A facile synthesis of optically active 3-ethyl and 3-n-butylphthalides via catalytic enantioselective addition of dialkylzinc reagents to o-phthaladehyde

The addition of dialkylzinc to o-phthalaldehyde in the presence of enantiomeric catalysts is a simplified method of preparing 3-ethyl- and 3-n-butylphthalides. The process involves enantioselective addition reaction and oxidation of the derived lactols utilizing chiral 1,2-disubstituted ferrocenyl amino alcohols as catalysts. The obtained 3-alkylphthalides have 80% to 81% yields without formation of unwanted products.