An Improved Method for the Preparation of 2,5-Disubstituted Thiophenes

Shridhar, D. R.; Jogibhukta, M.; Rao, P. Srinivasa; Handa, V. K.

doi:10.1055/s-1982-30065

Cited by 58 publications

(28 citation statements)

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“…Several methods are available for the synthesis of two ring systems, which contain the pyrrole, thiophene or furan ring linked to an imidazole, thiazole, or quinoline ring. One of these methods is the most versatile in terms of readily accessible starting compounds and involves the Paal-Knorr formation of the pyrrole, thiophene and furan rings from a 1,4-dicarbonyl systems of the imidazole, thiazole, or quinoline compounds by using ammonium acetate, Lawesson's reagent 39 or polyphosphoric acid, respectively. 20,21 It is also well known that 1,4-dicarbonyl derivatives are valuable intermediates for the preparation of cyclopentenones 40,41 and five membered heterocyclic compounds such as pyrroles, furans and thiophenes.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and characterization of novel substituted pyrrole, thiophene and furans

Kaniskan¹,

Elmalı²,

Civcir³

2008

Arkivoc

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Sixteen new compounds, including novel five-membered heterocyclic systems (pyrrole, thiophene, or furan) linked to imidazole, thiazole, or quinoline rings are reported. The intermediate 1,4-diketones were synthesized via the Stetter reaction in the presence of thiazolium salt as a catalyst. Cyclization reactions of the 1,4-dicarbonyl compounds with polyphosphoric acid, ammonium acetate or Lawesson's reagent by the Paal-Knorr synthesis, afforded unknown 2,5-disubstituted furan, pyrrole, or thiophene compounds in moderate yields, respectively. The structures of the synthesized compounds were confirmed by IR, 1 H NMR, 13 C NMR, and elemental analysis.

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Section: Introductionmentioning

confidence: 99%

Synthesis and characterization of novel substituted pyrrole, thiophene and furans

Kaniskan¹,

Elmalı²,

Civcir³

2008

Arkivoc

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“…The 1,4-dicarbonyl is presumed to originate from a Rh-catalyzed isomerization of the initially formed ghydroxy-a,b-enone. [11] The ability to access 1,4-dicarbonyl systems directly opened up a host of possibilities for further functionalization; Scheme 6 shows representative 1,4-dicarbonyl products (5 b-d), together with their conversion into pyrrole, [12] thiophene, [13] and pyridazine [14] heterocycles. In summary, we have demonstrated the applicability of a rhodium-catalyzed intermolecular hydroacylation to the synthesis of di-and trisubstituted furans in a regiocontrolled fashion; this reaction proceeds through a 100 % atomeconomic carbon-carbon bond forming step followed by a simple dehydrative cyclization.…”

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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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“…1-[4-(3-Thienyl)phenyl]ethanone (58,Ar 1 =4-AcC 6 H 4 ); Typical Procedure: [138] A mixture of 3-thienylboronic acid (57; 256 mg, 2.00 mmol), 4-bromoacetophenone (199 The nickel(II) pincer complex 60 [( Me NN 2 )NiCl] catalyzes the Kumada-Corriu-Tamao coupling of alkyl iodides with the hetaryl Grignard reagent 61. The catalysis demands only a relatively low loading of catalyst (3 mol%) and is completed within a short period of time (1 h).…”

Section: Scheme 25 Suzuki-type Coupling Reactions Of 3-thienylboronicmentioning

confidence: 99%