Esterification via Iron-Catalyzed Activation of Triphenylphosphine with Air

Iron phthalocyanine-catalyzed oxidative activation of triphenylphosphine by molecular oxygen of air occurs, and esters and triphenylphosphine oxide are obtained in the presence of alcohols and carboxylic acids. Experimental results indicate that reactivity of esterification is dependent on acidity of the carboxylic acids and that an acyloxyphosphonium ion intermediate participates in the reaction mechanism. Addition of pyridine N -oxide derivatives accelerated the reaction, and a wide range of alcohols and carboxylic acids can be employed in this reaction.