Diastereoselective Synthesis of Tetrahydrofurans by Lewis Acid Catalyzed Intermolecular Carbenoid鈥揅arbonyl Reaction鈥揅ycloaddition Sequences: Unusual Diastereoselectivity of Lewis Acid Catalyzed Cycloa

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• 作者：Yuta Hashimoto ; Kennosuke Itoh ; Akikazu Kakehi ; Motoo Shiro ; Hiroyuki Suga
• 刊名：The Journal of Organic Chemistry
• 出版年：2013
• 出版时间：June 21, 2013
• 年：2013
• 卷：78
• 期：12
• 页码：6182-6195
• 全文大小：493K
• 年卷期：v.78,no.12(June 21, 2013)
• ISSN：1520-6904

文摘

The effects of including metal salts for three-component reactions involving 伪-alkyl-伪-diazo esters, aromatic aldehydes, and 3-(2-alkenoyl)-2-oxazolidinones are described, in terms of yields and diastereoselectivities. Metal tetrafluoroborates (10鈥?0 mol %) such as Co(BF₄)₂路6H₂O, Ni(BF₄)₂路6H₂O, and AgBF₄ were effective in delivering high yields and diastereoselectivities (93:7 to 99:1) of the corresponding tetrahydrofuran derivatives while suppressing the competitive formation of 1,3-dioxolane. Using (S)-3-(2-alkenoyl)-4-isopropyl-2-oxazolidinones as the dipolarophiles in the three-component reactions, in the presence of Ni(BF₄)₂路6H₂O or Co(ClO₄)₂路6H₂O (10鈥?0 mol %), optically active tetrahydrofurans that possess four successive asymmetric centers were synthesized in high diastereoselectivities (99:1). On the basis of the configuration of the cycloadduct using the X-ray analysis, the high diastereoselectivity could be explained by the unusual Re-face approach to the dipolarophile in the presence of the Lewis acid, proceeding through the s-cis conformer of the 3-(2-alkenoyl)-2-oxazolidinone with the two carbonyls in opposing directions (dipole鈥揹ipole interaction).