Let the Best Ring Win: Selective Macrocycle Formation through Pd‐Catalyzed or Cu‐Mediated Alkyne Homocoupling

Abstract

Competition is good: The reported “Pd” homocoupling procedure is now a viable alternative to the traditional Cu‐mediated reaction for the formation of diacetylenic macrocycles. From the same starting material, use of Cu(OAc)2 or [PdCl2(dppe)]/I2 (dppe=1,2‐bis(diphenylphosphanyl)ethane) leads to selective formation of either the bis[15]‐ or bis[14]annulenes (see scheme).

Synthesis of extended polyynes: Toward carbyne

“…Further refinement of the typical homocoupling reactions has recently invoked the use of Pd catalysis instead of the traditional Cu(I)/Cu(II) system (Scheme 1d) [47,51]. The use of Pd catalysis can often lead to excellent yields of desired product when Cu catalysis fails in this regard [52,53]. Recently, it has also been reported that Pd-catalyzed homocoupling of acetylenes can also occur under aerobic conditions where oxygen in the air acts as the cooxidant to regenerate the active Pd(II) catalyst [54].…”

Synthesis and properties of annulenic subunits of graphyne and graphdiyne nanoarchitectures

“…As before, the wavy lines and the bold lines in 26-29 show the key bonds formed by the protiodesilylation/alkynylation and intramolecular homocoupling reactions, respectively. For the latter transformation, both Cu-mediated [39] and Pd-catalyzed [40] macrocyclization conditions were explored (1-49 % yields). The "G2" targets and all intermediate structures feature appended 3,5-di-t-butylphenyl groups.…”

Copper(I) complexes supported by a heavily fluorinated bis(pyrazolyl)borate: syntheses and characterization of [H2B(3,5-(CF3)2Pz)2]CuL (where L = PPh3, N CCH3, HC CPh, H2C CHPh) and {[H2B(3,5-(CF3)2Pz)2]Cu}2(1,5-COD)

“…We previously reported the synthesis of a copper phosphine complex [H 2 B(3,5-(CF 3 ) 2 Pz) 2 ]Cu(PPh 3 ) 2 8 using (PPh 3 ) 2 -CuBH 4 and 3,5-(CF 3 ) 2 PzH [19]. It has two PPh 3 ligands on the copper center, which is the type of product more Table 1 X-ray crystallographic data and structure refinement for LCu(PPh 3 ), LCu(PhC"CH), LCu(PhCH@CH 2 ) AE 0.5 hexane, and {LCu} 2 (1,5- (8) Cu (2) Such compounds are of interest, because they serve as models for intermediates in copper mediated activation of C sp -H bonds of terminal alkynes and for other processes involving copper catalysts and alkynes [57][58][59][60][61][62][63][64]. Structurally characterized copper complexes of terminal alkynes are also rare [65][66][67][68][69].…”