Hydroalumination of Ketenimines and Subsequent Reactions with Heterocumulenes: Synthesis of Unsaturated Amide Derivatives and 1,3-Diimines

The
series of differently substituted ketenimines 1 was hydroluminated
using di-iso-butyl aluminum
hydride. For the sterically congested ketenimine 1a,
preferred hydroalumination of the CN-bond was proven by X-ray
crystallography (compound 5a). In situ treatment of the
hydroaluminated ketenimines 5 with various heterocumulenes
like carbodiimides, isocycanates, isothiocyanates and ketenimines
as electrophiles and subsequent hydrolytic workup resulted in novel
enamine derived amide species in case of N-attack
(sterically less hindered ketenimines) under formation of a new C–N-bond
or in 1,3-diimines by C–C-bond-formation in case of bulky substituents
at the ketenimine-nitrogen atom. Furthermore, domino reactions with
more than 1 equiv of the electrophile or by subsequent addition of
two different electrophiles are possible and lead to polyfunctional
amide derivatives of the biuret type which are otherwise not easily
accessible.

本研究采用二异丁基氢化铝对一系列不同取代的烯酮亚胺（ketenimines）1进行氢铝化反应。对于空间位阻较大的烯酮亚胺1a，其C=N键优先发生氢铝化的结论通过X射线晶体衍射法（化合物5a）得以验证。将氢铝化后的烯酮亚胺5与碳二亚胺、异氰酸酯、异硫氰酸酯及烯酮亚胺等多种杂累积烯烃亲电试剂进行原位处理，随后经水解后处理：当亲电试剂发生N-进攻时（适用于空间位阻较小的烯酮亚胺），可形成新的C-N键，得到烯胺衍生的新型酰胺类产物；而当烯酮亚胺氮原子上带有大位阻取代基时，则通过C-C键的形成得到1,3-二亚胺类产物。此外，通过使用1当量以上的亲电试剂开展多米诺反应，或依次加入两种不同的亲电试剂，可获得常规方法难以合成的缩二脲型多官能团酰胺衍生物。