Chiral terpene auxiliaries V: Synthesis of new chiral γ-hydroxyphosphine oxides derived from α-pinene

• Anna Kmieciak and
• Marek P. Krzemiński

Beilstein J. Org. Chem. 2019, 15, 2493–2499, doi:10.3762/bjoc.15.242

• gas evolution ceased. Solvents were removed using a rotary evaporator and the resulting intermediate was dissolved in dichloromethane (6 mL). meta-Chloroperbenzoic acid (75%, 2.301 g, 10 mmol) was dissolved in dichloromethane (10 mL), cooled in a dry ice–acetone bath, and the intermediate solution was

Anion-driven encapsulation of cationic guests inside pyridine[4]arene dimers

• Anniina Kiesilä,
• Jani O. Moilanen,
• Anneli Kruve,
• Christoph A. Schalley,
• Perdita Barran and
• Elina Kalenius

Beilstein J. Org. Chem. 2019, 15, 2486–2492, doi:10.3762/bjoc.15.241

• an Ionspec QFT-7 ESI-FT-ICR with a 7 T superconducting magnet. Samples for all mass spectrometric experiments were prepared with 10 or 20 µM concentration and 1:3 host–guest ratio in acetone. Theoretical CCS values were calculated using IMoS [20][21]. NMR experiments were performed with a Bruker

• found in Supporting Information File 1. Spectra of 1 + Me4NPF6 1:3 in acetone in a) (+)ESI-MS and b) (−)ESI-MS. Insets showing arrival time distributions for selected ions. Identical drift times demonstrate the same structural diameters and CCS values for these ions. Separate arrival time distributions

Experimental and computational electrochemistry of quinazolinespirohexadienone molecular switches – differential electrochromic vs photochromic behavior

• Eric W. Webb,
• Jonathan P. Moerdyk,
• Kyndra B. Sluiter,
• Benjamin J. Pollock,
• Amy L. Speelman,
• Eugene J. Lynch,
• William F. Polik and
• Jason G. Gillmore

Beilstein J. Org. Chem. 2019, 15, 2473–2485, doi:10.3762/bjoc.15.240

• nitrogen-purged MBraun MBS-SPS 07-299 solvent purification system) or highest anhydrous grade (used as received). Acetonitrile-d3 and acetone-d6 were used as received in 1 g ampules (Cambridge Isotope Labs). Ferrocene, tetrabutylammonioum hexafluorophosphate (TBAH), and silver nitrate were of

• on 5a were performed on an argon-purged, ca. 24 mM solution in acetone-d6. 1D NOE spectra were collected using 400 manually interleaved scans with a 4 s relaxation delay, targeting a single peak per experiment, in a manner similar to that previously reported [21] for photogenerated 4a,b

• photolysis (dashed orange). 1H NMR distinction between SW 3a, thermal/eLW 5a, and pLW 4a, in acetone-d6, as observed a) before and b) after photolysis. HOMO (MO 105, red and blue) and LUMO (MO 106, green and yellow) computed for 3a in its ground (S0) state. Similar results were observed for the frontier

Indium-mediated C-allylation of melibiose

• Christian Denner,
• Manuel Gintner,
• Hanspeter Kählig and
• Walther Schmid

Beilstein J. Org. Chem. 2019, 15, 2458–2464, doi:10.3762/bjoc.15.238

• by TLC analysis (1-butanol/acetone/water 5:4:1, v/v/v). The reaction mixture was filtered over celite and the filtrate concentrated under reduced pressure, leaving a colorless oil. The crude material was dissolved in pyridine (10 mL) and treated with acetic anhydride (10 mL). A catalytic amount of

• with NaOMe (pH 9) until a pH around 9 was reached. The solution was stirred at rt for 2 h, until reaction monitoring via TLC analysis (1-butanol/acetone/H2O 5:4:1, v/v/v) showed complete conversion of the starting material. The reaction mixture was diluted with dichloromethane (dichloromethane/MeOH, 1

Reversible switching of arylazopyrazole within a metal–organic cage

• Anton I. Hanopolskyi,
• Soumen De,
• Michał J. Białek,
• Yael Diskin-Posner,
• Liat Avram,
• Moran Feller and
• Rafal Klajn

