The Regioselective Arylation of 1,3‐Benzodioxoles

Abstract

The direct arylation of 1,3‐benzodioxole and 2,2‐difluorobenzo[1,3]dioxole with 26 different aryl bromides yields the respective 4‐substitued products in yields of >80% requiring between 0.05–1 mol % Na2PdCl4, 30 mol % pivalic acid, 1.3 equivs. K2CO3 and ca. 250 equivs. of diethylacetamide per Pd at T=120 °C. The nature of the amide and the concentration of the reactants are crucial for the optimization of the reaction conditions. The primary role of the acetamide is that of a ligand to Pd, it is not needed as a solvent.

Fluorescent organometallic dyads and triads: establishing spatial relationships

“…Since it is known, that direct arylation reactions do not necessarily require additional phosphine ligands, ligand-free approaches for the cyclization were tested and optimized. 49,50 Using Pd(OAc) 2 in DMF in the absence of phosphine provides the a-isomer as the predominant cyclization product in 70% yield (b-isomer <1%). The detosylation of spiro-pyrrole was done by simply stirring the protected pyrrole with Cs 2 CO 3 base in THF/MeOH and gave spiro-pyrrole 3 in 85% yield.…”

Fluorescent Organometallic Dyads and Triads: Establishing spatial Relationships

“…Since it is known, that direct arylation reactions do not necessarily require additional phosphine ligands, ligand-free approaches for the cyclization were tested and optimized. 49,50 Using Pd(OAc)2 in DMF in the absence of phosphine provides the -isomer as the predominant cyclization product in 70% yield (-isomer <1%). The detosylation of spiro-pyrrole was done by simply stirring the protected pyrrole with Cs2CO3 base in THF/MeOH and gave spiro-pyrrole 3 in 85% yield.…”

Ligandless Palladium-Catalyzed Direct C-5 Arylation of Azoles Promoted by Benzoic Acid in Anisole

“…To overcome this relevant issue, research has almost always been oriented towards an optimization of the pre-catalyst/ligand system along with the search for the best inorganic base, while the potential effect of the solvent on the outcome of the coupling has been rarely discussed [ 84 , 85 , 86 , 87 ]. In fact, even in cases where a solvent screening has been reported, no comment has been added to justify the different outcome of the arylation.…”