Allenes, versatile unsaturated motifs in transitionmetal-catalysed [2+2+2] cycloaddition reactions

We gratefully acknowledge the financial support of our own research in this area by the Spanish Ministry of Education and Science (MINECO) (Project CTQ2014-54306-P and a RyC contract to A. L.) and the DIUE of the Generalitat de Catalunya (Project 2014-SGR-931)