Diacylated diols

Until the mid-1960s, phenylenediamines were used primarily for oxidative purposes the para isomer was of major importance. Since then, the use of phenylenediamines to manufacture polymers has far exceeded their use for oxidative purposes. The y -phenylenediamines, (2,4 and 2,6)-toluenediamine, are widely used for the manufacture of polyurethanes. Phenylenediamines are dihinctional and react with other dihinctional compounds, such as dianhydrides, diacyl chlorides, dicarboxyHc acids, and disulfonyl chlorides to give polyamides. Phenylenediamines also give polymers with epoxides, diols, diacetals. 

These authors have prepared quite a variety of crown-related esters and have incorporated numerous heterocyclic subunits in the macrorings. The structural variety can be gleaned from a perusal of the tables at the end of this chapter. Despite this variety, one basic approach has been utilized in most of the syntheses thus far presented. This method involves simultaneous addition of separate benzene solutions of the diacyl halide and diol to an additional several volumes of benzene heated at 45—60°. After the ad-... 

The common condensation polymers and the reactions by which they are formed are shown in Table 1-1. It should be noted from Table 1-1 that for many of the condensation polymers there are different combinations of reactants that can be employed for their synthesis. Thus polyamides can be synthesized by the reactions of diamines with diacids or diacyl chlorides and by the self-condensation of amino acids. Similarly, polyesters can be synthesized from diols by esterification with diacids or ester interchange with diesters. 

The desymmetrization of meso diols requires selective chemical transformation of one of the two enantiotopic hydroxyl functions. Among other possibilities this transformation can consist in acylation or - less commonly - oxidation to a ketone (Scheme 13.19). It should be noted that the enantiomeric purity of the initial reaction products can be upgraded by subsequent conversion of the unwanted enantiomer into the diacylated compound (or diketone), i.e. by subsequent kinetic resolution. 

The Leukart reaction has also been used in the conversion of dehydroepiandro-sterone into 17/3-formylamino-3/3-formyloxyandrost-5-ene, which on reduction with lithium aluminium hydride afforded 3/3-hydroxy-17/3-me thylaminoandrost-5-ene. Acylation with isocaproyl chloride then furnished the N-methyl-N-isocaproyl steroid (197), after selective ester hydrolysis of the initially formed ON-diacyl derivative. The amide (197) was further converted into its 3,5-cyclo-6-ketone via the 3,5-cyclo-6/3-alcohol and thence by reaction with hydrogen bromide into the corresponding 3/3-bromo-5a-6-ketone which upon dehydrobromination furnished a A2-5a-6-ketone and ultimately the 2-monoacetate of the 2/3,3/3-diol (198) after reaction with silver acetate and iodine. Hydrolysis to the 2/3,3/3-diol (198) gave a separable mixture of the 2/3,3/8-dihydroxy-5a- and -5/3-ketones.88... 

Diacyl chlorides react with glycols or other diols such as bisphenols without catalyst, forming polyesters in the presence of an acid acceptor removal of the hydrochloric acid formed is important to the equilibrium... 

Early studies on KRP focused on the enantioselective condensation polymerization of an activated chiral diacyl donor (21) with achiral diols such as 22 (Scheme 11.6a) [29]. Lipases of different origin were tested and the formation of optically active trimers and pentamers was demonstrated for the dibromo monomer. The isolated oligomers were end capped with free hydroxy groups and showed small optical rotation values ([a]D25 +4.5 and +4.3 for the trimer and pentamer, respectively). Similarly, the condensation polymerization of achiral diacyl donors 23 with diastereomeric mixtures of chiral diols (24) was shown as well, affording optically active oligomers (Scheme 11.6b) [29]. 

Scheme 11.6 First examples of enantioselective lipase-catalyzed oligomerization of (a) a diastereomeric chiral diacyl donor with a diol and (b) achiral diacyl donors with...

The reaction of acylphosphonate diesters with alcohols was reported early to lead to dialkyl hydrogenphosphonates and carboxylate esters In a more recent systematic study, conditions were developed to use acylphosphonates for the acylation of alcohols. It was found that 1,5-diazabicyclo [5.4.0] undec-7-ene (dbu) is a highly effective catalyst for acylation of alcohols by acylphosphonates. Two special aspects deserve mention (1) /er butyl alcohol could be acylated with diethyl benzoylphosphonate, in the presence of dbu and 4-dimethylaminopyridine, to give r r/-butyl benzoate in 57% yield (2) the primary hydroxy group of a diol (e.g. butane 1,3-diol) could be acylated fairly selectively in the presence of a secondary hydroxy group by this methodology (ratio of mono to diacyl product =88 12). 

