PbBr2/Al-Promoted Reductive Addition of 1,1,1-Trichloro-2,2,2-trifluoroethane (Flon) to Aldehydes

Abstract

Introduction of CF3CCl2 unit into aldehydes with CF3CCl3 has been performed successfully by the action of catalytic PbBr2 and Al foils in DMF.

Polyfluorinated Ethanes as Versatile Fluorinated C2-Building Blocks for Organic Synthesis

“…The mechanism of the reaction was not clarified. However, the authors supposed that in situ formed Pb(0) on the Al foils is effective for generation of CF 3 CCl 2 PbCl intermediate, which is reactive enough for the subsequent addition to aldehydes (Scheme , Table ) …”

“…However, the authors supposed that in situ formed Pb(0) on the Al foils is effective for generation of CF 3 CCl 2 PbCl intermediate, which is reactive enough for the subsequent addition to aldehydes (Scheme 171, Table 26). 377 In the case of piperonal, prolonged reaction time resulted in the dehalogenation to give the allyl alcohol 246i, which was converted into the acyl fluoride 305 by treatment with aqueous H 2 SO 4 . 378 The reaction of C 2 F 5 -lead derivatives with DMF gave perfluoropropanal in high yields, accompanied by the formation of minor amounts of pentafluoroethane and amide 306 (Scheme 172).…”

Reactions of polyfluorinated thietanes

“…Indeed, reducing agents such as Al/PbX 2 [16][17][18][19][20] or P[N(C 2 H 5 ) 3 ] 3 [21,22] are known to activate C-Hal bonds in CCl 4 , FCCl 3 , CF 3 CCl 3 through SET mechanism. For example, recently Zeifman and Postovoii employed an Al/HgCl 2 system for alkylation of polyfluorinated ketones [20,[23][24][25] and esters [26] by CCl 4 , FCCl 3 and CF 3 CCl 3 and also reported a very interesting reductive defluorination process under action of Al/HgCl 2 on fluorinated ketones leading to the formation of polyfluorinated enols after acidic hydrolysis [27,28].…”