Palladium(II) catalyzed cyclization of alkynoic acids
作者:Claude Lambert、Kiitiro Utimoto、Hitosi Nozaki
DOI:10.1016/s0040-4039(01)81594-x
日期:——
Under the catalytic action of palladium(II) in the presence of triethylamine, 3-, 4-, and 5-alkynoic acids afford 3-buten-4-olides, 4-penten-4-olides, and 5-hexen-5-olide, respectively, in good to excellent yields.
Cycloisomerization of Acetylenic Acids to γ-Alkylidene Lactones using a Palladium(II) Catalyst Supported on Amino-Functionalized Siliceous Mesocellular Foam
作者:Anuja Nagendiran、Oscar Verho、Clémence Haller、Eric V. Johnston、Jan-E. Bäckvall
DOI:10.1021/jo4028006
日期:2014.2.7
Cycloisomerization of various γ-acetylenic acids to their corresponding γ-alkylidenelactones by the use of a heterogeneous Pd(II) catalystsupported on amino-functionalized siliceousmesocellularfoam is described. Substrates containing terminal as well as internal alkynes were cyclized in high to excellent yields within 2–24 h under mild reaction conditions. The protocol exhibited high regio- and
a high‐yielding access to a non‐symmetrical palladium NNC pincercomplex. A number of terminal and internal alkynoic acids with different substitution patterns at the α‐ and β‐positions are regio‐ and diastereoselectively cycloisomerized to the corresponding exocyclic enol lactones in the presence of exceedingly low amounts of the latter palladiumcomplex, so that unprecedented turnover numbers and
两步(通过氧化加成进行亲核取代/钯化)序列提供了对非对称钯NNC钳形复合物的高收益途径。在存在极低量的后者钯络合物的情况下,许多在α和β位置具有不同取代方式的末端和内部链烷酸被区域和非对映选择性环异构化为相应的环外烯醇内酯,从而使空位转换数空前和频率范围为1,000,000至700,000和41,667至9722 h -1分别实现。基于使用催化量的三乙胺作为碱的优化方案,可以通过NMR光谱轻松地实时监控反应。从动力学和中毒实验中收集了一些证据,这些证据支持上述钳形配合物直接参与反应的催化剂。
Metal–Ligand Cooperation in the Cycloisomerization of Alkynoic Acids with Indenediide Palladium Pincer Complexes
1a–c are shown to very efficiently catalyze the cycloisomerization of alkynoicacids into alkylidenelactones via metal–ligand cooperation (TON up to 2000). Complexes 1a–c are competent toward a broad range of alkynoicacids, including functionalized and internal ones, and give access to 5- as well as 6- and 7-membered lactones in excellent yields and with very high selectivities.