Architecture and synthesis of P,N-heterocyclic phosphine ligands

• Wisdom A. Munzeiwa,
• Bernard Omondi and
• Vincent O. Nyamori

Beilstein J. Org. Chem. 2020, 16, 362–383, doi:10.3762/bjoc.16.35

• yields starting from the corresponding N-vinylpyrroles 103 and 104 (Scheme 19). The N-isopropenylpyrrole precursor 104 gave the adducts with 100% regioselectivity. More recently a solvent and catalyst-free method has been reported for vinylpyridines [97]. Preparation of N-heterocyclic phosphines via P–N

Microwave-assisted synthesis of 2-substituted 4,5,6,7-tetrahydro-1,3-thiazepines from 4-aminobutanol

• María C. Mollo,
• Natalia B. Kilimciler,
• Juan A. Bisceglia and
• Liliana R. Orelli

Beilstein J. Org. Chem. 2020, 16, 32–38, doi:10.3762/bjoc.16.5

• catalyst free. The scope of the method includes the synthesis of unprecedented examples of 2-alkyl, aralkyl and alkenyl derivatives. Chemical shift data for N-thiobenzoylpiperidine and compound 4a. PPSE promoted ring closure reactions of amido- and thioamido alcohols. Synthesis of compounds 3. Synthesis of

Why do thioureas and squaramides slow down the Ireland–Claisen rearrangement?

• Dominika Krištofíková,
• Juraj Filo,
• Mária Mečiarová and
• Radovan Šebesta

Beilstein J. Org. Chem. 2019, 15, 2948–2957, doi:10.3762/bjoc.15.290

• rearrangements. Furthermore, these organocatalysts slowed down the Ireland–Claisen rearrangement in comparison to an uncatalyzed reaction. The catalyst-free reaction proceeded well in green solvents or without any solvent. DFT calculations showed that the activation barriers are higher for reactions involving

• hand, catalyst-free Ireland–Claisen rearrangements proceed well in green solvents such as CpOMe or under solvent-free conditions. NMR kinetic measurements supported the notion that thiourea and squaramide organocatalysts bind strongly to the starting silyl ketene acetals and prevent the Ireland–Claisen

Facile regiodivergent synthesis of spiro pyrrole-substituted pseudothiohydantoins and thiohydantoins via reaction of [e]-fused 1H-pyrrole-2,3-diones with thiourea

• Aleksandr I. Kobelev,
• Nikita A. Tretyakov,
• Ekaterina E. Stepanova,
• Maksim V. Dmitriev,
• Michael Rubin and
• Andrey N. Maslivets

Beilstein J. Org. Chem. 2019, 15, 2864–2871, doi:10.3762/bjoc.15.280

• pyrrole-2-one fragment involving the reaction of [e]-fused 1H-pyrrole-2,3-diones with thioureas was developed. The obtained spiro pseudothiohydantoin derivatives were found to undergo a pseudothiohydantoin–thiohydantoin rearrangement. The reactions were shown to proceed under catalyst-free conditions in

• pseudothiohydantoin–thiohydantoin rearrangement. Therein, the substituents of the thiourea moiety were found to be crucial for tuning the conditions of this rearrangement. Notably, the reactions proceeded under catalyst-free conditions with good yields. Hydantoin-based commercially available drugs. Electrophilic

In water multicomponent synthesis of low-molecular-mass 4,7-dihydrotetrazolo[1,5-a]pyrimidines

• Irina G. Tkachenko,
• Sergey A. Komykhov,
• Vladimir I. Musatov,
• Svitlana V. Shishkina,
• Viktoriya V. Dyakonenko,
• Vladimir N. Shvets,
• Mikhail V. Diachkov,
• Valentyn A. Chebanov and
• Sergey M. Desenko

Beilstein J. Org. Chem. 2019, 15, 2390–2397, doi:10.3762/bjoc.15.231

• -mass 4,7-dihydrotetrazolo[1,5-a]pyrimidines. The use of acetoacetic ester derivatives as 1,3-dicarbonyl compounds in the reaction showed high selectivity under catalyst-free conditions, whereas in the case of acetylacetone the formation of a side product was observed. The desired product could be