Beilstein J. Org. Chem. 2019, 15, 2398–2407, doi:10.3762/bjoc.15.232

• was slowly added to 1,3,5-tri(1H-imidazol-1-yl)benzene (106 mg, 0.384 mmol) and the resulting mixture was stirred for 24 h at room temperature. Then, all the insoluble materials were removed by centrifugation and the supernatant was concentrated in vacuo. Crystalline 2 was obtained by acetone vapor

1,2,3-Triazolium macrocycles in supramolecular chemistry

• Mastaneh Safarnejad Shad,
• Pulikkal Veettil Santhini and
• Wim Dehaen

Beilstein J. Org. Chem. 2019, 15, 2142–2155, doi:10.3762/bjoc.15.211

• synthesized the novel tetra-1,2,3-triazolium zinc porphyrin cage 3 (Figure 4) and have probed its characteristics by using UV–visible spectroscopy, determining the association constants for complex formation in 5% water/acetone. This receptor has shown affinity toward all of the halide ions and especially

• association constant of macrocycle 3 in the more competitive 15% water/acetone medium, still demonstrating a high binding affinity for sulfate anion (Ka = 2.5 × 105 M−1) while the cage 3 did not show any binding toward the other tested anions in the more aqueous solvent mixture. 2.3. Redox-active 1,2,3

1,2,3,4-Tetrahydro-1,4,5,8-tetraazaanthracene revisited: properties and structural evidence of aromaticity loss

• Arnault Heynderickx,
• Sébastien Nénon,
• Olivier Siri,
• Vladimir Lokshin and
• Vladimir Khodorkovsky

Beilstein J. Org. Chem. 2019, 15, 2059–2068, doi:10.3762/bjoc.15.203

• . For instance, the energy difference between the dication 6 and a hypothetic dication with protonated amino groups is 51 kcal/mol in favor of 6. UV–vis absorption spectra In solution, 3 is characterized by a strong absorption band, at 402 nm (toluene), 406 nm (acetone), 413 nm (water) and 422 nm

• (ethanol) (ε ≈ 20,000). Whereas a 5 nm shift between the absorption maximum in toluene and acetone evidences the presence of slight positive solvatochromism, the band shapes in water and ethanol are irregular and reflect rather specific interaction with these solvents. The shoulder extending from 450 till

• % yield (756 mg). 1H NMR (acetone-d6) δ 3.53 (s, 4H), 6.92 (s, 2H), 7.88 (br s, 2H), 8.33 (s, 2H); anal. calcd. for C10H12N4·2BF4: C, 33.19; H, 3.34; N, 15.48; found: C, 33.26; H, 3.22; N, 15.91. 6-Methyl-1,2,3,4-tetrahydropyrazino[2,3-g]quinoxalinium iodide (7a): A solution of 1,2,3,4-tetrahydropyrazino

Synthesis and anion binding properties of phthalimide-containing corona[6]arenes

• Meng-Di Gu,
• Yao Lu and
• Mei-Xiang Wang

Beilstein J. Org. Chem. 2019, 15, 1976–1983, doi:10.3762/bjoc.15.193

• ]tetrazines 3 displayed only one set of proton and carbon signals in the 1H and 13C NMR spectra, respectively, in acetone-d6 at room temperature (Figure 2). This is in sharp contradiction to O6-corona[3]arene[3]tetrazines composed of diethyl terephthalate which give several sets of resonance peaks [23][24

• . After filtration and concentration, the residue was chromatographed on a silica gel column using a mixture of DCM and EtOAc (v/v = 100:1) as an eluent to give product 3a–e. 3a: 140 mg, yield 42%, red solid, mp 275 °C (decomp.); 1H NMR (400 MHz, acetone-d6, 25 °C) δ 8.00 (s, 6H), 7.20–7.34 (m, 15H); 13C

• NMR (101 MHz, acetone-d6, 25 °C) δ 168.8, 164.4, 147.1, 132.2, 132.1, 129.6, 128.8, 127.5, 125.6; IR (KBr, cm−1) ν: 3078, 1777, 1724, 1494, 1384, 1230, 1115, 955; HRMS-APCI: [M + H]+ calcd for C48H22N15O12, 1000.1567; found, 1000.1553; anal. calcd for C48H21N15O12: C, 57.66; H, 2.12; N, 21.01; found

Complexation of chiral amines by resorcin[4]arene sulfonic acids in polar media – circular dichroism and diffusion studies of chirality transfer and solvent dependence

