Synthesis of Siloxy-α-Lapachone Derivatives by Chemo- and Regioselective Diels-Alder Reactions of 3-Methylene-1,2,4-naphthotriones with Silyl Enol Ethers
2-hydroxy-1,4-naphthoquinone with aliphatic and aromatic aldehydes, take part in chemoselective hetero-Diels-Alder reactions with silyl enolethers to give a series of siloxy-containing naphtho[2,3- B]pyran-5,10-dione (α-lapachone) derivatives in moderate to high yield. These reactions regio-selectively gave α-lapachone derivatives with an acetal structure. This regioselectivity can be rationalized by