Synthesis of ([1,2,4]triazolo[4,3-a]pyridin-3-ylmethyl)phosphonates and their benzo derivatives via 5-exo-dig cyclization

• Aleksandr S. Krylov,
• Artem A. Petrosian,
• Julia L. Piterskaya,
• Nataly I. Svintsitskaya and
• Albina V. Dogadina

Beilstein J. Org. Chem. 2019, 15, 1563–1568, doi:10.3762/bjoc.15.159

• ). Conclusion In conclusion, a series of new 3-methylphosphonylated [1,2,4]triazolo[4,3-a]pyridines, [1,2,4]triazolo[3,4-a]isoquinolines and 1-methylphosphonylated [1,2,4]triazolo[4,3-a]quinolines were synthesized through a catalyst-free 5-exo-dig-type cyclization of chloroethynylphosphonates and commercially

A novel three-component reaction between isocyanides, alcohols or thiols and elemental sulfur: a mild, catalyst-free approach towards O-thiocarbamates and dithiocarbamates

• András György Németh,
• György Miklós Keserű and
• Péter Ábrányi-Balogh

Beilstein J. Org. Chem. 2019, 15, 1523–1533, doi:10.3762/bjoc.15.155

• been developed between isocyanides, sulfur and alcohols or thiols under mild reaction conditions to afford O-thiocarbamates and dithiocarbamates in moderate to good yields. The one-pot reaction cascade involves the formation of an isothiocyanate intermediate, thus a catalyst-free synthesis of

• and improved a catalyst-free method for the preparation of isothiocyanates. Results and Discussion The model reaction of 2,6-dimethylphenyl isocyanide (1a), elemental sulfur (S8) and methanol (2a) was employed to screen for the optimal reaction conditions (Table 1). The reactions were followed by TLC

• , we have developed an efficient, convenient and scalable multicomponent method for the synthesis of O-thiocarbamates and dithiocarbamates under mild reaction conditions. This approach includes an improved catalyst-free synthesis of isothiocyanates from elemental sulfur and isocyanides, and shows good

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

• formylbenzoate 29 has also been used in another three-component synthesis along with amines 2 and ketones 31 (Scheme 8) [82]. This Mannich/lactamization reaction achieves good yields for a broad scope of 3-substituted isoindolinones 32, in either catalyst-free conditions or using p-toluenesulfonic acid. Ortho

• a photoinduced, catalyst-free three-component reaction (Scheme 32) [110]. In this way, a variety of (2-oxoindolin-3-yl)methanesulfonohydrazides 115 with diverse substituents in the aromatic ring and hydrazine nitrogen, were prepared with moderate to good yields. This transformation may be explained

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

• –5 min) and reflux of the equimolar amounts of amines 1, para-substituted benzaldehydes 2, and Meldrum’s acid 3 in 2-propanol led to Knoevenagel–Michael adducts 4a–h (Table 1). Beside the short reaction times and mild conditions, this catalyst-free three-component condensation is characterized by a

SO₂F₂-mediated transformation of 2'-hydroxyacetophenones to benzo-oxetes

• Revathi Lekkala,
• Ravindar Lekkala,
• Balakrishna Moku,
• K. P. Rakesh and
• Hua-Li Qin

Beilstein J. Org. Chem. 2019, 15, 976–980, doi:10.3762/bjoc.15.95

• catalyst-free novel and efficient methodology for the challenging synthesis of benzo-oxetes from 2'-hydroxyacetophenones mediated by sulfuryl fluoride (SO2F2) gas has been realized. The combination of 2'-hydroxyacetophenones and SO2F2 furnishes synthetically challenging benzo-oxetanes in moderate to

• through a catalyst-free cascade method (Scheme 1c). Results and Discussion Initially, we screened various reaction conditions (see Supporting Information File 1) using 1-(2-hydroxyphenyl)ethanone (1a) as a model substrate. As illustrated in Table 1, the desired product 2a was produced in 50–76% yield when

Catalyst-free assembly of giant tris(heteroaryl)methanes: synthesis of novel pharmacophoric triads and model sterically crowded tris(heteroaryl/aryl)methyl cation salts

