Asymmetric synthesis of 3,4-dihydrocoumarins by rhodium-catalyzed reaction of 3-(2-hydroxyphenyl)cyclobutanones

3,4-Dihydrocoumarin derivatives were synthesized in a highly enantioselective manner from 3-(2-hydroxyphenyl)cyclobutanones through enantioselective carbon-carbon bond cleavage. A cascade reaction with electron-deficient alkenes introduced a carbon-carbon bond at the 5-position of the dihydrocoumarins.