A-Sulfoxide substituents

Functionality can be built into either the diene or dienophile for purposes of subsequent transformations. For example, in the synthesis of prephenic acid, the diene has the capacity to generate an enone. The dienophile contains a sulfoxide substituent that is subsequently used to introduce a second double bond by elimination. 

The observed effects on the triene (Z,Z/Z.ZT(-product ratios are compared in Table 4. Similar to the system 51 (see p4443) a sulfoxide substituent in 56 exerts a substantial wr/i-directing effect on the [1,5] sigmatropic hydrogen migration of the vinylallenes. A (Z,Z/Z, )-product ratio of 3 1 is observed for 56a-56c which is again enhanced to a ratio of 82 18 by a gcminal... 

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