5 -Oxazolones structural analysis

The X-ray crystal structure of fZ)-4-[(5)-2,2-dimethyl-l,3-dioxolan -ylmethyl-ene]-2-phenyl-5(4//)-oxazolone has been determined. " The analysis shows an almost planar disposition for the entire molecule with the exception of the dioxolane ring that adopts an envelope conformation. As such, the dioxolane ring is mainly situated on the si,si diastereotopic face of the olefinic bond, a situation that accounts for the observed diastereoselectivity in Diels-Alder reactions. 

Dimethylamino-2-isocyanoacrylates (179) react with arenesulfenyl chlorides or acyl chlorides to furnish 4-dimethylaminoniethylene-5(4 -oxazolones (Scheme 87) <93JCR(S)i, 93JHC575). The structure of the acyl chloride product was secured through x-ray analysis. 

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