• Rodrigo Abonia,
• Luisa F. Gutiérrez,
• Braulio Insuasty,
• Jairo Quiroga,
• Kenneth K. Laali,
• Chunqing Zhao,
• Gabriela L. Borosky,
• Samantha M. Horwitz and
• Scott D. Bunge

Beilstein J. Org. Chem. 2019, 15, 642–654, doi:10.3762/bjoc.15.60

• /HPF6 and studied by NMR and by DFT and GIAO-DFT. Keywords: model heteroarylmethylium salts; multicomponent; one-pot catalyst-free assembly; pharmacophoric triads; three-component synthesis; tris(heteroaryl)methanes; Yonemitsu-type reaction; Introduction During the last few decades multicomponent

Microwave-assisted synthesis of N,N-bis(phosphinoylmethyl)amines and N,N,N-tris(phosphinoylmethyl)amines bearing different substituents on the phosphorus atoms

• Erika Bálint,
• Anna Tripolszky,
• László Hegedűs and
• György Keglevich

Beilstein J. Org. Chem. 2019, 15, 469–473, doi:10.3762/bjoc.15.40

• phosphorus atoms was synthesized by the microwave-assisted and catalyst-free Kabachnik–Fields reaction of (aminomethyl)phosphine oxides with paraformaldehyde and diphenylphosphine oxide. The three-component condensation of N,N-bis(phosphinoylmethyl)amine, paraformaldehyde and a secondary phosphine oxide

• well as by the reaction of (hydroxymethyl)dibenzylphosphine oxide and aniline [8]. The condensation of butylamine, paraformaldehyde and di(p-tolyl)phosphine oxide to afford (butylaminomethyl)di(p-tolyl)phosphine oxide was also described [9]. A microwave (MW)-assisted, catalyst-free method was

• now. In this paper, we report the efficient, catalyst-free and MW-assisted synthesis of N,N-bis(phosphinoylmethyl)amine and N,N,N-tris(phosphinoylmethyl)amine derivatives bearing different substituents on the phosphorus atoms. Results and Discussion Synthesis of N,N-bis(phosphinoylmethyl)alkylamines

Annulation of 1H-pyrrole-2,3-diones by thioacetamide: an approach to 5-azaisatins

• Aleksandr I. Kobelev,
• Ekaterina E. Stepanova,
• Maksim V. Dmitriev and
• Andrey N. Maslivets

Beilstein J. Org. Chem. 2019, 15, 364–370, doi:10.3762/bjoc.15.32

• developed via an unprecedented annulation of pyrrolo[2,1-c][1,4]benzoxazine-1,2,4-triones by thioacetamide. A new way of C–H functionalization of thioacetamide has been discovered. The reaction proceeds under green catalyst-free conditions. Keywords: annulation; domino reactions; isatin; nitrogen

• and Discussion Previously, we reported an efficient catalyst-free synthesis of spiro[thiazolo-5,2'-pyrroles] 1 via interaction of pyrrolobenzoxazinetriones (PBTs) 2 with thiobenzamide (Scheme 2) [17][18]. In continuation of this research [17][18], and in order to extend the scope of the reaction, we

• -azaisatins) via unprecedented annulation of pyrrolo[2,1-c][1,4]benzoxazine-1,2,4-triones by thioacetamide. The reaction proceeds under green catalyst-free conditions, at room temperature and air atmosphere. The products can be easily isolated directly from the reaction mixture without use of column

Catalyst-free synthesis of 4-acyl-NH-1,2,3-triazoles by water-mediated cycloaddition reactions of enaminones and tosyl azide

• Lu Yang,
• Yuwei Wu,
• Yiming Yang,
• Chengping Wen and
• Jie-Ping Wan

Beilstein J. Org. Chem. 2018, 14, 2348–2353, doi:10.3762/bjoc.14.210

• , authentically mild conditions (40 °C stirring) as well as practical scalability. Keywords: additive-free; catalyst-free; cycloaddition; enaminones; on water; 1,2,3-triazole; Introduction Discovering sustainable chemical syntheses constitutes one central issue of modern organic chemistry. A large number of

