Study on generation of conjugated heterocumulene

1)通过酰基酮与受保护的1，3-二羟基-2-丙酮[4+2]环加成，然后脱保护羟基，合成了一系列前手性2，2-二(羟甲基)-1，3-二恶英-4-酮。前手性二恶英在脂肪酶催化的单乙酰化反应中发生不对称反应，得到光学活性2-羟甲基二恶英。分子内光[2+2]环加成反应为环丁醇的区域、非对映和对映选择性合成提供了一种有效的方法。2)通过分子内[4+2]环加成反应，可以方便地合成3-和6-位多亚甲基桥联的4-羟基-2-吡喃酮衍生物。在氨水加热下，桥式2-吡喃得到相应的2，6-桥式4-吡啶酮。这些方法对桥长具有广泛的适用性，以令人满意的产率合成了短桥(n=8)和长桥(n=18)的化合物。3)通过分子内[4+2]环加成双酰基酮，合成了二甘醇单元桥联的脱氢醋酸衍生物。用氨水加热桥联脱氢乙酸乙酯得到冠醚型吡啶并(12-冠-4)。

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).