Dichloromethyl complex

Scheme 56). Though no definitive mechanism was established, it was noted that the analogous reaction between Tp Rh(CO)2 and chloroform did not proceed to the corresponding dichloromethyl complex, suggesting that the tridentate coordination mode in the latter might preclude clean oxidative addition. 

Phosphine, (2-bromophenyl)dichloro-, 2,991 Phosphine, (w-chloroalkyl)dichloro-, 2, 991 Phosphine, chlorodimethyl-, 2, 991 Phosphine, chloro(dimethylamino)-, 2, 991 Phosphine, chlorodiphenyl-, 2, 990 Phosphine, cyclohexyl(o-anisyl)methyl-rhodium complexes asymmetric hydrogenation, 6, 251 Phosphine, [(dialkylphosphino)alkyl]diphenyl-, 2, 994 Phosphine, dichloromethyl-, 2, 991 Phosphine, dichlorophenyl-, 2, 990 Phosphine, diethylphenyl-, 2, 992 Phosphine, dimethyl-, 2,992 Phosphine, dimethylphenyl-, 2,992 Phosphine, diphenyl-, 2, 992 Phosphine, ethyldiphenyl-, 2, 992 Phosphine, ethylenebis(diethyl-, 2, 993 Phosphine, ethylenebis(diphenyl-, 2,993 Phosphine, ethylenebis(phenyl-, 2,992 Phosphine, ethylidynetris[methylene(diphenyl-, 2,994 Phosphine, [(ethylphenylphosphino)hexyl]diphenyl-, 2, 994... 

The metal-centered complexes can also be used as multifunctional initiators. For example, Fe2+(4,4 dichloromethyl-2,2 -bipyridine)3 or the Ru2+ complex have been used as initiators for the living cationic polymerization of 2-ethyl-2-oxazoline [120],... 

Interestingly, the Fe2+ ion in the core can be easily removed by base, the complex dissociates and the individual polymer dimers can be analyzed. Block copolymers of 2-ethyl-2-oxazoline with other substituted oxazolines have also been made [121]. Ru2+(4,4 dichloromethyl-2,2 bipyridine)3 has also been used as the multifunctional initiator for the ATRP of styrene at 110°C [122], It is interesting to note that the Cu+ ions necessary for the polymerization reaction are solubilized via complexation with other bipyridine species. 

If the pKa of the corresponding acid R1 - H from the stabilized carbanion is smaller than 35, the migration of R1 fails in (dichloromethyl)borate complexes. Failure to convert pinanediol [(phenylthio)methyl]boronate to an a-chloro boronic ester has been reported15. Reaction of (dichloromethyl)lithium with an acetylenic boronic ester resulted in loss of the acetylenic group to form the (dichloromethyl)boronate, and various attempts to react (dichloromethyl)boronic esters with lithium enolates have failed17. Dissociation of the carbanion is suspected as the cause, but in most cases the products have not been rigorously identified. 

Chiral cyclic boronic esters with (dichloroniethyl)lithium at —100 C form borate complexes4. Borate complexes cart also be formed by generation of (dichloromethyl)lithium from dichloro-methane and lithium diisopropylamide in the presence of a boronic ester at —78 C to — 5 C (Section 1.1.2.1.2.2,)28,19. In situ generation of (dibromomethyl)lilhium is required for preparing a-bromo boronic esters (see Sections 1.1.2.1.1.2. and 1.1.2.1.3.2.). 

S)-Pinanediol boronic esters 2 with (dichloromethyl)lithium produce (aS)-a-chloro boronic esters 3. The first experiments provided diastereomerie ratios in the range 75 25 to 98 2. The best results (>94 6) were obtained with phenyl, ethenyl, or 1-phenylethyl attached to the boron atom39 40. The diastereomerie ratios were estimated from the rotations of esters of derived secondary alcohols. It was subsequently found that zinc chloride catalysis of the rearrangement of the intermediate borate complexes 2 improved the yields, usually to 85-95%, with diastereo-meric ratios often >99 1 when R1 = alkyl, as shown by NMR measurements15,43. 

