Nucleophilic Aromatic Substitution on 1-Alkoxy-2-naphthoates with 1-Naphthyl Grignard Reagents. A Practical and Convenient Asymmetric Synthesis of 1,1′-Binaphthyl-2-carboxylates

Abstract 1-Naphthyl Grignard reagents efficiently displace the 1-alkoxyl group of 1-alkoxy-2-naphthoic esters to provide an easy access to the corresponding 1,1′-binaphthyl-2-carboxylates in excellent yields; isopropyl ester is bulky enough to prevent the Grignard addition to the ester carbonyl function. High levels of asymmetric induction (up to 98% optical yield) have been achieved in the joining of the two naphthalene rings by using 1-(l-p-menth-3-yloxy)-2-naphthoates, while the reaction of chiral alkyl esters of 1-methoxy-2-naphthoic acid proceeded with appreciable to moderate stereoselectivity. The probable reaction mechanisms are discussed for the binaphthyl coupling and the asymmetric induction.