Pyrazole Synthesis Using a Titanium-Catalyzed Multicomponent Coupling Reaction and Synthesis of Withasomnine
作者:Supriyo Majumder、Kevin R. Gipson、Richard J. Staples、Aaron L. Odom
DOI:10.1002/adsc.200900293
日期:2009.8
coupling of an alkyne, isonitrile, and amine can be used to generate tautomers of 1,3-diimines. These diimines produced in situ undergo cyclization with hydrazine and hydrazine derivatives in a one-pot procedure to provide pyrazoles. Seventeen examples of pyrazoles are provided using this one-pot, 4-component procedure from simple starting materials. The regioselectivity of the alkyne addition can be
炔烃,异腈和胺的钛催化的三组分偶联可用于生成1,3-二亚胺的互变异构体。这些原位生成的二亚胺通过一锅法与肼和肼衍生物进行环化反应,从而提供吡唑。使用这种一锅四组分方法,由简单的起始原料提供了17个吡唑实例。在某些情况下,可以使用催化剂结构控制炔烃加成的区域选择性,并讨论了单取代肼对不对称1,3-二亚胺的区域选择性。这种多组分偶联策略以一种有效的方法应用于了withasomnine的合成,该方法从4-pentyn-1-ol中获得的天然产物的总收率为24%。