• -triazoles [56][57][58][59][60][61] as well as the urgent desire in finding more sustainable methods enabling 1,2,3-triazole synthesis, we report herein our results in the water-mediated, catalyst-free synthesis of NH-1,2,3-triazoles through the cycloaddition of enaminone and sulfonyl azide with mild heating

• ), satisfactory tolerance of this water-mediated, catalyst-free protocol was verified by the smooth synthesis of the 4-acyl-NH-1,2,3-triazoles 3a–t containing versatile substructures (Figure 1). Besides the successful reactions employing enaminones independently containing electron-withdrawing and donating groups

Tetrathiafulvalene – a redox-switchable building block to control motion in mechanically interlocked molecules

• Hendrik V. Schröder and
• Christoph A. Schalley

Beilstein J. Org. Chem. 2018, 14, 2163–2185, doi:10.3762/bjoc.14.190

• . Very recently, our group reported on a crown/ammonium rotaxane 17 in which a TTF unit is implemented in the crown-ether wheel (Figure 15) [82]. The rotaxane was synthesized by a catalyst-free nitrile oxide capping strategy in 67% yield. In the neutral state, the wheel is strongly bound to the ammonium

DFT calculations on the mechanism of copper-catalysed tandem arylation–cyclisation reactions of alkynes and diaryliodonium salts

• Tamás Károly Stenczel,
• Ádám Sinai,
• Zoltán Novák and
• András Stirling

Beilstein J. Org. Chem. 2018, 14, 1743–1749, doi:10.3762/bjoc.14.148

• released (more than 70 kcal/mol) by the formation of the adduct of the protonated product and the catalyst (free energy level of −50.5 kcal/mol, not shown in Scheme 3). In contrast the route starting with the aryl transfer from Cu(III) to the activated reactant features a two-step mechanism (red in Scheme

Synthesis and stability of strongly acidic benzamide derivatives

• Frederik Diness,
• Niels J. Bjerrum and
• Mikael Begtrup

Beilstein J. Org. Chem. 2018, 14, 523–530, doi:10.3762/bjoc.14.38

• of the corresponding imidoyl chlorides 10 with PCl5 in POCl3, followed by the additional reaction with trifluoromethanesulfonamide (1) and protonation by sulfuric acid (Scheme 1) [10]. In recent years, we have reported high yielding catalyst-free N-arylation by SNAr reaction of mono- or

Regiodivergent condensation of 5-alkoxycarbonyl-1H-pyrrol-2,3-diones with cyclic ketazinones en route to spirocyclic scaffolds

• Alexey Yu. Dubovtsev,
• Maksim V. Dmitriev,
• Аndrey N. Maslivets and
• Michael Rubin

Beilstein J. Org. Chem. 2017, 13, 2179–2185, doi:10.3762/bjoc.13.218

• spirocondensation of 5-alkoxycarbonyl-1H-pyrrole-2,3-diones (serving as 1,2-bis-electrophiles) with cyclic ketazinones (serving as either 1,3-C,N- or 1,3-C,O-bis-nucleophiles). Results and Discussion Previously, we demonstrated a convenient approach towards spiro[indole-3,2’-pyrroles] 3 based on catalyst-free

Transition-metal-free synthesis of 3-sulfenylated chromones via KIO₃-catalyzed radical C(sp²)–H sulfenylation

• Yanhui Guo,
• Shanshan Zhong,
• Li Wei and
• Jie-Ping Wan

Beilstein J. Org. Chem. 2017, 13, 2017–2022, doi:10.3762/bjoc.13.199

• Discussion Initially, the reaction of enaminone 1a and sulfonyl hydrazine 2a was tentatively subjected to different iodine reagents or catalyst-free conditions. The results indicated that no product was observed in the reaction without catalyst (entry 1, Table 1), and different types of iodine reagents such

Mechanochemical Knoevenagel condensation investigated in situ

• Sebastian Haferkamp,
• Franziska Fischer,
• Werner Kraus and
• Franziska Emmerling

Beilstein J. Org. Chem. 2017, 13, 2010–2014, doi:10.3762/bjoc.13.197

• ]. In an extended study, including different aldehydes, Ondruschka et al. reported a solvent- and catalyst-free Knoevenagel condensation of p-nitrobenzaldehyde and malononitrile in a vibrational mill [23]. Here, we report the first direct in situ investigation of a Knoevenagel condensation followed by

