The unique reactivity of 5,6-unsubstituted 1,4-dihydropyridine in the Huisgen 1,4-diploar cycloaddition and formal [2 + 2] cycloaddition

• Xiu-Yu Chen,
• Hui Zheng,
• Ying Han,
• Jing Sun and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2023, 19, 982–990, doi:10.3762/bjoc.19.73

• Xiu-Yu Chen Hui Zheng Ying Han Jing Sun Chao-Guo Yan College of Chemistry & Chemical Engineering, Yangzhou University, Jiangsu, Yangzhou 225002, China 10.3762/bjoc.19.73 Abstract The three-component reaction of isoquinolines, dialkyl acetylenedicarboxylates, and 5,6-unsubstituted 1,4

• -dihydropyridines in acetonitrile at room temperature afforded functionalized isoquinolino[1,2-f][1,6]naphthyridines in good yields and with high diastereoselectivity. More importantly, the formal [2 + 2] cycloaddition reaction of dialkyl acetylenedicarboxylates and 5,6-unsubstituted 1,4-dihydropyridines in

• successfully used in the reaction. Dimethyl or diethyl acetylenedicarboxylates gave the products in comparable yields in the reaction. The 5,6-unsubstituted 1,4-dihydropyridines with an N-benzyl group usually gave the products in good yields (Table 2, entries 1–12). It should be pointed out that 6

Nucleophile-induced ring contraction in pyrrolo[2,1-c][1,4]benzothiazines: access to pyrrolo[2,1-b][1,3]benzothiazoles

• Ekaterina A. Lystsova,
• Maksim V. Dmitriev,
• Andrey N. Maslivets and
• Ekaterina E. Khramtsova

Beilstein J. Org. Chem. 2023, 19, 646–657, doi:10.3762/bjoc.19.46

• cycloadditions of N-alkylbenzothiazolium salts (Scheme 1, entry 6) [17][18][19][20][21][22], MCRs of 2-methylbenzothiazole, acetylenedicarboxylates and active methylene compounds (Scheme 1, entry 7) [23][24][25], MCRs of (1,3-benzothiazol-2-yl)acetonitrile, aldehydes and acylcyanides (Scheme 1, enry 8) [3][26

Synthesis of functionalized imidazo[4,5-e]thiazolo[3,2-b]triazines by condensation of imidazo[4,5-e]triazinethiones with DMAD or DEAD and rearrangement to imidazo[4,5-e]thiazolo[2,3-c]triazines

• Alexei N. Izmest’ev,
• Dmitry B. Vinogradov,
• Natalya G. Kolotyrkina,
• Angelina N. Kravchenko and
• Galina A. Gazieva

Beilstein J. Org. Chem. 2021, 17, 1141–1148, doi:10.3762/bjoc.17.87

• derivatives consists in the condensation of acetylenedicarboxylic acid esters with heterocyclic compounds containing a thiourea fragment, e.g., pyrimidinethiones [18][19], 1,2,4-triazolethiols [20], and 1,2,4-triazinethiones [21][22]. An important feature of the reactions of dialkyl acetylenedicarboxylates

Recent developments in enantioselective photocatalysis

• Callum Prentice,
• James Morrisson,
• Andrew D. Smith and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2020, 16, 2363–2441, doi:10.3762/bjoc.16.197

• the [2 + 2] photocycloaddition of 2-pyridones 186 and acetylenedicarboxylates 187 catalysed by ent-183 to give cyclobutenes 188 (Scheme 28b) [82]. Another intermolecular reaction was later developed, this time using catalyst 185 for the [2 + 2] photocycloaddition of quinolones 189 and electron

Synthesis of 1,4-benzothiazinones from acylpyruvic acids or furan-2,3-diones and o-aminothiophenol

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

Beilstein J. Org. Chem. 2020, 16, 2322–2331, doi:10.3762/bjoc.16.193

• -diones V, and acetylenedicarboxylates VI with o-aminophenols or o-phenylenediamines (Scheme 3) [1][2][3][4][5][6]. Since the approach to alkoxy-substituted BTAs III (Figure 1, R = OAlk) has already been reported (Scheme 2) [21], we focused our research on aryl/alkyl-substituted BTAs III (Figure 1, R = Ar

1,5-Phosphonium betaines from N-triflylpropiolamides, triphenylphosphane, and active methylene compounds

• Vito A. Fiore,
• Chiara Freisler and
• Gerhard Maas

Beilstein J. Org. Chem. 2019, 15, 2603–2611, doi:10.3762/bjoc.15.253

• triphenylphosphane with alkyl propiolates [9][10] or dialkyl acetylenedicarboxylates [11] and strong CH-acids, such as Meldrum’s acid, 1,3-dimethylbarbituric acid, dimedone and indane-1,3-dione, leads to stable 1,4-diionic phosphonium betaines I or II (Scheme 1) in high yields. An analogous reaction has been

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

• synthesis where the benzene moiety is created from non-aromatic substrates. Certainly, this three-component protocol includes an aromatization step in the course of the acid-catalysed reaction of cyclohexa-1,3-dione (136), amines 2 and alkyl acetylenedicarboxylates 137, to produce the final phenolic

• -1,3-dione (136), amines 2 and alkyl acetylenedicarboxylates 137. Proposed mechanism for the formation of 2-oxindoles 138. Acknowledgements Financial support by Ministerio de Economía, Industria y Competitividad (MINECO, CTQ-2015-67871R) and Gobierno Vasco (GV, IT 992-16) is gratefully acknowledged.

