Unusual in Situ Ligand Modification to Generate a Catalyst for Room Temperature Aromatic C−O Bond Formation

Abstract

Unusual in situ Ligand Modification to Generate a Catalyst for Room Temperature Aromatic C-O Bond Formation.-The formation of an aromatic carbon-oxygen bond in the presence of a Pd(dba) 2 -Fc-P(tBu) 2 (Fc = ferrocenyl) catalyst is studied. Model reactions reveal that the free cyclopentadienyl ring of the ligand is perarylated first and that this novel ferrocenyl ligand is part of the catalytically active species. Thus, etherification reactions conducted in the presence of a pentaphenylated Fc-P(tBu) 2 ligand proceed with higher yields, higher reaction rates and without the previously observed induction period. The applicability of this method is demonstrated with the synthesis of a wide range of aryl alkyl ethers, diaryl ethers and aryl silyl ethers (III) as well as benzofused cyclic ethers (V).

Reductive Elimination of Ether from T‐Shaped, Monomeric Arylpalladium Alkoxides

“…In all cases the [L 2 Pd 0 ] species was the only palladium product observed. These results are consistent with the intermediacy of 3 and 4 in the palladium-catalyzed formation of biaryl and tert-butyl aryl ethers from aryl halides and NaOAr [5,6,9,14] and NaOtBu. [10,23,24] Complexes 6a and 6b constitute rare isolated and fully characterized alkoxide complexes that reductively eliminate ether.…”

“…Only reductive eliminations of alkyl aryl ethers from complexes generated in situ, reductive elimination of an oxygen heterocycle from a single oxapalladacycle,[2] reductive eliminations from arylpalladium alkoxides containing activating groups on the aryl ring, [3,4] and reductive eliminations of biaryl ethers in low yield from isolated complexes [5,6] are documented. Most importantly, the most active catalysts for the palladium-catalyzed etherification of aryl halides contain sterically hindered monophosphines, [1,[6][7][8][9][10][11][12][13][14][15] and no reductive eliminations from arylpalladium alkoxides containing hindered monophosphines have been described.We report reductive eliminations from isolated and structurally characterized examples of such arylpalladium alkoxides. We show that reductive eliminations occur from the observed species containing one aryl, one alkoxide, and one phosphine ligand.…”

Catalyst-Controlled Site-Selectivity Switching in Pd-Catalyzed Cross-Coupling of Dihaloarenes

“…In fact, a DPPF-based catalyst exclusively gave 2-phenylated product 36 (Entry 1, Table 4). Interestingly, the use of 1,2,3,4,5-pentaphenyl-1'-(di-t-butylphosphino)ferrocene (Q-Phos) [39] as the ligand switched the site-selectivity (Entry 2, Table 4). Under the optimized conditions (KF as the base and toluene as the solvent), a 2.4:1 ratio of 35:36 was obtained.…”

Synthesis and Structure of New Compounds NSAIDs-Like Using a Heterogeneous Recyclable Catalyst

“…There are several ways to synthesis of aryl ethers is typically achieved via a nucleophilic aromatic substitution (NAS) process or transition metal catalyzed Ullmann-type [5,6] and Hartwig [7,8] or Buchwald-type [9,10] O-arylation reactions. The NAS approach requires the use of phenoxide to displace aryl fluorides or chlorides that are activated by strong electron withdrawing groups (EWG) located in the ortho, para, or, in rare cases, meta positions.…”