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). 

A chiral Lewis acid-catalysed method for the 1,2-migration of (dichloromethyl)borate complexes to provide synthetically useful (a-chloroalkyl)boronates has been developed,557 and the diastereoselective rearrangement of the a,a-dichloromethylboronate derivatives of 1,2-diols, (427) —> (429), has been explained558 on the basis of a bidentate interaction between the catalytic Lewis acid and the substrate, leading to a favoured transition state (428). 

Transition metal complexes such as Fe(CO)5, in the presence of alcohols, cause a trichloromethyl compound to be selectively reduced to the corresponding dichloromethyl compound. This reaction has been reviewed elsewhere and is a very useful means of generating a dihalomethyl group130. Also chromium(II) complexes have been used to reduce aryl bromides131,132. Aromatic compounds such as benzene, aniline and pyridine have been used as hydrogen donors for the hydrodehalogenation of a-haloketones in the presence of tin(II) and iron(II) salts133. 

Regioselective reaction of phenols. Reaction of phenols with chloroform in aqueous alkaline solution catalyzed by P-cyclodextrin results in virtually complete attack at the para-position by dichlorocarbene to give, after hydrolysis, 4-hydroxybenzaldehydes. If the para-position is substituted, 4-(dichloromethyl)-2,5-cyclohexadienones are obtained as the major product. The selectivity results from formation of a ternary complex from P-cyclodextrin, chloroform, and the phenol. ... 

Cyclopropanation of alkenes carrying electron-withdrawing groups with dihalo-carbenes does not take place under the normal reaction conditions unless the dihalocar-bene is generated from trihalomethylphenylmercury compounds. By this procedure acrylonitrile was converted into l-cyano-2, 2-dichlorocyclopropane in 78% yield and other acrylic derivatives are transformed into dichloromethyl cyclopropane carboxylates (186) (equation 46). Treatment of electron-deficient olefins with dibromomethane in the presence of Ni(0) complex/Zinc/Lewis acid seems to be very effective for cyclopropanation. ... 

Trichloromethyl thioalkyl compounds of formula RSCXClj (a, b, X = Cl, R = Ph or CHjPh) as well as dichloromethyl benzyl thioether react with iron(II) tetraphenylporphyrin (TPP) (233), in the presence of a reducing agent (iron powder or Na2S204), to produce chlorocarbene complexes of type 234 (158). 

Chloride extraction from [2-(dichloromethyl)-7r-allyl] palladium chloride gave a trimethylenemethane palladium complex (J71)-. 

Macrocyclic Thiophens. - Novel macrocyclic Schiff-bases (161), containing thiophen, have been prepared by the non-template condensation of a,co-amino-ethers with thiophen-2,5-dicarbaldehyde. Silver complexes were prepared and crystal structures were determined both for some macrocycles and for a silver complex. In attempts to prepare bridged thia[17]-annulenes, (162) was prepared through the reaction of 2,5-dichloromethyl-thiophen with p-carboxytoluene-a-thiol. Transformation of the carboxyl groups of (162) into bromomethyl, followed by reaction with sodium sulphide,gave (163). The Wittig reaction of 3,4-diformyl-2,5-dimethylthiophen... 

In other cases, the course of a simple interaction can be complex, as in, for example, reactions between methoxide and phosphonothioates based an halomethyl phospho-nothioic acids. Inch s group " examined the behaviour of (7 )-(+)-0-ethyl S-methyl (dichloromethyl)phosphonothioate (139) this could be dechlorinated with H2-Pd/C in a stepwise fashion, and so eventually correlated with the methylphosphonothioate diester of identical configuration at phosphorus furthermore, chlorination of 139 with BuLi-CCl4... 

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