New synthetic technology for the synthesis of hindered alpha-diazoketones via acyl mesylates

[GRAPHICS] A mild and reliable one pot protocol for the elaboration of sterically dema nding carboxylic acids into alpha-diazoketones via acyl mesylates has been developed. Aside from delineating the reaction parameters which render this strategy quite general for hindered carboxylic acids, we have directly pro ven the existence of the fleeting acyl mesylate group as the reactive speci es in these reactions and shed light onto the differing mechanisms which ar e operative in the activation of hindered and simple carboxylic acids with methanesulfonyl chloride.