Reactivity of a palladium fluoro complex towards silanes and Bu₃SnCHCH₂: catalytic derivatisation of pentafluoropyridine based on carbon–fluorine bond activation reactions

Abstract

The chloro and azido complexes trans-[PdCl(4-C5NF4)(PiPr3)2] (3) and trans-[Pd(N3)(4-C5NF4)(PiPr3)2] (4) can be prepared by reaction of [PdF(4-C5NF4)(PiPr3)2] (2) with Et3SiCl or MeSiN3, respectively. In contrast, reactions of 2 with Ph3SiH or Me2FSiSiFMe2 give the products of reductive elimination 2,3,5,6-tetrafluoropyridine (5) or 4-(fluorodimethylsilyl)tetrafluoropyridine (6) as well as [Pd(PiPr3)2] (1). In a catalytic experiment, pentafluoropyridine can be converted with Ph3SiH into 5 in 62% yield, when 10% of 2 is employed as catalyst. Treatment of trans-[PdF(4-C5NF4)(PiPr3)2] (2) with Bu3SnCH=CH2 in THF at 50 degrees C results in the formation of [Pd(PiPr3)2] (1) and 4-vinyltetrafluoropyridine (7). Complex 2 is also active as a catalyst towards a Stille cross-coupling reaction of pentafluoropyridine with Bu3SnCH=CH2 to give 4-vinyltetrafluoropyridine (7) with a TON of 6. The molecular structure of the complex 3 has been determined by X-ray crystallography.

Nickel fluoro complexes as intermediates in catalytic cross-coupling reactions

“…The nickel fluoro complexes which have been synthesized can be considered as essential intermediates of a putative catalytic cycle. Note that it has been shown before that fluoro complexes often exhibit a higher reactivity than their chloro or bromo counterparts [18,19,[21][22][23][24][25][26][27][28][29]31,51,69]. Representative results of the cross coupling reactions of pentafluoropyridine Scheme 4.…”

“…Catalytic cross-coupling reactions of 2,3,5,6-tetrafluoropyridine. [4,14,17,21,[23][24][25][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47]51,70]. Chambers and Sandford described palladium catalysed Suzuki cross-coupling reactions via C-Br activation of 2,4,6-tribromo-3,5-difluoropyridine and aromatic boronic acids.…”

Pd-catalyzed sp2–sp cross-coupling reactions involving C–F bond activation in highly fluorinated nitrobenzene systems

“…5,6 Braun has successfully carried out nickelcatalyzed Stille 7,8 and Suzuki 9 coupling reactions of several perfluoroheteroaromatic derivatives, pentafluoropyridine and 2,4,6-trifluoro-5-chloropyrimidine, respectively. Radius has also reported similar Suzuki cross -coupling reactions between octafluorotoluene and decafluorobiphenyl and various electron rich aryl boronic acid derivatives in which the C-F bond para to the trifluoromethyl or pentafluorophenyl group was activated and fluorine displaced by an aryl group.…”

Synthese fluorierter Bausteine durch Übergangsmetall‐vermittelte Hydrodefluorierungsreaktionen

“…(101) erhalten, der durch reduktive Eliminierung 2,3,5,6-Tetrafluorpyridin freisetzt; [55] ein davon abgeleiteter katalytischer Prozess zeigte jedoch nur eine geringe Effizienz (TON = 5.2; Schema 25). Das Methoxy-substituierte Derivat 102 weist dagegen eine erhçhte Aktivität auf, wodurch die katalytische HDF bei niedrigerer Temperatur effektiver abläuft (TON = 16).…”