Divergent synthesis of spirocyclopentene-pyrazolones and pyrano[2,3-c]-pyrazoles via Lewis base controlled annulation reactions
作者:Wenjun Luo、Bingxuan Shao、Jingyi Li、Dingguo Song、Xiao Yi、Fei Ling、Weihui Zhong
DOI:10.1016/j.tetlet.2019.151206
日期:2019.10
An effective Lewis base catalyst-controlled α-regioselective annulation reaction of γ-substituted allenoates with unsaturated pyrazolones has been developed, affording various spiro-cyclopentene-pyrazolones and pyrano[2,3-c]pyrazoles. The combination of PPh3 and K2CO3 promoted the [3+2] annulation to access the spiro-cyclopentene-pyrazolones in moderate to good yields (up to 90%) with excellent di
已经开发出有效的路易斯碱催化剂控制的γ-取代的烯酸酯与不饱和吡唑酮的α-区域选择性环化反应,提供了各种螺-环戊烯-吡唑酮和吡喃并[2,3-c]吡唑。PPh 3和K 2 CO 3的组合促进了[3 + 2]环化反应,以中等至良好的产率(高达90%)具有优异的非对映选择性(dr> 19:1)进入螺环戊烯-吡唑啉酮。通过使用DBU作为催化剂成功地实现了生成吡喃并[2,3-c]吡唑的4 + 2]环化反应(产率高达92%)。重要的是,使用我们以前报道的手性二茂铁基膦催化剂可以实现螺环-环戊烯-吡唑啉酮的不对称合成。