Chloromethylation procedure

A homogeneous anion-exchange membrane can be obtained by introducing a quaternary amine group into polystyrene by a chloromethylation procedure followed by an amination with a tertiary amine according to the following reaction scheme ... 

Frank and Hagenmaier [70] in a detailed study investigated the influence of various chloromethylation procedures and varying degrees of cross-linkage of polystyrene on the course of the Merrifield synthesis of a model pentapeptide, performed on the supports. 

Table 4 very clearly verifies our lengthy experience that the best synthetic results are gained on polymers which are cross-linked to the lowest possible degree. Because the interplay between the swelling properties of a support and the type of chloromethylation procedures has an influence on the success of Merrifield syntheses, these correlations will be discussed in more detail in the light of general aspects on functionalization regarding the chloromethylation as a model reaction. 

Table 4. The influence of chloromethylation procedures and of the degree of cross-linkage on the functionalization of polystyrenes, according to Frank and Hagenmaier [701...

This procedure is called chloromethylation and will not only turn 1,3-benzodioxole into a methyl chloride but will work equally well in converting plain old benzene into benzyl chloride. Both are important stepping stones towards the production of X and meth. For example, benzyl chloride is a schedule I controlled substance because it will beget benzaldehyde and phenylacetonitrile (a precursor for phenylacetic acid). 

CH3OCH2CI, i-Pr2NEt, 0 , 1 h 25°, 8 h, 86% yield. This is the most commonly employed procedure for introduction of the MOM group. The reagent chloromethyl methyl ether is reported to be carcinogenic. 

This procedure illustrates a general method for the stereoselective synthesis of ( P)-disubstitnted alkenyl alcohols. The reductive elimination of cyclic /3-halo-ethers with metals was first introduced by Paul3 and one example, the conversion of tetrahydrofurfuryl chloride [2-(chloromethyl)tetrahydrofuran] to 4-penten-l-ol, is described in an earlier volume of this series.4 In 1947 Paul and Riobe5 prepared 4-nonen-l-ol by this method, and the general method has subsequently been applied to obtain alkenyl alcohols with other substitution patterns.2,6-8 (I )-4-Hexen-l-ol has been prepared by this method9 and in lower yield by an analogous reaction with 3-bromo-2-methyltetra-hydropyran.10... 

Hexen-l-ol and triethylamine were purchased from Acros Organics and used without further purification. Alternatively, 5-hexen-l-ol may be prepared from 2-(chloromethyl)tetrahydropyran according to the literature procedure for the preparation of 4-penten-l-ol (Brooks, L. A. Snyder, H. R. Org. Synth. Coll. Vol. Ill 1955, 698). Dichloromethane (certified ACS) was purchased from Fisher Scientific and was used as received. 

The same procedure can be employed to make well defined comb-like polymers Living polystyrene can be grafted onto a partially chloromethylated polystyrene89 146), or onto a random copolymer of styrene and methyl methacrylate containing less than 10% of the latter monomer I48). 

Substitution of a dipeptide unit by a cychc dipeptide derivative within a peptide chain can induce certain conformational restraints that may alter the biological response via changing receptor selectivity. A facile procedure for synthesis of pyrazinone ring-containing opioid mimetics [21] has been elaborated, based on the cycHzation of readily available dipep-tidyl chloromethyl ketones [22] (Scheme 6). This method affords 2(IH)-pyrazinone derivatives containing substituents with desired functional groups at positions 3 and 6 in high yield. 

Suitable precautions should be taken in utilizing this procedure, since substantial quantities of the volatile, known carcinogen, chloromethyl methyl ether, as well as the volatile and flammable methyl chloride, form under the reaction conditions. While intermediates like 15 and 16 have been postulated in a number of publications and patents in this area, no experimental evidence has been reported that describes the presence or foimation of detectable quantities of these species. 

In 1995 Vanderzande et al. [89] published a novel, modified Gilch procedure to unsubstituted PPV 60 starting from l-chloromethyl-4-(alkylsulfinyl)methyl-benzenes (68). The initial step, elimination of HCl with NaH as a strong base in NMP or DMF, leads to the formation of the sulfinyl-substituted 1,4-xylylene... 

Poly(l,4-naphthylenevinylene) (106) is accessible via the Wessling polymerization procedure. Lenz, Karasz, Wegner et al. have published the synthesis of PNV 106, starting from l,4-bis(chloromethyl)naphthalene [127, 128]. The poly(l,4-naphthylenevinylene) (106) displays an optical absorption energy of 2.05 eV, slightly red-shifted by about 0,3 eV relative to the parent PPV 60-system, due to the electronic effect of the annelated benzene ring. 

Alkenylsilanes can be prepared from aldehydes and ketones using lithio(chloromethyl)trimethylsilane. The adducts are subjected to a reductive elimination by lithium naphthalenide. This procedure is stereoselective for the E-isomer with both alkyl and aryl aldehydes.82... 

Scheme 11.5 gives some examples of these acylation reactions. Entry 1 is an example of a chloromethylation reaction. Entry 2 is a formylation using carbon monoxide. Entry 3 is an example of formylation via to-chloromethyl ether. A cautionary note on this procedure is the potent carcinogenicity of this reagent. Entries 4 and 5 are examples of formylation and acetylation, using HCN and acetonitrile, respectively. Entries 6 to 8 are examples of Vilsmeier-Haack reactions, all of which are conducted on strongly activated aromatics. 

