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

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.