Tandem Brønsted Acid Promoted and Nazarov Carbocyclizations of Enyne Acetals to Hydroazulenones


  • We thank the MICINN [Projects CTQ2011-28258, Consolider Ingenio 2010 (CSD2007-00006)] and Xunta de Galicia (2007/XA084 and CN2011/054) for financial support. L.E. thanks Fundayacucho (Venezuela) and Xunta de Galicia for predoctoral grants and C. G.-R. thanks the MICINN for a Juan de la Cierva Contract (JCI-2011-09946).


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Ring the changes: Enyne acetals were easily converted into hydroazulene skeletons by a new and efficient metal-free route involving a Brønsted acid promoted carbocyclization and a subsequent stereospecific Nazarov cyclization (see scheme). The versatility of this transformation also allowed assembly of interesting heteroaromatic tricyclic systems.