All solvents used for general applications were of reagent grade. For special purposes, purification of solvents was effected using standard procedures. All other reagents were used as supplied commercially except as noted. A solution of chloromethyl methyl ether (6 mmole/mL) in methyl acetate was prepared by adding acetyl chloride (141.2 g, 1.96 mol) to a mixture of dimethoxy methane (180 mL, 2.02 mol) and anhydrous methanol (5.0 mL, 0.12 mol).20 The solution was diluted with 300 mL of 1,1,2,2-tetrachloroethane and used as a stock solution for the chloromethylation experiments. 

Bromobenzyl groups were introduced into PPO by radical bromination of the methyl groups. The PPO bromobenzyl groups and PECH chloromethyl groups were then esterified under phase-transfer-catalyzed reaction conditions with the potassium carboxylates just described. This procedure has been described previously (29). The sodium salt of 4-methoxy-4 -hydroxybiphenyl was also reacted with PECH (no spacer). 

A Michaelis-Arbusov rearrangement followed by a Wittig-Horner reaction is involved in preparation of the distyrylbenzene derivative 11.37, as shown in Scheme 11.15. Precautions must be taken in the first stage to minimise formation of the carcinogenic by-product bis(chloromethyl) ether 11.16. The stilbene bis-ester 11.38 can be made by a similar procedure, or alternatively by the reaction of ethyl acrylate with 4,4 -dibromostilbene in the presence of a palladium-based catalyst (Scheme 11.16), a synthesis that yields the required trans form of the brightener. 

Methoxymethylation of alcohols is generally achieved through alkylation with chloromethyl methyl ether. The procedure described here for the preparation of Bu3SnCH20CH20CH3 avoids the use of the highly toxic chloromethyl ether by employing an acid-catalyzed acetal exchange reaction with dimethoxymethane for the... 

The synthetic procedure described by Arora and Binger [lb] to prepare 461 was extensively applied to the synthesis of unbranched 634 [172,6e] and branched 633, and 635—636 [173,172b] triangulanes. The sequence is based on the addition of a chloromethyl carbene to an appropriate methylenecyclo-... 

Chloromethyl-l,2,4-triazoles can be valuable intermediates in the synthesis of more complex compounds containing a 1,2,4-triazole moiety, and they can be accessed using a number of established methods for the synthesis of the triazole ring system. However, these processes often give variable yields and require much work to construct the starting material. A more convenient procedure has been developed, by which a hydroxymethyl-1,2,4-triazole is converted to the chloromethyl derivative by reaction with thionyl chloride (Equation 20 and Table 6) <2006S156>. 

Several reports have been made of the application of this procedure for the preparation of vinylphosphonates129-131 as well as tertiary vinylphosphine oxides132 in good yield. When formaldehyde is used, this approach provides a convenient method for the preparation of chloromethylphosphonic dichloride.133 Extreme caution needs to be exercised in the performance of this reaction because the extremely hazardous bis-chloromethyl ether is generated as an intermediate and may remain in the product or escape the reaction mixture during performance of the reaction. 

Lee [42] determined pentachlorophenol and 19 other chlorinated phenols in sediments. Acidified sediment samples were Soxhlet extracted (acetone-hexane), back extracted into potassium bicarbonate, acetylated with acetic anhydride and re-extracted into petroleum ether for gas chromatographic analysis using an electron capture or a mass spectrometric detector. Procedures were validated with spiked sediment samples at 100,10 and lng chlorophenols per g. Recoveries of monochlorophenols and polychlorophenols (including dichlorophenols) were 65-85% and 80-95%, respectively. However, chloromethyl phenols were less than 50% recovered and results for phenol itself were very variable. The estimated lower detection limit was about 0.2ng per g. 

Saltar and Paasivirta [155] have described a method for the analysis in soils of MCPA (4-chloro-2-methyl phenoxy acetic acid) and two of its main metabolites, 4-chloro-o-cresol and 6-chloromethyl catechol by gas chromatography of their pentafluorobenzyl derivatives (Fig. 9.12). After derivitization of the residue extract, a clean-up procedure was applied. The best recoveries of compounds from soil were obtained when the extraction was performed by shaking with ether-acetone-heptane-hexane (2 1 1 1) from acidified soil and when the clean-up was done by thin layer chromatography (Table 9.17). Detection limits were in the range 20-25ng absolute. 

A second, and potentially more useful feature is the stability of these unimolecu-lar initiators to a wide variety of reaction and polymerization conditions which is in sharp contrast to traditional initiators for anionic procedures, such as n-butyl lithium. This allows the initiators to be fully characterized, purified and handled by normal techniques, thus simplifying the polymerization process. It also permits a variety of chemical transformations to be performed on the initiator prior to polymerization, which greatly facilitates the preparation of chain end functionalized macromolecules. For example, the chloromethyl functionalized al-koxyamine, 18, can be readily converted in high yield to the corresponding aminomethyl derivative, 19, followed by polymerization to give well-defined linear polymers, 20, with a single primary amine at the chain end (Scheme 12). 

The cycloaddition reaction of the allenyl chloromethyl sulfone 130c was successfully applied to an iterative ring-annulation procedure [115]. 

Gafarov, et al.1 2 3 reported that heating neat tris(chloromethyl)acetic acid to a higher temperature cleanly affords the final product, 3-chloro-2-(chloromethyl)-1-propene. The present procedure allows for the pyrolysis of the crude material obtained in Step B to be used in Step C, thus eliminating the use of large amounts of solvents for recrystallization. 

Reactions that were stirred for up to 5 or 6 days had slightly higher yields (up to 80%) and needed minimum purification. Reactions that were stirred for less than 3 days or more than 6 days had slightly lower yields (60% after recrystallization). The checkers found that distilled 1,1-dibromo-2,2-bis(chloromethyl)cyclopropane was sufficiently pure (1H NMR and mp) for the subsequent step and did not require recrystallization. The procedure has been carried out on a 1-mol scale with comparable results. 

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