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1.
2,5-Disubstituted 3-iodofurans are readily prepared under very mild reaction conditions by the palladium/copper-catalyzed cross-coupling of (Z)-β-bromoenol acetates and terminal alkynes, followed by iodocyclization. The useful intermediates conjugated enyne acetates are obtained in high yields in the transformation. Aryl- and alkyl-substituted alkynes undergo iodocyclization in good yields. The resulting iodine-containing furans can be readily elaborated to 2,3,5-trisubstituted furans.  相似文献   

2.
Manojit Pal 《Tetrahedron letters》2003,44(45):8221-8225
An efficient synthesis of 2-alkyl/aryl substituted benzo[b]furans/nitrobenzo[b]furans in water has been accomplished via Pd/C catalyzed reaction of o-iodophenols with terminal alkynes in the presence of PPh3, CuI and prolinol. This method can tolerate a variety of functional groups present in the alkynes as well as base labile nitro group in the o-iodophenols. The protocol does not require the use of a phase transfer catalyst or water-soluble phosphine ligands and is free from the use of any organic co-solvent.  相似文献   

3.
A novel silver-mediated highly selective oxidative C-H/C-H functionalization of 1,3-dicarbonyl compounds with terminal alkynes for the creation of polysubstituted furans and pyrroles in one step has been demonstrated. Promoted by the crucial silver species, perfect selectivity and good to excellent yields could be achieved. This protocol represents an extremely simple and atom-economic way to construct polysubstituted furans and pyrroles from basic starting materials under mild conditions.  相似文献   

4.
The solution-phase parallel synthesis of a 121-member library of multi-substituted benzo[ b]furans is described. 2,3,5-Trisubstituted benzo[ b]furans have been prepared by the palladium-catalyzed substitution of 3-iodobenzofurans by Suzuki-Miyaura, carbonylative Suzuki, Sonogashira, Heck, and carboalkoxylation chemistry. The 3-iodobenzofurans are readily prepared in good to excellent yields by the palladium/copper-catalyzed cross-coupling of various o-iodoanisoles and terminal alkynes, followed by electrophilic cyclization with ICl.  相似文献   

5.
The palladium-catalysed coupling of bromofurans with activated alkenes and of furanoyl chlorides with either terminal alkynes or alkynyl stannanes gave good yields of the corresponding vinyl furans and alkynyl ketones. These studies culminated in a short synthesis of the antifungal agent dihydrowyerone.  相似文献   

6.
[reaction: see text] 2,3-Disubstituted benzo[b]furans are readily prepared under very mild reaction conditions by the palladium/copper-catalyzed cross-coupling of various o-iodoanisoles and terminal alkynes, followed by electrophilic cyclization with I2, PhSeCl, or p-O2NC6H4SCl. Aryl- and vinylic-substituted alkynes undergo electrophilic cyclization in excellent yields. Biologically important furopyridines can be prepared by this approach in high yields.  相似文献   

7.
Different furans containing an ynamide or alkynyl ether moiety in the side chain were prepared. The gold-catalyzed transformation of these compounds delivered dihydroindole, dihydrobenzofuran, chroman, and tetrahydroquinoline derivatives at room temperature through very fast reactions. Furthermore, the stabilizing effect of the heteroatom directly attached to the intermediate arene oxides led to highly selective reactions, even in the case of only mono-substituted furans, which is quite different from previous results obtained with non-heteroatom-substituted alkynes.  相似文献   

8.
A microwave-enhanced, solventless Mannich condensation of terminal alkynes and secondary amines with para-formaldehyde on cuprous iodide doped alumina has been developed. β-Aminoalkynes are generated in good yields. The reaction can be extended to include a cyclization, which affords 2-substituted benzo[b]furans. The chemoselectivity of the reaction indicates that terminal alkynes are much more reactive than enolizable ketones under the reaction conditions.  相似文献   

9.
A site-specific synthesis of 4-substituted-6-fluoro(carboalkoxyl)benzo[b]furans and benzo[b]thiophenes is described. The reactions of heterocyclic aromatic aldehydes with a Wittig reagent, followed by Sonogashira reaction with terminal alkynes, and subsequent base-catalyzed cyclization site-specifically provide 4-substituted-6-fluoro(carboalkoxyl)benzo[b]furans and benzo[b]thiophenes in good yields.  相似文献   

