The synthesis and Diels-Alder reactions of (E)- and (Z)-1-methoxy-3-(phenylsulfinyl)-1,3-butadienes

The mild and efficient generation of benzenesulfenic acid by the thermolysis of Et 2-ethoxycarbonyl-3-(phenylsulfinyl)butanoate in refluxing dichloromethane, its in situ trapping with (E)- and (Z)-1-methoxy-2-buten-3-yne to form (E)-1-methoxy-3-(phenylsulfinyl)-1,3-butadiene and (Z)-1-methoxy-3-(phenylsulfinyl)-1,3-butadienes resp. proceeds in high yield. The lithium perchlorate catalyzed Diels-Alder reaction of (E)-1-methoxy-3-(phenylsulfinyl)-1,3-butadiene with both sym. and unsym. carbonyl activated dienophiles proceeds with complete regioselectivity and in some cases complete endo-selectivity.