A reinvestigation of the claisen rearrangement of methyl γ-aryloxycrotonates a convenient synthesis of 3-ethylidenebenzofuran-2(3H)-ones
TL;DR: In this paper, the synthesis and Claisen rearrangement of methyl γ-aryloxycrotonates have been investigated and a number of them have been successfully rearranged to a mixture of Z and E 3-ethylidenebenzofuran-2(3H)ones in refluxing ethylene glycol.
About: This article is published in Tetrahedron.The article was published on 1987-01-01. It has received 15 citations till now. The article focuses on the topics: Carroll rearrangement & Sigmatropic reaction.
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49 citations
TL;DR: A metal-free tandem Friedel-Crafts/lactonization reaction to 3,3-diaryl or 3-alkyl-3-aryl benzofuranones catalyzed by HClO(4) was reported, showing a variety of tertiary α-hydroxy acid esters could readily react with substituted phenols to afford the desired products in rich diversity.
Abstract: A metal-free tandem Friedel–Crafts/lactonization reaction to 3,3-diaryl or 3-alkyl-3-aryl benzofuranones catalyzed by HClO4 was reported. A variety of tertiary α-hydroxy acid esters could readily react with substituted phenols to afford the desired products in rich diversity. The synthetic utility of the products was demonstrated by the synthesis of polycyclic compounds. 1H NMR studies supported that this tandem reaction proceeded via tandem Friedel–Crafts/lactonization sequence.
44 citations
TL;DR: In this article, the first asymmetric synthesis of a D-erythro-ceramide analogue that contains a C(5)-C(6) trans double bond, together with its biological evaluation in a viral-liposome fusion system, is described.
Abstract: Intensive interest is currently focused on the role of ceramide (1), a key lipid molecule that functions as a second messenger. The first asymmetric synthesis of a D-erythro-ceramide analogue that contains a C(5)-C(6) trans double bond (3), together with its biological evaluation in a viral-liposome fusion system, is described. Sharpless asymmetric dihydroxylation of 4'-methoxyphenyl trans-5-octadecyn-2-enyl ether (enyne 8a), prepared by the coupling reaction of 1-[(E)-(4'-bromo-2'-butenyl)oxy]-4-methoxybenzene (7) with Lithium tetradecyne, generated yne-diol 9 in 96% yield with the desired stereochemistry at the C(2)and (3) positions and high enantiomeric purity (95% enantiomeric excess). Birch reduction (Li/EtNH2) of yne-diol 9 furnished (2R,3R,5E)-octadecene-1,2,3-triol (10) stereospecifically. The latter was converted to 2 azido derivative 13 in three steps (via a 2-O-triflate-1,3-O-benzylidene intermediate) and 55% overall yield. Reduction of azide 13 and in situ N-acylation with p-nitrophenyl cis-hexadec-4-enoate provided D-erythro-Delta(5)-trans-ceramide (3) in 91% yield. The role of the trans double bond of ceramide in mediating fusion of an alphavirus (Semliki Forest virus) was assessed in a liposomal model system, using target phospholipid/cholesterol vesicles containing either D-erythro-ceramide 1 or 3. The kinetics of virus fusion, as monitored by a change in pyrene excimer fluorescence over a period of 60 s, showed that Delta(5)-trans-ceramide 3 was completely inactive, indicating that there is an absolute requirement for the trans double bond to be located between C(4) and C(5). These data indicate that the molecular determinants on the viral envelope glycoprotein are highly specific for recognition of the unsaturated site in the ceramide molecule.
27 citations
TL;DR: Although conformational constraint has led to high-affinity 5-HT(2A) ligands with partial agonist activity, all of the spatial and steric properties of the ligand necessary for full receptor activation have not yet been identified.
Abstract: In studies of the SAR of phenethylamine-type serotonin 5-HT2A receptor agonists, substituted conformationally constrained tetrahydronaphthofurans were designed to investigate the optimal conformation of the 2-aminoethyl moiety. These compounds were tested using in vitro assays for affinity at 5-HT1A, 5-HT2A, and 5-HT2C receptors. The benzofuran-containing analogues, 6a and 6b, had significantly higher affinity for the 5-HT receptors tested than did the benzodihydrofuran-containing compounds, 4a, 4b, 5a, and 5b. The most potent compound (8-bromo-6-methoxy-4,5-dihydro-3H-naphtho[1,8-bc]furan-5-yl)aminomethane, 6b, had Ki values for displacement of [125I]-DOI from 5-HT2A and 5-HT2C cloned rat receptors of 2.6 and 1.1 nM, respectively. Despite their high affinity, the compounds of this naphthofuran series lacked high intrinsic activity at the 5-HT2A receptor as measured using the phosphoinositide hydrolysis assay. The most potent compound in vitro, 6b, was tested in the two-lever drug discrimination assay in ...
24 citations
TL;DR: In this article, the Wittig reactions of ylides with p-nitrobenzaldehyde and with coumarins 8a and 29 resulted in compounds 14a, 14c, 26 and 30 respectively.
Abstract: The reactions of ortho-quinones 1a, 1c and 1d with ylide 2 in the presence of triphenylphosphine afforded the ylides 11a, 11c and 11d and compound 12. The reactions of 1a and 1c with 2 in refluxing methanol or ethanol gave compounds 16 and 17 respectively, while the reactions of 1a–d with 2 in acetic anhydride yielded the acetates 18a, 18b, 18d and 19b, 19d, the furan derivative 24 and the ylide 25. Compounds 8 and 9 were also obtained in most of the above reactions. Wittig reactions of ylides 11a, 11c with p-nitrobenzaldehyde and of ylide 2 with coumarins 8a and 29 resulted in compounds 14a, 14c, 26 and 30 respectively. The transformations of compounds 18, 19 into 8, 9 as well as of compound 26 into 28 were also studied.
24 citations
References
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25 citations
TL;DR: In this article, two conceivable mechanistic pathways in the conversion of 1,4-diaryloxy-2butynes to benzofurobenzopyrans, one is eliminated and the other validated.
23 citations
10 citations
TL;DR: In this paper, the structure of α-Aryloxymethylacrylic acids and their derivatives has been revised on the basis of degradation studies, extensive spectral data and isolation of intermediates.
9 citations