10.
An efficient methodology for the indirect anti-Markovnikov hydration of unsymmetrically substituted terminal and internal alkynes is based on TiCl4-catalyzed hydroamination reactions. Its application to ortho-alkynylhaloarenes, followed by a copper-catalyzed O-arylation, provides flexible access to substituted benzo[b]furans.  相似文献   

11.
A golden switch: Doubly stabilized sulfonium ylides can be coupled with alkynes in a gold-catalyzed synthesis of heterocycles. This method hinges on a switch in the reactivity of the sulfur ylide resulting from the simple modification of the electron-withdrawing moieties and leads to either furans or furanones bearing a quaternary center.  相似文献   

12.
In sharp contrast to the gold‐catalyzed reactions of alkynes/allenes with nucleophiles, gold‐catalyzed oxidative cross‐couplings and especially C H/C H cross‐coupling have been under represented. By taking advantage of the unique redox property and carbophilic π acidity of gold, this work realizes the first gold‐catalyzed direct C(sp3) H alkynylation of 1,3‐dicarbonyl compounds with terminal alkynes under mild reaction conditions, with subsequent cyclization and in situ oxidative alkynylation. A variety of terminal alkynes including aryl, heteroaryl, alkenyl, alkynyl, alkyl, and cyclopropyl alkynes all successfully participate in the domino reaction. The protocol offers a simple and region‐defined approach to 3‐alkynyl polysubstituted furans.  相似文献   

13.
An efficient domino process for the construction of 2,3-disubstituted benzo[b]furans has been developed via copper-catalyzed three-component coupling reactions of salicylaldehydes, amines, and alkynes followed by base-assisted O-annulation reaction.  相似文献   

14.
A convenient, two-step synthesis of substituted furans from readily available aryl alkynes and ketones is reported. The furan-forming oxidative cyclization is mediated by the combination of cerium(IV) ammonium nitrate and potassium bromide and can be carried out in an open flask.  相似文献   

15.
In sharp contrast to the gold‐catalyzed reactions of alkynes/allenes with nucleophiles, gold‐catalyzed oxidative cross‐couplings and especially C? H/C? H cross‐coupling have been under represented. By taking advantage of the unique redox property and carbophilic π acidity of gold, this work realizes the first gold‐catalyzed direct C(sp3)? H alkynylation of 1,3‐dicarbonyl compounds with terminal alkynes under mild reaction conditions, with subsequent cyclization and in situ oxidative alkynylation. A variety of terminal alkynes including aryl, heteroaryl, alkenyl, alkynyl, alkyl, and cyclopropyl alkynes all successfully participate in the domino reaction. The protocol offers a simple and region‐defined approach to 3‐alkynyl polysubstituted furans.  相似文献   

16.
Cyclobutenones 1 which are readily prepared from alkynes and keteniminium salts 2 were-regiospecifically converted into Δα,β butenolides 4 or cyclopentenones 7. Reaction of 4 with diisobutylaluminum hydride yielded the corresponding substituted furans.  相似文献   

17.
An efficient palladium/copper-catalyzed approach to the synthesis of highly substituted 3-formyl furans from the reactions of readily available α-bromoenaminones with terminal alkynes has been developed. This methodology was realized by the cascade reactions of Sonogashira coupling and the subsequent intramolecular cyclization.  相似文献   

18.
A convenient Cu(i)-catalyzed cycloaddition of electron rich internal aryl alkynes and diazoacetates was discovered for the chemoselective and regioselective synthesis of tetra-substituted furans and cyclopropenes in moderate isolated yields (18-67%), and alkyne conversion (29-73%).  相似文献   

19.
CuI/proline-catalyzed coupling reaction of 2-iodo-phenols with terminal alkynes and the following cyclization process is carried out successively in DMSO at 80?°C. Under this tandem process, 2-substituted benzo[b]furans/furo-pyridines were synthesized in good to excellent yields with a great diversity.  相似文献   

20.
Wang T  Chen XL  Chen L  Zhan ZP 《Organic letters》2011,13(13):3324-3327
Under different conditions, the reaction of propargyl alcohols and terminal alkynes leads to the selective formation of 1,4-diynes and polysubstituted furans/pyrroles. Water is the only byproduct in the selective synthesis of 1,4-diynes and pyrroles, and the strategy for the furan synthesis is of 100% atom economy.  相似文献   

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