Synthesis of polyfunctionalized furans from 3-acetyl-1-aryl-2-pentene-1,4-diones

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• 作者：Onitsuka ; Satoaki ; Nishino ; Hiroshi
• 关键词：BF₃-catalyzed cyclization ; 3-acetyl-1-aryl-2-pentene-1 ; 4-diones ; polyfunctionalized furans ; bis(furyl)methanes ; trisubstituted furans ; tetrasubstituted furans ; furfuryl carbocation intermediate ; Diels&ndash ; Alder reaction
• 刊名：Tetrahedron
• 出版年：2003
• 出版时间：February 3, 2003
• 年：2003
• 卷：59
• 期：6
• 页码：755-765
• 全文大小：505 K

文摘

The BF₃-catalyzed cyclization of 3-acetyl-1-aryl-2-pentene-1,4-diones 1a–e in the presence of water in boiling tetrahydrofuran gave bis(3-acetyl-5-aryl-2-furyl)methanes 2a–e in 26–79 % yields along with a small amount of 3-acetyl-5-aryl-2-methylfurans 3a–e. The exact structure of 2a was determined by X-ray crystallography. The use of a half volume of the solvent for the reaction of 1a resulted in the formation of 2,4-bis(3-acetyl-5-phenyl-2-furfuryl)-3-acetyl-5-phenylfuran (4) together with 2a and 3a. A similar reaction of 1a was carried out in the presence of 3-acetyl-5-(4-methylphenyl)-2-methylfuran (3d) to afford 4-(3-acetyl-5-phenyl-2-furfuryl)-3-acetyl-5-(4-methylphenyl)-2-methylfuran (5) in 49 % yield. The BF₃-catalyzed reaction of 1a with 2,4-pentanedione in dry tetrahydrofuran at 23°C gave 3-(3-acetyl-5-phenyl-2-furfuryl)-4-hydroxy-3-penten-2-one (6a) and 3-(3-acetyl-2-methyl-4-phenyl-5-furyl)-4-hydroxy-3-penten-2-one (7a) in 66 and 24 % yields, respectively. The product distribution depended on the reaction temperature. A similar reaction of 1b–e also yielded the corresponding trisubstituted furans 6b–e and tetrasubstituted furans 7b–e in good yields. These results suggested the presence of the furfuryl carbocation intermediate A during the reaction. The one-pot synthesis of 6a and 7a was also achieved by a similar reaction using phenylglyoxal. The deoxygenation of 1a with triphenylphosphine gave 3a in 88 % yield, while 1a was treated with concentrated hydrochloric acid to yield 3-acetyl-2-chloromethyl-5-phenylfuran (8) which was quantitatively transformed in ethanol into 3-acetyl-2-ethoxymethyl-5-phenylfuran (9) and in water into 3-acetyl-5-phenylfurfuryl alcohol (10), respectively. In addition, the Diels–Alder reaction of cyclopantadiene with 1a gave the corresponding [4+2] cycloaddition products 11 and 12.