Trifluoromethanesulphonic anhydride

Pyridinium chlorochromate, described as a safe, stable, and readily prepared alternative to the chromium trioxide-pyridine complex, is a convenient oxidant for primary and secondary alcohols84 and should find use in steroid chemistry. Dimethyl sulphide ditriflate , prepared from DMSO and trifluoromethanesulphonic anhydride at —78°C, has been used to oxidize 3-hydroxy-steroids.85 The biological... 

The product from Step 3 (0.11 mol) was suspended in 500ml of CHjClj containing 17.4 ml triethylamine, the mixture cooled to -70 °C, trifluoromethanesulphonic anhydride (0.12 mol) added, and the reaction stirred 1 hour at ambient temperature. Thereafter, it was washed with 200 ml water and 100 ml ice cold 1M HCl solution. The organic phase was dried, concentrated, purified by chromatography on a silica gel using CH2Cl2/methyl alcohol, 98 2, and the product isolated in 98% yieid, mp = 68-70 °C. 

In the second procedure, the dehydration of dialkyl [(perfluoroacyl)methyl]phospho-nates (through their enol forms) with trifluoromethanesulphonic anhydride -R3N leads to dialkyl (perfluoroalk-1 -ynyl)phosphonates ... 

Reference has already been made to properties of mixed phosphinic-sulphonic anhydrides. / rr-Butylphenylphosphinothioic trifluoromethanesulphonic anhydride (101) was prepared, in both racemic and optically active forms, from the phosphinothioic acid and trifluoromethanesulphonic anhydride in dichloromethane at -50 °C... 

Earlier, reference was made to the potential third mechanism associated with nucleophilic displacements at phosphoryl phosphorus, namely that which might involve the participation of a phosphaacylium cation. Mixed sulphonic-phosphonic or sulphonic-phosphinic anhydrides 645 (Z = O, R = Me or 4-methylphenyl) have been obtained from the free phosphorus(V) acid and the 1,2,4-triazole 646 in the presence of trifluoromethanesulphonic acid, or 645 (Z = O, R = CF3) from the imidazolides 647 and trifluoromethanesulphonic acid and / r/-butylphenylphosphinothioic acid with trifluoromethanesulphonic anhydride yield the mixed 0-anhydride 648 (R = CF3), some reactions of which are illustrated in Scheme 76 ". Of those reactions, the formation of the iodide 649, albeit in low yield when the reaction is carried out in MeOH, with stereochemical retention of configuration at phosphorus, contrasts with the inversion of configuration observed for the remainder, and which is normally encountered for Sn2(P) displacements. The reaction of648 with methoxybenzene to yield the phosphine sulphide 650 in a solvent of high ionizing power (1,1,1,3,3,3-hexafluoropropan-2-ol a lower yield was obtained in a... 

Malathion, the well-known insecticide, and the much more toxic isomalathion, (83) have one and two chiral centres, respectively. Chiral forms of the former have been prepared from the appropriate diethyl malate by sequential reaction with trifluoromethanesulphonic anhydride and sodium 0,0-dimethyl phosphorodithioate thus, for example, (-)-malic acid yields (/f )-malathion (84). Monodemethylation of the malathion enantiomers with strychnine, and methylation (dimethyl sulphate) of the... 

Indazoles.—iV-Aryl-o-azidobenzamides (391) yield the chloro-indazoles (392) on treatment with thionyl chloride.The formation of 1,3-diphenylindazole (393) by the action of trifluoromethanesulphonic anhydride on benzaldehyde... 

Enol triflates are also excellent substrates in the Heck reaction. They may be prepared by the reaction of enolizable ketones with trifluoromethanesulphonic anhydride or the crystalline A, A -bis(trifluoromethanesulphonyl)anilide (A/ -phenyltriflide) [46]. The enol triflates derived from 2,2,6-trimethylcyclohexanone (90), from the r-butyldi methyl si lyl ether of 3-hydroxy-2,2,6-trimethylcyclohexanone (91), and from 2,2,5-trimethylcyclopentanone (92) couple in excellent yields (88-93%) to methyl vinyl ketone (10) in the presence of bis(triphenyl-phosphine)palladium(n) dichloride [PdCl2(PPh2)2l, to give p-ionone (2) [47], the 3-hydroxy-P-ionone derivative 93 [48], and the 5-membered-ring P-ionone analogue 94 [49], respectively (Scheme 22). 

When copper(i) oxide is treated in benzene with trifluoromethanesulphonic anhydride, the complex (Cu0 S02 CF3)2(C H,), which releases benzene only above 120 °C, is obtained. The trifluoromethanesulphonate ion does not compete with olefins for co-ordination sites on the copper cf. ref. 28, p. 2%) and cationic Cu complexes are formed. Oxidation of alkyl radicals by copper(ii) trifluoromethanesulphonate in acetic acid gives more of the alkyl acetate, by oxidative solvolysis, and less olefin, than oxidation by copper(ii) acetate, the difference in product ratio being due to the greater dissociation of the copper trifluoromethanesulphonate. Silver(ii) complexes Ag (bipy)2-(O3S CF,) (bipy = 2,2 -bipyridyl) may be prepared from the silver(i) complex either by electrolysis or by treatment with silver(ii) oxide and trifluoro-methanesulphonic acid. ... 

Phase-transfer catalysts e.g. benzyltriethylammonium chloride and tetrabutyl-ammonium bromide) have been used in the preparation of O-methyl and 0-benzyl ethers and acetals of formaldehyde e.g. methyl 4,6-O-benzylidene-2,3-0-methylene-a-D-mannopyranoside). A new cyclic ether, methyl 4,6-0-benzylidene-2,3-0-ethylene-a-D-glucopyranoside, resulted when methyl 4,6-0-benzylidene-a-D-glucopyranoside reacted with 1,2-dichloroethane under basic aqueous conditions in the presence of a phase-transfer catalyst. Partially protected sugars e.g. l,2 5,6-di-0-isopropylidene-a-D-gIucofuranose) have also been methylated and benzylated by reaction with methyl and benzyl trifluoro-methanesulphonate (triflate), respectively, using 2,6-di-t-butylpyridine as base. The reactions with benzyl triflate, prepared in situ from benzyl alcohol and trifluoromethanesulphonic anhydride, occurred readily at ca. — 70 °C, whereas those with methyl triflate were performed in refluxing dichloromethane. 

Generally, the Vilsmeier reaction fails for benzene, alkylbenzenes and naphthalene. The reaction gives low yields in the case of phenol ethers if the para-position is already occupied and fails for highly substituted benzofurans, indicating that the presence of a sufficiently reactive (labile) hydrogen atom on the aromatic ring is necessary for successful application. However, Martinez et al. reported the formylation of 1,3,5-trimethylbenzene, naphthalene, acenaphthene, anthracene and phenanthrene in fair yield using the trifluoromethanesulphonic anhydride/dimethylformamide complex (Eq 1.29). 

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