New conditions for dearomatizingsamarium‐ketyl (hetero)arene cyclizations are reported. In many examples of these samariumdiiodide‐mediated reactions, lithium bromide and water can be used as additives instead of the carcinogenic and mutagenic hexamethylphosphoramide (HMPA). The best results were obtained for the cyclizations of N‐acylatedindolederivatives delivering the expected indolines in good
Synthesis and Evaluation of Enantiopure HMPA Analogs in Samarium‐Diiodide‐Promoted Dearomatizations of N‐Acylated Indole Derivatives
作者:Chintada Nageswara Rao、Hans‐Ulrich Reissig
DOI:10.1002/ejoc.202101065
日期:2021.12.14
Among several chiral (S)-proline-based HMPAanalogs, the shown ligand strongly activates samariumdiiodide allowing the very fast and efficient conversion of an N-acylated indole into an indoline derivative. So far the achieved enantioselectivity is at best moderate.
在几种基于手性 ( S )-脯氨酸的 HMPA 类似物中,所示配体强烈激活二碘化钐,允许 N-酰化吲哚非常快速有效地转化为二氢吲哚衍生物。到目前为止,实现的对映选择性充其量是中等的。
Samarium(II)‐Promoted Cyclizations of Nonactivated Indolyl Sulfinyl Imines to Polycyclic Tertiary Carbinamines
作者:Chintada Nageswara Rao、Hans‐Ulrich Reissig
DOI:10.1002/ejoc.202200264
日期:2022.4.12
of samarium diiodide in the presence of water and lithium bromide efficiently converts nonactivated N-acylated indolyl sulfinyl imines into polycyclic indoline derivatives containing a tertiary carbinamine moiety. Mechanistic aspects of this reaction are discussed which first involves a reductive N−S cleavage followed by a dearomatizing cyclization.