The rhodium catalysed 1,4-carbonylative addition of arylboronic acids to methyl vinylketone under carbon monoxide pressure was studied. High yields of 1,4-diketones were obtained using a catalytic system formed from Rh(COD)2BF4 (COD=1,5-cyclooctadiene) and triphenylphosphine even at very low catalyst loading (0.02 mol %). A short synthetic procedure combining this carbonylation reaction with a subsequent