Bioinspired Polyene Cyclization Promoted by Intermolecular Chiral Acetal-SnCl<sub>4</sub> or Chiral <i>N</i>-Acetal-TiCl<sub>4</sub>: Investigation of the Mechanism and Identification of the Key Intermediates
作者:Yu-Jun Zhao、Teck-Peng Loh
DOI:10.1021/ja802896n
日期:2008.7.1
New strategies using chiralacetal or chiral mixed-acetal in the presence of Lewis acids (SnCl4 or TiCl4) to promote polyene cyclization reaction are described. Acetal-promoted and mixed-acetal-promoted polyene cyclization products are very versatile and can easily be converted into various optically active tricyclic and tetracyclic terpenoids. One of the derivatives of the cyclization products was
Specific and Strong Acceleration of Nitrosation by Nitrosyl Sulfonates Using the Bis-Coordinating Lewis Acid TiCl<sub>4</sub> or SnCl<sub>4</sub>
作者:G. Sudhakar Reddy、E. J. Corey
DOI:10.1021/acs.orglett.3c03768
日期:2024.1.19
Nitrosyl triflate is an excellent donor of NO+ to C═C and very unreactive benzenoids, in contrast to the much less reactive nitrosyl mesylate. However, both of these reagents are strongly activated by the bis-coordinating Lewis acids TiCl4 and SnCl4 and become super reactive NO+ donors. Strong catalysis and activation are even observed with the inherently less electrophilic nitrosyl trifluoroacetate
与活性较低的甲磺酸亚硝酰酯相比,三氟甲磺酸亚硝酰酯是 NO +向 C=C 和非常不活泼的苯类化合物的极佳供体。然而,这两种试剂均被双配位路易斯酸TiCl 4和SnCl 4强烈活化,并成为超反应性NO +供体。甚至用本身亲电性较低的三氟乙酸亚硝酰酯也观察到强催化和活化作用。单配位强路易斯酸,例如MeAlCl 2 ,相对无效。
NXS, Morpholine, and HFIP: The Ideal Combination for Biomimetic Haliranium-Induced Polyene Cyclizations
作者:Andreas M. Arnold、Alexander Pöthig、Markus Drees、Tanja Gulder
DOI:10.1021/jacs.8b00113
日期:2018.3.28
contrast to Nature that accomplishes polyenecyclizations seemingly with ease, such transformations are difficult to conduct in the lab. In our program dealing with the development of selective halogenations of alkenes, we now asserted that standard X+ reagents are perfectly suited for the biomimetic cation-π cyclization of both electron rich and poor linear polyenes in the presence of the Lewis base