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Search for "conjugate addition" in Full Text gives 138 result(s) in Beilstein Journal of Organic Chemistry.
(Bio)isosteres of ortho- and meta-substituted benzenes
Beilstein J. Org. Chem. 2024, 20, 859–890, doi:10.3762/bjoc.20.78
- 1,4-BCHs (Scheme 11B) [55]. From carboxylic acid 100e, Curtius rearrangement led to amine 101 and a photoredox decarboxylative conjugate addition to diester 102. From boronate ester 100f, oxidative deborylation led to alcohol 103, arylation led to furan 104 and Matteson homologation to boronate ester
Mechanisms for radical reactions initiating from N-hydroxyphthalimide esters
Beilstein J. Org. Chem. 2024, 20, 346–378, doi:10.3762/bjoc.20.35
- esters for the construction of quaternary carbons via conjugate addition of 3° radicals [39][40]. In general, this transformation operates under a reductive quenching photocatalytic cycle, requiring a stoichiometric reductant (Scheme 4A). Both TM complexes, and organic dyes such as eosin Y [41][42][43
- CO2. Radical 12 undergoes intermolecular addition to the olefin acceptor 13 to form radical intermediate 14. Finally, under reductive conditions radical 14 can undergo hydrogen atom transfer (HAT) or sequential electron transfer and proton transfer (ET/PT) to form the conjugate addition product 15
Additive-controlled chemoselective inter-/intramolecular hydroamination via electrochemical PCET process
Beilstein J. Org. Chem. 2024, 20, 264–271, doi:10.3762/bjoc.20.27
- of conjugate addition of a cathodically generated carbamate anion was ruled out, prompting us to consider that N-alkylation proceeded via a radical mechanism. On the other hand, the addition of 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) led to the predominant formation of cyclized dimer 4 without N
Catalytic multi-step domino and one-pot reactions
Beilstein J. Org. Chem. 2024, 20, 254–256, doi:10.3762/bjoc.20.25
- facile stereoselective tandem reaction based on the asymmetric conjugate addition of dialkylzinc reagents to unsaturated acylimidazoles, followed by trapping of the intermediate zinc enolate with carbocations [12]. A practical one-pot synthesis of fluorescent pyrazolo[3,4-b]pyridin-6-ones by reacting 5
Using the phospha-Michael reaction for making phosphonium phenolate zwitterions
Beilstein J. Org. Chem. 2024, 20, 41–51, doi:10.3762/bjoc.20.6
- the mentioned reactions, the first step of the catalytic cycle is the nucleophilic attack of the phosphine on the electrophile, in many cases an electron-deficient olefin. The zwitterion formed from this conjugate addition can subsequently act as a nucleophile or as a base [3][4][5]. The efficiency of
- this zwitterion formation is of great importance since it is the initiation step for the catalytic cycle in Michael reactions [8]. Generally, the conjugate addition is favored for strong nucleophiles, which is why electron-rich trialkylphosphines were among the first catalysts used in this type of
- for the conversion of acrylamide, which is probably disturbed when the hydrogen bond donor solvent methanol is interacting with the amide group and/or the hydroxy group. Conclusion The conjugate addition of 2,4-di-tert-butyl-6-(diphenylphosphino)phenol to Michael acceptor molecules allows for a facile
Application of N-heterocyclic carbene–Cu(I) complexes as catalysts in organic synthesis: a review
Beilstein J. Org. Chem. 2023, 19, 1408–1442, doi:10.3762/bjoc.19.102
- diversity, low cost, and versatile applications. This article overviews applications of NHC–Cu(I) complexes as catalysts in organic synthesis over the last 12 years, which include hydrosilylation reactions, conjugate addition, [3 + 2] cycloaddition, A3 reaction, boration and hydroboration, N–H and C(sp2)–H
- complex 57 was obtained through reduction of the phenoxyimine-imidazolium bromide 55a (R = t-Bu) with NaBH4 followed by successive alkylation with iPrBr and reaction with Cu2O (Scheme 19) [32]. The use of the synthesized complexes 56a and 57 as precatalysts for the 1,4-conjugate addition to enones and the
