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

The mild and efficient generation of benzenesulfenic acid by the thermolysis of ethyl 2-ethoxycarbonyl-3-(phenylsulfinyl)butanoate 8 in refluxing dichloromethane, and its in situ trapping with (E)- and (Z)-1-methoxybut-2-en-3-yne to form (E)-1-methoxy-3-(phenylsulfinyl)buta-1,3-diene 10 and (Z)-1-methoxy-3-(phenylsulfinyl)buta-1,3-dienes 11 respectively proceeds in high yield. The lithium perchlorate catalysed Diels-Alder reaction of 10 with both symmetrical and unsymmetrical carbonyl activated dienophiles proceeds with complete regioselectivity and in some cases complete endo-selectivity.