Couplings with Monoorganotin Compounds: A “Radical” Twist from the Original Stille Reaction

Nickel-Catalyzed Stille Cross Coupling of C-O Electrophiles

Aryl sulfamates, tosylates, and mesylates undergo efficient Ni-catalyzed cross coupling with diverse organostannanes in the presence of relatively unhindered alkylphosphine ligands and KF. The coupling is valuable for difficult bond constructions, such as aryl- heteroaryl, aryl-alkenyl, and aryl-alkynyl, using non-triflate phenol derivatives. A combination of experimental and computational studies implicate an unusual mechanism for transmetalation involving an 8-centered cyclic transition state. This reaction is inhibited by chloride sources due to slow transmetalation of organostannanes at a Ni(II)-chloride intermediate. These studies help to explain why prior efforts to achieve Ni-catalyzed Stille coupling of phenol derivatives were unsuccessful.

A Highly Efficient and Recyclable Pd(Pph3)4/Peg-400 System for Stille Cross-Coupling Reactions of Organostannanes with Aryl Bromides

Pd(PPh3)4 in PEG-400 is shown to be a highly efficient catalyst for the Stille cross-coupling reactions of various organotin compounds with aryl bromides. The reaction could be conducted at 80 °C using NaOAc as base, yielding a variety of biaryls, alkynes and alkenes in good to excellent yields. The isolation of the products was readily performed by extraction with petroleum ether and the Pd(PPh3)4/PEG-400 system could be easily recycled and reused five times without any significant loss of activity.

Radicals in transition metal catalyzed reactions? transition metal catalyzed radical reactions?: a fruitful interplay anyway: part 3: catalysis by group 10 and 11 elements and bimetallic catalysis

This review summarizes the current status of transition metal catalyzed reactions involving radical intermediates in organic chemistry. This part focuses on radical-based methods catalyzed by group 10 and group 11 metal complexes. Reductive and redox-neutral C-C bond formations catalyzed by low-valent metal complexes as well as catalytic oxidative methods are reviewed. Catalytic processes which rely on the combination of two metal complexes are also covered.

Vinyl Tris(trimethylsilyl)silanes: Substrates for Hiyama Coupling

The oxidative treatment of vinyl tris(trimethylsilyl)silanes with hydrogen peroxide in aqueous sodium hydroxide in tetrahydrofuran generates reactive silanol or siloxane species that undergo Pd-catalyzed cross-couplings with aryl, heterocyclic and alkenyl halides in the presence of Pd(PPh(3))(4) and tetrabutylammonium fluoride. Hydrogen peroxide and base are necessary for the coupling to occur while activation of the silanes with fluoride is not required. The conjugated and unconjugated tris(trimethylsilyl)silanes serve as good cross-coupling substrates. The (E)-silanes undergo coupling with retention of stereochemistry while coupling of (Z)-silanes occurred with lower stereoselectivity to produce an E/Z mixture of products.

Titanocene(II)-Promoted Stereoselective Alkenylation Utilizing (Z)-Alkenyl Sulfones

The stereoselective alkenylation of unsaturated compounds by means of a (Z)-alkenyl sulfone-titanocene(II) system is described. Treatment of alkynes and (Z)-alkenyl methyl sulfones with the titanocene(II) reagent Cp2Ti[P(OEt)3]2 produced conjugated dienes. This alkenylation system is also applicable to polar C=O bonds; the simple mixing of carbonyl compounds, (Z)-alkenyl methyl sulfones, and the titanocene(II) reagent formed allylic alcohols. The advantages of alkenylation are that it requires no prepreparation of the alkenylmetal reagent and that it proceeds with complete stereoselectivity.

Indium-Mediated Synthesis of Heterobiaryls

The palladium-mediated coupling reaction between triorganoindium reagents and organic electrophiles is extended to the synthesis of heteroaromatic compounds. Both electron-rich and electron-poor heterocycles can act as the organic electrophile or as the organoindium derivative.

One-pot synthesis of trisubstituted conjugated dienes via sequential Suzuki-Miyaura cross-coupling with alkenyl- and alkyltrifluoroborates

The sequential, stereoselective disubstitution of 1,1-dibromoalkenes using a variety of alkenyltrifluoroborates followed by alkyltrifluoroborates in the presence of Pd(PPh3)4 is described. This synthetic method proceeds smoothly in one pot under mild reaction conditions to provide the corresponding trisubstituted, conjugated dienes in excellent yield. Moreover, the method is operationally very simple because the organotrifluoroborates are stable in air, and the byproducts are innocuous inorganic salts.

Methyl transfer reaction from monomethyltin reagent under palladium(0) catalysis: a versatile method for labelling with carbon-11

The 11C-monomethylstannate prepared from [11C]-methyl iodide and Lappert's stannylene, was subject to a palladium-mediated cross-coupling reaction with an aryl halide under ligand-free conditions, to afford easily purified 11C-methyl(hetero)arenes in high radiochemical yields.