Synthesis of furans, pyrroles and pyridazines by a ruthenium-catalysed isomerisation of alkynediols and in situ cyclisation

Pridmore, Simon J.; Slatford, Paul A.; Taylor, James E.; Whittlesey, Michael K.; Williams, Jonathan M. J.

doi:10.1016/j.tet.2009.06.108

Cited by 55 publications

(20 citation statements)

References 46 publications

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“…2-Methyl-5-(4-nitrophenyl)furan (13) [32] 2-Methylfuran (177 mL, 2mmol) and 4-nitrobenzenesulfonyl chloride (0.221 g, 1mmol) were used, and the residue was purified by flash chromatography on silica gel (heptane/ethyl acetate, 75:25) to affordt he desired compound 13 in 67 %( 0.136 g) yield. 2-(4-Cyanophenyl)-5-methylfuran (14) [33] 2-Methylfuran (177 mL, 2mmol) and 4-cyanobenzenesulfonyl chloride (0.201 g, 1mmol) were used, and the residue was purified by flash chromatography on silica gel (heptane/ethyl acetate, 85:15) to affordt he desired compound 14 in 48 %( 0.088 g) yield. 2-(4-Nitrophenyl)benzofuran (16) [34] Benzofuran (0.118 g, 1mmol) and 4-nitrobenzenesulfonyl chloride (0.331 g, 1.5 mmol) were used, and the residue was purified by flash chromatography on silica gel (heptane/ethyl acetate, 80:20) to affordt he desired compound 16 in 83 %( 0.198 g) yield.…”

Section: -N-butyl-5-(24-dinitrophenyl)furan (9)mentioning

confidence: 99%

“…2-n-Butyl-5-naphthalen-1-ylfuran (10) [31] 2-n-Butylfuran (0.124 g, 1mmol) and 1-naphthalenesulfonyl chloride (0.340 g, 1.5 mmol) were used, and the residue was purified by flash chromatography on silica gel (heptane/ethyl acetate, 90:10) to affordt he desired compound 10 in 55 %( 0.138 g) yield. 2-(4-Cyanophenyl)-5-methylfuran (14) [33] 2-(4-Nitrophenyl)benzofuran (16) [34] Benzofuran (0.118 g, 1mmol) and 4-nitrobenzenesulfonyl chloride (0.331 g, 1. 2-(4-Methoxyphenyl)benzofuran (17) [34] Benzofuran (0.118 g, 1mmol) and 4-methoxybenzenesulfonyl chloride (0.310 g, 1.5 mmol) were used, and the residue was purified by flash chromatography on silica gel (heptane/ethyl acetate, 70:30) to affordt he desired compound 17 in 38 %( 0.085 g) yield.…”

Section: -N-butyl-5-(3-(trifluoromethyl)phenyl)furan (7) [10b]mentioning

confidence: 99%

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Eco‐Friendly Solvents for Palladium‐Catalyzed Desulfitative CH Bond Arylation of Heteroarenes

et al. 2015

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Herein, we report the Pd-catalyzed regioselective direct arylation of heteroarenes in which benzenesulfonyl chlorides are used as coupling partners through a desulfitative cross-coupling that can be performed in diethyl carbonate (DEC) or cyclopentyl methyl ether (CPME) as green and renewable solvents or even in neat conditions instead of dioxane or dimethylacetamide (DMA). Under these solvent conditions, the reaction proceeds with a wide range of heteroarenes. C2- or C5-arylated products were obtained with furan and pyrrole derivatives. Benzofuran was also arylated regioselectively at the C2-position, whereas the reaction proceeds selectively at the C3- or C4-positions if thiophenes and benzothiophenes are used. Moreover, in some cases, especially with 1-methylindole, solvent-free conditions afforded better regioselectivities and/or yields than the reaction performed in the presence of solvents.

