5-Aryl-2-furaldehydes in the synthesis of tetrahydropyrimidinones by Biginelli reaction

5-Aryl-2-furaldehydes, obtained by furfural arylation with arenediazonium salts, react with ethyl acetoacetate or acetylacetone and (thio)- urea in the presence of FeCl3·6H2O as a catalyst. A series of ethyl 4-(5-aryl-2-furyl)-6-methyl-2-oxo(thioxo)-1,2,3,4-tetrahydropyrimidine- 5-carboxylates was obtained. © 2018 Springer Science+Business Media, LLC

(6aS*,6bS*,11R*,11aR*)-6-(2-Furylmethyl)-5, 12-dioxo-5,6,6a,6b,7,11,11a,12-octahydrofuro[3′,2′:5,6]isoindolo[2, 1-a]quinazoline-11-carboxylic acid

The title compound, C23H18N2O6, is the product of an intra-molecular thermal cyclo-addition within 1-malein-2-[(E)-2-(2-fur-yl)vin-yl]-4-oxo-3,4-dihydro-quinazoline. The mol-ecule comprises a previously unknown fused penta-cyclic system containing two five-membered rings (2-pyrrolidinone and furan) and three six-membered rings (benzene, 2,3-dihydro-4-pyrimidinone and dihydro-cyclo-hexa-ne). The central five-membered pyrrolidinone ring has the usual envelope conformation. The six-membered dihydro-pyrimidinone and dihydro-cyclo-hexane rings adopt a half-boat and a half-chair conformation, respectively. The dihedral angle between the planes of the terminal benzene and furan rings is 45.99 (7)°. In the crystal, O - H⋯O hydrogen bonds link the mol-ecules into centrosymmetric dimers. Weak C - H⋯O hydrogen bonds consolidate further the crystal packing, which exhibits π-π inter-actions, with a short distance of 3.556 (3) Å between the centroids of benzene rings of neighbouring mol-ecules. © Obushak et al. 2011

5-Aryl-2-furaldehydes in the synthesis of tetrahydropyrimidinones by Biginelli reaction

5-Aryl-2-furaldehydes, obtained by furfural arylation with arenediazonium salts, react with ethyl acetoacetate or acetylacetone and (thio)- urea in the presence of FeCl3·6H2O as a catalyst. A series of ethyl 4-(5-aryl-2-furyl)-6-methyl-2-oxo(thioxo)-1,2,3,4-tetrahydropyrimidine- 5-carboxylates was obtained. © 2018 Springer Science+Business Media, LLC

(4R*,4aR*,7aS*)-5-Oxo-6-phenyl-4a,5,6,7,7a, 8-hexahydro-4H-furo[2,3-f]isoindole-4-carboxylic acid

The asymmetric unit of the title compound, C17H 15NO4, contains two independent molecules with similar geometric parameters. In both molecules, the conformation of the cyclohexene ring is half-chair, while the pyrrolidinone ring adopts an envelope conformation with the γ-carbon atom of the -pyrrolidinone ring as the flap. In the crystal, O - H⋯O hydrogen bonds between the carboxylic and carbonyl groups link alternate independent molecules into chains propagating in the b-axis direction. The crystal packing also features weak C - H⋯π interactions

(4R*,4aR*,7aS*)-5-Oxo-6-phenyl-4a,5,6,7,7a, 8-hexahydro-4H-furo[2,3-f]isoindole-4-carboxylic acid

The asymmetric unit of the title compound, C17H 15NO4, contains two independent molecules with similar geometric parameters. In both molecules, the conformation of the cyclohexene ring is half-chair, while the pyrrolidinone ring adopts an envelope conformation with the γ-carbon atom of the -pyrrolidinone ring as the flap. In the crystal, O - H⋯O hydrogen bonds between the carboxylic and carbonyl groups link alternate independent molecules into chains propagating in the b-axis direction. The crystal packing also features weak C - H⋯π interactions

The intramolecular Diels-Alder vinylthiophen (IMDAV) reaction: An easy approach to thieno[2,3-f]isoindole-4-carboxylic acids

The reaction of readily accessible 3-(thien-2-yl)allylamines with maleic anhydride, followed by a domino sequence involving successive acylation/[4+2] cycloaddition steps, leads to the formation of the thieno[2,3-f]isoindole core. The key step, the intramolecular Diels-Alder vinylaren (IMDAV) reaction, proceeds with high level of diastereoselectivity and with formation of a single diastereoisomer of the target product 4,4a,5,6,7,7a-hexahydro-3aH-thieno[2,3-f]isoindole-4-carboxylic acids in excellent yields. If the reaction is carried out at room temperature, it occurs in 2–3 days and the proton migration (H-shift) does not take place at the last stage. In boiling benzene, the reaction is complete after three hours, but in this case a slight impurity of byproducts bearing aromatic thiophene ring – 4a,5,6,7,7a,8-hexahydro-4H-thieno[2,3-f]isoindole-4-carboxylic acids is formed. © 2017 Elsevier Lt

Easy construction of furo[2,3-f]isoindole core by the IMDAV reaction between 3-(furyl)allylamines and α,β-unsaturated acid anhydrides

The vinylogues of furfurylamines, easily available in two steps from furylacroleins (3-(furyl)allylamines), were studied in a tandem N-acylation/intramolecular [4+2] cycloaddition with maleic, pyrocinchonic, and citraconic anhydrides, as well as furylacryloyl and cinnamoyl chlorides. By using a domino reaction of 3-(furyl)allylamines and α,β-unsaturated acid anhydrides under mild conditions, various hexahydro-4H-furo[2,3-f]isoindoles and their carboxyl derivatives were synthesized efficiently. The domino sequence includes three steps: acylation of the nitrogen atom in 3-(furyl)allylamines, intramolecular Diels-Alder cycloaddition in the resulting N-acyl vinylfurans (IMDAV reaction), and prototropic shift of the adducts followed by recovery of aromaticity of the furan nucleus. The key step, IMDAV reaction, leads to the target products, furo[2,3-f]isoindoles, diastereoselectively and with relatively high yields. © 2016 Elsevier Ltd. All rights reserved

The intramolecular Diels-Alder vinylthiophen (IMDAV) reaction: An easy approach to thieno[2,3-f]isoindole-4-carboxylic acids

The reaction of readily accessible 3-(thien-2-yl)allylamines with maleic anhydride, followed by a domino sequence involving successive acylation/[4+2] cycloaddition steps, leads to the formation of the thieno[2,3-f]isoindole core. The key step, the intramolecular Diels-Alder vinylaren (IMDAV) reaction, proceeds with high level of diastereoselectivity and with formation of a single diastereoisomer of the target product 4,4a,5,6,7,7a-hexahydro-3aH-thieno[2,3-f]isoindole-4-carboxylic acids in excellent yields. If the reaction is carried out at room temperature, it occurs in 2–3 days and the proton migration (H-shift) does not take place at the last stage. In boiling benzene, the reaction is complete after three hours, but in this case a slight impurity of byproducts bearing aromatic thiophene ring – 4a,5,6,7,7a,8-hexahydro-4H-thieno[2,3-f]isoindole-4-carboxylic acids is formed. © 2017 Elsevier Lt