- [(IMes)2Cu]+FHF− (91) was also obtained. These complexes exhibit an interesting catalytic activity that will be described later. 2 Application as catalysts In 2001, Woodward, for the first time, reported an NHC–Cu-mediated catalysis in the conjugate addition of diethylzinc to enones (Scheme 33) [46
Non-noble metal-catalyzed cross-dehydrogenation coupling (CDC) involving ether α-C(sp3)–H to construct C–C bonds
Beilstein J. Org. Chem. 2023, 19, 1259–1288, doi:10.3762/bjoc.19.94
- reaction. First, ether radicals A are produced by the reaction with a tert-butoxyl radical. The ether radicals A could undergo a conjugate addition to the 1,4-unsaturated system to form a new radical intermediate B. This intermediate extracts a hydrogen from tert-butanol to form a neutral target product
Metal catalyst-free N-allylation/alkylation of imidazole and benzimidazole with Morita–Baylis–Hillman (MBH) alcohols and acetates
Beilstein J. Org. Chem. 2023, 19, 1251–1258, doi:10.3762/bjoc.19.93
- alcohols 4, such as 4a, starts with a conjugate addition of imidazole (2a) at the C-β position of the Michael acceptor 4a, followed by elimination of the hydroxy moiety, affording the intermediate I. Similarly, a further second β’-conjugate addition of imidazole (2a) to I might occur, followed by
First synthesis of acylated nitrocyclopropanes
Beilstein J. Org. Chem. 2023, 19, 892–900, doi:10.3762/bjoc.19.67
- bulkier. The obtained nitrocyclopropane was transformed into furan upon treatment with tin(II) chloride via a ring-opening/ring-closure process. Keywords: acetoxyiodine; conjugate addition; dihydrofuran; nitroalkene; nitrocyclopropane; Introduction 3-Arylated 2-nitrocyclopropane-1,1-dicarbonylic acid
- ). These structural features enable the construction of a five-membered ring upon treatment with alkenes [9], diazo compounds (reaction g) [10], and nitriles [11]. Several approaches are available for the synthesis of cyclopropanedicarboxylates 1a, which consist of three steps: 1) conjugate addition, 2
- ) halogenation, and 3) ring closure (Scheme 2). β-Nitrostyrene 2 serves as an appropriate acceptor for conjugate addition by diethyl malonate (3a) to afford adduct 4a, in which the methine group flanked by two carbonyl groups is readily halogenated, and the subsequent intramolecular nucleophilic substitution by
Asymmetric tandem conjugate addition and reaction with carbocations on acylimidazole Michael acceptors
Beilstein J. Org. Chem. 2023, 19, 881–888, doi:10.3762/bjoc.19.65
- 10.3762/bjoc.19.65 Abstract We present here a stereoselective tandem reaction based on the asymmetric conjugate addition of dialkylzinc reagents to unsaturated acylimidazoles followed by trapping of the intermediate zinc enolate with carbocations. The use of a chiral NHC ligand provides chiral zinc
- obtained by other conjugate addition reactions. Keywords: acylimidazole; asymmetric catalysis; carbocation; conjugate addition; enolate; Introduction Asymmetric metal-catalyzed conjugate additions provide access to numerous chiral scaffolds. This type of C–C bond formation efficiently enables the
- . Results and Discussion For initial experiments, we have selected the conjugate addition of Me2Zn to acylimidazole 1a catalyzed by a chiral NHC ligand derived from imidazolium salt L1. This NHC precursor has been described previously by Gérard, Mauduit, Campagne and co-workers [19]. The ligand L1 is
Enolates ambushed – asymmetric tandem conjugate addition and subsequent enolate trapping with conventional and less traditional electrophiles
Beilstein J. Org. Chem. 2023, 19, 593–634, doi:10.3762/bjoc.19.44
- years of development. The effort of our group to broaden possibilities to engage metal enolates in reactions with new electrophiles is described. The material is divided according to the organometallic reagent employed in the conjugate addition step, and thus to the particular metal enolate formed
