One-Step Synthesis of Isocoumarins and 3-Benzylidenephthalides via Ligandless Pd-Catalyzed Oxidative Coupling of Benzoic Acids and Vinylarenes
作者:Debkumar Nandi、Debalina Ghosh、Shih-Ji Chen、Bing-Chiuan Kuo、Nancy M. Wang、Hon Man Lee
DOI:10.1021/jo400174w
日期:2013.4.5
A straightforward synthetic method for the preparation of isocoumarins and 3-benzylidenephthalides via C–H olefination and oxidative coupling of readily available benzoicacids and vinylarenes was developed. The directing effect of the substituents on the benzoicacid allows for the synthesis of both types of lactone in pure form.
An original Pd(II)-catalyzed domino two C-H activations strategy has been designed to synthesize pyrano[4,3-b]indol-1(5H)-one motifs from inexpensive and commercially available olefins and heteroaromatic acids by carboxylate-directed sequential ortho-C-H alkenylation and remote C-H lactonization. Importantly, this protocol overcomes the selectivity for carboxylic acids with acrylates of the conventional Michael addition-type process. Preliminary studies of mechanism indicate that both aryl and olefinlic C-H activations may participate in this catalytic system.