Selective and reversible 1,3-dipolar cycloaddition of 6-aryl-1,5-diazabicyclo[3.1.0]hexanes with 1,3-diphenylprop-2-en-1-ones under microwave irradiation

• Alexander P. Molchanov,
• Mariia M. Efremova,
• Mariya A. Kryukova and
• Mikhail A. Kuznetsov

Beilstein J. Org. Chem. 2020, 16, 2679–2686, doi:10.3762/bjoc.16.218

• pyrazolidinone derivatives like LY186826 and its analogues with antibacterial activity [8][9][10][11][12]. The chemistry of azomethine imines has been actively investigated since the second half of the last century but their reactivity is still far less studied compared with nitrones or azomethine ylides – other

Synthesis of 2H-furo[2,3-c]pyrazole ring systems through silver(I) ion-mediated ring-closure reaction

• Vaida Milišiūnaitė,
• Rūta Paulavičiūtė,
• Eglė Arbačiauskienė,
• Vytas Martynaitis,
• Wolfgang Holzer and
• Algirdas Šačkus

Beilstein J. Org. Chem. 2019, 15, 679–684, doi:10.3762/bjoc.15.62

• -furo[2,3-c]pyrazole ring system employs a hydroxyethynyl substrate that contains adjacent ethyne and hydroxy groups on the pyrazole core (Scheme 1). As a starting material, we used 1-phenyl-1H-pyrazol-3-ol (1), which is readily accessible from the oxidation of 1-phenyl-3-pyrazolidinone [25][26

Dipolar addition to cyclic vinyl sulfones leading to dual conformation tricycles

• Steven S. Y. Wong,
• Michael G. Brant,
• Christopher Barr,
• Allen G. Oliver and
• Jeremy E. Wulff

Beilstein J. Org. Chem. 2013, 9, 1419–1425, doi:10.3762/bjoc.9.159

• keeping with our interest in the synthesis and utilization of conformationally constrained polycyclic sulfones, we sought to explore the cycloaddition between 2-sulfolene (1a) [32] and 1,3-dipoles (2, Table 1, see below) derived from 3-pyrazolidinone [33]. Reaction of 2 with acetylenic sulfones has been

• reported [34], but cyclic alkyl vinyl sulfones have not previously been demonstrated as coupling partners for 2. Results and Discussion A brief survey of reaction conditions revealed that dipole 2b (easily prepared by condensing 3-pyrazolidinone with benzaldehyde) [33] could be reacted with 1a in DMSO

• shielded by the electron-rich aromatic ring, as would be expected for the conformation observed in the X-ray structure (Figure 1). This upfield shift was not present in the minor conformer, suggesting that the pyrazolidinone ring had moved away from the aromatic ring’s magnetic influence. Analysis of

Ugi post-condensation copper-triggered oxidative cascade towards pyrazoles

• Aurélie Dos Santos,
• Laurent El Kaim,
• Laurence Grimaud and
• Caroline Ronsseray

Beilstein J. Org. Chem. 2011, 7, 1310–1314, doi:10.3762/bjoc.7.153

• ; isocyanide; pyrazolidinone; Introduction In the last twenty years, the Ugi reaction coupled with its various post-condensations towards heterocyclic libraries has established the success of isocyanide-based multicomponent reactions [1][2][3][4][5][6][7]. Chemists in both academia and industry have taken

• pyrazolidinone under oxidative conditions from simple hydrazone derivatives (Scheme 1) [13]. The cascade features a [3 + 2] cycloaddition coupled with an aerobic oxidation of the resulting pyrazolidine. A further oxidative coupling may be observed according to the substitution pattern of the starting acyl

• . The first attempted oxidative cyclization of 2a was made with one equivalent of copper acetate in acetic acid as solvent and gave the expected pyrazolidinone 3a in a 57% isolated yield (Scheme 2, condition A). Based on our previous study, the yield was improved to reach 84% with a mixture of acetic

Recent advances in the gold-catalyzed additions to C–C multiple bonds

• He Huang,
• Yu Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2011, 7, 897–936, doi:10.3762/bjoc.7.103

• the pyrazolidinone generally provides the bicyclic product 166 with high cis selectivity, which is determined during ring closing rather than in the formation of allyl–gold intermediate [76]. Gold-catalyzed cycloisomerization reaction of alkynyl aziridines 167 can give 2,5-disubstituted pyrroles 168