Efficient Synthesis of 4-(2‘-Alkenyl)-2,5-dihydrofurans and 5,6-Dihydro-2H-pyrans via the Pd-Catalyzed Cyclizative Coupling Reaction of 2,3- or 3,4-Allenols with Allylic Halides
摘要:
In the absence of a base, palladium(II) catalysts, such as PdCl2, PdCl2(CH3CN)(2), Pd(OAc)(2), and [(pi-C3H5)PdCl](2), can catalyze the cyclizative coupling reaction of 2,3- or 3,4-allenols with allylic halides in DMA at room temperature to provide 2,5-dihydrofurans and 5,6-dihydro-2H-pyrans, respectively, in moderate to good yields. Under similar reaction conditions, nonsubstituted 2,3-allenol 1s affords bimolecular cyclizative coupling product 5s as the major product. The scope of the reaction and its mechanism have been studied briefly. On the basis of the experimental results, the transformation was believed to proceed via a divalent palladium-catalyzed pathway.
Palladium-Catalyzed Cyclization Reaction of Allylic Bromides with 1,2-Dienyl Ketones. An Efficient Synthesis of 3-Allylic Polysubstituted Furans
作者:Shengming Ma、Lintao Li
DOI:10.1021/ol0055871
日期:2000.4.1
3-Allylic polysubstituted furans were synthesized via a palladium-catalyzed cyclization reaction of allylic bromides with differently substituted 1,2-allenyl ketones. This process may occur via the reaction of a furanyl palladium intermediate with allylic bromide.
Pd0-Catalyzed Coupling Cyclization Reaction of Aryl or 1Alkenyl Halides with 1,2-Allenyl Ketones: Scope and Mechanism. An Efficient Assembly of 2,3,4-, 2,3,5-Tri- and 2,3,4,5-Tetrasubstituted Furans
作者:Shengming Ma、Junliang Zhang、Lianghua Lu
DOI:10.1002/chem.200204664
日期:2003.6.6
Described herein is the Pd(0)-catalyzedcoupling cyclization reaction of 1,2-allenyl ketones with organichalides leading efficiently and conveniently to not only 2,3,4- and 2,3,5-trisubstituted furans but also 2,3,4,5-tetrasubstituted furans. Furthermore, this method showed high substituent-loading capability and tolerance of various substituents. The reactions of 1,2-allenyl ketones 1 e, 1 p, 1 q
Pd0-catalyzed cyclization reaction of aryl or alk-1-enyl halides with 1,2-dienyl ketones: a general and efficient synthesis of polysubstituted furans
作者:Shengming Ma、Junliang Zhang
DOI:10.1039/a908627g
日期:——
Under catalysis by Pd0 and Ag2CO3, the reaction of 1,2-allenyl ketones and organic halides in PhMe using Et3N as the base provides a new general access to polysubstituted furans with good to excellent yields.
Studies on t-BuOK-catalyzed Michael addition of 1,2-allenic ketones with 2-substituted diethyl malonates: highly selective synthesis of β,γ-unsaturated enones
作者:Shengming Ma、Shichao Yu、Wenjian Qian
DOI:10.1016/j.tet.2005.01.131
日期:2005.4
In this paper, we have demonstrated a facile nucleophilic addition of 2-substituted diethyl malonate to various substituted 1,2-allenic ketones to afford beta,gamma-unsaturated enones using a catalytic amount of t-BuOK as the base. The reaction usually completes within 10 min in acetone at room temperature. The stereoselectivity of the reaction with gamma-substituted allenic ketones is very high affording the beta,gamma-unsaturated E-enones. (c) 2005 Elsevier Ltd. All rights reserved.