Syntheses of 1,3,3-trimethyl-2-oxabicyclo[2.2.2]oct-5-ene(2,3-didehydro-1, 8-cineole), 6,6-dimethyl-2-methylene-7-oxabicyclo[3.2.1]octane (Isopinol), 2,6,6-trimethyl-7-oxabicyclo[1.2.1]oct-2-ene (Pinol) and 1-(3-isopropylidenecyclopentyl)ethanone (Pinolone) from hydroxy- and bromo-derivatives of Cineole