• Bartosz Setner and
• Agnieszka Szumna

Beilstein J. Org. Chem. 2019, 15, 1913–1924, doi:10.3762/bjoc.15.187

• MHz instrument. Spectra were referenced to the residual solvent signals (acetone-d6, 2.05 ppm; dimethyl sulfoxide-d6, 2.50 ppm and [13C]dimethyl sulfoxide, 39.5 ppm; methanol-d4, 3.31 ppm and [13C]methanol, 49.0 ppm). NMR DOSY experiments were performed on a Varian VNMRS-600 spectrometer equipped with

• . Analytical data are in agreement with literature data [27]. The product was obtained as yellow powder, yield: 93% (33.12 g). 1H NMR (400 MHz, acetone-d6, δ) 8.45 (s, 8H), 7.55 (s, 4H), 6.25 (s, 4H), 4.47 (t, J = 8.0 Hz, 4H), 2.17 (bt, 8H), 1.48 (m, 4H), 0.95 (d, J = 6.7 Hz, 24H). Figure S1 (Supporting

Tautomerism as primary signaling mechanism in metal sensing: the case of amide group

• Vera Deneva,
• Georgi Dobrikov,
• Aurelien Crochet,
• Daniela Nedeltcheva,
• Katharina M. Fromm and
• Liudmil Antonov

Beilstein J. Org. Chem. 2019, 15, 1898–1906, doi:10.3762/bjoc.15.185

• , acetone-d6, acetonitrile-d3 etc.) are not informative. In all cases a complicated mixture of tautomers and lack of signals was observed. Therefore, the NMR spectra were recorded in strong basic media, in order to obtain a single tautomeric skeleton. Nevertheless, some signals in the 13C NMR spectra do

Complexation of 2,6-helic[6]arene and its derivatives with 1,1′-dimethyl-4,4′-bipyridinium salts and protonated 4,4'-bipyridinium salts: an acid–base controllable complexation

• Jing Li,
• Qiang Shi,
• Ying Han and
• Chuan-Feng Chen

Beilstein J. Org. Chem. 2019, 15, 1795–1804, doi:10.3762/bjoc.15.173

•  1, Figures S1–S8). Host–guest complexation in solution Firstly, we tested the complexation between hosts H1 and H4 with guest G1 in solution by 1H NMR spectroscopy. As shown in Figure 2, when mixing equivalent amounts of host and guest in CDCl3/acetone-d6 1:2 (v/v), the 1H NMR spectrum showed a new

• different polarity can also affect the complexation between the hosts and the guests. As shown in Table 2, we found that performing the 1H NMR titrations of the host–guest complexation in CDCl3/acetone-d6 1:2 (v/v), the Ka values of the 1:1 host–guest complexes were about 103 M−1 except for H2 that showed

• -polar solvent, acetone hampers or competes the intermolecular non-covalent interactions between the hosts and the guests, and thus resulted in a decrease of the host–guest complexation. ESIMS studies of the formation of host–guest complexes The electrospray ionization (ESI) mass spectra also confirmed

N-(1-Phenylethyl)aziridine-2-carboxylate esters in the synthesis of biologically relevant compounds

• Iwona E. Głowacka,
• Aleksandra Trocha,
• Andrzej E. Wróblewski and
• Dorota G. Piotrowska

Beilstein J. Org. Chem. 2019, 15, 1722–1757, doi:10.3762/bjoc.15.168

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

• Gagandeep Kour Reen,
• Ashok Kumar and
• Pratibha Sharma

Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165

Synthesis, enantioseparation and photophysical properties of planar-chiral pillar[5]arene derivatives bearing fluorophore fragments

• Guojuan Li,
• Chunying Fan,
• Guo Cheng,
• Wanhua Wu and
• Cheng Yang

Beilstein J. Org. Chem. 2019, 15, 1601–1611, doi:10.3762/bjoc.15.164

• , Supporting Information File 1. HRESIMS (m/z): [M − H]− calcd for [C26H17O]−, 345.1279; found, 345.1277. Synthesis of 5: Under nitrogen atmosphere, a mixture of compound 4 (800.0 mg, 2.3 mmol), K2CO3 (952.2 mg, 6.9 mmol) and 1,5-dibromopentane (1.1 g, 4.6 mmol) was dissolved in 30 mL dry acetone and the

