Asymmetric N-Heterocyclic Carbene-catalyzed [4+2] Cycloaddition of Ketenes with alpha-cyanochalcones
文献类型：期刊论文
| 作者 | Sun Lihui; Liang Zhiqin; Ye Song |
| 刊名 | ACTA CHIMICA SINICA
 |
| 出版日期 | 2014-07-15 |
| 卷号 | 72期号:7页码:841-844 |
| 关键词 | N-heterocyclic Carbenes [4+2] Cycloaddition Asymmetric Catalysis Dihydropyranones |
| ISSN号 | 0567-7351 |
| DOI | 10.6023/A14040334 |
| 英文摘要 | The N-heterocyclic carbene (NHC)-catalyzed enantioselective cycloaddition reactions of ketenes are powerful methods for the synthesis of chiral heterocycles. Followed by the previous reported NHC-catalyzed [2+2] and [4+2] cycloaddtion of ketenes with imines, ketones and various heterodienes, the NHC-catalyzed enantioselective [4+2] cycloaddition of ketenes with alpha-cyanochalcones was investigated in this paper. In the presence of the bulky N-heterocyclic carbene derived from L-pyrogutamic acid, the reaction of ketenes with alpha-cyanochalcones went smoothly, giving the corresponding chiral multisubstituted dihydropyranones in good yields with good diastereoselectivities and high enantioselectivities. Initially, several NHCs derived from L-pyrogultamic acids were screened for the reaction. The NHC 4b with bulkyl dimethyl(tert-butyl)silyl group and N-isopropylphenyl performed better than others. The reaction catalyzed by NHCs 4c similar to 4d with a free hydroxyl group gave the dihydropyranones with reversed diastereoselectivity but decreased enantioselectivity. The reaction went well in THF, toluene, dichloromethane or ether, while the one in toluene showed best results. Better yield was reached when the reaction was carried out at 0 or -20 degrees C. Under optimized reaction conditions, a variety of aryl(alkyl)ketenes were investigated for the reaction. It was found that both electron-donating and electron-withdrawing groups in the aryl(alkyl)ketene are tolerable for the reaction. The one with electron-withdrawing substituent gave the product in better yield and diastereoselectivity, while the one with electron-donating substituent resulted in better enantioselectivity. The alkyl chain of the ketenes could be ethyl, n-propyl and n-butyl. All the alpha-cyanochalcones with para-, meta- or ortho-substitutent went well for the reaction. The absolute configuration of resulted dihydropyranone 3e was established by the X-ray analysis of its crystal. The reaction is proposed to initialize with the addition of NHC to ketenes to give the enolate I. The adduct II is formed from enolate I and alpha-cyanochalcone via stepwise Michael addition and cyclization or simultaneous Diels-Alder reaction. The elimination of NHC from adduct II gives final dihydropyranone 3. |
| 语种 | 英语 |
| WOS记录号 | WOS:000340842000012 |
| 出版者 | SCIENCE PRESS |
| 源URL | [http://ir.iccas.ac.cn/handle/121111/52463]  |
| 专题 | 中国科学院化学研究所 |
| 通讯作者 | Sun Lihui |
| 作者单位 | Chinese Acad Sci, Inst Chem, CAS Key Lab Mol Recognit & Funct, Beijing Natl Lab Mol Sci, Beijing 100190, Peoples R China |
| 推荐引用方式 GB/T 7714 | Sun Lihui,Liang Zhiqin,Ye Song. Asymmetric N-Heterocyclic Carbene-catalyzed [4+2] Cycloaddition of Ketenes with alpha-cyanochalcones[J]. ACTA CHIMICA SINICA,2014,72(7):841-844. |
| APA | Sun Lihui,Liang Zhiqin,&Ye Song.(2014).Asymmetric N-Heterocyclic Carbene-catalyzed [4+2] Cycloaddition of Ketenes with alpha-cyanochalcones.ACTA CHIMICA SINICA,72(7),841-844. |
| MLA | Sun Lihui,et al."Asymmetric N-Heterocyclic Carbene-catalyzed [4+2] Cycloaddition of Ketenes with alpha-cyanochalcones".ACTA CHIMICA SINICA 72.7(2014):841-844. |
入库方式： OAI收割
来源：化学研究所
浏览0
下载0
收藏0
其他版本
除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。