Synthesis of polyfunctionalized furans from 3-acetyl-1-aryl-2-pentene-1,4-diones
摘要:
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 la 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 la 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-(4methylphenyl)-2-methylfuran (5) in 49% yield. The BF3-catalyzed reaction of la with 2,4-pentanedione in dry tetrahydrofuran at 23degreesC 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-2one (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 la with triphenylphosphine gave 3a in 88% yield, while la 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-5phenylfuran (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. (C) 2003 Elsevier Science Ltd. All rights reserved.
Photooxygenation of 3-acetyl-5-aryl-2-methylfurans via endoperoxide intermediate and the following reactions
摘要:
The photooxygenation of 3-acetyl-5-aryl-2-methylfurans la-e selectively produced 2,2-diacetyl-3-aroyloxiranes 2a-e, 3-acetyl-1-aryl-2-pentene-1,4-diones 3a-e, and 3-acetyl-1-aryl-2-hydroxy-2-pentene-1,4-diones 4a-d via the endoperoxide intermediate A depending on the reaction conditions and the work-up procedure. The oxiranes 2a-e were mainly obtained in 56-77% yields by allowing the reaction mixture to stand at ambient temperature after the irradiation, while the treatment of the reaction mixture with water mainly gave the 1,4-diones 3a-e (62-69%). Heating the reaction mixture at 80 degreesC after the irradiation decreased the total yield of the products, however, the enols 4a-d were newly formed in 8-12% yields. Direct UV irradiation of the endoperoxide intermediate A led to the homolytic fission of the peroxide linkage to produce the same enols 4a-e (16-39%). The self-sensitized photooxygenation of 1a-d using a UV light also gave 4a-d in a similar yield. The reaction pathway is discussed based on these results. (C) 2001 Elsevier Science Ltd. All rights reserved.
2-Indolymethanols as 4-atom-synthons in oxa-Michael reaction cascade: access to tetracyclic indoles
作者:Tian-Jiao Han、Min-Can Wang、Guang-Jian Mei
DOI:10.1039/d1cc03653j
日期:——
The first Brønstedacid-catalyzed oxa-Michael reactioncascade of 2-indolylmethanols with trione alkenes was accomplished. By using this practical approach, a variety of tetracyclic indoles were readily created in an ordered sequence with excellent regio- and diastereoselectivity. 2-Indolylmethanols commendably served as four-atom synthons, as opposed to the common three-atom synthons in the previous
Acid-catalyzed convenient transformation of 1-aryl-2-pentene-1,4-diones into polyfunctionalized furans
作者:Satoaki Onitsuka、Hiroshi Nishino、Kazu Kurosawa
DOI:10.1016/s0040-4039(00)00373-7
日期:2000.4
of boron trifluoride gave the unstable 3-acetyl-1-phenyl-2-pentene-1,4-dione intermediate which was converted in situ by the reaction with an excess amount of 2,4-pentanedione into new crystalline tri- and tetra-substituted furans. Other unstable 1-aryl-2-pentene-1,4-diones, which were obtained by the photooxygenation of 3-acetyl-5-aryl-2-methylfurans, were trapped by the acid-catalyzed reaction, giving
Catalyst-free racemic and H<sub>2</sub>O/CPA-catalyzed asymmetric regio-reversed domino processes of triketone enones with azlactones
作者:Yun-Dong Fu、Xiang Gao、Shi-Kun Jia、Xiao Xiao、Min-Can Wang、Lihua Huang、Guang-Jian Mei
DOI:10.1039/d3gc01445b
日期:——
Regio-reversed domino processes of triketone enones with azlactones have been established. Opposite to the previous β-addition-triggered domino processes, this protocol is initiated by a regio-reversed α-addition. Under catalyst-free conditions, the dominoreaction readily occurred, leading to the formation of a variety of bicyclic furofurans bearing vicinal quaternary carbons in good to excellent
Diastereodivergent and Regioselective Synthesis of Tetrahydrofuro[2,3-<i>b</i>]furans with Four Consecutive Stereocenters
作者:Jing Zhang、Wen-Na Sun、Zhiwei Jiang、Shi-Kun Jia、Guang-Jian Mei
DOI:10.1021/acs.joc.4c00069
日期:2024.3.15
Base-catalyzed diastereodivergent and regioselective domino processes of triketone enones with arylacetaldehydes for the synthesis of tetrahydrofuro[2,3-b]furans with four consecutive stereocenters are reported. Good yields and diastereoselectivities are obtained when DBU is employed as a catalyst; in contrast, Et3N delivers a different diastereomer in excellent diastereoselectivity. This work offers
报道了三酮烯酮与芳基乙醛的碱催化非对映发散和区域选择性多米诺过程,用于合成具有四个连续立体中心的四氢呋喃并[2,3- b ]呋喃。使用DBU作为催化剂可以获得良好的产率和非对映选择性;相比之下,Et 3 N 则以优异的非对映选择性提供不同的非对映异构体。这项工作具有许多优点,包括可切换的非对映选择性、廉价的碱性催化剂和简单的操作。