A highly regio- and stereoselective synthesis of (Z)-3-arylidene-2,3-dihydro-5H-1,4-benzodioxepin-5-ones and (Z)-3-arylidene-1,2,3,5-tetrahydro-4,1-benzoxazepin-5-ones through palladium–copper catalysis

Abstract

Sodium 2-(prop-2′-ynyloxy)benzoate 1a reacted with the aryl iodides 2–10 in the presence of bis(triphenylphosphine)palladium(II) chloride, cuprous iodide and triethylamine in CH₃CN–DMF to yield the disubstituted alkynes 11–19 in good yields (48–58%). Similarly, sodium 2-[N-benzyl-N-(prop-2′-ynyl)]aminobenzoate 1b on reaction with aryl iodides under palladium–copper catalysis afforded the disubstituted alkynes 20–22. Compounds 11–19 on cyclisation with cuprous iodide in the presence of triethylamine in acetonitrile yielded the 3-arylidene-2,3-dihydro-5H-1,4-benzodioxepin-5-ones 23–31 in 61–83% yields. Similarly, compounds 20–22 on cyclisation gave 3-arylidene-1,2,3,5-tetrahydro-4,1-benzoxazepin-5-ones 32–34.