Mechanochemical synthesis of thioureas, ureas and guanidines

• Vjekoslav Štrukil

Beilstein J. Org. Chem. 2017, 13, 1828–1849, doi:10.3762/bjoc.13.178

• ). Sulfonylureas could also be obtained by coupling of sulfonyl isocyanates with amines which was demonstrated by an efficient solvent-, base- and catalyst-free synthesis of tolbutamide (93%) starting from p-toluenesulfonyl isocyanate and n-butylamine. However, this approach was not further pursued due to the air

Mechanochemical borylation of aryldiazonium salts; merging light and ball milling

• José G. Hernández

Beilstein J. Org. Chem. 2017, 13, 1463–1469, doi:10.3762/bjoc.13.144

• . Simultaneous neat grinding/irradiation of the reactants and the photocatalyst led to the formation of boronates in a molten state. On the other hand, the catalyst-free liquid-assisted grinding/irradiation reaction also led to product formation, featuring a direct photolysis pathway facilitated by substrate

• yielded the same negative result proving that ambient light did not mediate the photoredox catalytic borylation reaction under mechanochemical conditions (Table 1, entry 3). Furthermore, neat grinding of a catalyst-free mixture of 1a and 2 under blue LEDs (light-emitting diodes) light did not afford the

• grinding conditions the PC does play a role in initiating a SET borylation. Furthermore, the implementation of a LAG/irradiation approach allowed the borylation reaction to occur under catalyst-free conditions. This observation is supported by the tendency of the electrophilic aryldiazonium salts to

N-Propargylamines: versatile building blocks in the construction of thiazole cores

• S. Arshadi,
• E. Vessally,
• L. Edjlali,
• R. Hosseinzadeh-Khanmiri and
• E. Ghorbani-Kalhor

Beilstein J. Org. Chem. 2017, 13, 625–638, doi:10.3762/bjoc.13.61

• α,α-disubstituted N-propargylamines 9 with isothiocyanates 10 through a catalyst-free thiourea formation/intramolecular thia-Michael cyclization in ether (Scheme 3a). They also showed that the treatment of primary α,α-disubstituted N-propargylamines with isothiocyanates led to the corresponding N

Fast and efficient synthesis of microporous polymer nanomembranes via light-induced click reaction

• Qi An,
• Youssef Hassan,
• Xiaotong Yan,
• Peter Krolla-Sidenstein,
• Tawheed Mohammed,
• Mathias Lang,
• Stefan Bräse and
• Manuel Tsotsalas

Beilstein J. Org. Chem. 2017, 13, 558–563, doi:10.3762/bjoc.13.54

• catalyst-free thiol–yne coupling (TYC) reaction. TYC has gained large attention as a representative of the click chemistry concept [17]. In the TYC reaction, usually a photoinitiator creates thiyl radicals [18][19][20], which react with nearby alkyne moieties to form covalent sulfur–carbon bonds and vinyl

Effect of the ortho-hydroxy group of salicylaldehyde in the A³ coupling reaction: A metal-catalyst-free synthesis of propargylamine

• Sujit Ghosh,
• Kinkar Biswas,
• Suchandra Bhattacharya,
• Pranab Ghosh and
• Basudeb Basu

Beilstein J. Org. Chem. 2017, 13, 552–557, doi:10.3762/bjoc.13.53

• acetylene, established as a general protocol, and is believed to be of interest for synthetic chemists from green chemistry. Keywords: A3 coupling; metal-catalyst-free; propargylamine; salicylaldehyde; terminal alkyne; Introduction Propargylamines are important synthetic intermediates for the preparation

• was made by varying the other two components viz. the secondary cyclic amine and the terminal alkyne. The results are not only encouraging but constitute a hitherto unknown general protocol for the preparation of propargylamines under metal-catalyst-free A3 coupling of salicylaldehyde as the aldehyde

• only metal-catalyst-free approach from acetylene carboxylic acids that are difficultly accessible and with low atom economy. Thus the present reaction from easily available A3 components leading to the formation of propargylamine under metal-catalyst-free and solvent-free conditions could attract the