title: A facile phenol-driven intramolecular diastereoselective thermal/base-catalyzed dipolar [2+2] annulation reactions: an easy access to complex bioactive natural and unnatural benzopyran congeners.
abstract: The complex bioactive natural and unnatural benzopyran congeners have been synthesized using one-/two-step approaches in very good yields from the reactions of two different dihydroxyphthalides, natural resorcyclic acid derivative, and trihydroxybenzophenone with citral and/or farnesal, via the phenol-driven intramolecular diastereoselective thermal/base-catalyzed dipolar [2+2] cycloaddition reactions and three different thermal intramolecular cyclization reactions. The effects of the nature and the position of phenolic groups in the starting materials on the course of these cycloaddition reactions have also been described. Depending upon the absence or presence of intramolecular hydrogen bonding of the phenolic group with the carbonyl moiety in the starting materials, these phenol-driven intramolecular thermal/base-catalyzed dipolar [2+2] cycloaddition reactions either furnished the kinetically controlled products or directly formed the thermodynamically controlled rearranged products, respectively.
authors.affiliation: Division of Organic Chemistry (Synthesis) and Centre for Material Characterization, National Chemical Laboratory, Pune 411 008, India.
authors.forename: Mukulesh
authors.initials: M
authors.lastname: Mondal
authors.forename: Vedavati G
authors.initials: VG
authors.lastname: Puranik
authors.forename: Narshinha P
authors.initials: NP
authors.lastname: Argade
mesh_terms: D001578:Benzopyrans / Q000138:chemical synthesis*; D001688:Biological Products; D002384:Catalysis; D006358:Hot Temperature; D019800:Phenol / Q000138:chemical synthesis; D013237:Stereoisomerism
chemical_list: D001578:Benzopyrans; D001688:Biological Products; D019800:Phenol