From bromochloromethanes

An ester derived from prednisolone has found use as a topical ophthalmic antiinflammatory dmg. Cleavage of the side chain in prednisolone (31-1) with sodium periodate affords the corresponding carboxylic acid (30-2). Treatment of that product with propionyl chloride affords initially the ester at 17 along with some of the mixed anhydride. The anhydride is then hydrolyzed with a mild base to afford the 17-ester (31-3). Alkylation of the carboxylic acid with chloromethylchlorosufonyl chloride (from bromochloromethane and sulfonyl chloride) leads to the chloromethyl ester (31-4) and thus loteprednol [26]. 

At 225—275°C, bromination of the vapor yields bromochloromethanes CCl Br, CCl2Br2, and CClBr. Chloroform reacts with aluminum bromide to form bromoform, CHBr. Chloroform cannot be direcdy fluorinated with elementary flourine fluoroform, CHF, is produced from chloroform by reaction with hydrogen fluoride in the presence of a metallic fluoride catalyst (8). It is also a coproduct of monochlorodifluoromethane from the HF—CHCl reaction over antimony chlorofluoride. Iodine gives a characteristic purple solution in chloroform but does not react even at the boiling point. Iodoform, CHI, may be produced from chloroform by reaction with ethyl iodide in the presence of aluminum chloride however, this is not the route normally used for its preparation. 

Hydrogen bromide, trimethylsilyl bromide and acetyl bromide have all been proven to be suitable bromide transfer agents [e.g. 12, 13]. Tetra-n-butylammonium salts catalyse the interconversion of dichloroalkanes into bromochloroalkanes and chloroiodoalkanes upon reaction with an excess of bromo- and iodobutane, respectively [14]. Similarly, mixed bromochloromethanes are obtained from the reaction of dibromochloromethane with benzyltriethylammonium chloride under basic conditions [15]. 

Bromochloromethane used in place of chloroiodomethane gives slightly lower yields49. Another route from R1 — B(OR2)2 to R1 — CH2 — B(OR2)2 via R1 — CHC1 — B(ORz)250 52 is essentially the same as the route to deuterated compounds (Section 1.1.2.1.5.). 

The sacrificial zinc anode process has also been used to perform the electrochemical cyclopropanation of alkenes from dibromomethane or bromochloromethane in CH2C12/... 

Dibromomethane [74-95-3] (methylene bromide), CH2Br2, is a similar liquid, mp — 52.7° C, bp 96.9°C, Water solubility is 1.17 g/100 g at 15°C. It is prepared by the same methods as bromochloromethane, allowing the reaction to proceed to completion. A laboratory preparation involves removing a bromine from bromoform using sodium arsenite (86). The compound is used as a solvent, as a gauge fluid, and in producing pesticides. Both of these dihalomethanes can be used as dense, readily volatile media for mineral and salt separations. 

Formation of trihalomethanes. Reactions of chlorine with organic compounds such as fulvic and humic acids and humin produce undesirable by-products. These by-products are known as disinfection by-products, DBFs. Examples of DBFs are chloroform and bromochloromethane these DBFs are suspected carcinogens. Snoeyink and Jenkins (1980) wrote a series of reactions that demonstrate the basic steps by which chloroform may be formed from an acetyl-group containing organic compounds. These reactions are shown in Figure 17.4. 

Bromochloromethane was purchased from Tokyo Kasel Kogyo Company, Ltd. or from Aldrich Chemical Company, Inc. and was used without purification. 

A related crown ether (148) has been made from ethyl 3,4-dihydroxyfuran-2,5-dicarboxylate, bromochloromethane, and base, but it has not been much studied.264 Crown ethers containing nitrogen atoms are easily obtained from... 

Diphenylfulvene does not react with dichloromethyllithium. Similarly, 6,6-dimethylfulvene does not react with chlorocarbene (generated from dichloromethane and methyllithium). The non-nucleophilic base, sodium hexamethyldisilazanide, has been used for the generation of chlorocarbene from dichloromethane or bromochloromethane. The latter reaction, carried out with cyclooctene, gave chlorocarbene and bromocarbene adducts (95 and 5% of the mixture, respectively) (see Houben-Weyl, Vol. El9b, p 1506). 

Cram reported the preparation of the first soluble carceplex, carceplex 2 guest, from the shell closure reaction between two bowl-shaped tetrol molecules la, base, and four molecules of bromochloromethane under conditions of high dilution in dipolar, aprotic solvents (Scheme 4-1) [12, 13],... 

Bromochloromethane was used to introduce a chloromethyl group via a selective reaction at the C-Br bond (Fig. 47).260 The reaction stops at the chlorohydrin stage when nm with aldehydic substrates. From ketones, cyclization to the epoxide occurs spontaneously, possibly because of the so-called Thorpe-Ingold effect.261 This reaction confirms that the reactive species is not a chloromethyl anion, highly unstable at the reaction temperature. 

The - t-butylphenol and all the phase transfer catalysts and crown ethers were purchased commercially. The NMP used was purchased from Burdick and Jackson the methylene chloride, methylene bromide, bromochloromethane and chlorobenzene were reagent grade. The sodium hydroxide was Baker Reagent (97%) and the potassium hydroxide was also Baker Reagent (86%). Sodium 4-methylphenoxide... 

MDOT derivatives have been known since the pioneering work of Dallacker and Mues from the year 1975. The synthesis of MDOT-dicarboxylic acid follows the versatile route also useful for 3,4-ethylenedioxythiophene (EDOT), using bromochloromethane instead of 1,2-dihalogenoethanes (Figure 13.1). 

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