Reactivity differences between 2,4- and 2,5-disubstituted zirconacyclopentadienes: A highly selective and general approach to 2,4-disubstituted phospholes

Article abstract of DOI:10.1039/c3dt51158h

Mixtures of 2,4- and 2,5-disubstituted zirconacyclopentadienes were obtained by the reductive dimerisation of terminal alkynes using the Cp ₂ZrCl₂/lanthanum system. Reactions of dihalophosphines with these mixtures afforded selectively the corresponding 2,4-disubstituted phospholes and 1,4-disubstituted butadienes. A new series of phospholes was characterized by multi-nuclear NMR spectroscopy and X-ray analysis. A possible explanation for the observed selectivity was obtained from X-ray studies and DFT analysis of the intermediate zirconacyclopentadienes. The Royal Society of Chemistry 2013.