Application of N-heterocyclic carbene–Cu(I) complexes as catalysts in organic synthesis: a review

• Nosheen Beig,
• Varsha Goyal and
• Raj K. Bansal

Beilstein J. Org. Chem. 2023, 19, 1408–1442, doi:10.3762/bjoc.19.102

• of internal alkynes with bis(pinacolato)diboron to obtain vinylboranes. The reaction could be performed in air. Tsuji and co-workers [84] prepared 2-boryl-substituted 1,3-butadienes, which are otherwise difficult to synthesize, through NHC–CuCl-catalyzed borylation of α-alkoxyallenes with B2(pin)2

Chemistry of polyhalogenated nitrobutadienes, 17: Efficient synthesis of persubstituted chloroquinolinyl-1H-pyrazoles and evaluation of their antimalarial, anti-SARS-CoV-2, antibacterial, and cytotoxic activities

• Viktor A. Zapol’skii,
• Isabell Berneburg,
• Ursula Bilitewski,
• Melissa Dillenberger,
• Katja Becker,
• Stefan Jungwirth,
• Aditya Shekhar,
• Bastian Krueger and
• Dieter E. Kaufmann

Beilstein J. Org. Chem. 2022, 18, 524–532, doi:10.3762/bjoc.18.54

• position 1 of the pyrazole ring with the aim to obtain new compounds with antimalarial and/or anti-SARS-CoV activity. Polyhalo-1,3-butadienes, carrying at least one nitro group, are valuable starting materials for the directed synthesis of highly functionalized heterocycles. During the past years, we have

• –e [14], 4f [9], 4i [14], 4j [9], 4k [26], and 4m,n [27], and led to dienes 4a, 4g, 4h, 4l, and 4o, respectively, in yields of 52–85%. The subsequent treatment of the butadienes 4 with 2.20 equivalents of 7-chloro-4-hydrazinylquinoline in methanol or ethanol led to the formation of pyrazoles 5 in

Valorisation of plastic waste via metal-catalysed depolymerisation

• Francesca Liguori,
• Carmen Moreno-Marrodán and
• Pierluigi Barbaro

Beilstein J. Org. Chem. 2021, 17, 589–621, doi:10.3762/bjoc.17.53

• temperature (35 °C) but toxic CH2Cl2 solvent (Scheme 1). The reaction using second-generation N-heterocyclic carbene ligands was faster and preferably yielded cyclododecatriene. Larger cyclic butadienes may be used in the production of flame retardants, lubricants and specialty polymers [149][150]. 3.1.3

Recent advances in Cu-catalyzed C(sp³)–Si and C(sp³)–B bond formation

• Balaram S. Takale,
• Ruchita R. Thakore,
• Elham Etemadi-Davan and
• Bruce H. Lipshutz

Beilstein J. Org. Chem. 2020, 16, 691–737, doi:10.3762/bjoc.16.67

Different reactivity of phosphorylallenes under the action of Brønsted or Lewis acids: a crucial role of involvement of the P=O group in intra- or intermolecular interactions at the formation of cationic intermediates

• Stanislav V. Lozovskiy,
• Alexander Yu. Ivanov and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2019, 15, 1491–1504, doi:10.3762/bjoc.15.151

• calculations. Hydrolysis of these species resulted in the formation of phosphoryl-substituted allyl alcohols and 1,3-butadienes. A strong coordination of the oxygen of the P=O group with AlCl3 prevented the formation of cyclic 1,2-oxaphospholium ions and played a crucial role in the different reactivity of

• Lewis acid AlCl3 proceeded through the formation of non-cyclic intermediates. Hydrolysis of the latter afforded phosphorylallyl alcohols and butadienes. For the first time, the intermolecular hydroarylation of the allene system of dichlorophosphorylallenes by arenes under the action of AlCl3 was

Generation of 1,2-oxathiolium ions from (arysulfonyl)- and (arylsulfinyl)allenes in Brønsted acids. NMR and DFT study of these cations and their reactions

