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A decarboxylative Claisen condensation involving substituted malonic acid half oxyesters (SMAHOs) as pronucleophiles has been developed. The addition of their magnesium enolates to various acyl donors allows the synthesis of functionalized α-substituted β-keto esters in moderate to excellent yields (13–96%). In addition to acyl chlorides and acid anhydrides, these conditions proved efficient for the use of carboxylic acids as acylating agents, thus allowing to greatly extend the scope of this transformation (32 examples overall).

The first examples of cobalt-catalyzed multicomponent couplings of mixed aromatic arylzinc reagents with Michael acceptors and carbonyl compounds or imines is described. The reaction system employs a cobalt(II)-2,2′-bipyridine or a cobalt(II)-1,10-phenanthroline complex as a catalyst for both organozinc generation and subsequent multicomponent assembly by formal Michael addition/aldol coupling or Mannich reaction. This study brings new insights into the synthetic scope and mechanism of the reaction.