Oxidations trifluoromethanesulfonic anhydride

Triphenylphosphine oxide-Trifluoromethanesulfonic anhydride (C6H5)3P)20 20Tf (1). The reagent (1) is prepared in situ in 1,2-dichloroethane. 

Direct oxidation of bis-sulfides by trifluoromethanesulfonic anhydride was suggested only recently.57 For example, treatment of 10 with triflic anhydride affords the corresponding dication salt 34 in high yield via intermediate formation of a sulfonyl sulfonium salt 33.58 A number of other cyclic and acyclic bis-sulfides 35 undergo facile oxidation to dications under these conditions (Scheme ll).57... 

Beccalli et al. reported a new synthesis of staurosporinone (293) from 3-cyano-3-(lH-indol-3-yl)-2-oxo propionic acid ethyl ester (1464) (790). The reaction of 1464 with ethyl chlorocarbonate and triethylamine afforded the compound 1465, which, on treatment with dimethylamine, led to the corresponding hydroxy derivative 1466. The triflate 1467 was prepared from 1466 by reaction with trifluoromethanesulfonic anhydride (Tf20) in the presence of ethyldiisopropylamine. The palladium(O)-catalyzed cross-coupling of the triflate 1467 with the 3-(tributylstannyl)indole 1468 afforded the vinylindole 1469 in 89% yield. Deprotection of both nitrogen atoms with sodium ethoxide in ethanol to 1470, followed by photocyclization in the presence of iodine as the oxidizing agent provided the indolocarbazole 1471. Finally, reductive cyclization of 1471 with sodium borohydride-cobaltous chloride led to staurosporinone (293) in 40% yield (790) (Scheme 5.248). 

In a modern version of well-established Af-oxide chemistry, l,3-dimethyllumazine-5-oxide was converted into the corresponding 6-triflate using trifluoromethanesulfonic anhydride thereby opening the way to many reactions mentioned in Section 10.18.7.2 <1997PTR1> <2002H(57)1841>. Similar reactions with acetyl chloride and acetyl bromide afforded the corresponding 6-chloro- and 6-bromolumazines. 

The total synthesis of mniopetal E (5) was achieved in a six-step sequence from the cycloadduct 125 (Scheme 21). The treatment of 125 with trifluoromethanesulfonic anhydride (Tf20) afforded triflate 129. Elimination of trifluoromethanesulfonic acid to introduce a double bond was accomplished in 2,6-lutidine at 100 °C, giving 130 in 84% yield. Deprotection of TBDPS ether was followed by Parikh-Doering oxidation of the resulting 131 by the same procedure used in the case of 127. Taking advantage of the electron-rich double bond between C-l... 

Tin hydroxides and oxides are also employed for the syntheses of heteroatom-substituted organotin compounds the treatment of trifluoromethanesulfonic anhydride with bis(trialkyltin)oxides affords trialkyltin triflates (eq (142)) [137] and the reaction of trialkylchlorostannanes with thiols proceeds via trialkylhydroxystannanes to give trialkylstannyl sulfides (eq (143)) [138]. 

The reagent is prepared by the reaction of triphenylphosphine oxide with trifluoromethanesulfonic anhydride at 0°. It is unstable to air or moisture, but can be stored for some time under nitrogen. 

The benzo derivatives (41) and (42) of the disulfide dication (36) can also be prepared in the reaction of the corresponding 5 -oxides with cone. H2SO4. However, since the resulting bis(hydrogen-sulfate) salts are very hygroscopic, the structures are identified only on the basis of elemental analyses. The dication (36) is an intermediate in the Pummerer reaction of the S -oxide (37) with acetic anhydride, shown in Scheme 12, giving the a-acetoxylated product (43). However, when trifluoromethanesulfonic anhydride is used instead, the dication (36) can be isolated as a triflate... 

Stille et al. completed the total synthesis of amphimedine (297) in eight steps and overall 21-23% yield (Scheme 33) (136). Their synthesis started with the readily available 4-quinolinone 298 (144), which was reacted with trifluoromethanesulfonic anhydride to give the triflate 299. Coupling of 299 with the organostannane 302 in the presence of Pd(PPhs)4 yielded the 4-arylquinoline 303, oxidation of which with ceric ammonium nitrate (CAN) or silver(II) oxide failed to produce any of the expected quinone. Thus,... 

The 1,5-dithiocane dication (141) is most readily prepared by treatment of 1,5-dithiocane-l-oxide (142) with trifluoromethanesulfonic anhydride <92RHA263>. This and related reactions, although clearly involving removal of a substituent attached to a ring heteroatom, are included in the discussion of the reactivity of the dithiocane ring (see Section 9.24.8.3), as the dicationic species is clearly implicated as an intermediate in many of these reactions. 

Reaction with P2O5. Trifluoromethanesulfonic acid (TfOH) reacts with an excess of Phosphorus(V) Oxide to give Trifluoromethanesulfonic Anhydride (eq 1), while treatment with a smaller amount of P2O5 (Tf0H P205 = 6 1) and slower distillation leads to trifluoromethyl triflate (eq 2)f... 

Despite this they should be considered as possible alternatives in cases where more familiar methods fail, i ongst this group of activators are p-toluenesulfonyl chloride, trifluoromethanesulfonic anhydride, silver tetrafluoroborate, molybdenum oxide, phosphorous pentoxide, trichloromediyl chloroformate, 2-fluoro-l-methylpyridiniumsulfonate, chlorosulfonyl isocyanate, antimony penta-chloride (for which an X-ray structure of the DMSO-SbCls complex was obtained) and phenyl dichlo-rophosphate. ... 

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