Vinylphosphonium and 2-aminovinylphosphonium salts – preparation and applications in organic synthesis

• Anna Kuźnik,
• Roman Mazurkiewicz and
• Beata Fryczkowska

Beilstein J. Org. Chem. 2017, 13, 2710–2738, doi:10.3762/bjoc.13.269

• carried out by Yavari and Nourmohammadian in good yields of 80–85% (Scheme 49) [22]. A facile route to N-acylated α,β-unsaturated γ-lactams 80 was reported by Asghari et al. The reaction of acetylenedicarboxylates with triphenylphosphine and N-acetylaminocyanoacetate gave the corresponding ylide 79. The

• derivatives from 2-hydroxyketones 100, triphenylphosphine, and dialkyl acetylenedicarboxylates. The intermediate vinylphosphonium salt 101 was attacked here at the β-position by the nucleophilic oxygen atom of the hydroxyketone anion. The final product of this reaction was the expected furan derivative 102

• closure and the formation of dialkyl 2-(alkylamino)-5-aryl-3,4-furanedicarboxylate 124 in a yield of 69–88% (Scheme 69). The reaction was carried out for several hours at room temperature in anhydrous CH2Cl2 [81]. Recently, an interesting one-pot condensation of acetylenedicarboxylates with phosphines and

Multicomponent reactions: A simple and efficient route to heterocyclic phosphonates

• Mohammad Haji

Beilstein J. Org. Chem. 2016, 12, 1269–1301, doi:10.3762/bjoc.12.121

• acyl chlorides 191, isocyanides 193 and dialkyl acetylenedicarboxylates 194 to afford 2-phosphonofuran derivatives 196 has been reported by our group (Scheme 41) [79]. The desired furanylphosphonates were isolated in 52–67% yield at rt in CH2Cl2. In this transformation the zwitterionic intermediate 195

• stereoselective synthesis of 1,2-dihydroquinolin-2-ylphosphonates 271 and 1,2-dihydroisoquinolin-1-ylphosphonates 272 via the three-component reactions of quinoline or isoquinoline, dialkyl acetylenedicarboxylates 269, and dialkyl phosphonates 270 has been described by Shaabani et al. (Scheme 56) [94]. The

• -dioxohexahydropyrimidines 311 via a three-component reaction [102]. This method involved the one-pot reaction of N,N'-dimethylurea (310) and dialkyl acetylenedicarboxylates 309 in the presence of trialkyl phosphites 308 at room temperature (Scheme 64). The desired products were obtained in high yields between 84 and 94

Copper–phenanthroline catalysts for regioselective synthesis of pyrrolo[3′,4′:3,4]pyrrolo[1,2-a]furoquinolines/phenanthrolines and of pyrrolo[1,2-a]phenanthrolines under mild conditions

• Rupankar Paira,
• Tarique Anwar,
• Maitreyee Banerjee,
• Yogesh P. Bharitkar,
• Shyamal Mondal,
• Sandip Kundu,
• Abhijit Hazra,
• Prakas R. Maulik and
• Nirup B. Mondal

Beilstein J. Org. Chem. 2014, 10, 692–700, doi:10.3762/bjoc.10.62

• 14a–c in high yield. It is interesting to note that every reaction proceeded only up to the cycloaddition stage, without any aromatization of the final cycloadduct. However, a similar reaction of phenanthroliniums 12a,b with alkyne dipolarophiles like acetylenedicarboxylates or monocarboxylates 13a–d

• /dialkyl acetylenedicarboxylates 13a–b/monoalkyl acetylenemonocarboxylates 13c,d was placed in a round bottomed flask (25 mL). To this MeCN (50 mL) and DBU (1 mmol) were added and the mixture was stirred for 30 min. Then 5 mol % CuCl2 and 5 mol % of either L1, L2 were added to the reaction mixture and

A one-pot catalyst-free synthesis of functionalized pyrrolo[1,2-a]quinoxaline derivatives from benzene-1,2-diamine, acetylenedicarboxylates and ethyl bromopyruvate

• Mohammad Piltan,
• Loghman Moradi,
• Golaleh Abasi and
• Seyed Amir Zarei

Beilstein J. Org. Chem. 2013, 9, 510–515, doi:10.3762/bjoc.9.55

• -diaminobenzene, dialkyl acetylenedicarboxylates, and ethyl bromopyruvate forms pyrrolo[1,2-a]quinoxaline derivatives in good yields. Ethylenediamine also reacts under similar conditions to produce new pyrrolo[1,2-a]pyrazine derivatives. Keywords: acetylenedicarboxylates; benzene-1,2-diamine; ethyl bromopyruvate

• -diaminobenzenes 1 with dialkyl acetylenedicarboxylates 2a–c in the presence of ethyl bromopyruvate (3) was performed in acetonitrile under reflux over 12 hours. The 1H and 13C NMR spectra of the crude products clearly indicated the formation of polysubstituted pyrrolo[1,2-a]quinoxaline derivatives 4a–h in 88–93

• acetylenedicarboxylates in the presence of ethyl bromopyruvate provides a simple, catalyst-free one-pot entry to the synthesis of pyrrolo[1,2-a]quinoxaline derivatives having potential synthetic and pharmacological interest. The simplicity of the present procedure makes it an interesting alternative to other approaches