Efficient synthesis of dihydropyrimidinones via a three-component Biginelli-type reaction of urea, alkylaldehyde and arylaldehyde

• Haijun Qu,
• Xuejian Li,
• Fan Mo and
• Xufeng Lin

Beilstein J. Org. Chem. 2013, 9, 2846–2851, doi:10.3762/bjoc.9.320

• chemistry [5][6][7][8]. Recently, many one-pot variants of Biginelli-type reactions for the preparation of novel DHPMs using various active methylene compounds [9][10][11][12][13][14][15], such as enaminone, cyclic β-diketones, acetophenone, benzocyclic ketones and β-oxodithioesters etc., have also been

Mechanistic studies on the CAN-mediated intramolecular cyclization of δ-aryl-β-dicarbonyl compounds

• Brian M. Casey,
• Dhandapani V. Sadasivam and
• Robert A. Flowers II

Beilstein J. Org. Chem. 2013, 9, 1472–1479, doi:10.3762/bjoc.9.167

• 73% yield. To examine the breadth of this method, a series of δ-aryl-β-dicarbonyl substrates was prepared by a previously reported procedure [17]. As shown in Table 1, the intramolecular cyclization of δ-aryl-β-diketones with unsubstituted aryl rings (Table 1, entries 1 and 3) afforded 2-tetralone

• oxidation of several β-diketones and their related silyl enol ethers by CAN and the more lipophilic ceric tetra-n-butylammonium nitrate (CTAN) were measured in MeOH, MeCN and CH2Cl2 by using stopped-flow spectrophotometry [16]. In these experiments, initial oxidation of substrates generated radical cation

Features of the behavior of 4-amino-5-carboxamido-1,2,3-triazole in multicomponent heterocyclizations with carbonyl compounds

• Eugene S. Gladkov,
• Katerina A. Gura,
• Svetlana M. Sirko,
• Sergey M. Desenko,
• Ulrich Groth and
• Valentin A. Chebanov

Beilstein J. Org. Chem. 2012, 8, 2100–2105, doi:10.3762/bjoc.8.236

• polyfunctional aminoazoles that have been studied in heterocyclization reactions [5][6][7][8][20], derivatives of 4-amino-1,2,3-triazole have been less well investigated. There are only a few examples of their heterocyclizations with β-diketones [21], N-cyanomethaneimidates [22], isocyanates [23], chalcones [24

Cyclization of 5-hexynoic acid to 3-alkoxy-2-cyclohexenones

• Anne T. Hylden,
• Eric J. Uzelac,
• Zeljko Ostojic,
• Ting-Ting Wu,
• Keely L. Sacry,
• Krista L. Sacry,
• Lin Xi and
• T. Nicholas Jones

Beilstein J. Org. Chem. 2011, 7, 1323–1326, doi:10.3762/bjoc.7.155

• trifluoroacetic anhydride followed by decomposition of the reaction mixture in methanol under reflux yielded 1,3-cyclohexandione in 25% yield. Later, Smit and coworkers reported the closely related acyclic reaction between alkynes and acyl cations leading to β-diketones in 25–76% yield [8][9]. Interestingly, only

Synthesis of some novel annulated pyrido[2,3-d]pyrimidines via stereoselective intramolecular hetero Diels–Alder reactions of 1-oxa-1,3-butadienes

• Mohit L. Deb and
• Pulak J. Bhuyan

Beilstein J. Org. Chem. 2010, 6, No. 11, doi:10.3762/bjoc.6.11

• + POCl3) using excess phosphorous oxychloride as solvent following our published method [51]. The nucleophilic substitution of the chloro group of 1 by allyl amines 2 afforded the 6-N-allyl-1,3-dimethyl-5-formyl uracils 3. Compounds 3 were then reacted with cyclic β-diamides/β-diketones 4 in presence of a

• 3a as a yellow solid 568 mg (95%). Similarly, 3b–c were prepared from the reaction of 1 with 2b–c. Knoevenagel condensation of 3 with cyclic β-diamide/β-diketones 4 and synthesis of 5: Equimolar amounts of 3a (2 mmol, 598 mg) and 4a (2 mmol, 312 mg) were mixed thoroughly in a round-bottomed flask