moieties are included, two of them being of the styrene type and one of the 1,2-diaryloxyethene type, the reaction is again specific for the styrene moieties, giving only the bis-adduct. The high siteselectivity observed in these reactions is especially noteworthy in view of the observation that monofunctional molecules containing all three of these moieties are found to be reactive toward Diels–Alder