A Concise Diastereoselective Photochemical Synthesis of 3-Hydroxyfuran-2(3H)-ones (original) (raw)
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Highly Stereoselective Synthesis oftrans-3-Aryl-4-carbethoxy-2,3-dihydro-2-fur-2′-oyl-5-methylfurans
Chinese J Chem, 2007
Multi-substituted dihydrofurans are valuable intermediates for the synthesis of natural products and pharmaceuticals. Considerable attention has been focused on the development of efficient and regioselective methods for their preparation. Using K 2 CO 3 as a base, with the reaction of fur-2-oylmethyltriphenylarsonium bromide 1 and ethyl 2-acetyl-3-arylacrylate 2 in tetrahydrofuran at room temperature, we found an efficient protocol was achieved to synthesize trans-3-aryl-4-carbethoxy-2,3-dihydro-2-fur-2'-oyl-5-methylfurans 3 in good yield with high stereoselectivity. The structure of compound 3 was confirmed by IR, 1 H NMR, MS and HRMS. The mechanism for the formation of 3 was proposed.
Stereoselective |2+2| photocycloaddition of chiral 2(5H)-furanones to alkenes
Tetrahedron: Asymmetry, 1991
The steric and stereoelectronic dependence of the diastereoselectivity in the photoche~c~ i2+21 ~ycloaddjt~on of chiral Z(S~-f~r~ones to alkenes is investigate to prepare eventuaily cyclobutanic natural products. It is shown that the alkenes approach to d~fe~nt chiral S-subst~tu~d ~(5~~fu~nones mainly by the less hinde~d side, Conveniently substituted cyclobutane rings are present in some natural products: spatane diterpenes,t ~urbenez and c~yophyIlene3 sesquite~enes, (~}-grand~sol monote~ene~ etc, To generate such rings in the total synthesis of some of these substances, 2(W)-furanones have been succesfully used via a 12+21 pbot~ycloaddition to alkenes? The photochem~~~ ~havio~r of these ~,~-butenolides has been widely studiedP but the stereoselective control (mainly face ~~tereoselectivity~ of ~e~cycloaddition to olefmes has not received so much attentions ff a certain control for this cycloaddition could exist and the 2(5N)furanone is homochiral the reactions would lead to good diastereomeric excesses and ultimately to enantiomericaily pure natural pr&cts. In fact, this approach has been widely used through thermal cycloadditions and Michael addifinns. We can imaging that steric and ste~oelectrooic effects can force the olefine to approach the furauone through its less hindered side thus creating a diastereofacial diff~ntiation. To clarify the extend of these effects we have piped some optically pure 5-a1~~-2(5~-1391 R. A~m~serai. furanones, l-5. and we have f&owed the diastereoselective course of their photochemical 12+21 cycloaddition to ~~e~yle~yiene WE) and ethylene.
Carbohydrate Research, 1989
nosyl)-Zphenylfuran (lc and Id), 3-acetyl-5-(2,3-di-O-acetyl+-D-erythrofuranosyl)-2-methylfuran (le), %acetyl-5-(2,3-di-@acetyl-cY-D-and-P-u-threofuranosyl)-2-methylfuran (lfand lg) have been transformed, through the corresponding endoperoxides, into 3-C-acetyl-6,7,8,9-tetra-O-acetyl-l,3,4-trideoxy-D-arabino-non-3eno-2,5-diulose (3a), ethyl (E)-2-C-benzoyl-2,3,4-trideoxy-5,6:7,8-di-O-isopropylidene-D-arubino-act-2-en-4-ulosonate (3b), ethyl (E)-5,8-anhydro-2-C-benzoyl-2,3,4-trideoxy-6,7-O-isopropylidene-rwibo-(3~) and-D-arabino-act-2-en-4-ulosonate (3d), 2,3-di-O-acetyl-@-erythro-(4e) and-aD -threo-furanosyl3-C-acetyl-C oxopent-Zenoate (4f), and 3-C-acetyl-7,8-di-O-acetyl-6,9-anhydro-l,3,Ctrideoxy-D-xylo-non-3-eno-2,5-diulose (3g). The above y-diketones and y-ketoesters reacted with methyl diazoacetate to yield 5
Tetrahedron, 2008
The photochemical [2þ2] cycloaddition of 1,1-diethoxyethylene to chiral 2(5H)-furanones is investigated. The effect of the substituents of the lactone and the polarity of the solvents on the chemical yield, regioselectivity, and facial diastereoselectivity is evaluated. The reactions in ether proceed with excellent regioselectivity and good yields. Hydrolysis of the ketal group of the major cycloadducts afforded enantiopure cyclobutanones fused to g-lactones.
ChemInform, 2011
Photooxygenation of (b-keto)-2-substituted furans leads, in a one pot operation, to functionalized 3(2H)-furanones with good to excellent yields. This methodology was applied as a key-step to the concise and biomimetic synthesis of the sesquiterpene merrekentrone C. The precursor to merrekentrone C, keto difuran, was synthesized using a cross coupling of a-iodo-3-acetylfuran with an alkenyl furan under Fentontype conditions. Recently, we became interested in synthesizing members of the hygrophorone 1 family of natural products. These cyclopentenones exhibit fungicidal activity. Following the retrosynthetic analysis shown in Scheme 1, b-keto-2-furan 1 was proposed as the starting material. Phootoxygenation 2 of 1 should provide triketone 2, which in turn might be a reasonable precursor to the hygrophorone's skeleton via an intramolecular aldol reaction. 3 However, when we first investigated this proposed reaction, we found that the only product formed upon reaction of 1 with singlet oxygen (1 O 2) in MeOH, followed by treatment with Me 2 S (4 equiv) Scheme 1 Retrosynthetic analysis for hygrophorones C-D, via photooxygenation of keto furan 1.
Regio- and stereoselectivity in the Paternò–Büchi reaction on furan derivatives
Journal of Photochemistry and Photobiology A: Chemistry, 2004
The photochemical coupling reaction between 2,3-dihydrofuran and benzaldehyde was studied by using DFT/B3LYP/6 − 31G + (d, p) method. The regiocontrol of the attack of the benzaldehyde on the double bond is related to the different stabilities of the biradical intermediates. The endo stereoselectivity of the reaction depends on the superposition between HSOMO and LSOMO in the biradical intermediate. In the photochemical reaction between furan and benzaldehyde also the regiocontrol depends on the relative stability of the possible biradical intermediates. The exo stereoselectivity of the coupling reaction depends on the superposition between the HSOMO and LSOMO of the biradical intermediate. The reaction of chiral phenylglyoxylates with furan gave the corresponding adducts with de = 15-95%. The stereocontrol can be explained considering the energy gap between the biradical intermediates in the coupling reaction. When the reaction was performed in the presence of zeolite, the diastereoisomeric excess increased. The reaction of benzoin and 2-phenylpropiophenone with furan gave the cycloadduct with high diastereocontrol. All the products were obtained with de > 98%. The Paterrnò-Büchi reaction between 2-furylmethanols with aromatic carbonyl compounds also showed high regio-and stereocontrol. On the contrary, when 5-methyl derivatives were used, a lack of regiocontrol was observed. Furthermore, with aliphatic carbonyl compounds, no diastereoselectivity was observed. These results were explained assuming the attack of the excited carbonyl compound on the same side as the hydroxyl group, through the formation of a hydrogen bond or of a complex. This type of attack gave the biradical intermediate in preferential conformations. The relative energies of these conformers account for the observed diastereoselectivity.