Study on generation of conjugated heterocumulene

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1) A series of prochiral 2, 2-bis(hydroxylmethyl)-1, 3-dioxin-4-ones was synthesized by [4+2]cycloaddition of acylketene to protected 1, 3-dihydroxy-2-propanones followed by deprotection of the hydroxyl groups. Dissymmetrization of the prochiral dioxinones by lipase-catalyzed monoacetylation afforded optically active 2-(hydroxymethyl)dioxinones. Intramolecular photo[2+2]cycloaddition of the alkenoates of these alcohols provided an efficient method for regio-, diastereo-, and enantioselective synthesis of cyclobutanols.2) 4-Hydroxy-2-pyrone derivative bridged by polymethylenes at the 3- and 6-positions are readily synthesized by intramolecular [4+2]cycloaddition of bis(acylketene). On heating with ammonia, the bridge 2-pyrones afforded the corresponding 2, 6-bridged 4-pyridones. This methods have a wide applicability to the bridge length; compounds with a short bridge (n = 8) as well as long bridge (n = 18) are synthesized in satisfactory yields.3) Dehydroacetic acid derivative bridged by di(ethylene glycol) unit was synthesized by intramolecular [4+2]cycloaddition of a bis(acylketene). Heating the bridged dehydroacetic derivative with ammonia afforded crown ether type pyridinophane (12-crown-4).