C(sp²)‐C(sp) and C(sp)‐C(sp) Coupling Reactions Catalyzed by Oxime‐Derived Palladacycles

Abstract

Oxime-derived chloro-bridged palladacycle 8a, derived from 4,4'-dichlorobenzophenone, is an efficient pre-catalyst for the copper-and amine-free Sonogashira coupling between terminal acetylenes and aryl iodides and aryl and vinyl bromides achieving turnover numbers (TON) of up to 72000. Catalyst 8a has also been shown as a effective promoter for the sila-Sonogashira coupling between 1-(trimethylsilyl)alkynes and aryl iodides and bromides in the presence of CuI or Bu 4 NBr as co-catalysts. This complex also catalyzes efficiently the homocoupling reaction (Glaser-type coupling) between 1-alkynes in NMP at room temperature with TONs of up to 1000. All the reactions can be performed under air and employing reagent-grade chemicals under very low loading conditions, which demonstrates the versatility and high activity of oxime-derived palladacycles.

A Novel Water‐Soluble m‐TPPTC Ligand: Steric and Electronic Features –Recent Developments in Pd‐ and Rh‐Catalyzed CC Bond Formations

“…Florisil (100 -200 mesh) was purchased from Acros or Avocado. The spectral data of alkynes 10a, [24] 10c, [25] …”

“…The reaction of 2-iodoanilines with various alkynes afforded this time exclusively the linear products 10a -d, with no traces of the cyclized indoles (entries 1 -4). The isolated yields were generally good with unprotected anilines 10a [24] and 10b (entries 1 and 2) and quite modest with the acetyl-protected substrates 10c [25] and 10d (entries 3 and 4). The Sonogashira cross-coupling/ intramolecular cyclization sequence was observed in the case of the oxygenated compounds, as the functionalized benzofurans 9e…”

Copper‐Free Oxime–Palladacycle‐Catalyzed Sonogashira Alkynylation of Deactivated Aryl Bromides and Chlorides in Water under Microwave Irradiation

“…As catalyst, oxime palladacycle 1a (1 mol% Pd) in the presence of 2-dicyclohexylphosphino-2',6'-dimethoxybiphenyl (SPhos, 2 mol%) was selected due to the high activity of this catalytic system for the alkynylation of aryl imidazolylsulfonates in water. [6,15] Unfortunately, under these conditions ( Table 1, entry 1), the reaction afforded 1-methyl-4-(phenylethynyl)benzene (4a) in a 14% isolated yield together with the enyne (E)-but-1-en-3-yne-1,4-diyldibenzene (5a) in a 7% yield. The formation of compound 5a has been previously detected in Heck alkynylations of deactivated aryl chlorides and it is postulated to occur via a Pd-catalyzed head-to-head dimerization of phenylacetylene.…”

Direct Coupling Reactions of Alkynylsilanes Catalyzed by Palladium(II) Chloride and a Di(2‐pyridyl)methylamine‐Derived Palladium(II) Chloride Complex in Water and in NMP

“…Compounds 3aa, 3bb, 3ac, 3ad, and 3bc are commercially available and compounds 3cc, [6] 3ae, [6] 3af, [7] and 3bd [16] have been previously reported and were characterized by comparison with their reported data. Physical, analytical and spectroscopic data of the newly synthesized compound is gevine below.…”

“…[6] Oxime-derived palladacycles have been used as catalysts in our group to promote the diarylation of TMSA and BTMSA in the presence of CuI or tetra-n-butylammonium bromide (TBAB) as co-catalysts. [7] Copper-free sila-Sonogashira diarylation of TMSA with aryl iodides in the presence of MeONa in methanol has been performed with Pd-A C H T U N G T R E N N U N G (PPh 3 ) 4 as catalyst. [8] The main advantage of the use of trimethylsilylprotected terminal alkynes instead of unprotected acetylenes (Sonogashira versus sila-Sonogashira reaction) is to suppress the formation of by-products from alkynes, such as diynes and enynes.…”