Ethers alkyl dichloromethyl

Preparation of alkoxydiacyloxymethanes by reaction of carboxylic acids with alkyl dichloromethyl ethers in the presence of tertiary amines [203]. 

This type of carbenoid can also be generated from alkyl dichloromethyl ethers by halogen-metal exchange employing methyllithium in the presence of lithium iodide5. Interestingly, in certain cases, this method provides cyclopropanes with remarkably high cis or endo selectivity (for procedures, see Vol. E 19b, pp 1631 -1639). 

The C=0 of alkoxycarbonyl groups are rarely attacked by PC15, but the exceptions in which attack does occur are preparatively important. Alkyl formates and PC15 give good yields of alkyl dichloromethyl ethers,1134,1135 which can be separated from POCl3 by fractional distillation. 

A variant of the Gattermann-Koch reaction due to Rieche, Gross, and Hoft594 and applicable to aromatic hydrocarbons, phenols and their ethers, and heterocyclic compounds consists of the reaction of these compounds with alkyl dichloromethyl ethers in the presence of tin tetrachloride or aluminum... 

This method is very convenient, requires relatively little time, and gives yields of 70-90%. It can be applied to condensed aromatic systems such as pyrene594 and coronene595 and to ferrocene596 and colchicine.597 Results are equally good when the alkyl dichloromethyl ether is replaced by dichloromethyl methyl sulfide.598 An example is the formylation of veratrole described below, and the same procedure can be used for preparation of mesitylenecarbaldehyde from mesitylene ... 

Addition of the carbenoids derived from alkyl dichloromethyl ethers to the exo-methyleneketal (81) shows an increasing exo-selectivity as the bulk of the alkyl group increases (cyclohexyl > Bu > n-hexyl, methyl) but the effect is not very marked owing to the remoteness of the alkyl group. 

Several chlorophyll derivatives have been prepared by electrophilic substitution, inter alia by formylation reactions. Adopting methods from corrin chemistry.50 alkylation with chloro-methyl methyl ether (caution toxic),32k chloromethyl methyl sulfide,51 and dichloromethyl methyl ether (caution toxic)52 in the presence of Lewis acids are the methods of choice to introduce carbon residues into the chlorin frame work. The compounds listed below have been prepared by these methods. 

Many specific examples of these reactions can be found in reviews in the Organic Reactions series.65 Dichloromethyl ethers are also precursors of the formyl group via alkylation catalyzed by SnCl4 or TiCl4.66 The dichloromethyl group is hydrolyzed to a formyl group. 

Alkyl- or aryl-dibenzothiophenes are conveniently prepared from the 2-arylthio-cyclohexanones, which are readily cyclized and dehydrogenated to yield the respective 1-, 2-, 3- or 4-substituted dibenzothiophenes (382 equation 9 Section 3.15.2.3.2). More complex polycyclic systems are available, using suitable aryenethiols, such as naph-thalenethiols, and 2-bromo-l-tetralone to synthesize the appropriate 2-arylthio ketones. Diaryl sulfides can be converted to dibenzothiophene derivatives in satisfactory yields by photolysis in the presence of iodine (equation 10) (75S532). Several alkyldibenzothiophenes with substituents in the 2- and/or 3-positions were prepared in satisfactory yield by the condensation of dichloromethyl methyl ether with substituted allylbenzo[6]thiophenes (equation 11) (74JCS(P1)1744). 

Chloromethyl methyl ether and bis-chloromethyl ether (CICH2 OCH2Cl) in common with several alkylating agents possess carcinogenic properties in experimental animals and have been listed as assumed human carcinogens similar hazardous properties associated with dichloromethyl methyl ether have not been reported but it would be prudent to handle this compound with due care. 

Trialkylboranes react rapidly with dichloromethyl methyl ether in the presence of a hindered base. Transfer of all three alkyl groups from the boron atom of the intermediate organoborate occurs and subsequent oxidation produces the tertiary alcohol derived from the three alkyl groups of the alkylborane (Equation B3.15). 

Tertiary alkyl groups cannot be transferred readily in the carbonylation reaction or the cyanoborate process. In contrast, transfer of tertiary alkyl groups occurs smoothly in the dichloromethyl methyl ether reaction (Equation B3.16). 

Migration of tertiary alkyl groups in the dichloromethyl methyl ether reaction does however mean that ketones cannot be synthesized using thexylborane and the approach adopted in the carbonylation and cyanidation processes. In order to obtain ketones by this route, boranes bearing chloro or alkoxy groups, i.e. groups of very low migratory aptitude, have to be used as substrates (Equation B3.17). 

Butyl dichloromethyl ether/zinc chloride served as the reagent for the conversion of aryl m-carboxyalkyl Lelluriums and 2-carboxyphenyl organo telluriums to acid chlorides. These reactions should be carried out at below 20°. At higher temperatures the 2-chlorocarbonyl-phenyl aryl telluriums will rearrange to 2-arylcarbonylphenyl tellurium chlorides5,6 (p.244). 2-Chlorocarbonylphenyl alkyl telluriums do not rearrange at 50°7,8. 

The use of a,a-dichloromethyl alkyl ethers for the conversion of carboxylic acids to acid chlorides was first reported by Heslinga et al. in 1957.4 The submitters have found that the readily available a,a-dichlo-romethyl methyl ether2 is the reagent of choice for the preparation of pyruvoyl chloride.6 This simple and economical procedure has been used in other laboratories,51213 and the submitters have applied the method to the preparation of three other a-keto acid chlorides 2-oxobutanoyl chloride (32%), 3-methyl-2-oxobutanoyl chloride (10%), and phenylglyoxylyl chloride (78%).6... 

Chiral boronic esters react with organolithium reagents to form diorganylalkoxyboranes (borinic esters). Subsequent reaction with the anion of dichloromethyl methyl ether then yields chiral ketones by rearrangement of both of the groups on boron (Scheme 42). No racemization is observed in this sequence and alkyl-, aryl- or alkynyl-lithium reagents can be used. 

We include in this section formylation reactions involving carbon monoxide, hydrogen cyanide, formyl fluoride and dichloromethyl alkyl ethers." The Vilsmeier and Reimer-Tiemann formylation reactions are the subjects of other chapters (Volume 2, Chapters 3.4 and 3.5). 

Arenes such as benzene, biphenyl and naphthalene are formylated using dichloromethyl alkyl ethers in the presence of a Lewis acid. The dichloromethyl alkyl ethers are easily prepared by the reaction of phosphorus pentachloride with alkyl formates. The most frequently used Lewis acids are titanium(IV) chloride and tin(IV) chloride. It is presumed that the electrophiles involved are alkoxychlorocarbenium... 

Dichloromethyl methyl ether, CH30CHC12, which can be regarded as the ester dichloride of orthoformic acid, does not give homogeneous products from alcohols and is thus, in general, unsuitable for preparation of alkyl chlorides.927... 

Disubstituted pyrroles lacking substituents at the 3- and S-positions are often required in porphyrin synthesis, and these can now be prepared from pyrrole itself. Thus, trichloroacetylation or trifluoroacetylation of pyrrole affords the 2-trihaloacetylpyrrole 8, which can be converted into the corresponding esters 9, carboxylic acids, or amides. The amides have been acetylated, or formylated, at the 4-position specifically, and the resulting acyl pyrroles (10) have been reduced to the alkyl pyrroles (11). This general procedure has now been improved by direct Friedel-Crafts formylation of the trichloroacetylpyrrole (8a) with dichloromethyl methyl ether (aluminium chloride) to the diacylpyrroles... 

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