through thermolysis in the presence of acetic anhydride." In the context of 31, this two-step process performs admirably and furnishes the desired trans alkene 33 in an overall yield of 40 % from 29. In the event, when diol 31 is heated in the presence of V, V-dimethylforrnamide dimethyl acetal, cyclic dimethylformamide acetal 32 forms. When this substance is heated further in the presence of acetic anhydride, an elimination reaction takes place to give trans olefin 33. Although the mechanism for the elimination step was not established, it was demonstrated in the original report that acetic acid, yV, V-dimethylacetamide, and carbon dioxide are produced in addition to the alkene product."... 

Polyesters have been obtained in organic medium by polyesterification of hydroxy acids,328,329 hydroxy esters,330 stoichiometric mixtures of diols and diacids,331-333 diols and diesters,334-339 and diols and cyclic anhydrides.340 Lipases have also been reported to catalyze ester-ester interchanges in solution or in die bulk at moderate temperature.341 Since lipases obviously catalyze the reverse reaction (i.e., hydrolysis or alcoholysis of polyester), lipase-catalyzed polyesterifications can be regarded as equilibrium polycondensations taking place in mild conditions (Scheme 2.35). 

The key to a controlled molecular weight build-up, which leads to the control of product properties such as glass transition temperature and melt viscosity, is the use of a molar excess of diisopropanolamine as a chain stopper. Thus, as a first step in the synthesis process, the cyclic anhydride is dosed slowly to an excess of amine to accommodate the exothermic reaction and prevent unwanted side reactions such as double acylation of diisopropanolamine. HPLC analysis has shown that the reaction mixture after the exothermic reaction is quite complex. Although the main component is the expected acid-diol, unreacted amine and amine salts are still present and small oligomers already formed. In the absence of any catalyst, a further increase of reaction temperature to 140-180°C leads to a rapid polycondensation. The expected amount of water is distilled (under vacuum, if required) from the hot polymer melt in approximately 2-6 h depending on the anhydride used. At the end of the synthesis the concentration of carboxylic acid groups value reaches the desired low level. 

The chemical transformation must not affect the stereogenic centers. Suitable acyclic candidates are compounds with easily convertible functional groups, such as diols, diamines, amino alcohols, dicarboxylic acids and so on. A number of procedures known before 1973 have been compiled, including conversion of diols and amino alcohols into sulfites or 1,3-dioxolanes by thionyl chloride, or acetalization with ketones31,1"319, as well as the conversions of dinitriles into imides320, dicarboxylic acids into cyclic anhydrides or imides321, and hydroxy acids into oxazolidones 322. 

The known adduct (385) of furan and vinylene carbonate, previously used for the synthesis of some cyclitols,256,257 has been transformed into DL-ribose derivatives. After hydroxylation of 385 and subsequent formation of the isopropylidene derivative, the carbonate group was removed by treatment with barium hydroxide, and the resulting diol was cleaved by oxidation with permanganate. Dicarboxyl-ic acid 386 gave, upon treatment with acetic anhydride, cyclic anhydride 387. The reaction of 387 with azidotrimethylsilane produced... 

LiAlH4 usually reduces open-chain anhydrides to give 2 moles of alcohol, With cyclic anhydrides the reaction with LiAIH4 can be controlled to give either diols or lactones572 (see 9-41). NaBH4 in THF, with dropwise addition of methanol, reduces open-chain anhydrides to one mole of primary alcohol and one mole of carboxylic acid.573 OS VI, 482. 

Acetals are readily formed with alcohols and cyclic acetals with 1,2 and 1,3-diols (19). Furfural reacts with poly(vinyl alcohol) under acid catalysis to effect acetalization of the hydroxyl groups (20,21). Reaction with acetic anhydride under appropriate conditions gives the acylal, furfurylidene diacetate [613-75-2] (22,23). 

Cyclic orthoesters derived from gem-diols offer a further route to alkenes. As part of a three-step conversion, they may be ring opened with hydrobromic acid to give O-acyl bromodeoxy compounds that undergo reductive elimination with copper-zinc. In this way, unsaturated nucleosides have been made by way of mixed 2y3,-bromo-2y3,-deoxy-3,/2, carboxyl-ates.174 A more direct route to alkenes from cyclic orthoesters involves heating in acetic anhydride together with zirconium oxide.175... 

