2-Acetonyl-2,4-di(hydroxy)tetrahydropyrans<b><i>versus</i></b>γ-Pyrones: A Chemodivergent Issue for the Condensation of Acetylacetone Dianion Equivalents with α,β-Disubstituted β-Hydroxyaldehydes Leading to Potential New Synthons for Spiroketals
作者:Jean-Pierre Férézou、Vivien Henryon、Lu Liu、Roman Lopez、Joëlle Prunet
DOI:10.1055/s-2001-18717
日期:——
of acetylacetone bis(silyl)enol ether 2-Si or acetylacetone lithium dianion 2-Li with various anti a,s-disubstituted s-hydroxy aldehydes 11 was studied. It has been shown that under Lewis acid-promoted Mukaiyama conditions it is possible to realize such condensation reactions without formation of the well-known Danishefsky ?-pyrones 8. The required 2-acetonyl-2,4-dihydroxytetrahydropyrans 1 for further
为了开发一种新的途径来获得许多天然产物中存在的缩酮或螺缩酮亚基,乙酰丙酮双(甲硅烷基)烯醇醚 2-Si 或乙酰丙酮锂双阴离子 2-Li 与各种抗α,s-二取代的 s-羟基醛缩合 11进行了研究。已经表明,在路易斯酸促进的 Mukaiyama 条件下,可以实现这样的缩合反应,而不会形成众所周知的 Danishefsky α-pyrones 8. 用于进一步合成目的所需的 2-acetonyl-2,4-dihydroxytetrahydropyrans 1 是由中间体无环羟醛加合物7以良好至高产率制备。特别重要的是i)用四丁基氟化铵在二甲基甲酰胺中的O-甲硅烷基保护的无环中间体7的脱保护条件,ii) 随后的蒙脱石 K10 促进了对半缩酮 1 羟基的保护。已经研究了控制初始缩合反应的立体选择性的参数。在明显的费尔金或反费尔金/克拉姆螯合条件下,从乙酰丙酮双(甲硅烷基)烯醇醚 2-Si 中以高选择