Pd-catalyzed formal [3+3] heteroannulation of allylic gem-diacetates: synthesis of chromene-based natural products and photophysical studies Prashant Kumar and S.S.V Ramasastry Indian Institute of Science Education and Research, India The novel classes of chromenes are achieved via the palladium-catalyzed [3+3] heteroannulation of allylic gem - diacetates and 2-naphthols (and meta -substituted phenols). This work unveils an unusual chemical reactivity pattern of allylic gem -diacetates towards the synthesis of complex benzo[ f ]chromene scaffolds. Under the reaction conditions, the diacetates behave as 1,3-dicationic equivalents and undergo a [3+3] heteroannulation with 2-naphthols (and meta-substituted phenols) to produce novel polycyclic chromenes possessing spiro-, tri-, and tetrasubstituted carbon centers. The described method is applicable in the synthesis of several chromene- based bioactive natural products. Furthermore, we have made elaborate efforts and discovered the interesting photochromic behavior of some of the newly synthesized benzochromenes. The reversible photo- and thermochromic behavior has been exploited in demonstrating image printing and erasing applications. References 1. Nicolaou, K. C.; Pfefferkorn, J. A.; Roecker, A. J.; Cao, G.-Q.; Barluenga, S.; Mitchell, H. J. J . Am . Chem . Soc . 2000 , 122 , 9939-9953. 2. Rawat, M.; Prutyanov, V.; Wulff, W. D. J . Am . Chem . Soc . 2006 , 128 , 11044-11053. 3. Trost, B. M.; Vercauteren, J. Tetrahedron Lett . 1985 , 26 , 131-134. 4. Huang, Y.; Lu, X. Tetrahedron Lett . 1987 , 28 , 6219-6220. 5. Kumar, P.; Kumar, P.; Venkataramani, S.; Ramasastry, S. S. V. ACS Catal . 2022 , 12 , 963-970. 6. Park, B.-H.; Lee, Y.-R.; Kim, S.-H. Bull . Korean Chem . Soc . 011 , 32 , 566-570. 7. Kn lker, H.-J.; Reddy, K. R. Chem . Rev . 2002 , 102 , 4303-4428.
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