• Stanislav V. Lozovskiy,
• Alexander Yu. Ivanov,
• Olesya V. Khoroshilova and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2018, 14, 2897–2906, doi:10.3762/bjoc.14.268

• , leads to their deprotonation with a stereoselective formation of (arysulfonyl)butadienes (for instance, ArSO2–CR1=C–C(Me)=CH2, for R2 = R3 = Me, yields of 87–98%). Reactions of (arysulfonyl)allenes in the system TfOH (0.1 equiv)–HFIP (hexafluoropropan-2-ol) followed by hydrolysis give rise to allyl

• mixtures, (arylsulfinyl)allenes give allyl alcohols (ArSO2–CR1=CH–C(OH)R2R3). Plausible reaction mechanisms have been proposed for all studied reactions. Keywords: (arylsulfinyl)allenes; (arylsulfonyl)allenes; butadienes; 1,2-oxathiolium ions; thiochromene 1,1-dioxides; Introduction Allenes are widely

• decided to achieve the selective formation of each of these different products, butadienes 3, adducts with nucleophiles 4, and thiochromene 1,1-dioxides 5, from allenes 2. The preparation of compounds 3a–h was done by the following method (Scheme 3). Reactions of 2a–h were carried out in CH2Cl2 with 1

Stereo- and regioselectivity of the hetero-Diels–Alder reaction of nitroso derivatives with conjugated dienes

• Lucie Brulíková,
• Aidan Harrison,
• Marvin J. Miller and
• Jan Hlaváč

Beilstein J. Org. Chem. 2016, 12, 1949–1980, doi:10.3762/bjoc.12.184

• , the Marchand–Brynaert group published several results of asymmetric hetero-Diels–Alder reactions of phosphonyl-1,3-butadienes with various nitroso dienophiles [21][85][86][87]. A computational investigation of the hetero-Diels–Alder reactions of 1-diethoxyphosphonyl-1,3-butadiene (28) with various

• -butadienes. Regioselectivity of the nitroso hetero-Diels–Alder reaction Because two regioisomeric adducts can be formed when an unsymmetrical diene reacts with a nitroso species, the regioselectivity is an important issue of nitroso hetero-Diels–Alder reactions. Thus, the regioselectivity of this reaction

• -lactams 63 (Scheme 16) [95], which is in accordance with the general prediction. The exclusive regioselectivity of this reaction is due to steric effects. Similar conclusions result from the reaction of 1,3-butadienes 65 with various nitroso heterodienophiles 66, giving proximal isomer 67 (Scheme 17) [85

Cupreines and cupreidines: an established class of bifunctional cinchona organocatalysts

• Laura A. Bryant,
• Rossana Fanelli and
• Alexander J. A. Cobb

Beilstein J. Org. Chem. 2016, 12, 429–443, doi:10.3762/bjoc.12.46

• developed an aza-MBH process using β-ICPD in the reaction between N-sulfonyl-1-aza-1,3-butadienes and activated alkenes (Scheme 4) [25]. In this report, optimal selectivity required (R)-BINOL as a co-catalyst (see inset for proposed catalytic transition state – (R)-BINOL shown in red). Furthermore, the

Palladium-catalysed cyclisation of alkenols: Synthesis of oxaheterocycles as core intermediates of natural compounds

• Miroslav Palík,
• Jozef Kožíšek,
• Peter Koóš and
• Tibor Gracza

Beilstein J. Org. Chem. 2014, 10, 2077–2086, doi:10.3762/bjoc.10.216

• =C bond in the cyclisation reactions. Unfortunately, butadienes rac-42 and 43 underwent uncontrollable transformations under these conditions providing a complex mixture of products. Similarly, the transformations of substrates 20, Z-21, 22 and 34 failed, while the reaction of E-21 (Table 1, entry 5