- . Short information on applications in total synthesis is also given. Keywords: asymmetric catalysis; conjugate addition; electrophile; enolate; tandem reaction; Introduction The formation of complex chiral molecules is a crucial task of organic synthesis that enables the synthesis of pharmaceuticals
- , and Mannich-type reactions, Michael addition, nucleophilic substitutions, cyclopropanations, and reactions with carbocations. The field of asymmetric conjugate addition with its extension into enolate trapping reactions began to develop approximately in 1996. In this review article, we analyze more
An accelerated Rauhut–Currier dimerization enabled the synthesis of (±)-incarvilleatone and anticancer studies
Beilstein J. Org. Chem. 2023, 19, 204–211, doi:10.3762/bjoc.19.19
- addition reaction involved. The low reactivity of intermolecular RC reactions can be improved by incorporating the nucleophilic functionality within a molecule like I (Scheme 1). This nucleophilic functionality present within the enone system first undergoes an intramolecular conjugate addition and is
- followed by an intermolecular conjugate addition to form a C–C bond (path A). In an alternative approach (path B) first I undergoes a nucleophilic conjugate addition in intermolecular fashion to give intermediate III and followed by an intramolecular addition to give compound IV. In both paths, the
- involvement of one intramolecular and one intermolecular conjugate addition reaction leads to notable high acceleration in RC reactions. Based on the accelerated intermolecular Rauhut–Currier reaction reported in the literature [7][8][9] and our interest in the synthesis of dimeric complex natural products
Synthetic study toward tridachiapyrone B
Beilstein J. Org. Chem. 2022, 18, 1741–1748, doi:10.3762/bjoc.18.183
- chiral tetrahydrofuran (Scheme 1b). To assemble the skeleton of the natural product, we developed a new strategy in which the α,α’-dimethoxy-γ-pyrone motif 2 was first desymmetrized by a sequence encompassing the conjugate addition of 2-lithio-1,3-dithiane, elimination of methoxide lithium, and
- ambitious coupling, however, met a dead-end and a less direct approach was explored. With a more reactive and less hindered nucleophile, we explored the coupling of lithiocyclopentadiene to compound 2. After conjugate addition and elimination of lithium methoxide, the resulting 6a would be deprotonated by
- AlMe3 to 4,4-dimethyl-2,5-cyclohexadienone in the presence of a copper salt/chiral ligand and silylating reagent [37][38]. The racemic conjugate addition of nucleophiles to 5 was first investigated, starting with the Gilman reagent which was used in Takemoto and Iwata study (Scheme 6). In addition, a
Total synthesis of grayanane natural products
Beilstein J. Org. Chem. 2022, 18, 1707–1719, doi:10.3762/bjoc.18.181
- radical cyclization of an alkynyl ketone as the key step. The synthesis started by a Cu-catalyzed conjugate addition of the vinyl Grignard reagent, followed by TMS α-propargylation under basic conditions, affording the TMS-alkynyl ketone 76 as the major diastereomer (Scheme 11). Originally a Au-catalyzed
Synthetic study toward the diterpenoid aberrarone
Beilstein J. Org. Chem. 2022, 18, 1625–1628, doi:10.3762/bjoc.18.173
- functional transformation from 10, which itself would be prepared through methylation and conjugate addition from Pauson–Khand adduct 11. This cyclopentenone could be readily accessed from 1,7-enyne 12 which could be obtained through the reported procedure [35] from the commercially available 5-hexenoic acid
- strategy, the stereogenic center at C1 was synthesized, along with a smooth attachment of the cyanate group served for further functional group transformation to construct the C ring through C–H insertion. The stereochemistry finding of this conjugate addition from the convex face of the 6-5 ring system