• %; ii) N-bromosuccinimide, chloroform, 60 °C, yield: 87%; iii) (4-hydroxyphenyl)boronic acid, Pd(PPh3)4, K2CO3, CsF, toluene/THF/H2O, reflux, 8 h, yield: 70%; iv) K2CO3, 1,5-dibromopentane, acetone, 80 °C, yield: 67%; v) NaN3, DMF, yield: 84%; vi) paraformaldehyde, BF3·OEt2, 1,2-dichloroethane, yield

Transient and intermediate carbocations in ruthenium tetroxide oxidation of saturated rings

• Manuel Pedrón,
• Laura Legnani,
• Maria-Assunta Chiacchio,
• Pierluigi Caramella,
• Tomás Tejero and
• Pedro Merino

Beilstein J. Org. Chem. 2019, 15, 1552–1562, doi:10.3762/bjoc.15.158

• decalines in acetonitrile and acetone) were in the following ranges: the C–H bonds were 1.37–1.41 Å, the O–H bonds were 1.19–1.22 Å, and the C–O bonds were 2.57–2.84 Å. The observed values for TS1 in water (C–H: 1.34 Å; O–H: 1.24 Å and C–O: 2.65 Å) and acetonitrile (C–H: 1.34 Å; O–H: 1.24 Å and C–O: 2.64 Å

Reaction of oxiranes with cyclodextrins under high-energy ball-milling conditions

• László Jicsinszky,
• Federica Calsolaro,
• Katia Martina,
• Fabio Bucciol,
• Maela Manzoli and
• Giancarlo Cravotto

Beilstein J. Org. Chem. 2019, 15, 1448–1459, doi:10.3762/bjoc.15.145

• removed (by aluminium oxide) and “recrystallisation” (from acetone) eliminates (oligo)-PG to a pharmaceutically acceptable level [6][7]. However, the low boiling point of the 1,2-propylene oxide generates some safety concerns. The low reaction temperature favours the secondary hydroxy group in CD

• methods. In order to reduce the colour intensity and remove the few insolubles, such as unsubstituted CDs, etc., from the solution, 5% charcoal was used. The addition of acetone to the concentrated MeOH solution, to around 50% product content, completely removed the formed PGs. It was found that sometimes

• in similar DS values within the calculation limits. The lack of sharp signals in both the core- and methyl signal regions allowed us to assume that PGs were present in amounts that were below the detection limits. The mother liquors of the MeOH–acetone crystallisation of the products were hygroscopic

Selenophene-containing heterotriacenes by a C–Se coupling/cyclization reaction

• Pierre-Olivier Schwartz,
• Sebastian Förtsch,
• Astrid Vogt,
• Elena Mena-Osteritz and
• Peter Bäuerle

Beilstein J. Org. Chem. 2019, 15, 1379–1393, doi:10.3762/bjoc.15.138

• 1,1’-bis(diphenylphosphino)ferrocene (dppf) from Frontier Scientific. Absolute tetrahydrofuran, dichloromethane, and toluene were provided from Sigma-Aldrich and purified using a Büchi MB SPS-800. Dimethyl sulfoxide, acetonitrile, and acetone were purchased from Merck and Sigma-Aldrich, purified, and

Doebner-type pyrazolopyridine carboxylic acids in an Ugi four-component reaction

• Maryna V. Murlykina,
• Oleksandr V. Kolomiets,
• Maryna M. Kornet,
• Yana I. Sakhno,
• Sergey M. Desenko,
• Victoriya V. Dyakonenko,
• Svetlana V. Shishkina,
• Oleksandr A. Brazhko,
• Vladimir I. Musatov,
• Alexander V. Tsygankov,
• Erik V. Van der Eycken and
• Valentyn A. Chebanov

Beilstein J. Org. Chem. 2019, 15, 1281–1288, doi:10.3762/bjoc.15.126

• are soluble in MeOH, EtOH, iPrOH, acetone, EtOAc, CH3CN, DCM, CHCl3 and compounds 12 are soluble in acetone, CH3CN, DCM, CHCl3 and partially soluble when heated in EtOAc, MeOH, EtOH, showing the advantages of this protocol for investigating the activity of pyrazolo[3,4-b]pyridine moiety in biological

Ugi reaction-derived prolyl peptide catalysts grafted on the renewable polymer polyfurfuryl alcohol for applications in heterogeneous enamine catalysis

