Ethers, dialkyl chlorination

Brominated dimethyisulphone dialkyl ether Bromine/chlorine containing flame-retardant Blend aromatic bromine, aliphatic chlorine... 

This review groups the information published on degradation of the main families of extractants studied in the frame of long-lived minor-actinide and fission-product recovery (1-4) (see Chapter 1) alkyl-phosphorus compounds (phosphates, phosphonic acids, bifunctional compounds like CMPO), amide compounds (dialkyl-amides, malonamides, and diglycolamides), N-donor compounds, and macrocycles like crown ethers and calixarenes (Table 8.1). The multicomponent systems based on the chlorinated cobalt dicarbollide process have not been considered. 

Dialkyl 1-formylmethylphosphonates and their enol ethers react with molecular chlorine or bromine at 0 C by an addition-elimination mechanism to give the a-monohalogenated 1-formyl-methylphosphonates in good yields (66-92%). The reaction temperature has to be carefully controlled in order to avoid a second halogenation. 

Because the exploitation of the chemistry of unprotected phosphonylated acetaldehydes is handicapped by the sensitivity of the P-C bond in acidic media, a reliable alternative procedure for the preparation of dialkyl 1-chloro-1-formylmethylphosphonates from dialkyl 2-ethoxy-vinylphosphonates has been developed. Room-temperatme chlorination of 2-ethoxyvinylphosphonates with dry chlorine in CCI4 followed by hydrolysis of the phosphonylated a,p-dichloro ethers with water at 50-60°C gives the expected monochlorinated aldehydes in 73-82% yields (Scheme 5.70). A similar treatment with bromine in water at 0°C converts diisopropyl 2-ethoxyvinylphosphonate smoothly into diisopropyl 1-bromo-1-formylmethylphosphonate in 92% yield. ... 

Other asymmetric chlorinations are possible by the use of tert-butyl hypochlorite. A hydroxi-molactone is stereoselcctively transformed to an a-chloro nitroso ether by this chlorination reagent in 89 % yield191. Allylic chlorination of ethyl 2,3-dialkyl-2-cyclopropenecarboxylate is also highly stereoselective192. 

With alcohols, chlorine produces alkyl hypochlorites, which explode on exposure to sunlight or heat. Reaction of chlorine with formaldehyde, acetaldehyde, or diethyl ether is violent. Liquid chlorine reacts explosively with carbon disulfide, glycerol, dialkyl phthalates, polypropylene, wax, rubber, and linseed oil. 

The advantages of the partial chlorination of alcohols (60-95% conversion) with HCl and completion of the chlorination by a catalytic phosgenation and subsequent decarboxylation of the resulting chloroformates have been combined in a two-stage process [974, 982]. Only small amounts of dialkyl ethers, alkenes, isomeric chloroalkanes, or dialkyl carbonates are claimed to be formed as side products. 

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