Carbonic acid esters ethers, cyclic

Without additional reagents Cyclic ethers via cyclic carbonic acid esters Transesterification s. 72, 350 Thermal cleavage of dicyclopentadienes... 

Further data from the polarography and cyclic voltammetry in dimethylformamide are given in Table 5.1 for a series of overall two-electron processes leading to cleavage of a benzyl-heteroatom bond. The first electron transfer step is of the dissociative electron transfer type leading to a benzyl radical. This radical is reduced firrther, at the working potential, to the benzyl carbanion. The carbanion fi om benzyl chlorides, esters, ethers, sulphides, sulphones and quaternary ammonium salts can be trapped by carbon dioxide to form phenylacetic acid [2]. Reac-... 

To 5.69 g of this acetal in 410 ml of t-butanol and 11 ml of water was added a mixture of 5.80 g of potassium carbonate, 22,8 g of sodium periodate, and 270 mg of potassium permanganate in 1230 ml of water. The reaction mixture was stirred at 20-25°C for 20 hours and concentrated in vacuo to remove t-butanol. Ethylene glycole (0.5 ml) was added and reaction mixture extracted with 1 1 ether-benzene to remove neutral material. The aqueous layer acidified with solid sodium dihydrogen phosphate and extracted 4 times with 1 1 ethyl acetate-benzene. The organic layer was dried over sodium sulfate and evaporated to dryness in vacuo affording (+/-)-3-acetyl-2a-(2-carboxyethyl)-5-oxo-ip-cyclopentaneheptanoic acid methyl ester, 5-cyclic ethylene acetal as a mixture of the 3a and 3p isomers. 

Unsymmetrical alkyl phenyl tellurium derivatives were prepared in good yields from phenyl trimethylsilyl tellurium and epoxides, carboxylic acid esters, and linear or cyclic ethers under very mild conditions. In these reactions, which proceed in dichloromethane in the presence of a catalytic amount of zinc iodide, a carbon-oxygen single bond is cleaved. The highly nucleophilic benzenetellurolate binds to the carbon fragment, whereas the trimethylsilyl group becomes linked to the oxygen. 

Phosgene is reported to combine with a wide range of oxygenated materials, including alcohols, ethers, ketones, carboxylic acids, anhydrides, lactones, esters, carbonic acid derivatives, etc. Only the reactions of COCIF with alcohols, phenols and cyclic ethers have been reported, resulting usually in the generation of fluoroformates. Such materials can often be usefully converted into the corresponding fluoro compound by means of decarboxylation in the presence of BF3, EtjO, pyridine, or other materials. 

All esters discussed so far are acyclic molecules (this means they do not contain rings), but there are also cyclic esters, where both the acyl carbon and the alcohol oxygen are constituent members of a ring, as in 88-90. These cyclic esters are called lactones. The common names for structurally simple lactones arise by using the suffix for the open chain carboxylic acid precursor and the word lactone. Compound 88 is y-butyrolactone and 89 is 6-valerolactone, where the name is taken from the common names for the four-carbon acid (butyric acid) and the five-carbon acid (valeric acid). The lUPAC names are based on the cyclic ether, so 88 is 2-oxoolane and 89 is 2-oxooxane. 

The other significant variation of the prototypical Kulinkovich reaction is the so-called Kulinkovich-de Meijere reaction, where de Meijere extended the substrates from esters to amides. Other carboxylic acid derivatives including (cyclic) carbonate, imides, and nitriles also react with the key Kulinkovich intermediate. Szymoniak developed an efficient new synthesis of cyclopropanes via hydrozirconation of allylic ethers (e.g., using Cp2Zr(H)Cl) followed by addition of a Lewis acid (e.g., BFa OEta). Casey et al. further investigated the stereochemistry of this interesting cyclopropanation reaction using deuterated allylic ethers. ... 

