Optically Pure 1-Sulfinyldienes

In order to justify the stereochemistry of the major adducts 155, the authors proposed that they result from an exclusive endo approach toward the less hindered face of the diene (opposite to the p-tolyl group), with the sulfinyl group adopting the s-trans conformation with respect to the C(l)-C(2) double bond (B in Fig. 13). Nevertheless, this conformational preference is not rationalized in the paper. Aversa et al. [137c] have recently reported that uncatalyzed reactions of (Rs)-152 with maleimide and N-phenyl maleimide occurred with complete endo- and very high facial diastereoselectivities. In this sense, the results ob- 

The formation of chelated species such as D (Fig. 13) would better explain the stereochemical results. 

Asymmetric Diels-Alder reactions of 1-p-tolylsulfinyldienes 161 with AT-methyl-maleimide (NMM) were completely stereoselective both under thermal and catalyzed conditions [142], yielding the same compounds endo-162 as sole 

The formation of lactone 167 as the major compound derived from 166 was rationalized as follows the intramolecular acylation of the sulfinyl oxygen 

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