The Preparation of Substituted 3,4-Dihydro-1H-2-benzopyran-1-ones from the Dianions ofOrtho-Toluic Acids

Abstract
The dianions of ortho-toluic and α-phenyl-ortho-toluic acids were prepared with lithium diisopropylamide (LDA), condensed with certain aldehydes or ketones, and the resulting intermediates were acid-cyclized to substituted 3,4-dihydro-1H-2-benzopyran-1-ones (dihydroisocoumarins).