Zirconoarylation of alkynes through p-chloranil-promoted reductive elimination of arylzirconates

• Xiaoyu Yan,
• Chao Chen and
• Chanjuan Xi

Beilstein J. Org. Chem. 2014, 10, 528–534, doi:10.3762/bjoc.10.48

• aryllithium compounds were coupled in one-pot in the presence of Cp2Zr species to afford highly substituted 1,3-butadienes. The pathway of the oxidation of zirconate 2 to vinylzirconocene 4 is not yet clear. A possible mechanism is proposed in Scheme 6. Coordination of TCQ to zirconium results in reductive

Recent applications of the divinylcyclopropane–cycloheptadiene rearrangement in organic synthesis

• Sebastian Krüger and
• Tanja Gaich

Beilstein J. Org. Chem. 2014, 10, 163–193, doi:10.3762/bjoc.10.14

• transition metal mediated diazo decomposition [223]. The in situ generated rhodium-carbenoid formed upon diazo decomposition of 308 underwent cyclopropanation with butadienes like 309. The resulting vinyl-epoxide ketone underwent rearrangement to give dihydrooxepine 310 in good yield. Vinylcyclopropane

Chemistry of polyhalogenated nitrobutadienes, 10: Synthesis of highly functionalized heterocycles with a rigid 6-amino-3-azabicyclo[3.1.0]hexane moiety

• Viktor A. Zapol’skii,
• Jan C. Namyslo,
• Armin de Meijere and
• Dieter E. Kaufmann

Beilstein J. Org. Chem. 2012, 8, 621–628, doi:10.3762/bjoc.8.69

• mellitus and entered the market in 2009 (Figure 2) [16]. Results and Discussion Driven by the promising stepwise reactivity of the highly substituted butadienes 3, 4 and with the above mentioned hints to biological activities in mind, we set out to develop structural conjunctions of the

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

• Diels–Alder reactions involving 1-oxa-1,3-butadienes. Keywords: β-halo aldehydes; hetero Diels–Alder reaction; 1-oxa-1,3-butadiene; pyrido[2,3-d]pyrimidines; uracil; Introduction The importance of uracil and its annulated derivatives is well recognized by synthetic as well as biological chemists [1][2

• complex annulated pyrido[2,3-d]pyrimidines by intramolecular hetero Diels–Alder reactions involving 1-oxa-1,3-butadienes (Scheme 1). The key intermediate, the 2-chloro-3-formyl uracil derivative 1 (β-halo aldehyde), was prepared by the reaction of N,N-dimethyl barbituric acid with Vielsmeier reagent (DMF

• base catalyst (usually piperidine) to produce the 1-oxa-1,3-butadienes 5 which underwent intramolecular Diels–Alder reaction under reflux conditions in toluene (12 to 15 h) to give the cycloadducts. In most of cases the formation of two compounds was observed. The compounds were separated by column

Preparation and Diels–Alder/cross coupling reactions of a 2-diethanolaminoboron- substituted 1,3-diene

• Liqiong Wang,
• Cynthia S. Day,
• Marcus W. Wright and
• Mark E. Welker

Beilstein J. Org. Chem. 2009, 5, No. 45, doi:10.3762/bjoc.5.45

• groups have now made use of the cycloadducts thus prepared [6] as well as the methodology [7]. We have now subsequently reported the preparation of 2-BF3 substituted 1,3-butadienes and demonstrated that they can be used in sequential Diels–Alder/cross coupling reactions [8][9]. These trifluoroborate

Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

Beilstein J. Org. Chem. 2009, 5, No. 33, doi:10.3762/bjoc.5.33

• -butadienes Reinhoudt illustrated the stereoselective thermal rearrangement of 1-(1-pyrrolidinyl)-1,3-butadienes for the synthesis of mitosane analogs [103][104][105]. They proposed that the transformation proceeded through two consecutive pericyclic reactions (Scheme 38). Starting from compound 131, a [1][6