Novel (imino-η6-arene)chromium-complexes and their diastereoselective intramolecular hetero-Diels-Alder reactions

Abstract

Novel (imino-η6-arene)chromium complexes 3 with nonactivated olefins tethered to the 2-azadiene system were prepared and further used in a new diastereoselective intramolecular Lewis-acid-catalyzed hetero-Diels-Alder reaction to give (η6-octahydroacridine)chromium complexes 4. The trans selectivity of the cyclization reaction is mainly controlled by the Cr- (CO)3 fragment and to a minor extent by the catalyst, solvent, and substituents. Complexes 4 also could be obtained by a one-pot reaction starting from aldehyde 1, (o-toluidine)Cr(CO)3 (2), and Lewis acid. The stereochemistry of 4a was established by single-crystal X-ray structure analysis.