Synthesis of (R)-(-)-3-Methoxymethyl-3-propyl-3, 4-dihydrocoumarin from a Chiral Michael Adduct : Absolute Configurations of the Allylated Products of Enantioselective Radical-Mediated Reactions

Abstract

(R)-3-Methoxymethyl-3-propyl-3, 4-dihydrocoumarin was synthesized, starting from a chiral Michael adduct [(S)-methyl 2, 3-dihydro-1-oxo-2-(3-oxobutyl)-1H-indene-2-carboxylate], in order to determine the absolute configurations of the products obtained by enantioselective radical-mediated allylation. Aldol cyclization of the Michael adduct proceeded smoothly with suppression of the retro Michael reaction to afford an optically active cyclized product. The Baeyer-Villiger reaction of (R)-2-methoxymethyl-2-propylindanone in the presence of BF₃·Et₂O afforded the desired dihydrocoumarin.