Isocyanates, reaction with hydroxy-esters

Chemical methods used for the determination of hydroxyl groups or alcoholic constituents in polymers are based on acetylation [16-18], phthalation [18], and reaction with phenyl isocyanate [18,19] or, when two adjacent hydroxy groups are present in the polymers, by reaction with potassium periodate [9,17]. Alcoholic hydroxyl groups may be found in the following polymers (1) poly(ethylene terephthalate) (PET) [20], (2) poly(methyl acrylate), [21], (3) poly(methyl methacrylate) [21], and (4) polyhydric alcohols in hydrolysates of poly(ester) resins [22]. 

PROPANOIC ACID, 2-HYDROXY-, BUTYL ESTER (79-09-4) Forms explosive mixture with air (flash point 126°F/52°C). Violent reaction with strong oxidizers, caustic substances. Incompatible with aliphatic amines, alkalis, alkanolamines, ammonia, alkylene oxides, epichlorohydrin, isocyanates, sulfuric acid. Attacks many metals, forming explosive hydrogen gas. Flow or agitation of substance may generate electrostatic charges due to low conductivity. 

Apart from the preceding processes, the hydroxy group in hydroxyalkyl-phosphonic or -phosphinic esters has been acylated straightforwardly or by carboxylic acids in the presence of dicyclohexylcarbodiimide " , a procedure also particularly useful for the N-acylation of aminoalkylphosphonic acids for the purpose of enantiomer analysis, phos-phitylated ", phosphorylated and replaced by halogen (Chapter 3, Section II.C. 1). Carbamates have been prepared from isocyanates or isothiocyanates " and hemiacetals formed in reactions with trichloroacetaldehyde the acetal 200 was prepared from ben-zaldehyde and the bis(a-hydroxybenzyl)phosphinic acid. Cyclic boron diesters have also been prepared. ... 

Similar simple reactions can be carried out in solution. Terminal hydroxy groups can be esterified with trifluoroacetic anhydride or glutaric anhydride , although the reaction in the latter case is probably incomplete. Amino groups in the monolayer of cysteamine were reported to react with active esters, such as JV-hydroxysuccinimide (equation 8) . No characterization of the resultant monolayer was, however, given. Cysteamine mono-layers were also acylated with terephthaloyl chloride and an isocyanate derivative . ... 

A practical and effective crossHnking mechanism in cathodic electrocoating is done with polyfunctional blocked isocyanates. The mechanism involves the reaction of an isocyanate group (NCO) with the hydroxy group of the epoxy backbone and liberation of the blocking group. Other crossHnking mechanisms that have been studied are use of addition polymers, Mannich bases, Michael adducts [110] sulfonium stabilized polymers, transesterification reaction of hydroxy, alkoxy, amido and ester systems with hydroxy functional cathodic backbone (Fig. 7-5) [111-114]. 

In an extension of this reaction, the same group prepared functionalized 4-hydroxy-2(l//)-pyridones by reacting vinyl isocyanates with ester eno-lates (Scheme 54). The reaction of 2-azadienes 232 with enolates derived... 

Urethanes (or carbamate esters) are compounds that are the product of the reaction of isocyanates -N=C=0 with a hydroxy compound. This reaction can be written as follows ... 

Two different polyurethanes were used as starting materials a solid elastomer based on a trifunctional polyethertriol, 1,4-butanediol and methylenebis(phenyl isocyanate) and a flexible foam where the diol was replaced by water. The ammonolysis reactions were carried out at 139 °C and 140 atm for 120 min, and with a polyurethane/ammonia weight ratio of 1. Under these conditions the polyurethane conversion was practically total. The ammonolysis reaction transforms the CO group into urea and the ester groups and derivatives of carboxylic acids into amides, whereas ether and hydroxy groups are inert towards ammonia. Scheme 2.7 illustrates the stoichiometry proposed by the authors for the ammonolysis of the polyether urethane. 

Most carbamates used as insecticides are esters of aromatic and heterocyclic hydroxy derivatives of N-methyl- and N,N-dimethylcarbamic acids. They are usually prepared by the reaction of methyl- or dimethylcarbamoyl chloride with the alkali metal salt of the corresponding hydroxy derivative, or alternatively, the hydroxy derivative is carbamoylated with methyl isocyanate (Gysin, 1952). 

Alper and coworkers successfully exploited the cydocarbonylation reactions of o-iodophenols 1, 2-hydroxy-3-iodopyridine 2, and o-iodoanilines 3 with heterocumu-lenes, giving rise to benzo(e]-l,3-oxazin-4-one 4, pyrido[3,2-e]-l,3-oxazin-4-one 5, 4 (3H)-quinazolinone 6, and 4(3H)-quinazolindione 7 derivatives (Scheme 13.2) (21,22]. The reactions proceed in the presence of equimolar amount of palladium acetate and a bidentate phosphine ligand (dppb or dppf) and a base (i-Pr2NEt or K2CO3), in benzene or THF at 80-100 °C under a pressure of 20 atm of carbon monoxide. Carbodumides, isocyanate, and ketenimines were used as cumulenes, and good regioselectivities were achieved with unsymmetrical reactants. The reaction mechanism is beheved to involve in situ formation of a carbamate ester or urea-type intermediate followed by palladium-catalyzed carbonylation and cyclization to yield the products. 

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