Compounds which dissolve in concentrated sulphuric acid may be further subdivided into those which are soluble in syrupy phosphoric acid (A) and those which are insoluble in this solvent (B) in general, dissolution takes place without the production of appreciable heat or colour. Those in class A include alcohols, esters, aldehydes, methyl ketones and cyclic ketones provided that they contain less than nine carbon atoms. The solubility limit is somewhat lower than this for ethers thus re-propyl ether dissolves in 85 per cent, phosphoric acid but re-butyl ether and anisole do not. Ethyl benzoate and ethyl malonate are insoluble. 

Alcohols, esters (but not ethyl benzoate, ethyl malonate or ethyl oxalate), aldehydes, methyl ketones and cyclic ketones containing less than nine carbon atoms as well as ethers containing less than seven carbon atoms are soluble in 85 p>er cent, phosphoric acid. 

The addition of nucleophiles to cyclic fluoroolefins has been reviewed by Park et al. [2 ]. The reaction with alcohols proceeds by addition-elimination to yield the cyclic vinylic ether, as illustrated by tlie reaction of l,2-dichloro-3,3-di-fluorocyclopropene Further reaction results in cyclopropane ring opening at the bond opposite the difluoromethylene carbon to give preferentially the methyl and ortho esters of (Z)-3-chloro-2-fluoroacrylic acid and a small amount of dimethyl malonate [29] (equation 8). 

The reagent most commonly used for oxidation of ethers is RuO. The subject is well summarized in an early review by Gore [75], Primary methyl ethers RCHjOCHj are oxidised to esters RCOOCH, and secondary methyl ethers R R CjHjOCHj to ketones R COR while with benzyl ethers PhCH OR the esters PhCOOR are formed. For cyclic ethers, the carbon atoms adjacent to the O atom are oxidised, and if there are two secondary carbon atoms the main products are lactones, sometimes with partial hydrolysis to carboxylic acids [75], There is a short review on oxidation of ethers by RuO, principally on the mechanisms involved [76],... 

Because of the special structural requirements of the resin-bound substrate, this type of cleavage reaction lacks general applicability. Some of the few examples that have been reported are listed in Table 3.19. Lactones have also been obtained by acid-catalyzed lactonization of resin-bound 4-hydroxy or 3-oxiranyl carboxylic acids [399]. Treatment of polystyrene-bound cyclic acetals with Jones reagent also leads to the release of lactones into solution (Entry 5, Table 3.19). Resin-bound benzylic aryl or alkyl carbonates have been converted into esters by treatment with acyl halides and Lewis acids (Entry 6, Table 3.19). Similarly, alcohols bound to insoluble supports as benzyl ethers can be cleaved from the support and simultaneously converted into esters by treatment with acyl halides [400]. Esters have also been prepared by treatment of carboxylic acids with an excess of polystyrene-bound triazenes here, diazo-nium salts are released into solution, which serve to O-alkylate the acid (Entry 7, Table 3.19). This strategy can also be used to prepare sulfonates [401]. 

A significant portion of the neutral ethyl ether extract from the salts of carboxylated methyl linoleate consists of ,/3-unsaturated cyclic ketones. This material is produced in small but significant amounts (4-10%) (Table I) from the carboxylation of polyunsaturates but not from the corresponding monounsaturated fatty acids and esters (19). These ,/ -unsaturated cyclic ketones were identified spectroscopically (IR, UV, and NMR) as 4. This structural assignment was firmly established by mass spectral analyses before and after hydrogenation of the carbon-carbon double bond. 

Common synthetic methods for the preparation of cyclic 8-enamino esters are the condensation between a lactim ether and benzyl cyanoacetate followed by hydrogenolytic decarboxylation, or the imino ester carbon-carbon condensation with tert-butyl cyanoacetate followed by a trifluoroacetic acid treatment. The use of a thiolactam condensed with ethyl bromoacetate gives, after sulfur extrusion by triphenylphosphine, cyclic 8-enamino esters. Compared with these methods, the Meldrum s acid condensation followed by the monodecarboxylating transesterification described here is more convenient and practical. An extension of this procedure permits preparation of smaller... 

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