Silver trifluoromethyl derivatives

Silver(I) complexes are known with the tris(pyrazolyl)borate [HB(pz)3] and the methyl, phenyl, bromo, or trifluoromethyl-substituted derivatives. The structure of the silver tri(pyrazolyl)borato species has been a puzzle since it was first reported.385,386 It was suggested that the structure could be oligomeric, but recently the crystal structure of the compound [Ag HB(3,5-Me2pz)3 ]2 shows that it has a dimeric structure387 where the silver(I) centers are tricoordinated by a bidentate arm of one ligand and a monodentate arm of the other ligand (29). The related complexes [Ag HB(4-Brpz)3 ]2, [Ag HB(4-Mepz)3 ]2, [Ag HB(3,5-Me2pz)3 ]2, [Ag HB(3-Mepz)3 ] , [Ag B(pz)4 ], and... 

Taking into account the lack of chemoselectivity and stereoselectivity of these silver ion-mediated reactions, it is reasonable to postulate an SNl-type mechanism for this process, leading to the formation of oxonium ion 14, despite the electron-withdrawing effect of the CF3 group (see Scheme 6.8). The stereochemical outcome should be ascribed to the steric or electronic preference of methanol addition to two possible diastereo-faces of the trifluoromethyl oxonium ion 14, in which the interactions are probably different from those in nonfluorinated DHA derivatives. In order to disfavor the formation of oxonium 14, the reaction was performed without silver salt in MeOH. While the reaction rate did not decrease significantly, only 23% of glycal 18 was obtained. Furthermore, the... 

Other addition/elimination sequence was utilized for monofluorination of benzofuran and its derivatives. Thus, the reaction of benzofuran 11 with trifluoromethyl hypofluorite (CF3OF) furnished 2-fluoro-3-trifluoromethoxy-2,3-dihydrobenzofurans 16 (43 % cis- and 15 % franx-isomer) and dx-difluoroderivative 17 (19 %). Treatment of the derivative 17 with ethanohc potassium hydroxide produced 3-fluorobenzofuran 18 in 61 % yield [20], 3-Fluorobenzofuran 18 was also synthesized from the compound 19 using silver fluoride as fluorinating and dehydrohalogenating reagent at the second step [21],... 

Ring-opening of 2,2,4,4-tetrakis(trifluoromethyl)-l,3-dithietan occurs on treatment with potassium fluoride, hexafluoropropene, and cuprous bromide, or with potassium fluoride, alcohols, and copper(i) or silver salts. Treatment of the desaurin (80) with o-amino-phenols gives oxazepine derivatives, and with o-phenylenediamines, diazepines. ... 

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