Difluoromethane, reaction

A global electrophilicity index of common benzylating and acylating agents has been established from MO calculations and it shows a quantitative linear correlation with the experimental substrate selectivity index from a series of benzylation and acylation reactions.21 The values of relative rate coefficients predicted from the index may be accurate to within 10%. The reaction of /-butyl chloride with anisole catalysed by /Moluenesulfonic acid in supercritical difluoromethane has been subject to kinetic analysis.22 The proportions of substitution at the ortho -position and disubstitution increase at lower pressures, attributed to the decrease in the hydrogen-bonding ability of the solvent. 

Single crystals of difluoromethane bis(sulfinic acid) anhydride 17 were isolated, after the cesium salt 119 was stored in the presence of traces of water vapor for several weeks <1998JFC(89)55>. Treatment of difluoromethane-l,l-bis(sulfonyl fluoride) 120 with liquid ammonia led to the formation of the cyclic ammonium imide 121 <1997ZNB359, 1997WO9731909>, while reaction of sulfamide 122 with trifluoroacetaldehyde O-ethyl hemiacetal afforded the cyclic aminal 60 (Scheme 41) < 1999S1731 >. 

Jiang has expanded the Carreira method of alkyne addition to aldehydes to include other ligands and Zn(II) salts (Eq. 13) [17]. Thus use of stoichiometric quantities of Zn(II) difluoromethane sulfonate salt and (lS,2S)-3-(tert-butyldi-methylsilyloxy)-2-N,N-dimethylamino-l-(p-nitrophenyl)propane-l-ol (3) in the addition reaction can afford propargylic alcohols in high ee. Difluoromethanesul-fonic acid is prepared from 3,3,4-,4-tetrafluoro[1.2]oxathietane the amino alcohol has been used in the synthesis of chloramphenicol and is also readily accessible. Application of a combination of this same amino alcohol ligand with Zn(OTf)2 has also been shown to afford products in high yield and ee in addition reactions (Eq. 14) [18]. 

Reactions of methane and ethane with HF recyclable metal fluorides to give fluorocarbons have been reported briefly in the patent and journal literature [16-18], Reaction of methane with hydrogen fluoride in the presence of oxygen and the salt or oxide of a variable valency metal as catalyst yielded small amounts of fluoromethane and difluoromethane at temperatures above 500°C. Olsen et al. [17] reacted copper(ll) fluoride with methane at high temperatures (>600°C) and found products that always included copper metal, hydrogen fluoride, fluoromethane and carbon. Although activity was first detected around... 

A solution (Section 2.2) of 4-(difluoroiodo)toluene (538 mg, 2.1 mmol) in dichloromethane (2 ml) was added dropwise to a cooled (at 0°C) and stirred solution of the dithianic acetal of 4-methylbenzophenone (287 mg, 1 mmol) in dichloromethane (10 ml). The reaction was performed in a PTFE conical flask under an inert atmosphere. On completion, solvent removal and chromatography (silica gel) afforded the 4-tolyl-phenyl-difluoromethane (186 mg, 85%), m.p. not given. 

In the case of thiophenoxide and dichlorodifluoromethane, such a reaction forms chlorodifluoromethyl carbanion, which dissociates to difluorocarbene and chloride anion. Difluorocarbene reacts with the thiophenoxide anion to form phenylthiodifluoromethyl anion. This unstable species reacts in two ways. (1) It abstracts chlorine from another molecule of dichlorodifluoromethane and forms chlorodifluoromethyl phenyl sulfide Y. (2) It reacts with hydrogen of water to form difluoromethyl phenyl sulfide Y. Product Y can also react with two molecules of thiophenoxide anion to give bis(thiophenyl)difluoromethane Y" [SO]. 

Addition of anionic nucleophiles to alkenes and to heteronuclear double bond systems (C=0, C=S) also lies within the scope of this Section. Chloride and cyanide ions are effieient initiators of the polymerization and copolymerization of acrylonitrile in dipolar non-HBD solvents, as reported by Parker [6], Even some 1,3-dipolar cycloaddition reactions leading to heterocyclic compounds are often better carried out in dipolar non-HBD solvents in order to increase rates and yields [311], The rate of alkaline hydrolysis of ethyl and 4-nitrophenyl acetate in dimethyl sulfoxide/water mixtures increases with increasing dimethyl sulfoxide concentration due to the increased activity of the hydroxide ion. This is presumably caused by its reduced solvation in the dipolar non-HBD solvent [312, 313]. Dimethyl sulfoxide greatly accelerates the formation of oximes from carbonyl compounds and hydroxylamine, as shown for substituted 9-oxofluorenes [314]. Nucleophilic attack on carbon disulfide by cyanide ion is possible only in A,A-dimethylformamide [315]. The fluoride ion, dissolved as tetraalkylammo-nium fluoride in dipolar difluoromethane, even reacts with carbon dioxide to yield the fluorocarbonate ion, F-C02 [840]. 

The 1,3-dithianes derived From aromatic ketones give comparable yields in this reaction di-fluorodiphenylmethane is obtained in 49% yield, while bis(4-chlorophenyl)difluoromethane... 

Incomplete conversion of carbon dioxide may occur if the reaction vessel is not properly fluorinated, if a deficiency of fluorine is used, or if the reaction time is too short. Bis-(fluoroxy)difluoromethane can be separated from most impurities... 

They concluded that the driving force behind all reactions in which anomeric effects are believed to be operative is the generation of the hardest possible species. For instance, for the reaction between methane (69) and difluoromethane (61),... 

A. E. Croce and E. Castellano [Int. J. Chem. Kinet., 14, 647 (1982)] studied the kinetics of the gas-phase thermal reaction between bis(fluoroxy)difluoromethane CF2(OF)2 and carbon monoxide over the temperature range 110 to 140°C ... 

Generation of the ylide by reaction of triphenylphosphine with dibromo-difluoromethane... 

A full report (c/. Vol. 1, p. 169) of the photochemical reaction of dibromo-difluoromethane with pentacarbonyliron, to give a low yield of the complex (21), has now appeared. The compound (CF2Br)2Fe(CO)4 obtained in liquid-phase reactions is also obtained from photochemical reactions with 1,2-dibromotetrafluoroethane (thermal reactions lead only to general decomposition ), and is identified as the mononuclear complex... 

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