1261085-76-0Relevant articles and documents
Synthesis of Functionalized Dihydrocoumarins by NHC-Catalyzed [3 + 3] Annulation of Enals with 2-Substituted Naphthoquinones
Shee, Sayan,Barik, Soumen,Ghosh, Arghya,Biju, Akkattu T.
supporting information, p. 8039 - 8044 (2021/10/20)
The [3 + 3] annulation of α,β-unsaturated aldehydes with 2-substituted 1,4-naphthoquinones allowing the facile synthesis of functionalized dihydrocoumarins catalyzed by N-heterocyclic carbene (NHC) is reported. The initially formed NHC-homoenolates underwent an efficient Michael-isomerization-lactonization cascade to furnish the products. Preliminary studies on mechanism shed light on the homoenolate pathway over the intermediacy of the α,β-unsaturated acylazolium intermediates. Moreover, using chiral NHCs, the desired products were formed in up to 49% yield and 99:1 er.
Pendant Alkoxy Groups on N-Aryl Substitutions Drive the Efficiency of Imidazolylidene Catalysts for Homoenolate Annulation from Enal and Aldehyde
Kyan, Ryuji,Mase, Nobuyuki,Narumi, Tetsuo,Sato, Kohei
supporting information, p. 19031 - 19036 (2020/08/25)
Hydrogen-transfer in the tetrahedral intermediate generated from an imidazolylidene catalyst and α,β-unsaturated aldehyde forms a conjugated Breslow intermediate. This is a critical step affecting the efficiency of the NHC-catalyzed γ-butyrolactone formation via homoenolate addition to aryl aldehydes. A novel type of imidazolylidene catalyst with pendant alkoxy groups on the ortho-N-aryl groups is described. Catalyst of this sort facilitates the formation of the conjugated Breslow intermediate. Studies of the rate constants for homoenolate annulation affording γ-butyrolactones, reveal that introduction of the oxygen atoms in the appropriate position of the N-aryl substituents can increase the efficiency of imidazolylidene catalysts. Structural and mechanistic studies revealed that pendant alkoxy groups can be located close to the proton of the tetrahedral intermediate, thereby facilitating the proton transfer.
Polyhalides as Efficient and Mild Oxidants for Oxidative Carbene Organocatalysis by Radical Processes
Wu, Xingxing,Zhang, Yuexia,Wang, Yuhuang,Ke, Jie,Jeret, Martin,Reddi, Rambabu N.,Yang, Song,Song, Bao-An,Chi, Yonggui Robin
supporting information, p. 2942 - 2946 (2017/03/13)
Simple and inexpensive polyhalides (CCl4 and C2Cl6) have been found to be effective and versatile oxidants in removing electrons from Breslow intermediates under N-heterocyclic carbene (NHC) catalysis. This oxidative react
