Lewis acid (FeCl3) mediated dual bond (C-C and C-O) formation for synthesis of 3,4-dihydrocoumarins is presented. This method has successfully delivered a number of dihydrocoumarins containing dense functionalities on the aromatic ring. Significantly, the present method enabled achieving dihydrocoumarins with tertiary as well as quaternary carbon atoms at the benzylic position. Gratifyingly, the novel spiro-tetracyclic lactones have also been dextrously prepared using this process.
An efficient one‐pot synthesis of indenes from simple starting materials is presented. This process involves a dual C–C bond formation through an intermolecular Heck coupling reaction followed by acid‐mediated intramolecular cyclodehydration. The strategy is amenable to various substituted aromatics to give indenes. In addition, the regioselective synthesis of benzyl styrenes in a single column purification technique through in‐situ reduction of Heck products (ketones) followed by acid mediated dehydration of crude reaction mixture is presented.
An enantioselective
cyclization of diazoindolinones with o-hydroxymethyl
chalcones has been established by a cooperative
dirhodium complex and chiral phosphonic acid catalysis under mild
conditions. This reaction is the first example of catalytic asymmetric
intramolecular Michael-type trapping of oxonium ylide enabled by phosphoric
acid through a dual H-bonding activation model, which provides an
efficient access to the chiral spirochroman-3,3-oxindoles, with vicinal
quaternary and tertiary stereocenters, in good to excellent yields
and enantioselectivities.
An efficient and practical method is described for the direct synthesis of 1,3-dihydroisobenzofurans, an important structural motif present in biologically active natural or synthetic compounds.
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