One-pot oxo-amination of unactivated cyclopropanes with safe, green dioxygen as an oxidant and low-cost amines as nitrogen sources has generated interest since this can directly result in uniform β-located difunctional units. Formation of the three-electron cation radical followed by the nucleophilic attack of amines to open the strained ring of cyclopropanes catalyzed by classic noble-complex photocatalysts
使用安全、绿色的双氧作为氧化剂和低成本的胺作为氮源,对未活化的环丙烷进行一锅法氧代胺化引起了人们的兴趣,因为这可以直接产生均匀的 β 位双功能单元。形成三电子阳离子自由基,然后胺的亲核攻击打开由经典贵金属络合物光催化剂催化的环丙烷的应变环是一种有前途的策略。然而,这种开环途径无法维持整个二级亲核取代(S N2) 转化率,这通常导致对映体选择性不令人满意(对映体过量(ee)值~60%)。在这里,我们证明了对于环丙烷与良性分子氧和吡唑的这种一步氧代胺化,可以首先通过 TiO 2光催化剂实现高度均匀的构型反转。该策略具有低成本、半多相光催化和环境友好的反应条件,无需使用任何牺牲试剂或添加剂。重要的是,我们的方案不仅提供了相对广泛的底物范围,可耐受一定范围的取代环丙烷和吡唑,从而产生具有出色转化率和收率的各种 β-氨基酮产品(~50 个示例),而且还保留了出色的对映选择性(ee 值~99%)。一致
A convenient approach to β-heteroarylated (C–N bond) ketones from Cs2CO3 promoted reaction between propargyl alcohols and nitrogen-heterocycles
作者:M. Bhanuchandra、Malleswara Rao Kuram、Akhila K. Sahoo
DOI:10.1039/c2ob25165e
日期:——
effectively undergo redox-isomerization conjugate addition (RICA) with NH-heteroarenes. Reaction of 3-substituted pyrazoles or indazole with propargyl alcohols enables highly regioselective products. A diverse range of NH-bearing nucleophiles such as: pyrazoles, imidazole, triazoles, pyrrole, indoles and aniline participate in this reaction and deliver the corresponding β-heteroarylated ketones.