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Lewis acid-catalyzed tandem acylation–Nazarov cyclization for the syntheses of fused cyclopentenones
Ertong Li Changwei Li Jing Wang Jinqian Wang Lihong Dong Xiaohe Guo Chuanjun Song Junbiao Chang 《Tetrahedron》2014
Treatment of N-tosylpyrroles or N-tosylindoles with α-unsubstituted α,β-unsaturated carboxylic acids or unsaturated carboxylic acids having an α electron-withdrawing substituent in the presence of TFAA and a Lewis acid catalyst resulted in the formation of fused cyclopentenones via a tandem acylation–Nazarov cyclization sequence, while either the acylation product obtained or no reaction occurred in the absence of the Lewis acid catalyst. 相似文献
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Hukum P. Acharya 《Tetrahedron letters》2004,45(6):1199-1202
A key cyclopentenone possessing the α-chain was synthesized from TBS ether of 4-cyclopentene-1,3-diol monoacetate, and submitted to aldol reaction at the α′-position with the ω-chain aldehydes followed by dehydration to produce the title compounds. In a similar manner, 5-dehydro compounds (acetylene analogues) were synthesized successfully. In addition, palladium-catalyzed reaction of 4-cyclopentene-1,3-diol monoacetate with methyl malonate, the first step of the synthesis, was improved to afford the product in high yield by using t-BuOK or LDA in place of NaH. 相似文献
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Hukum P. Acharya 《Tetrahedron》2006,62(14):3329-3343
Palladium-catalyzed reaction of TBS ether of 4-cyclopentene-1,3-diol monoacetate (>95% ee) with an anion derived from methyl malonate and a base such as t-BuOK and LDA proceeded highly efficiently and reproducibly. The product obtained in >90% isolated yield was transformed in five steps into the key cyclopentenone possessing the α-chain at the γ position. Aldol reaction of this enone with the ω-chain aldehyde afforded the aldol adduct, and exposure of the derived mesylate to Al2O3 furnished the cross-conjugated dienone of the full structure. Finally, functional group manipulation furnished Δ12-PGJ2 efficiently. Similarly, 15-deoxy-Δ12,14-PGJ2, 5,6-acetylene analogues, and a 5,6-dihydro analogue were synthesized. 相似文献
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Hukum P. Acharya 《Tetrahedron letters》2005,46(48):8435-8438
Use of the PMBOCH2 group (PMB: p-MeOC6H4CH2) as a substitute of CO2H provided high level of reproducibility and efficiency in construction of the full structure of 5,6-epoxyisoprostane A2. After the construction, the PMBOCH2 group was converted to CO2H by using (1) DDQ, (2) SO3·pyridine and (3) NaClO2 at pH 7. The acid, thus synthesized, was condensed with lyso-PC to furnish one of the title compounds. Similarly, 14,15-regioisomer was synthesized. 相似文献
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A new approach to 15-deoxy-Δ12,14-prostaglandin J2 and related structures based on the (±)-Corey lactone diol has been developed. The key stage of this approach involves building the structure of a prostaglandin (PG) derivative with leaving groups at positions 9, 13, and 15, followed by elimination of these groups by treatment with an organic base. 相似文献
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Michael Harre Peter Raddatz Rainer Walenta Ekkehard Winterfeldt 《Angewandte Chemie (International ed. in English)》1982,21(7):480-492
The present day importance of cyclopentenone derivatives in preparative organic chemistry and especially in natural product chemistry is demonstrated by the stereoselective synthesis of substituted and annelated cyclopentanone derivatives. It has been found that 4-oxo-2-cyclopentenyl acetate (“4-acetoxy-2-cyclopenten-1-one”) can be used in many reactions as a substitute for cyclopentadienone, which is itself too unstable to be isolated. A large variety of polyfunctionalized cyclopentanone derivatives, as well as carbocyclic and heterocyclic annelation products, can thus be obtained in a simple way. Various stereoselective transformations of the adducts so formed are presented, using the total synthesis of brefeldin A—a typical natural product of this series—as example. Several methods for the synthesis of 4-oxo-2-cyclopentenyl acetate are outlined and, in addition, the more important methods for the enantioselective synthesis of other 4-substituted 2-cyclopenten-1-ones are discussed. 相似文献
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Developed a convenient and mild one pot synthesis of cyclopentenone derivatives using 1-acetyl-1-cyclohexene and wide range of aldehydes. Aromatic and heterocyclic aldehydes with electron donating and withdrawing groups were conveniently converted to the corresponding cyclopentenone derivatives. 相似文献
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