The formation of 1,2-diol products from alkenes can be achieved using Prevost s reagent - a solution of iodine in carbon tetrachloride together with an equivalent of silver(l) acetate or silver(I) benzoate. " Under anhydrous conditions, this oxidant yields directly the diacyl derivative of the anh-diol (Prdvost conditions), while in the presence of water the monoester of the syn-diol is obtained (Woodward conditions). Thus, treatment of a cw-alkene with iodine and silver benzoate in boiling carbon tetrachloride under anhydrous conditions gives the tra 5-dibenzoate (5.92). With iodine and silver(I) acetate in moist acetic acid, however, the monoacetate of the cw-1,2-dihydroxy compound is formed. 

The value of these reagents results from their specificity and the mildness of the reaction conditions. The reaction proceeds through the formation of an iodonium ion which, in the presence of carboxylate and silver ions, forms the resonance-stabilized cation 93 (5.93). Attack on the cation by the carboxylate anion in an Sn2 process gives the trans-diacyl compound. In the presence of water, however, a hydroxy acetal is formed this breaks down to gives the c/s-monoacylated diol. Note that with conformationally rigid molecules, or indeed with any alkene in which there is a preference for initial attack on one of the two faces of the double bond, the cis-diol obtained by the Woodward-Prdvost method may not have the same configuration as that obtained with osmium tetroxide. Related procedures, that avoid the use of expensive silver salts, have been reported with, for example, iodine and thallium(I) acetate or bismuth(III) acetate. 

Dialkylstannylene acetals derived from a number of carbohydrate diols reacted with diacyl chlorides in the presence of a tertiary amine to give symmetrical, non-glycosidically linked disaccharides, such as compound The tungsten... 

To date, interfacial polycondensation has almost exclusively utilized the Schotten-Baumann reaction. In this reaction, a diacyl chloride in, for example, chloroform reacts with a diol or diamine in, for example, water according to... 

If both A-type monomeric units and both B-type monomeric units have the same reactivity and/or fast trans reactions such as transesterification, transamidation, etc., can occur, then the A and A" or B and B" residue distribution is always random. If the reactivities differ and chain transfer reactions do not occur, then kinetically controlled sequential distributions are obtained. In the simplest case, two groups, A and A can each react with a group, B, with reactions between A and A, A and A, A and A, as well as between B and B being excluded. An example is the reaction between a diol and two different diacyl chlorides. The decrease with time in A and A concentrations is then given as... 

Dichloride and Another Diacyl Dichloride in the Ratio 1 1 1 in Pyridine (Sixfold Quantity of Diol) or Triethyl Amine (Twofold Quantity of Diol) at 40P C, The r Values for the Monochlorobisphenol A Were Set Equal to Unity for Reference Purposes... 

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. 

Only recently has the presence of diol lipids, such as diacyl propane-1,3-diol, been confirmed for a wide variety of tissues. This is probably because techniques for the elucidation of their structures are a recent development. Small quantities of such diols are found... 

DMAP-catalyzed acylation of various l, -liner diols (n = 2-5, and 5 ) with 1.03 equiv. of isobutyric anhydride gave 3 1 1 1 mixtures of the monoacylates and the diacylates as shown in Fig. 5b. On other hand, almost pure monoacylates were obtained by the acylation of diols in the presence of 10 mol% of catalyst 8 (Fig. 5a). However, a significant amount of the diacylate formed when further longer linear diols (n 6) were used as the substrates (data not shown). These results suggest that catalyst 8 is able to distinguish the diol structure from the monoacylated monool in the case where the chain length is shorter or equal to 5. 

Fig. 5 Ratios of the mono- and diacylates in the acylation of various linear diols catalyzed by (a) catalyst 8 and (b) DMAP...

Step-Growth Polymerization of a Diacyl Chloride and a Diol Gives a Polycarbonate (Section 29.5C)... 

The tin-containing compounds involved in the above processes exercise their template function by controlling the conversion of non-cyclic diols to cyclic stan-noxanes. This activates the corresponding oxygen atoms, thus facilitating interaction of diacyl dihalides with the latter, to give macrocyclic tetralactones as the only... 

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