• Alexander F. de la Torre,
• Gabriel S. Scatena,
• Oscar Valdés,
• Daniel G. Rivera and
• Márcio W. Paixão

Beilstein J. Org. Chem. 2019, 15, 1210–1216, doi:10.3762/bjoc.15.118

• incorporate proline [15] and the furan functionality into pseudo-peptide catalysts. As shown in Scheme 2, Boc-L-proline and acetone were employed as acid and oxo components, respectively, in combination either with furfurylamine and cyclohexyl isocyanide or with (S)-α-methylbenzylamine and furfuryl isocyanide

• . We have previously proven the feasibility of this multicomponent approach for the combinatorial synthesis and rapid screening of pseudo-peptide catalysts [7] and their silica gel-immobilized variants [8]. The choice of using acetone and the S-configured α-methylbenzylamine was made in agreement with

• . 241, (wavelength: 589 nm). Melting points were obtained in a MQAPF-301 apparatus. General procedure A. A suspension of the amine (1.0 mmol) and acetone (1.0 mmol) in MeOH (5 mL) was stirred for 1 h at room temperature. The carboxylic acid (1.0 mmol) and the isocyanide (1.0 mmol) were then added and

Alkylation of lithiated dimethyl tartrate acetonide with unactivated alkyl halides and application to an asymmetric synthesis of the 2,8-dioxabicyclo[3.2.1]octane core of squalestatins/zaragozic acids

• Herman O. Sintim,
• Hamad H. Al Mamari,
• Hasanain A. A. Almohseni,
• Younes Fegheh-Hassanpour and
• David M. Hodgson

Beilstein J. Org. Chem. 2019, 15, 1194–1202, doi:10.3762/bjoc.15.116

• pseudoaxial methyl of the gem-dimethyl group [18][24]; it was proposed that the axial methyl group directed electrophile incorporation away from itself (Scheme 4). The fragile nature of the lithium ester enolate of dimethyl tartrate acetonide (to β-elimination with loss of acetone) was evident from Seebach’s

• of an intermediate bromo acetonide, albeit in significantly reduced yield (33%). In contrast to a simple hydroxy acetonide (formally derived from an α-hydroxy aldehyde and acetone) [34], hydroxy acetonide 19a was found stable to mild bases such as Et3N and iPr2NH, whereas the use of NaH or NaHMDS in

• THF both decomposed 19a into unidentifiable polar products. Attempted acid-induced loss of acetone with PTSA in MeOH, PPTS in refluxing MeOH, or 80% AcOH at reflux [27] all led to quantitative recovery of hydroxy acetonide 19a, whereas 5% aq HCl resulted in acetonide removal and concomitant

Phylogenomic analyses and distribution of terpene synthases among Streptomyces

• Lara Martín-Sánchez,
• Kumar Saurabh Singh,
• Mariana Avalos,
• Gilles P. van Wezel,
• Jeroen S. Dickschat and
• Paolina Garbeva

Beilstein J. Org. Chem. 2019, 15, 1181–1193, doi:10.3762/bjoc.15.115

• ), and the C-terminal domain for its further conversion into geosmin with cleavage of 12 into acetone and the octalin 13 through a retro-Prins fragmentation (Scheme 1) [22][23][24]. The proposed neutral intermediate isolepidozene (11) has so far only been reported from the S233A enzyme variant of geosmin

Design of a double-decker coordination cage revisited to make new cages and exemplify ligand isomerism

• Sagarika Samantray,
• Sreenivasulu Bandi and
• Dillip K. Chand

Beilstein J. Org. Chem. 2019, 15, 1129–1140, doi:10.3762/bjoc.15.109

• (10.5 mg, 0.03 mmol) was added. The reaction mixture was stirred at room temperature for 10 min to obtain a clear yellow solution. The product was precipitated by the addition of ethyl acetate (10 mL), separated by centrifugation, washed with acetone (4 mL) and dried under vacuum to afford complex 1a

• temperature to give a clear yellow solution. The product was precipitated by the addition of 10 mL of ethyl acetate. The pale yellow precipitate was separated by centrifugation, washed with acetone and dried under vacuum to afford complex 3a (18.6 mg, isolated yield 66%). 1H NMR (500 MHz, DMSO-d6, 300 K) δ

