Synthesis of Lasofoxifene, Nafoxidine and Their Positional Isomers via the Novel Three-Component Coupling Reaction

Abstract

A Lewis acid-mediated three-component coupling reaction was successfully applied for the synthesis of lasofoxifene ( 1), nafoxidine ( 2), and their positional isomers, inv-lasofoxifene ( 3) and inv-nafoxidine ( 4). In the presence of HfCl ₄, the desired one-pot coupling reaction among 4-pivaloyloxybenzaldehyde ( 5), cinnamyltrimethylsilane ( 6), and anisole proceeded to afford the corresponding 3,4,4-triaryl-1-butene 7 in high yield. The iodocarbocyclization of the coupling product and the successive elimination of hydrogen iodide forming the olefin part, followed by the migration of the double-bond afforded the common synthetic intermediate of lasofoxifene ( 1) and nafoxidine ( 2) via a very concise procedure. Additionally, the syntheses of their positional isomers inv-lasofoxifene ( 3) and inv-nafoxidine ( 4) were also achieved through very convenient protocols.