Abstract

During synthetic studies toward bi-linderone, unexpected 6π-electrocyclizations of 4,5-dimethoxy-2-[(E)-1,3-dimethoxy-5-phenylpenta-2,4-dienylidene]cyclopent-4-ene-1,3-dione and 2-[(E)-1-hydroxy-3-methoxy-5-phenylpenta-2,4-dienylidene]-4,5-dimethoxycyclopent-4-ene-1,3-dione were observed. The cyclization of 4,5-dimethoxy-2-[(E)-1,3-dimethoxy-5-phenylpenta-2,4-dienylidene]cyclopent-4-ene-1,3-dione gave a rare example of a 6π-electrocyclization reaction that occurs readily at room temperature in the presence of silica gel. Meanwhile, the intramolecular hydrogen bonding existing in 2-[(E)-1-hydroxy-3-methoxy-5-phenylpenta-2,4-dienylidene]-4,5-dimethoxycyclopent-4-ene-1,3-dione afforded a strong contribution to the stability of the flat conformation, and this hampered the 6π-electrocyclization process. These 6π-electrocyclizations afforded a facile approach to highly congested spiro compounds.

During synthetic studies toward bi-linderone, unexpected 6π-electrocyclizations of 4,5-dimethoxy-2-[(E)-1,3-dimethoxy-5-phenylpenta-2,4-dienylidene]cyclopent-4-ene-1,3-dione and 2-[(E)-1-hydroxy-3-methoxy-5-phenylpenta-2,4-dienylidene]-4,5-dimethoxycyclopent-4-ene-1,3-dione were observed. The cyclization of 4,5-dimethoxy-2-[(E)-1,3-dimethoxy-5-phenylpenta-2,4-dienylidene]cyclopent-4-ene-1,3-dione gave a rare example of a 6π-electrocyclization reaction that occurs readily at room temperature in the presence of silica gel. Meanwhile, the intramolecular hydrogen bonding existing in 2-[(E)-1-hydroxy-3-methoxy-5-phenylpenta-2,4-dienylidene]-4,5-dimethoxycyclopent-4-ene-1,3-dione afforded a strong contribution to the stability of the flat conformation, and this hampered the 6π-electrocyclization process. These 6π-electrocyclizations afforded a facile approach to highly congested spiro compounds.

中文翻译：

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对双林​​德龙的合成研究导致意外的6π电环化反应：高度拥堵的螺化合物的简便构建

摘要

在对双亚麻酮的合成研究过程中，4,5-二甲氧基-2-[（（E）-1,3-二甲氧基-5-苯基戊-2,4-二烯叉]]环戊-4-烯-1发生了意外的6π电环化，观察到3-二酮和2-[（（E）-1-羟基-3-甲氧基-5-苯基戊-2，4-二烯叉]]-4，5-二甲氧基环戊-4-烯-1，3-二酮。4,5-二甲氧基-2-[（E）-1,3-二甲氧基-5-苯基戊-2,4-二烯叉]环戊-4-烯-1,3-二酮的环化给出了一个罕见的6π例子-在硅胶存在下于室温下容易发生的电环化反应。同时，2-[（E）-1-羟基-3-甲氧基-5-苯基戊基-2,4-二烯叉] -4,5-二甲氧基环戊-4-烯-1,3-二酮对平面构象的稳定性有很强的贡献，阻碍了6π电环化过程。这些6π-电环化为高度拥挤的螺环化合物提供了一种简便的方法。

在对双亚麻酮的合成研究过程中，4,5-二甲氧基-2-[（（E）-1,3-二甲氧基-5-苯基戊-2,4-二烯叉]]环戊-4-烯-1发生了意外的6π电环化，观察到3-二酮和2-[（（E）-1-羟基-3-甲氧基-5-苯基戊-2，4-二烯叉]]-4，5-二甲氧基环戊-4-烯-1，3-二酮。4,5-二甲氧基-2-[（E）-1,3-二甲氧基-5-苯基戊-2,4-二烯叉]环戊-4-烯-1,3-二酮的环化给出了一个罕见的6π例子-在硅胶存在下于室温下容易发生的电环化反应。同时，2-[（E）-1-羟基-3-甲氧基-5-苯基戊基-2,4-二烯叉] -4,5-二甲氧基环戊-4-烯-1,3-二酮对平面构象的稳定性有很强的贡献，阻碍了6π电环化过程。这些6π-电环化为高度拥挤的螺环化合物提供了一种简便的方法。