• was precipitated by the addition of 10 mL of ethyl acetate. The pale yellow precipitate was separated by centrifugation, washed with acetone and dried under vacuum to afford the complex 4a (15.6 mg, isolated yield 75%). 1H NMR (500 MHz, DMSO-d6, 300 K) δ 10.54 (d, J = 1.4 Hz, 1H, Ha), 9.74 (s, 1H, Hf

Multicomponent reactions (MCRs): a useful access to the synthesis of benzo-fused γ-lactams

• Edorta Martínez de Marigorta,
• Jesús M. de Los Santos,
• Ana M. Ochoa de Retana,
• Javier Vicario and
• Francisco Palacios

Beilstein J. Org. Chem. 2019, 15, 1065–1085, doi:10.3762/bjoc.15.104

• in this manner, although, once again, ortho-substituted anilines 2 did not render the cyclic product, as the final lactamization step is probably impeded by sterical reasons. On the other hand, silyl enol ethers of acetone, acetophenone, methyl acetate, 2-hydroxyfuran and cyclohexanone worked well

Stereo- and regioselective hydroboration of 1-exo-methylene pyranoses: discovery of aryltriazolylmethyl C-galactopyranosides as selective galectin-1 inhibitors

• Alexander Dahlqvist,
• Axel Furevi,
• Niklas Warlin,
• Hakon Leffler and
• Ulf J. Nilsson

Beilstein J. Org. Chem. 2019, 15, 1046–1060, doi:10.3762/bjoc.15.102

• mg of 7 α/β-mixture as clear and viscous oils. The diastereoselectivity was determined to be α:β 1:2.3 by HPLC using the same protocol as is used for purity determinations. The stereochemistry was assigned using NOESY. Data for α-7: [α]D20 52 (c 0.2, CH3CN); 1H NMR (400 MHz, acetone-d6) δ 7.44–7.24

• (m, 20H), 4.93 (d, J = 11.5 Hz, 1H), 4.84 (d, J = 11.0 Hz, 1H), 4.81 (d, J = 11.3 Hz, 1H), 4.76 (m, 2H), 4.66–4.53 (m, 3H), 4.18–4.12 (m, 1H), 4.08–4.00 (m, 1H), 3.93–3.69 (m, 5H), 3.64–3.56 (m, 2H); 13C NMR (100 MHz, acetone-d6) δ 139.3, 139.0, 138.9, 138.8, 128.3, 128.2, 128.13, 128.11, 127.8

• , 129.10, 84.4, 81.6, 80.3, 77.1, 76.3, 76.1, 74.8, 74.7, 74.5, 71.5, 60.2; HRMS (m/z): [M + H]+ calcd for 555.2755; found, 555.2747. Data for β-7: [α]D20 20 (c 1.1, CH3CN); 1H NMR (400 MHz, acetone-d6) δ 7.43–7.24 (m, 20H), 4.93 (s, 2H), 4.89 (d, J = 7.8 Hz, 1H), 4.86 (d, J = 7.6 Hz, 1H), 4.75 (d, J

Novel (2-amino-4-arylimidazolyl)propanoic acids and pyrrolo[1,2-c]imidazoles via the domino reactions of 2-amino-4-arylimidazoles with carbonyl and methylene active compounds

• Victoria V. Lipson,
• Tetiana L. Pavlovska,
• Nataliya V. Svetlichnaya,
• Anna A. Poryvai,
• Nikolay Yu. Gorobets,
• Erik V. Van der Eycken,
• Irina S. Konovalova,
• Svetlana V. Shiskina,
• Alexander V. Borisov,
• Vladimir I. Musatov and
• Alexander V. Mazepa

Beilstein J. Org. Chem. 2019, 15, 1032–1045, doi:10.3762/bjoc.15.101

• the absence of the molecular ion peak and the presence of intense signals that occur due to cleavage of acetone and СО2 molecules from the dioxanedione moieties. Their further transformation took place in the presence of the catalytic amounts of TFA in toluene under short time reflux (3 min) or

• addition of the catalytic amounts of TFA to the initial three-component mixture (Table 2). The reaction proceeded via 1,3-dioxanedione cycle cleavage followed by elimination of acetone and CO2 to provide novel pyrrolo[1,2-c]imadazol-5-ones trifluoroacetates 9b,c,i precipitated from the reaction mixture