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Halohydrin esters

Several related procedures for syn hydroxylation of alkenes involve a halohydrin ester (32) as the key intermediate. In Woodward s procedure an alkene in glacial acetic acid is treated with iodine and silver acetate. Acetyl hypoiodite, MeCOjI, formed by reaction of the latter two reagents attacks the alkene, R R 0=CR R in an electrophilic manner, from the less hindered side to give, by overall anti addition. [Pg.444]

GLYCOLS Dimethyl sulfoxide. HALOHYDRIN ESTERS Phosphorus pentachloride. [Pg.590]

Oxiranes cannot be prepared directly from 1,2-diols by dehydration. Formation of the oxirane intermediate has been studied in connection with the mechanism of the pinacolic rearrangement. Oxiranes can be prepared stereoselectively from the acetals and ketals of 1,2-diols. D-(+)-2,3-epoxybutane has been obtained from an optically active diol via conversion of the ketal 64 to a halohydrin ester (Eq. 52). ... [Pg.41]

Alkenes, R2C = CR2, can react with chlorine and water to form halohydrins, R2C(OH)C(Cl)R2. With alcohol (R OH) solvents, the product is a haloether, R2C(0R )C(C1)R2. In the presence of a carboxylic acid (R C02H), the products include the corresponding halohydrin esters, R2C(02CR ) CCIR2 (Wagner and Zook, 1965b). [Pg.22]

Reactions of Oxirans with Organometallic Compounds. - A general method for the preparation of halohydrin esters via the reaction of organic halides with CO (20 atm) in the presence of PhPd(PPh3)2l has been described.In the particular case of benzyl chloride and cyclohexene oxide, (228) (57.5%) was obtained. A possible mechanism for this reaction is shown in Scheme 14. [Pg.38]

Addition of HOX by means of A-halo amides is important for, inter alia, steroid syntheses. A 9(ll)-double bond adds OH at position 11 (11/S-OH) and Br at position 9 (9oc-Br). Solvents used are mixtures of water with acetone, dioxane, pyridine, or tert-butyl alcohol. 0.46N-perchloric acid has proved particularly suitable as acid since it reduces any tendency to formation of halohydrin esters.295... [Pg.139]

J2J Methods Involving Halohydrin Esters as Intermediates 444... [Pg.437]

Oxirans. - The synthesis of l,2-anhydro-3,4-di-0-benzyl-6-deoxy-a-D-glucopyranose and its conformational analysis have been reported. A range of epoxides have been prepared by base treatment of bromohydrins, which were made by reaction of hydrogen bromide with aldonolactones. A one-pot conversion of vicinal diols into epoxides employs halohydrin ester intermediates generated from cyclic orthoacetates and either acetyl bromide or trimethylsilyl chloride. Levoglucosenone has been transformed into l,6 3,4-dianhydro-p-D-talopyranose by way of a trn/w-iodo-acetoxylation of the alkene moiety... [Pg.80]

General Synthesis and Reactions.—Linear primary alcohols with at least seven carbon atoms are transformed into esters in high yield using copper oxide at temperatures above 170 C in the liquid phase. RusfCO) catalyses the conversion of an aldehyde, or an alcohol with the same number of carbon atoms, into an ester in the presence of diphenylacetylene. " The carbonylation of organic halides in the presence of cyclic ethers is catalysed by PhPdI(PPh3)2 , it provides a synthesis of halohydrin esters in reasonable yield. Cyanohydrin esters have been synthesized by the sodium borohydride reduction of acyl cyanides in the presence of tetra-n-butylammonium bromide. ... [Pg.109]


See other pages where Halohydrin esters is mentioned: [Pg.341]    [Pg.440]    [Pg.292]    [Pg.437]    [Pg.444]    [Pg.437]    [Pg.444]    [Pg.193]    [Pg.243]    [Pg.437]    [Pg.182]    [Pg.1159]    [Pg.342]    [Pg.444]   
See also in sourсe #XX -- [ Pg.388 ]

See also in sourсe #XX -- [ Pg.388 ]




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