Job/Unit: O20383 /KAP1 Date: 05-06-12 18:23:56 Pages: 18 MICROREVIEW DOI: 10.1002/ejoc.201200383 Recent Highlights in Ketenimine Chemistry Mateo Alajarin,* [a] Marta Marin-Luna, [a] and Angel Vidal* [a] Dedicated to Professor Francisco Palacios on the occasion of his 60th birthday Keywords: Reaction mechanisms / Cycloaddition / Electrocyclization / Sigmatropic rearrangement / Radicals / Biradical cyclization / Cumulenes / Ketenimines Selected recent developments in the chemistry of keten- imines are presented, demonstrating that heterocumulenes of this class are versatile reactive intermediates in the syn- thesis of nitrogenated heterocycles. This microreview in- Introduction Ketenimines are a class of nitrogenated heterocumulenes, the first member of which was synthesized by Staudinger [a] Departamento de Química Orgánica, Universidad de Murcia, Facultad de Química, Regional Campus of International Excellence “Campus Mare Nostrum”, Espinardo, 30100 Murcia, Spain Fax: +34-868-884149 E-mail: alajarin@um.es, vidal@um.es Mateo Alajarin was born in Alhama deMurcia (Spain). He graduated in chemistry at the University of Murcia, where he also received his PhD. After postdoctoral studies with Prof. AlanR. Katritzky at the University of Florida (USA) he returned to the University of Murcia where he is currently Full Professor at its Department of Organic Chemistry. His research interests include ketenimines and relatedheterocumulenes, supramolecular chemistry, organophosphorus reagents, tandem processes promoted by H shifts, and other pericyclic and pseudopericyclic reactions. Marta Marin-Luna was born in Cartagena (Murcia). In 2008 she graduated in chemistry from the University of Murcia, where she is currently a PhD student under the supervision of Drs. Mateo Alajarin and Angel Vidal. Her research interests focus on tandem reactions promoted by hydrogen shifts in ketenimines, allenes and fulvenes. Angel Vidal was born in Murcia, Spain, in 1964. He received his BSc degree at the University of Murcia, and his PhD at the same university under the direction of Prof.Dr. Pedro Molina and Prof.Dr. Mateo Alajarin. After postdoctoral work with Prof. Dr. Michael E. Jung at the University of California, Los Angeles, he joined the University of Murcia as Associ- ate Professor, and was promoted to Lecturer in 1999. His current research interests lie in the study of the chemistry of ketenimines and related heterocumulenes. Eur. J. Org. Chem. 0000, 0–0 © 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 1 cludes examples of intramolecular nucleophilic and radical additions, biradical cyclizations, 4π- and 6π-electrocyclic ring closures, [2+2], [3+2] and [4+2] cycloadditions, ketenimine- to-nitrile rearrangements and 1,3-X, 1,5-X and 1,5-H shifts. as long ago as 1919. [1] Their C=C=N cumulenic system, containing a central sp-hybridized carbon atom, is decisive in conferring high reactivity on the members of this class of organic compounds, opening a wide range of available reaction paths. In fact, the systematic study of their reac- tions has demonstrated that these species show a very rich and diverse chemistry, essentially based on the addition of nucleophiles and free radicals to the electrophilic sp-hy-