Freedom: a copper-free, oxidant-free and solvent-free palladium catalysed homocoupling reaction

Abstract

Herein, we describe a copper-free, oxidant-free, solvent-free homocoupling reaction using a palladium catalyst under mechanochemical conditions. We extended the methodology to palladium catalyst on solid support which showed a different reactivity and different product ratios from the non-supported catalyst.

Metal-catalyzed organic reactions using mechanochemistry

“…52 and b) palladium. 53 Surprisingly, using the potentially recycleable polymer-supported Pd(PPh 3 ) 4 readily produced the enyne as the major product (diyne:enyne ratio 12:88), demonstrating that polymer-supported catalysts under mechanochemical conditions can exhibit different behavior than in solution. The selectivity of the polymersupported Pd(PPh 3 ) 4 could be inverted by using excess triphenylphosphine, giving a diyne:enyne ratio 92:8.…”

“…In contrast to the mechanochemical copper-catalyzed Glaser protocol, 52 the palladium-based coupling avoids the need for external oxidant, and high yields were obtained even under inert atmosphere. 53 Aryl-, (hetero)aryl-, and alkyl-substituted terminal alkynes readily afforded the corresponding diynes in good yields. Using Pd(PPh 3 ) 2 Cl 2 instead of Pd(PPh 3 ) 4 in the coupling of phenylacetylene 1a generated selectively the (E)-1,4-diphenylbut-1-en-3-yne 3a as the major product, along with some of the diyne Glaser product 2a.…”

CHAPTER 8. A Chromatography-free Method for the Isolation of Products from Mechanochemical Reactions

“…35 The reaction of phenylacetylene with tetrakis(triphenylphosphine)palladium gave 1,4-diphenylbuta-1,3-diyne in high yields. When Bis(triphenylphosphine)palladium(II) dichloride was used as the catalyst, they observed 1,4-diphenylbut-1-en-3-yne as the primary product instead of the 1,4-diphenylbuta-1,3-diyne.…”

CHAPTER 2. Carbon–Carbon Bond Forming by Ball Milling

“…28 Application of [Pd(PPh 3 ) 4 ] gave 74% yield and with [PdCl 2 (PPh 3 ) 2 ], and an excess of PPh 3 , 90% homo-coupling product was generated. Reactions were performed in stainless steel or Teflon s milling vials, but the material showed no significant effect on the yield.…”