Directed lithiation of some chroman-4-ols

Directed lithiation of chroman-4-ols occurs predominantly at C-5 under kinetic control, but at C-8 at higher temperatures. Dehydration and oxidation of the products provides viable routes to 5-substituted 2H-chromenes and chroman-4-ones, respectively. The chroman-4-ones have been converted into novel pyrano[4,3,2-de] phthalazines. 2,2,5,7-Tetramethylchroman-4-ol is preferentially lithiated at the 5-methyl group and leads to the pyrano[2,3,4-de][1]benzopyran system.