01807nas a2200169   4500008004100000022001400041245019700055210006900252260007100321300001400392490000700406520103100413100002101444700002601465700001901491856012701510       2007                        eng d  a0022-326300aFacile phenol-driven intramolecular diastereoselective thermal/base-catalyzed dipolar [2+2] annulation reactions: an easy access to complex bioactive natural and unnatural benzopyran congeners0 aFacile phenoldriven intramolecular diastereoselective thermalbas  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcMAR  a2068-20760 v723 a<p>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.</p>1 aMondal, Mukulesh1 aPuranik, Vedavati, G.1 aArgade, N., P.  uhttps://library.ncl.res.in/content/facile-phenol-driven-intramolecular-diastereoselective-thermalbase-catalyzed-dipolar-22