Oxirane 2.3- dichloro

In reactions which have some analogy with the interaction of dichloro-carbene/trichloromethyl anions with ketones, 2-dichloromethyloxazolines yield chloro-oxiranes and a-chlorocarbonyl compounds (Scheme 7.18). The formation of the oxiranes is favoured with aldehydes and lower homologue ketones, whereas cyclic ketones and aryl ketones are converted preferentially into the a-chloro carbonyl derivatives [18]. 

Benzopyran 160 reacts with 2,3-dichloro-l, 4-naphthoquinone by substitution of both chlorine atoms. The unstable primary adduct 161 undergoes ring expansion of oxirane 162 to produce thieno benzoxipine 163 in 70% yield (Scheme 32 (1994JCS(P1)2191)). 

A novel method of opening of oxiranes involves the use of (chlo-romethylene)dimethyliminium chloride (39) [see Section II,2c p. 250], monochlorodeoxy or dichlorodideoxy derivatives are obtained, depending upon the reaction conditions employed.83 Thus, methyl 2,3-anhydro-4,6-0-benzylidene-a-D-allopyranoside (110) reacts with 39 in 1,1,2,2-tetrachloroethane at room temperature to give, upon hydrolysis of the primary adduct 111 with an aqueous solution of sodium hydrogen carbonate, methyl 4,6-0-benzylidene-2-chloro-2-deoxy-3-0-formyl-a-D-altropyranoside (112). If a solution of 39 and 110 in 1,1,2,2-tetrachloroethane is heated at reflux temperature, methyl 3,4-0-benzylidene-2,6-dichloro-2,6-dideoxy-o -D-altropyrano-side (113) is obtained in high yield the n.m.r. spectrum of 113, like that of 47 (see Section II, 2c p. 250), showed the presence of two diastereoisomers which differed in the configuration of the benzyl-idene-acetal carbon atom. 

Dichloro-heplafluoro-butyl)-trifluoro- El0b2, 14 (En -> Oxiran)... 

P. R. Lawrence, T. R. Proctor, and P. Politzer, Int. ]. Quantum Chem., 26, 425 (1984). Reactive Properties of rrans-Dichloro-oxirane in Relation to Carcinogenicities of Vinyl Chloride and truns-Dichloro-ethylene. J. S. Murray and P. Politzer, Int. J. Quantum Chem., 31, 569 (1987). A Computational Study of Isomerization Equilibria Relation to Vinyl Chloride Carcinogenicity. P. Politzer and J. S. Murray, in Reviews in Computational Chemistry, Vol. 2, K. B. Lipkowitz and D. B. Boyd, Eds., VCH Publishers, New York, 1991, pp. 273—312. Molecular Electrostatic Potentials and Chemical Reactivity. 

The earliest general method for the reductive deoxygenation of oxiranes to alkenes involved multistep procedures in which halohydrins were intermediates. Comforth, for example, used an oxirane deoxygenation in an early synthesis of squalene (Scheme 11). Diastereoselective double addition of ho-mogeranyllithium (23) to the dichloro diketone (24) gave the bis(chlorohydrin) (25), which was first converted to the diepoxide (26). Subsequent treatment with Nal and Zn in HOAc buffered with NaOAc gave squalene (27). 

C2-homologizati on of sugars with, 264-265 Acetamide, JV-bromo- (AcNHBr, NBA) bromohydrination with, 275-276, 287 Acetaminophen (= paracetamol), 301 Acetate, piperidinium cat. for aldol add., 82 —, sodium a-epimerization of ketones, 277 opening of oxiranes, 282 Acetic acid, anhydride (AcfO) protection with. See Protection Pummerer rearr. with, 51, 265 —, esters (See also Protection of hydroxy groups) C-H acidity, 10 1-methylethenyi ester pr., 174 transenolization, 58 —, bromo-, esters pr., 179 a2-synthon, 19, 65, 309 d2-synthon, 19, 301 —, chloro-, esters pr., 179 hydantoins from, 308 —, cyano-, esters pr., 177 pyrrolines from, 298 —, (dialkoxyphosphinyl)-, esters pr 188 Wittig-Horner olefinations, 267, 282 —, diazo-, ethyl ester pr, 176, 178 cyclopropanes from, 74—75 —, dichloro- deblocking of pixyl ethers, 342 —, hydroxy-, esters pr., 176 —, hydroxyphenyl-, (S)- (l-mandelic acid) ... 

Reaction with benzoyl chloride. Benzoyl chloride reacts with dichloro-methylUthium to give the oxirane (1) or the carbinol (2), depending on the reaction conditions. ... 

The first isolable dichloro-oxirans have been produced by the cycloaddition of dichlorocarbene to the carbonyl group of 7,7-dimethylbicyclo[3.2.0]hept-2-en-6-one under phase-transfer conditions. Both (79) and (80) were isolated from the product mixture. ... 

Under basic conditions chloroform reacts with [ CJacetone to give l,l-dichloro-2,2-dimethyl[2- C]oxirane (Figure 6.76). This product could be trapped in situ with p-chlorophenol and the resulting adduct hydrolyzed to give 2-(p-chlorophenoxy)-2-methyl[2- C]propionic acid ([2- C]clofibric acid, 2671. whose ethyl ester is used as an antihyperlipidemic drug " °. 

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