Carbenoid transfer reactions catalyzed by a ruthenium porphyrin macrocycle

Abstract

A ruthenium porphyrin functionalized with a cavity based on diphenylglycoluril is applied as a catalyst in carbenoid transfer reactions using α-diazoesters as substrates. The latter compounds contain a blocking group connected via an α,ω-dioxyalkyl spacer of 3 or 6 carbon atoms. The reaction of an excess of the α-diazoester with the short spacer with the ruthenium porphyrin macrocycle leads to two products, a [2]rotaxane and a maleate ester, which are the result of dimerization reactions at the inside and the outside of the cavity, respectively. A similar reaction using the α-diazoester with the long spacer also yields high molecular weight species. Mass spectrometric and NMR studies suggest that CH and/or CC insertion reactions take place on the thread of the initially formed rotaxane. It is proposed that these reactions are favoured by effective molarity effects because of the close proximity of reactive species in the interlocked geometry.