Most compounds of this type are cyclic sulfite and sulfate esters of aromatic 1,2-diols as well as anhydrides of aromatic 1,2-disulfonic acids. The simplest representatives with unsubstituted benzene rings are 1,3,2-benzodioxathiole 2-oxide (48) (catechol sulfite), the corresponding 2,2-dioxide (156) (catechol sulfate) and 2,1,3-benzoxadithiole 1,1,3,3-tetroxide (158) (1,2-benzenedisulfonic anhydride). Compound (48) was synthesized by refluxing catechol with thionyl chloride in the presence of pyridine. In a similar fashion, from 2-mercaptophenol 1,2,3-benzoxadithiole 2-oxide was prepared (81AG603). The dioxide (156) was obtained in two steps by reaction of catechol monosodium salt with sulfuryl chloride in benzene at 0-10 °C and subsequent reflux of the intermediate (155) in the presence of pyridine. 

Cyclic hydroboration of ( + )-limonene with thexylborane yields the pure borabicyclic compound (138), which is oxidized to the diol (32 X = OH) or protonol-ysed with acetic acid to yield pure (—)-carvomenthol (32 X = H) after the usual oxidation.227 The treatment of dialkylcyanothexylborates with trifluoroacetic anhydride followed by oxidation as a route to ketones has been used with ( + )-limonene to give the two bridged-ring ketones (139).228... 

Boronic acids readily undergo self-condensation to give cyclic anhydrides, and either these trisubstituted boroxins (11), or the acids themselves, react spontaneously, but not necessarily completely, in solution, with suitable diols, to give cyclic boronates 12 (see Scheme 1),... 

LAH, SAH and AIH3 in ethers, LAH-N-methylpyrrolidine complex, AlH3-Et3N, Li(MeO)3AlH, or Red-Al in C H at 80°C can be used to reduce acids and anhydrides to the corresponding alcohols [BK5, BYl, CB5, CB7, FSl, H3, M3]. Cyclic anhydrides are transformed into diols (Figure 3.58). Sodium diethyl-... 

In contrast to the usual reaction of aromatic aldehydes with cyclic ketones o-nitrobenzaldehyde condenses with 17-ketones to produce good yields of seco-acids, a reaction which has been applied to the preparation of 16-oxa-steroids. Thus, 3 -hydroxy-5a-androstan-17-one or its acetate affords the seco-steroid (153), which can be oxidised either as the free acid by ozone and alkaline hydrogen peroxide to the diacid (155) or, as its methyl ester (154), with chromium trioxide to the monomethyl ester (156). Diborane reduction of the diacid (155) or lithium aluminium hydride reduction of the dimethyl ester (157) gave the trans-diol (158), cyclised with toluene-p-sulphonic acid to 16-oxa-androstan-3)5-ol (159) or, by oxidation with Jones reagent to the lactone (152) (as 3-ketone) in quantitative yield. This lactone could also be obtained by lithium borohydride reduction of the monomethyl ester (156), whilst diborane reduction of (156) and cyclisation of the resulting (151) afforded the isomeric lactone (150). The diacid (155) reacted with acetic anhydride to afford exclusively the cis-anhydride (161) which was reduced directly with lithium aluminium hydride to the cis-lactone (160) or, as its derived dimethyl ester (162) to the cis-diol (163) which cyclised to 16-oxa-14)5-androstan-3) -ol (164). 

The polyester polyols are obtained by the polycondensation reactions between dicarboxylic acids (or derivatives such as esters or anhydrides) and diols (or polyols), or by the ring opening polymerisation of cyclic esters (lactones, cyclic carbonates). 

Anhydrides and cyclic carbonates. Symmetrical anhydrides are formed when acids are treated with (Cl jCOlaCO and Et3N. The transformation of the terminal glycol unit of a 1,2,3-triol to the cyclic carbonate can be accomplished with triphosgene and pyridine on the other hand, the internal diol system is protected using NaH and (MeO)2CO. 

Cyclic allq lene phosphonates, namely 2-oxo-l,3,2-dioxaphospholanes and 2-oxo-l,3,2-dioxaphosphorinanes, can be obtained through either the controlled hydrolysis of the corresponding phosphorus(III) derivative (Scheme 6.9, route A) or by a transesterification reaction between a diol and a diall l phosphonate (Scheme 6.9, route B). An alternative method has been described, based on the reaction of cyclic ethers with phosphonic acid in the presence of acetic anhydride. ... 

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