A New, Efficient and Stereoselective Synthesis of Tricyclic and Tetracyclic Compounds by Samarium Diiodide Induced Cyclisations of Naphthyl-Substituted Arylketones—An Easy Access to Steroid-Like Skeletons
we present the application of samariumdiiodide induced cyclisations of naphthyl-substituted ketones towards an easy and stereoselectiveaccess to tri- and tetracyclic-functionalised compounds. Typical naphthalene derivatives were studied to investigate the scope and limitations of this novel cyclisation process. The model substrates studied demonstrate that the samarium ketyl cyclisations are essentially
Synthesis of chiral spirocyclic ketones was accomplishedviathe Pd-catalyzed intramolecular α-arylation of α-substituted cyclic ketones. The obtained spirocyclic ketone could be converted into an acid–base organocatalyst.
Intramolecular arylation of properly designed substrates bearing a ketone, formyl, or nitro terminating group was achieved by use of a PdCl2(Ph3P)2–Cs2CO3 reaction system to form a variety of carbocyclic compounds. Arylation in ketone compounds afforded benzene-annulated bridged or spirocycloalkanone derivatives, depending on the structure of the cyclization precursors. Arylation in formyl compounds
通过使用PdCl 2(Ph 3 P)2 -Cs 2 CO 3,对设计适当的带有酮,甲酰基或硝基终止基团的底物进行分子内芳构化反应体系形成各种碳环化合物。取决于环化前体的结构,酮化合物中的芳基化可提供苯环化的桥环或螺环烷酮衍生物。取决于环化前体的结构和反应溶剂,甲酰基化合物中的芳基化发生在α位置(α-芳基化)或羰基碳(羰基芳基化)。α-芳基化的仲硝基以Nef反应的方式部分转化为酮,而叔硝基被部分消除,得到苯乙烯型烯烃。
A New Access to Multifunctional Linear Triquinanes and Their Homologues via ?,?-Unsaturated Fischer Carbene Complexes
作者:Yao-Ting Wu、Denis Vidovic、J�rg Magull、Armin de Meijere
DOI:10.1002/ejoc.200400858
日期:2005.4
corresponding protected (2'-oxocycloalkyl)methyl-substituted cyclopentadienes 6, which were obtained by cocyclization of the alkynes 5 with the β-dimethylamino-substituted α,β-unsaturated Fischercarbenecomplexes 4 in 38–81 % yield (6 examples with 66–81 %). In most cases, the cis,anti,cis-isomers anti-7 were the major products. While the twofold cis-fusion is favored by minimal ring strain, hydrogen
Intramolecular Ene and Related Reactions, Part 9. Photochemically Induced Synthesis of Allylsilane Carbaldehydes
作者:Lutz F. Tietze、Josef R. Wünsch
DOI:10.1055/s-1990-27070
日期:——
Allylsilane carbaldehydes are valuable substrates for the tandem Knoevenagel allylsilane and iminium cyclization. They can easily be prepared by a photochemical α-cleavage of cyclic ketones bearing a trimethylsilylmethyl group in the α-position (Norrish Type I cleavage). The photolytic process is facilitated by the silicon due to its stabilization of a radical in the β-position. Irradiation of the ketones 15a-d leads mainly to the aldehydes 16a-d. In addition irradiation of 19a gives mostly the aldehyde 20.