Facile construction of the 1-phenylnaphthyl skeleton via an ester-mediated nucleophilic aromatic substitution reaction. Applications to the synthesis of phenylnaphthalide lignans

Abstract

A convenient method is presented for the construction of the 1-phenylnaphthyl skeleton via an ester-mediated nucleophilic displacement of a methoxy group from an aromatic nucleus by Grignard nucleophiles. Thus, treatment of isopropyl 1-methoxy-2-naphthoate 1 with a phenyl Grignard reagent 2 or 8 affords the 1-phenyl-2-naphthoate ester 3 or 9 in good to excellent yield. Similarly, treatment of a 2,6-dialkylphenyl 2-methoxybenzoate 4b or c with a 1-naphthyl Grignard reagent 5 gives the 2-(1-naphthyl)benzoate ester 7. The methodology has been utilized in the synthesis of the naturally occurring phenylnaphthalide lignans, taiwanin C 12a and chinensin 12b.