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Studies on the Fischer indole synthesis 总被引:1,自引:0,他引:1
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[structure: see text] Various approaches to the indole bis-oxazole fragment of the marine secondary metabolite diazonamide A are described, all of which feature dirhodium(II)-catalyzed reactions of diazocarbonyl compounds in key steps. Thus, 3-bromophenylacetaldehyde is converted into an alpha-diazo-beta-ketoester, dirhodium(II)-catalyzed reaction of which with N-Boc-valinamide resulted in N-H insertion of the intermediate rhodium carbene to give a ketoamide that readily underwent cyclodehydration to give (S)-2-(1-tert-butoxycarbonylamino)-2-methylpropyl]-5-(3-bromobenzyl)oxazole-4-carboxamide, after ammonolysis of the initially formed ester. This aryl bromide was then coupled to a 3-formyl-indole-4-boronate under Pd catalysis to give the expected biaryl. Subsequent conversion of the aldehyde group into a second alpha-diazo-beta-ketoester gave a substrate for an intramolecular carbene N-H insertion, although attempts to effect this cyclization were unsuccessful. A second approach to an indole bis-oxazole involved an intermolecular rhodium carbene N-H insertion, followed by oxazole formation to give (S)-2-[1-tert-(butoxycarbonylamino)-2-methylpropyl]-5-methyloxazole-4-carboxamide. A further N-H insertion of this carboxmide with the rhodium carbene derived from ethyl 2-diazo-3-[1-(2-nitrobenzenesulfonyl)indol-3-yl]-3-oxopropanoate gave a ketoamide, cyclodehydration of which gave the desired indole bis-oxazole. Finally, the boronate formed from 4-bromotryptamine was coupled to another diazocarbonyl-derived oxazole to give the corresponding biaryl, deprotection and cyclization of which produced a macrocyclic indole-oxazole derivative. Subsequent oxidation and cyclodehydration incorporated the second oxazole and gave the macrocyclic indole bis-oxazole. 相似文献
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Helena Majgier-BaranowskaJohn D. Williams Bing LiNorton P. Peet 《Tetrahedron letters》2012,53(35):4785-4788
The Cadogan-Sundberg indole synthesis produces two major products from the treatment of 2-nitrostilbenes with triethyl phosphite, which are the 2-arylindoles and the corresponding 2-aryl-N-ethoxyindoles. We were interested in determining the origin of the oxygen atom in the 2-aryl-N-ethoxyindoles. In this study, we verify that this oxygen atom originates from the nitro group and not from the triethyl phosphite. 相似文献
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Photocyclization of 2-chloroacetyl-1,2,3,4,5,6-hexahydro-1, 5-methanoazocino[4,3-b]indole () takes place at the indole 4-position to give a 1 ,2 ,3 ,4 , 5 ,6-hexahydro-2 ,11-ethano-1 ,5-methanoazocino [4 , 3-6] indole system. Consequently, the method appears to be unsuitable for constructing the pyrrolidine ring of pentacyclic Strychnos indole alkaloids. 相似文献
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The biological activities of a series of 3,3-spirocyclic indole derivatives containing CF2, phosphine oxide,indole, and cyano functional groups were evaluated, and these derivatives were found to exhibit antiTMV, fungicidal, and insecticidal activities. 相似文献
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Stefano Marcaccini Roberto Pepino Carlos F. Marcos Cecilia Polo Toms Torroba 《Journal of heterocyclic chemistry》2000,37(6):1501-1503
The intramolecular Knoevenagel condensation of N‐cyclohexyl 3‐aryl‐2‐(2‐nitrophenyl)acetoxy‐3‐oxopropionamides 4 obtained from 2‐nitrophenylacetic acid (1), arylglyoxals 2 and cyclohexyl isocyanide (3) afforded N‐cyclohexyl 3‐aryl‐2,5‐dihydro‐2‐(2‐nitrophenyl)‐5‐oxofuran‐2‐carboxamides 6 which underwent reductive cleavage to N‐cyclohexyl (Z)‐3‐aryl‐2‐hydroxy‐3‐(2,3‐dihydro‐2‐oxoindol‐3‐ylidene)propionamides 8 probably via the labile intermediates 7. 相似文献
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《Tetrahedron letters》1988,29(19):2361-2364
A three step route to the title tetracyclic substructure of akuammiline-type alkaloids consisting in the nucleophilic addition of an ester α-anion to an N-alkylpyridinium salt, acid-induced cyclization of the resultant 1,4-dihydropyridine, and stereoselective elaboration of the ethylidene substituent is reported. 相似文献
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Franco Sannicolò 《Tetrahedron letters》1984,25(29):3101-3102
Heating 1,3-diphenyl-1,4,5,6-tetrahydropyridazine in PPA affords mainly 4-benzoyl-1,2,3,4-tetrahydroquinoline and 2-anilinopropiophenone. In analogous conditions 1,5-diphenyl-3-methyl-2-pyrazoline gives 2-styrylindole, benzidine and benzylideneacetone. 相似文献