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Section: -N-butyl-5-(24-dinitrophenyl)furan (9)mentioning

confidence: 99%

Section: -N-butyl-5-(3-(trifluoromethyl)phenyl)furan (7) [10b]mentioning

confidence: 99%

Eco‐Friendly Solvents for Palladium‐Catalyzed Desulfitative CH Bond Arylation of Heteroarenes

et al. 2015

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“…Given the known acid sensitivity of simple alkyl-substituted furans we speculated that the purification of the furan product by chromatography on silica gel might be responsible for the moderate yields of the isolated products. [8] Accordingly, although the use of neutral alumina offered no advantage, purifications employing Florisil (magnesium silicate) or triethylamine-doped silica allowed the furan to be isolated in significantly increased yields (entries 8-10).With the optimized conditions established, a short series of 2,5-disubstituted furans was prepared (Scheme 3). Propargylic aryl and heteroaryl substituents could be introduced Scheme 1.…”

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confidence: 99%

An Alkyne Hydroacylation Route to Highly Substituted Furans

2011

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Heterocyclic compounds, such as the bioactive natural products pukalide and nakadomarin A, and the hugely successful drug molecules ranitidine (Zantac) and atorvastatin (Lipitor) are of great importance in pharmaceutical, agrochemical, and other fine-chemical applications (Scheme 1).[1] While there exists a range of methods for transforming relatively complex starting materials into substituted heterocycles, and for the functionalization of existing heterocycles, there is less precedent for methodology which involves the direct, regiodefined synthesis of highly substituted heterocycles from simple starting materials.[2] As such, new methods for the synthesis of substituted heterocycles (or their precursors) are potentially of significant value. This is particularly true if such methods do not suffer from the same drawbacks as the traditional syntheses of 1,4-dicarbonyl compounds, the classic substrates for the preparation of furans, thiophenes, and pyrroles; these syntheses are often either step-or atom-inefficient. The recent advances achieved in intermolecular alkene and alkyne hydroacylation chemistry means that these transformations are now ideal methods to exploit for the synthesis of heterocyclic molecules, because they employ simple substrates and commercially available catalyst systems, and generate no by-products because of their 100 % atom-economy. [3][4][5] In addition, a broad range of aldehydes can now be employed, and particularly in the case of alkyne hydroacylation, significant substitution of the unsaturated component can be tolerated, thus allowing for the regioselective production of highly substituted complex molecules in one catalytic intermolecular carbon-carbon bond forming step. Herein, we demonstrate the utility of intermolecular alkyne hydroacylation in the efficient synthesis of di-and trisubstituted furans and related heterocycles.g-Hydroxy-a,b-enones are known to undergo acid-catalyzed dehydrative cyclization to form furans, and this transformation has been exploited by several research groups, [6] most notably in the recent work from Donohoe et al. [7] The intermolecular hydroacylation of an aldehyde with readily available propargylic alcohols would permit the synthesis of g-hydroxy-a,b-enones with 100 % atom efficiency; coupling this carbon-carbon bond formation with an acid-catalyzed dehydrative cyclization would allow for the regioselective synthesis of di-or trisubstituted furans. The associated disconnection is novel for this type of heterocycle (Scheme 2).Our initial investigations to realize the above route to furans focused on the combination of propargyl alcohol 1 a and the S-chelating alkyl aldehyde 2 a (Table 1). The hydroacylative union of these two substrates using a dppe-derived Rh catalyst proceeded without incident. However, attempts to achieve a dehydrative cyclization using TFA provided only a small amount of the desired furan 3 a (entry 1). Reducing the time for the cyclization event to 1 hour, and then to 10 minutes, increased the yield of furan up to 50 % (entrie...

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“…In contrast to the Lu’s chemistry, this reaction was proposed to occur via formation of 1,4-diketone intermediate 2-358 , which was always observed as a byproduct, followed by the Paal-Knorr cyclocondensation step. 187 …”

Section: Synthesis Of Furansmentioning

confidence: 99%

“…It was shown that the Ru-catalyzed isomerization of alkyne-1,4-diols 6-229 followed by a one-pot reaction with hydrazine affords pyridazines 6-230 in reasonable yields (Scheme 475). 187b Donohoe et al employed an RCM strategy for the synthesis of pyridazinones 6-232 from the corresponding N -allylacrylohydrazide precursors 6-231 via a one-pot procedure (Scheme 475). 695b …”

Section: Synthesis Of Six-membered Aromatic Heterocyclesmentioning

confidence: 99%