Solvent‐Less and Fluoride‐Free Hiyama Reaction of Arylsiloxanes with Aryl Bromides and Chlorides Promoted by Sodium Hydroxide: A Useful Protocol for Palladium Recycling and Product Isolation

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Abstract
Palladium salts and oxime‐derived palladacycles catalyze the cross‐coupling reaction of arylsiloxanes with aryl bromides and chlorides in low catalyst loading (0.001–0.1 mol % of Pd) under fluoride‐free conditions to provide biaryls and heterobiaryls. For some deactivated aryl bromides and for aryl chlorides, the corresponding cross‐couplings need TBAB as additive. Concentrated aqueous sodium hydroxide (50%) promoted this Hiyama reaction in practically the absence of solvents under air in good yields. The process can be performed at 120 °C either under heating in a pressure tube or under microwave irradiation. This protocol allows palladium recycling and facilitates the final isolation of the products simply by ether extraction.