A General Approach to Medium Ring Alkynes by Using Metathesis of Cobalt Hexacarbonyl Containing Dienes
摘要:
The assembly of medium sized rings (7-9) was achieved by using the metathesis of dienes linked by a cobalt hexacarbonyl complexed alkyne with either Grubbs' or Schrock's catalysts. The products of metathesis were subjected to transformations involving the dicobalt hexacarbonyl complexes, for example, decomplexation to liberate cyclic alkynes or Pauson-Khand reaction.
A General Approach to Medium Ring Alkynes by Using Metathesis of Cobalt Hexacarbonyl Containing Dienes
摘要:
The assembly of medium sized rings (7-9) was achieved by using the metathesis of dienes linked by a cobalt hexacarbonyl complexed alkyne with either Grubbs' or Schrock's catalysts. The products of metathesis were subjected to transformations involving the dicobalt hexacarbonyl complexes, for example, decomplexation to liberate cyclic alkynes or Pauson-Khand reaction.
Simultaneous Synthesis of Both Rings of Chromenes via a Benzannulation/<i>o</i>-Quinone Methide Formation/Electrocyclization Cascade
作者:Nilanjana Majumdar、Keith A. Korthals、William D. Wulff
DOI:10.1021/ja210655g
日期:2012.1.18
A new route to the chromene ring system has been developed which involves the reaction of an α,β-unsaturated Fischer carbenecomplex of chromium with a propargyl ether bearing an alkenyl group on the propargylic carbon. This transformation involves a cascade of reactions that begins with a benzannulation reaction and is followed by the formation of an o-quinone methide, and finally results in the emergence
开发了一种色烯环体系的新路线,该路线涉及铬的α,β-不饱和费歇尔卡宾络合物与在炔丙碳上带有烯基的炔丙醚的反应。这种转化涉及一系列反应,从苯并环化反应开始,然后形成邻醌甲基化物,最后在电环化时产生色烯。通过使用芳基卡宾络合物,该反应被扩展以提供通路。这是色烯的首次合成,其中色烯系统的两个环均在一步中生成,并在 lapachenole 和维生素 E 的合成中得到突出体现。
The synthesis of the highly functionalized tetracyclic skeleton of landomycinone (2), the aglycon of landomycins, was performed using two pivotal steps relying on metal-catalyzed reactions. They are (1) a [2 + 2 + 2] cycloaddition of alkynes promoted by Wilkinson's catalyst to build rings B and C concomitantly and (2) a ring-closing metathesis followed by aromatization to build ring D.