Study On Ring-opening Reactions Of2-butoxy-3,4-dihydropyrans With Dinucleophiles

Taking into account the ubiquitous presence of heterocyclic compounds in naturalproducts and drugs, development of new and efficient preparative protocols for thesestructures remains an urgent task in organic synthesis. Multi-component reaction (MCR)shows great advantages in the synthesis of heterocyclic compounds, especially MCRs areuseful for the expedient creation of chemical libraries of compounds with high levels ofmolecular complexity and diversity.In this article, it was proved that lithium bromide hydrate is an efficient andhigh-selectivity catalyst for the ring-opening reactions of2-butoxy-3,4-dihydropyrans with2-anthranilamide. This ring-open reaction could be used for the synthesis of3a-typenitrogenous multicycles, which possesses a new-framework structure and has never beenconstructed before. However, the scope of this reaction is rather limited. In order to solvethis problem, a three-component reaction of4H-3,1-benzoxazine-2,4(1H)-dione, primaryamine and2-butoxy-3,4-dihydropyrans was then developed by lithium bromide hydrateusing as catalyst, with which two types of products including6a and7a derivatives, couldbe obtained in moderate to excellent yields. In particular,7a-type quinazolinonesderivatives exhibited great potential in organic synthesis and pharmaceutical synthesisbecause it contains not only a fragment of dihydroquinazolinone, a kind of nitrogenousheterocyclic structure with biological and medical activity, but also a moiety ofβ-dicarbonyl compound that has been widely used in organic synthesis.