Chloromethyl compounds

Thiophene and selenophene can be chloromethylated by treatment with formaldehyde and hydrochloric acid. Depending on the conditions, 2-chloromethyl or 2,5-bis(chloromethyl) derivatives are obtained. The chloromethylation of benzo[6]thiophene gives the 3-chloromethyl derivative and that of benzo[6]furan the 2-chloromethyl compound (71AHC(13)235). 

Compound la with no substitution, showed good activity with increased hpophihcity activity. Further increases in lipophihcity led to a decrease in activity. Replacement of a proton of the methyl group by a hpophobic group (chloro) resulted in a further decrease in activity. The order of activity of substituents at the first position was methyl, ethyl, unsubstituted, propyl, and chloromethyl. Compounds with a small substituent at Ci seem to provide optimum activity. As the test compounds could not be converted to water soluble form, in vitro evaluation for antihistaminic activity could not be performed. 

Method A The chloromethyl compound (35 mmol) and aldehyde (25 mmol) are added with stirring to K2CO, (6.9 g) and TEBA-C1 (0.285 g, 1.25 mmol) in DMF (8 ml) under N2 at 40°C. When the reaction is complete, as indicated by GLC analysis, the mixture is poured into H20 (50 ml) and extracted with Et20 (2 x 50 ml). The extracts are washed well with H20, dried (Na2S04), and evaporated to yield the oxirane. 

Chloromethylation of dibenzofuran with paraformaldehyde in the presence of hydrogen chloride can be controlled to produce either the 2-chloro-methyF ° or the 2,8-bis(chloromethyl) compound. Phosphoric acid... 

Halogenoalkylpyridines also result from direct halogenation of alkylpyridines. For example, the chlorination of 2-methylpyridine gives 2-chloromethylpyridine with small amounts of the di- and tri-chloromethyl compounds (Scheme 48) (63AG(E)144). 

Chloromethylation occurred in high yield at C-3 and C-4 when thienothiophene (73) was treated with paraformaldehyde and HC1 at 50 °C, to give chloromethyl derivative (96 Scheme 28). Treatment of the chloromethyl compound (96) with sodium acetate or sodium ethoxide gave the corresponding acetoxymethyl or ethoxymethyl derivatives (97). Analogous reaction with primary amines led only to the formation of bis-aminoalkyl compounds (98) and no peri-annelated products (99) could be detected (Scheme 29) <76AHC(19)123>. 

A simple variant of this strategy has been applied to the successful synthesis of ( )-hippeastrine (180) (Scheme 20) (140). In the event, vigorous hydrolysis of the urethane ester 61 followed by the carbodiimide-induced cyclization of the resulting amino acid and N-methylation with sodium hydride in methyl iodide furnished the lactam 207. Conversion of 207 to 208 was achieved by chloromethylation followed by reaction of the intermediate chloromethyl compound... 

Methoxymethyl derivatives of polysilanes, which cannot be obtained from the corresponding chloromethyl compounds by nucleophilic substitution because of intramolecular rearrangement, are prepared successfully by the reaction of chloropolysilanes with monochloromethyl ether in the presence of magnesium in tetrahydrofuran. 

Chloromethylation of dihydrocodeinone (133) yields the 1-chloromethyl compound (139 R = Cl), reducible (by zinc and acid) to 1-methyldihydrocodeinone (139 R = H), which can be further reduced to 1-methyldihydrocodeine and 1-methyldihydrothebainone.157 Dihydrocodeinone reacts with dimethylsulphonium... 

Before filtering and washing this highly reactive chloromethyl compound, first a mixture of 625 ml of water (Note 4) and 625 ml of acetic acid in a 4-liter Erlenmeyer flask on a stirring hotplate is brought to 80-85 °C (Note 5). 

The slurry of chloromethylsalicylaldehyde is filtered on a chilled fritted funnel, sucked as well as practical in a minimum time ( < 1 min, tamped down with a glass or plastic utensil, not a metal spatula), and washed as rapidly as possible two or three times with small amounts of ice-cold water (do not let solid ice enter the funnel) (Note 6). The literature 2 2 2 reports a 43% yield of dried, recrystallized chloromethyl compound. 

Note 3. Temperature control is critical during the initial reaction in the ice bath and in the standing afterward. The purity of the crude product is drastically reduced if the reaction mixture ever reaches temperatures above ca. 35°C deep red gums are formed. The color is no doubt due to condensation of the chloromethyl compound with salicylaldehyde acting as a phenol to give aurin-like triarylmethyl dyestuffs see Note 1. 

Note 4. The water must be distilled or deionized, since traces of iron will form highly colored chelates that will contaminate the final product. Using a metal spatula to press the strongly acid filter cake of the chloromethyl compound may also color the material. 

Note 6. The ice must be made from metal-free water see Note 4. The washing is to remove the concentrated acid mother liquor. If the pH is too low during the next step, the hexamine will merely hydrolize more rapidly than it will be quatemized by the chloromethyl compound. The mechanism of the Sommelet reaction has been... 

Only furans with electron-withdrawing substituents can be successfully reacted e.g., Mndzhoyan143 converted 5-methyl-2-carbo-methoxyfuran to the 4-chloromethyl compound. 

The Shaw cyclopalladation reaction (equation 10), reported in 1978, has been developed sufficiently to conclude that it has considerable potenti for functionalization of unactivated methyl groups in die vicinity of a ketone, via the oxime. This was demonstrated with lanost-8-en-3-one, which furnished a cy-clopalladated derivative (32), which allowed functionalization of the 4-Me gro i to CH2D (NaBD4) and CH2I (Ij/CHCls). Attempted oxidation of the cyclohexanone derivative (33) with MCPBA unexpectedly provided the chloromethyl compound (Scheme 29). 

Phenyl-4-methyl-7azaindole-3-carboxaldehyde (148, B = H, R = Ph Scheme 10) was reduced with sodium borohydride to the 3-hydroxymethyl compound (145, R = H, R = Ph) in quantitative yield,whereas the 6-chloro compound (145, R = C1, R = H) was obtained in only 10 % yield. Treatment of 145 (R = H, R =Ph) with thionyl chloride gave the 3-chloromethyl compound (146), isolated in 99 % yield as the hydrochloride. With sodium bicarbonate in water, the 3-chloromethyl salt (146) is hydrolyzed rapidly back to the hydroxymethyl compound (145). An attempt to synthesize the 3-acetonitrile (147) by heating the 3-chloromethyl salt (146) with sodium cyanide in ethanol produced only the bisazaindolylmethylene ether (50%). Use of acetone cyanohydrin gave the acetonitrile (147) (50 %). It was hydrolyzed to give l-phenyl-4-methyl-7-azaindole-... 

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