Exploiting predisposition in the stereoselective synthesis of mono-, bi- and tetracyclic oxygen heterocycles: Equilibration between, and trapping of, alternative di- and tetraacetals
作者:Stephen Bartlett、Robert Hodgson、Joanne M. Holland、Matthew Jones、Colin Kilner、Adam Nelson、Stuart Warriner
DOI:10.1039/b303089j
日期:——
The desymmetrisation of 1,4-difuran-2-ylbutane-1,4-diol by Sharpless asymmetric oxidation gave the corresponding desymmetrised product in > 96% ee. However, the product existed as a mixture of two interconverting isomers, both of which were mixtures of anomers. The product could be trapped in high yield with a range of reagents to give stable adducts with embedded pyran-3-one, 1,6-dioxaspiro[4.5]decane or pyrano[3,2-b]pyran ring systems. The strategy was also applied in the interconversion between alternative tetracycles and, under acidic conditions, this process was thermodynamically controlled. The selectivity of the process was rationalised by molecular modelling using the HF/6-31G* parameter set.
通过 Sharpless 不对称氧化法对 1,4-二呋喃-2-基丁烷-1,4-二醇进行去对称化反应,得到了相应的去对称化产物,ee > 96%。不过,该产物是两种相互转化的异构体的混合物,这两种异构体都是同分异构体的混合物。利用一系列试剂可以高产率地捕获该产物,从而得到嵌入吡喃-3-酮、1,6-二氧杂螺[4.5]癸烷或吡喃并[3,2-b]吡喃环系统的稳定加合物。该策略还应用于替代四环之间的相互转化,在酸性条件下,该过程受热力学控制。通过使用 HF/6-31G* 参数集进行分子建模,该过程的选择性得到了合理的解释。