Synthesis of Dihydroisobenzofurans<i>via</i>Palladium-Catalyzed Sequential Alkynylation/Annulation of 2-Bromobenzyl and 2-Chlorobenzyl Alcohols under Microwave Irradiation
作者:Eduardo Buxaderas、Diego A. Alonso、Carmen Nájera
DOI:10.1002/adsc.201400457
日期:2014.11.3
AbstractThe palladium‐catalyzed synthesis of dihydroisobenzofurans has been performed by sequential Sonogashira cross‐coupling/cyclization reactions between terminal alkynes and 2‐(hydroxymethyl)bromo‐ and chlorobenzenes in methanol as solvent at 130 °C under microwave irradiation. A 4,4′‐dichlorobenzophenone oxime‐derived chloro‐bridged palladacycle is an efficient pre‐catalyst to perform this tandem process using 2‐dicyclohexylphosphanyl‐2′,4′,6′‐triisopropylbiphenyl (Xphos) as ancillary ligand and potassium hydroxide as base in the absence of a copper cocatalyst. Under these conditions, functionalized 2‐bromo‐ and 2‐chlorobenzaldehydes are also suitable partners in the domino process affording phthalans in good yields. All the reactions can be performed under air and employing reagent‐grade chemicals under low loading conditions (1 mol% Pd).magnified image