已为您找到该学者6条结果 成果回收站
冯小明, Weiqing Yang, † Deju Shang, † Yanling Liu, † Ying Du, † and Xiaoming Feng*, †, ‡
J. Org. Chem., Vol. 70, No. 21, 2005,-0001,():
-1年11月30日
An efficient enantioselective approach to chiral dihydropyrones has been developed by the hetero-Diels-Alder (HDA) reactions of (E)-4-methoxy-2-trimethylsiloxy-penta-1,3-diene (diene 1) withaldehydes and pyruvates. It has been found that the readily accessible (R)-BINOL-Ti(OiPr)4(1.1:1) complex was a very effective catalyst for this reaction. Aromatic, heteroaromatic, conjugated,and aliphatic aldehydes afforded the corresponding products in moderate to high isolated yields(up to 99%) with excellent enantioselectivities (up to 99% ee). The first example of highlyenantioselective synthesis of 2,2,6-trisubstituted dihydropyrones by the catalytic reaction of diene1 with pyruvates was reported. The isolated intermediates indicated that this asymmetric HDAreaction proceeded in a Mukaiyama aldol pathway. On the basis of the absolute configurations ofthe products, a possible mechanism was proposed. Moreover, the catalytic system could be used tosynthesize a series of enantioenriched
-
44浏览
-
0点赞
-
0收藏
-
0分享
-
127下载
-
0
-
引用
冯小明, Bo Gao, Zhengyan Fu, Zhipeng Yu, Lan Yu, Yaozong Huang and Xiaoming Feng*
Tetrahedron 61(2005)5822-5830,-0001,():
-1年11月30日
An efficient enantioselective approach to 2,5-disubstituted dihydropyrones was developed. Some easily accessible inexpensivediol ligand metal complexes were employed, and [(R)-BINOL]2–Ti(OiPr)4 complex was found to be the most effective catalyst (up to 99%yield and 99% ee in the presence of 5 mol% catalyst) for the hetero-Diels–Alder reaction between trans-1-methoxy-2-methyl-3-trimethylsiloxybuta-1,3-diene (1) and aldehydes. The potential and generality of this catalyst were evaluated by a variety of aldehydesincluding aromatic, heteroaromatic, a,b-unsaturated and aliphatic aldehydes. Based on the isolated intermediate from the reaction ofbenzaldehyde being confirmed by 1H, 13C NMR and HRMS data, the mechanism was proposed as a Mukaiyama aldol pathway.
-
39浏览
-
0点赞
-
0收藏
-
0分享
-
140下载
-
0
-
引用
冯小明, Ke Cheng, Lili Lin, Shikui Chen and Xiaoming Feng*
Tetrahedron 61(2005)9594-9599,-0001,():
-1年11月30日
The aza-Diels–Alder reaction of trans-1-methoxy-2-methyl-3-trimethylsiloxybuta-1,3-diene with N-benzhydryl imines in the presence of Yb(OTf)3 in toluene at room temperature gave the corresponding 2,5-disubstituted 2,3-dihydro-4-pyridones in high yields. This reaction can also be carried out with diene, aldehydes, and amine in a three-component one-pot reaction manner in moderate to high yields under solvent-free conditions. The relationship between Lewis acids and activity, solvents and catalyst loading were studied. Some investigation towards the reaction mechanism was discussed.
-
46浏览
-
0点赞
-
0收藏
-
0分享
-
259下载
-
0
-
引用
【期刊论文】Highly Enantioselective Cyanosilylation of Aldehydes Catalyzedby Novel
冯小明, Yan Li, † Bin He, † Bo Qin, † Xiaoming Feng, *, † and Guolin Zhang‡
J. Org. Chem. 2004, 69, 7910-7913,-0001,():
-1年11月30日
The
-
35浏览
-
0点赞
-
0收藏
-
0分享
-
84下载
-
0
-
引用
冯小明, Fu-Xue Chen, a Bo Qin, a Xiaoming Feng, a, * Guolin Zhangb and Yaozhong Jiangc
J. Org. Chem., Vol. 70, No. 21, 2005,-0001,():
-1年11月30日
Enantioselective addition of trimethylsilyl cyanide to ketones by a catalytic double-activation method is described. By combinatorially using 2.0mol% of a chiral salen-titanium complex and 1.0mol% of an achiral tertiary amine N-oxide, aromatic, aliphatic and a,b-unsaturated ketones are converted into corresponding cyanohydrin trimethylsilyl ethers with 50-93% yield and 59-86% ee. The effects of ligand structure, catalyst loading and substrate concentration, solvents, the nature of Lewis base, counter ion and other additives, temperature, and substrate structure on the enantioselectivity are discussed. Three possible paths to achieve the asymmetric version of double-activation catalysis and two independent examples of it are proposed.
-
44浏览
-
0点赞
-
0收藏
-
0分享
-
76下载
-
0
-
引用