- constructing the D ring is currently undergoing. Conclusion In summary, we have developed an approach to assemble the tricyclic skeleton of aberrarone through stereoselective methylation, conjugate addition and gold-catalyzed C–H insertion from the readily accessed cyclopentenone. Further work to access
Oxa-Michael-initiated cascade reactions of levoglucosenone
Beilstein J. Org. Chem. 2022, 18, 1457–1462, doi:10.3762/bjoc.18.151
- product 6n was also isolated (Table 1, entry 17), analogous to that reported for the reaction of 1, furfural and hydroxide in water [16]. The isolation of 6n was attributed to a slow second conjugate addition of the enolate (the reaction of 6 and 8, Scheme 1), while 7 was formed via an endocyclic
Heteroleptic metallosupramolecular aggregates/complexation for supramolecular catalysis
Beilstein J. Org. Chem. 2022, 18, 597–630, doi:10.3762/bjoc.18.62
- differently sized triangles (S)-40 and (S)-41 depending on the length of the organic spacer in the acceptor unit (Figure 9) [75]. Since the interior cavity of the homochiral macrocycles was equipped with BINOL units, they were utilized as catalysts for the asymmetric conjugate addition of chalcone 42 with
- one of the three ZnPor units being available for the attachment (immobilization) of an organocatalyst, we wondered about the catalytic activity of the dynamic three-component ensembles 89•(82•X) using N-methylpyrrolidine (89) as organocatalyst. For assessment, the conjugate addition of 86 and 87 was
Menadione: a platform and a target to valuable compounds synthesis
Beilstein J. Org. Chem. 2022, 18, 381–419, doi:10.3762/bjoc.18.43
Selective sulfonylation and isonitrilation of para-quinone methides employing TosMIC as a source of sulfonyl group or isonitrile group
Beilstein J. Org. Chem. 2021, 17, 2822–2831, doi:10.3762/bjoc.17.193
- reaction without adding bases, and unexpectedly found Ag salts could catalyze the 1,6-conjugate addition of TosMIC (2a) and p-QM 1a to provide aryl(phenol)methane isonitrile 4a under base-free conditions (Table 1, entries 6–8). When the silver salt was removed from the reaction conditions, the reaction did
- , under air atmosphere for 10 min; yields are reported for the isolated products. Cases encountered by other p-QMs examinations. DBU-catalyzed 1,6-conjugate addition for the synthesis of isonitrile diarylmethanes 4a–h. Reaction conditions unless otherwise specified: 1 (0.2 mmol), 2 (0.4 mmol), DBU (0.06
Highly stereocontrolled total synthesis of racemic codonopsinol B through isoxazolidine-4,5-diol vinylation
Beilstein J. Org. Chem. 2021, 17, 2781–2786, doi:10.3762/bjoc.17.188
- )-enantiomer [18]. We have used ᴅʟ-proline for three reasons: first, it provides the target compounds 1 and 2 in their racemic form, second, it is able to catalyze the conjugate addition between N-EWG-protected hydroxylamines and enals effectively, and third, based on our experience, the products obtained by
Recent advances in the asymmetric phosphoric acid-catalyzed synthesis of axially chiral compounds
Beilstein J. Org. Chem. 2021, 17, 2729–2764, doi:10.3762/bjoc.17.185
- -trifluoromethylpropargyl alcohol are very important for the reaction. Li and co-workers developed a chiral phosphoric acid-catalyzed asymmetric remote 1,8-conjugate addition of thiazolones 111 and azlactones 112 to propargyl alcohols 110 for the synthesis of the chiral allenes 113 and 114, respectively. In the presence of
- diastereoselectivity (10:1 to >20:1 dr). In addition, the enantioselective 1,8-conjugate addition of azlactones 112 to para-quinone methides generated in situ from propargyl alcohols 110 were carried out in the presence of 1 mol % chiral phosphoric acid CPA 7 and afforded the chiral allenes 114 in high yields (65–97
- reaction. Moreover, both electron-withdrawing and donating groups on the aromatic rings of propargyl alcohols or azlactones smoothly participated in the asymmetric 1,8-conjugate addition and afforded the corresponding chiral allenes in good yields with high enantioselectivity. The control experiments
Solvent-free synthesis of enantioenriched β-silyl nitroalkanes under organocatalytic conditions
