6121-42-2Relevant articles and documents
Direct Synthesis of Cyclopropanes from gem-Dialkyl Groups through Double C-H Activation
Clemenceau, Antonin,Thesmar, Pierre,Gicquel, Maxime,Le Flohic, Alexandre,Baudoin, Olivier
supporting information, p. 15355 - 15361 (2020/10/20)
Cyclopropanes are important structural motifs found in numerous bioactive molecules, and a number of methods are available for their synthesis. However, one of the simplest cyclopropanation reactions involving the intramolecular coupling of two C-H bonds on gem-dialkyl groups has remained an elusive transformation. We demonstrate herein that this reaction is accessible using aryl bromide or triflate precursors and the 1,4-Pd shift mechanism. The use of pivalate as the base was found to be crucial to divert the mechanistic pathway toward the cyclopropane instead of the previously obtained benzocyclobutene product. Stoichiometric mechanistic studies allowed the identification of aryl- and alkylpalladium pivalates, which are in equilibrium via a five-membered palladacycle. With pivalate, a second C(sp3)-H activation leading to the four-membered palladacycle intermediate and the cyclopropane product is favored. A catalytic reaction was developed and showed a broad scope for the generation of diverse arylcyclopropanes, including valuable bicyclo[3.1.0] systems. This method was applied to a concise synthesis of lemborexant, a recently approved anti-insomnia drug.
Electrophilic Bromolactonization of Cyclopropyl Diesters Using Lewis Basic Chalcogenide Catalysts
Gieuw, Matthew H.,Leung, Vincent Ming-Yau,Ke, Zhihai,Yeung, Ying-Yeung
, p. 4306 - 4311 (2018/10/02)
An efficient and regioselective electrophilic bromolactonization of cyclopropylmethyl diesters using triphenylphosphine sulfide (Ph3PS) or diphenyl selenide (Ph2Se) as the Lewis basic chalcogenide catalyst has been developed. It was observed that Ph3PS favored the formation of anti-diastereomer and yielded the multi-functional γ-lactones. Interestingly, the diastereoselectivity was reversed when using Ph2Se as a catalyst where the syn-product instead of the anti-product was favored. (Figure presented.).
Efficient cyclopropanation of aryl/heteroaryl acetates and acetonitriles with vinyl diphenyl sulfonium triflate
Zhou, Mingwei,Hu, Yimin,En, Ke,Tan, Xuefei,Shen, Hong C.,Qian, Xuhong
supporting information, p. 1443 - 1445 (2018/03/12)
A convenient method was developed for the cyclopropanation of aryl acetates and aryl acetonitrile using vinyl diphenyl sulfonium triflate salt. The newly developed conditions are simple, mild, and compatible with a wide range of functional groups, without the need to apply an inert atmosphere, or alkali bases.
