Oxirane reactions with carboxylic acids

Oxiranes yield oxazolines with nitriles in the presence of strong acids. The reaction proceeds with inversion, with complete stereospecificity. A new application of the Ritter reaction has been reported the opening of epimeric steroid-16,17-oxiranes in acidic medium with acetonitrile. The reactions of unsaturated hydroxynitriles formed from a-ethylenic oxiranes have been investigated. Numerous publications have appeared on the kinetics of reactions with carboxylic acids and their derivatives. ° ... 

The reaction of carboxylic acids with anhydrides is also commonly used for the cross-linking of diepoxide prepolymers. The reaction has to be carried out at higher temperature than previously and, in the presence of tertiary amines, occurs through ring-opening of the oxiranes by the carboxylate generated from anhydrides ... 

Group of plastics composed of resins produced by reactions of epoxides or oxiranes with compounds such as amines, phenols, alcohols, carboxylic acids, acid anhydrides and unsaturated compounds. 

The hydroxy oxygen of a peracid has a higher electrophilicity as compared to a carboxylic acid. A peracid 2 can react with an alkene 1 by transfer of that particular oxygen atom to yield an oxirane (an epoxide) 3 and a carboxylic acid 4. The reaction is likely to proceed via a transition state as shown in 5 (butterfly mechanism), where the electrophilic oxygen adds to the carbon-carbon n-hond and the proton simultaneously migrates to the carbonyl oxygen of the acid ... 

Dihydro-2f/-pyran-2-one has been prepared by reductive cycliza-tion of 5-hydroxy-2-pentynoic acid [2-Pentynoic acid, 5-hydroxy-], which is obtained in two steps from acetylene [Ethyne] and ethylene oxide [Oxirane] 3 and by the reaction of dihydropyran [277-Pyran, 3,4-dihydro-] with singlet oxygen [Oxygen, singlet].4,5 2ff-Pyran-2-one has been prepared by pyrolysis of heavy metal salts of coumalic acid [2//-Pyran-5-carboxylic acid, 2-oxo-],8 by pyrolysis of a-pyrone-6-carboxylic acid [211 - Pyran-6-carboxyl ic acid, 2-oxo-] over copper,7 and by pyrolysis of coumalic acid over copper (66-70% yield).8... 

Equation 1 expresses a state of equilibrium between an alcohol A. on a molecule whose degree of polymerization is j, the catalyst C and the alkoxide anion A.C. In Relation 2 this activated intermediate reacts with monomeric anhydride A, forming an acid adduct A.AC, which dissociates, forming an unassociable carboxylic acid A.A. Reactions 3-5 depict the union of a carboxylic intermediate with a monomeric epoxide E, or with pendant oxiranes on macromole- ... 

Polymerization of oxiranes with succinic anhydride proceeded in the presence of PPL at 60 °C or 80 °C [63]. The ring-opening of the oxirane might proceed by a carboxylic acid catalyst, which is formed by the reaction of succinic anhydride with serine residue of the lipase catalyst. 

The reactivity of oxiranes with lithium enoiates and related compounds has been widely explored and reviewed . Dianions derived from carboxylic acids react readily with oxiranes, but the reaction can be slowed by steric hindrance . The reaction of oxiranes with dianions of acetoacetates is greatly accelerated by the addition of BF3 Et20 " . Oxiranes react readily with lithium salts derived from nitriles , malonates and analogues , lithiated oxazolines and lithio enamines . 

An alternative route starting from serine 73 or threonine 68 74 makes use of diethoxy-triphenylphosphorane. Attempts to asymmetrically synthesize (25)-aziridine-2-carboxylic acid (1) by treating a, 3-dibromopropanoates with chiral amines 75 or by the Staudinger reaction from oxirane-2-carboxylic acid ester 70,76 leads to optically impure products, whereas 3-alkyl derivatives of tert-butyl aziridine-2-carboxylates can be prepared with high cis-selectivity from a-halo ester enolates and jV-trimethylsilyl imines. 77 Moreover, when optically... 

The Passerini reaction between a-chloroketones, isocyanides, and carboxylic acids afforded a-acyloxy-jS-chlorocarboxamides 52, which, on treatment with an excess of powdered KOH in tetrahydrofuran, underwent O-deacylation followed by a Darzens-type O-alkylation to give the functionalized oxiranes 53. When carboxamides 52 were treated with an excess of CsF, with or without a phase-transfer catalyst, a different ring closure took place to afford 3-acyloxy-2-azetidinones 54 in high yields (Scheme 2.21) [46]. 

The hydroxy function may originate from the reduction of an a-halogenated carbonyl compound or a Grignard reaction. The oxirane oxygen is not always incorporated directly from a hydroxy group for instance, in the case of a carboxylic acid ester, it is derived with neighboring-group participation from an ortho-monoester intermediate. 

The hydrochloride of the derivative of l,7-naphthyridine-3-carboxylic acid 336, which lowers high blood pressure, was prepared from 337 and oxirane 338 on refluxing in MeOH followed by saturation of the reaction mixture with HC1 (1984USP4551534). 

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