证明了由2-芳基吡啶和两当量的铑催化的电子等效的缺电子烯烃可高度区域选择性地合成吡啶并[ 2,1- a ]异吲哚盐。使用廉价的氧气作为氧化剂,在110℃的水性介质中进行反应。当用碱处理该盐以得到β-二取代的烯烃产物时,就会发生异吲哚鎓盐的反向氮杂-迈克尔加成反应。提出了一种反应机理,涉及烯烃与2-芳基吡啶的邻位C H烯化反应,分子内氮杂迈克尔基加成反应,烯烃片段β碳上的去质子化反应,然后另一种迈克尔加成反应生成最终产物。
Halogen−Metal Exchange in 1,2-Dibromobenzene and the Possible Intermediacy of 1,2-Dilithiobenzene
作者:Holger F. Bettinger、Matthias Filthaus
DOI:10.1021/jo7013033
日期:2007.12.1
The one-step high-yield synthesis of 1,2-bis(trimethylsilyl)benzene from 1,2-dibromobenzene using tert-butyllithium and trimethylsilyltriflate is reported. A mechanistic investigation shows that 1,2-dilithiobenzene is not an intermediate in this reaction; the coexistence of trimethylsilyltriflate and tert-butyllithium at very low temperatures allows a sequence of bromine−lithium exchange and subsequent
Rhodium(III)-Catalyzed [4+1] Annulation of Aromatic and Vinylic Carboxylic Acids with Allenes: An Efficient Method Towards Vinyl-Substituted Phthalides and 2-Furanones
A highly regio‐ and stereoselective synthesis of 3,3‐disubstituted phthalides from aryl carboxylic acids and allenes using a rhodium(III) catalyst has been demonstrated. The reaction features broad functional group tolerance and provides a simple and straightforward route to the synthesis of various 3‐vinyl‐substituted phthalides. Furthermore, the catalytic reaction can also be applied to the synthesis
pyridinium salts from the reaction of various 2‐aryl‐pyridines and 2‐aryl‐sp2‐nitrogen‐atom‐containing heterocycles with alkynesthroughrhodium(III)‐catalyzed CH activation and annulation under an O2 atmosphere is described. A possible mechanism that involves the chelation‐assisted CH activation of the 2‐aryl‐pyridine substrate, insertion of the alkyne, and reductive elimination is proposed. This
Palladium-Catalyzed Cascade Arene/Alkyne Annulation: Synthesis of Fluorene-Benzoxazine Derivatives
作者:Zhong-Jian Cai、Fang-Hui Li、Shun-Yi Wang、Shun-Jun Ji
DOI:10.1021/acs.orglett.6b02224
日期:2016.10.7
A palladium-catalyzed cascade arene/alkyneannulation reaction for the synthesis of fluorene-benzoxazine derivatives is developed. This transformation involves a 6-exo-dig cyclization, a 1,3-oxazine vinylpalladium intermediate, and a C–H bond activation.
Co(III)‐catalyzed [4+1] annulation of amides with allenes to synthesize isoindolone and 1,5‐dihydro‐pyrrol‐2‐one derivatives is reported. A wide range of aromatic and vinylic amides react with allenes to give the corresponding annulation products in good to excellent yields. The mechanistic studies strongly support that the catalytic reaction proceeds through an amide‐directed C−Hactivation, followed