Beilstein J. Org. Chem. 2021, 17, 2642–2649, doi:10.3762/bjoc.17.177
- Akhil K. Dubey Raghunath Chowdhury Bio-Organic Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India Homi Bhabha National Institute, Anushaktinagar, Mumbai-400094, India 10.3762/bjoc.17.177 Abstract An enantioselective 1,4-conjugate addition of nitromethane to β-silyl α,β
- -nitrosilanes through a Cu(II)–chiral bipyridine complex catalyzed enantioselective silyl transfer reaction to nitroalkenes using Suginome’s silylboron reagent (Scheme 1a) [28]. Recently, we have reported the synthesis of chiral β-nitrosilanes via an organocatalytic conjugate addition of nitromethane to β
- our work, the same group disclosed an organocatalyzed conjugate addition of thiols to β-silyl enones for the synthesis of chiral α-mercaptosilanes (Scheme 1g) [36]. As a part of our ongoing program for the development of asymmetric catalytic approaches for the synthesis of enantioenriched
Enantioenriched α-substituted glutamates/pyroglutamates via enantioselective cyclopropenimine-catalyzed Michael addition of amino ester imines
Beilstein J. Org. Chem. 2021, 17, 2077–2084, doi:10.3762/bjoc.17.134
- achieved [31], Michael reactions with these nucleophiles have met with limited success [32][33][34][35][36][37][38][39]. In terms of enantioselective catalytic strategies, Kobayashi has reported the conjugate addition of azlactones to acrylates using a calcium pybox complex, but with enantioselectivities
- strategy for the enanantioselective conjugate addition of amino acid derivatives for this reaction remains an unmet goal. Our group previously described a chiral cyclopropenimine catalyst that displayed outstanding reactivity for addition reactions of glycine imines [40][41]. We hypothesized that this
Asymmetric organocatalyzed synthesis of coumarin derivatives
Beilstein J. Org. Chem. 2021, 17, 1952–1980, doi:10.3762/bjoc.17.128
- acid (4) as catalyst [30]. Based on this pioneer work, our research group described an efficient, highly stereoselective, one-pot process comprising an organocatalytic conjugate addition of dimedone or 4-hydroxycoumarin 1 to α,β-unsaturated aldehydes 2 followed by an intramolecular isocyanide-based
- conjugate addition of 4-hydroxycoumarin (1) to β,γ-unsaturated α-ketoesters 106 was reported the Kim’s group [69]. In this case, a bifunctional binaphthyl-modified thiourea organocatalyst 108 was used, and among the solvents probed (such as CH2Cl2, CH3CN and toluene), the best results were achieved when the
- , respectively, has proved to be the most effective for the promotion of the conjugate addition of 4-hydroxycoumarins 1 to 2-hydroxycinnamaldehydes 109, leading to chiral bridged bicyclic acetal products 110 with high ee (Scheme 35). The mechanistic study performed showed that possibly the phenolic hydroxy group
Electron-rich triarylphosphines as nucleophilic catalysts for oxa-Michael reactions
Beilstein J. Org. Chem. 2021, 17, 1689–1697, doi:10.3762/bjoc.17.117
- chemistry; organocatalysis; phosphine; solvent-free synthesis; Introduction Phosphines are potent nucleophiles that are used as catalysts in many reactions, like Rauhut–Currier, Morita–Baylis–Hillman or Michael reactions [1][2][3]. The first step of these reactions is a conjugate addition of the phosphine
- formed by the conjugate addition of the phosphine to the Michael acceptor, is believed to be protonated by the alcohol forming the actual catalytically active species namely ion pair ii, consisting of a phosphonium cation and an alkoxide. The alkoxide in ii then reacts with another electrophile
- MCA is not correlating with the phosphines’ activities in conjugate addition reactions. Another approach for assessing the nucleophilicity of the phosphines is to compare their HOMO energy. The nucleophilicity should decrease with increasing s character of the orbital containing the lone pair, which
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