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

Abstract

Symmetrical internal alkynes can be prepared either by diarylation of mono-and bis(trimethylsilyl)acetylene (TMSA and BTMSA) catalyzed by ligand-less palladium(II) chloride or by a di(2-pyridyl)methylamine-derived palladium(II) chloride complex 1 (typical 0.1-1 mol % of Pd loading) in water using pyrrolidine as base and tetra-n-butylammonium bromide as additive. Alternatively, this same process is performed in NMP in the presence of tetra-n-butylammonium acetate (TBAA) as base with even lower Pd loadings (0.001-1 mol % Pd). The same reaction conditions are applied to the synthesis of unsymmetrical internal alkynes by monoarylation of silylated terminal alkynes. Aryl iodides can be coupled with TMSA, BTMSA and silylated terminal alkynes under heating or at room temperature, whereas for aryl bromides couplings are performed under water reflux or at 110 8C in the case of NMP. Complex 1 can be reused during several cycles either in water or in NMP without loss of catalytic activity. These simple reaction conditions allow the preparation of internal alkynes without secondary products, most probably by succesive protiodesilylation-Sonogashira coupling.

A Green Approach for Copper-Free Sonogashira Reaction of Aryl Halides with Phenylacetylene in the Presence of Nano-Pd/Phosphorylated Silica (SDPP/Pd0)

“…In the case of aryl Products are known compounds. [14][15][16][17][18][19][20][21][22][23] iodides and activated aryl bromides, the reaction mixture was placed in a 1008C oil bath; and in the case of the less active and deactivated aryl bromides and chlorides, the reaction mixture was placed in a 1208C oil bath. After completion of the reaction, the catalyst was removed by centrifugation and the remaining mixture was extracted with ethyl acetate (3 Â 10 mL) and water several times and dried over anhydrous Na 2 SO 4 .…”

Palladium‐catalyzed Coupling between Aryl Halides and Trimethylsilylacetylene Assisted by Dimethylaminotrimethyltin

“…Its advantage is that after the coupling is completed, the trimethylsilyl group can be removed easily to get terminal aryl acetylenes. 9 However, compared with alkyl or aryl acetylenes, trimethylsilylacetylene is less reactive in this reaction, giving low yields. 10 Here, we report a new and effective Pd catalyzed coupling between aryl halides and trimethylsilylacetylene in the presence of dimethylaminotrimethyltin, those reagents involving electron-rich aryl halides or N-heteroaryl halides.…”

Copper‐Free One‐Pot Sonogashira‐Type Coupling for the Efficient Preparation of Symmetric Diarylalkyne Ligands for Metal‐Organic Cages**

“…Glaser coupling [9] can also take place in the presence of the copper co‐catalyst with traces of oxygen, leading to side‐product formation [2a,10] and difficult purifications. As a result, one‐pot cross‐coupling methods using a variety of acetylene sources (e. g. gaseous acetylene, [11] calcium carbide, [12] propiolic acid [13] and silyl‐protected alkynes [14] ) as well as copper‐free Sonogashira‐type couplings [12–13,14b,15] ( e. g . replacing the copper co‐catalyst and amine with tetrabutylammonium fluoride (TBAF) [15a,b] ) have been developed to overcome these problems, respectively.…”

“…As a result, one-pot cross-coupling methods using a variety of acetylene sources (e.g. gaseous acetylene, [29][30][31] calcium carbide, 32 propiolic acid 33 and silylprotected alkynes [34][35][36] ) as well as copper-free Sonogashira-type couplings 32,33,35,37,38 (e.g. replacing the copper co-catalyst and amine with tetrabutylammonium fluoride (TBAF) 37,38 ) have been developed to overcome these problems, respectively.…”