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Search for "thioureas" in Full Text gives 63 result(s) in Beilstein Journal of Organic Chemistry.
5-Aminopyrazole as precursor in design and synthesis of fused pyrazoloazines
Beilstein J. Org. Chem. 2018, 14, 203–242, doi:10.3762/bjoc.14.15
Photocatalytic formation of carbon–sulfur bonds
Beilstein J. Org. Chem. 2018, 14, 54–83, doi:10.3762/bjoc.14.4
- procedure for the preparation of 2-aminobenzothioazoles from the respective N-aryl thioureas with Eosin Y as photoredox catalyst and molecular oxygen as terminal oxidant was shown (Scheme 33) [68]. They propose a mechanism where the excited state of Eosin Y is quenched reductively by the deprotonated
Reagent-controlled regiodivergent intermolecular cyclization of 2-aminobenzothiazoles with β-ketoesters and β-ketoamides
Beilstein J. Org. Chem. 2017, 13, 2739–2750, doi:10.3762/bjoc.13.270
- -efficient protocols, we have employed transition-metal-free approaches for the one-pot synthesis of imidazo[1,2-a]pyridines and thiazolamines by coupling β-ketoesters or their derivatives, phenylacetones and phenylacetophenones, with aminopyridines [20][21] and thioureas [22]. The strategy involves in situ
- -aminobenzothiazole with acetophenones [55] or aldehydes and nitroalkanes [56]. Because the bicyclic structure of 2-aminobenzothiazole is more stable than aminopyridines and thioureas, the nucleophilicity of the aromatic N atom is reduced. A stronger base, KOt-Bu, is therefore needed for in situ bromination to form
Mechanochemical synthesis of thioureas, ureas and guanidines
Beilstein J. Org. Chem. 2017, 13, 1828–1849, doi:10.3762/bjoc.13.178
- Vjekoslav Strukil Division of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia 10.3762/bjoc.13.178 Abstract In this review, the recent progress in the synthesis of ureas, thioureas and guanidines by solid-state mechanochemical ball milling is
- ; thioureas; ureas; Introduction The urea molecule played the central role in the development of organic chemistry since its first documented synthesis in 1828 when the German chemist Friedrich Wöhler prepared it starting from ammonium cyanate (Scheme 1) [1]. This simple, yet intriguing transformation of an
- Raman spectroscopy was devised [27]. Finally, these two in situ techniques have been successfully merged to allow simultaneous monitoring of mechanochemical reactions by PXRD and Raman spectroscopy [28][29]. Review Mechanochemical synthesis of (thio)ureas Thioureas In a paper by Kaupp et al. a study on
Construction of highly enantioenriched spirocyclopentaneoxindoles containing four consecutive stereocenters via thiourea-catalyzed asymmetric Michael–Henry cascade reactions
Beilstein J. Org. Chem. 2017, 13, 1342–1349, doi:10.3762/bjoc.13.131
- spirocyclopentaneoxindoles. Keywords: asymmetric synthesis; four consecutive stereocenters; Michael–Henry cascade reactions; spirocyclopentaneoxindoles; thioureas; Introduction The spirocyclic oxindole core represents an important scaffold that is encountered frequently in many biologically active molecules and natural
- functionalized nitrovinylacetamides are rare. Chiral thioureas [28][38][39] have evolved as powerful hydrogen bonding catalysts for the asymmetric synthesis of spirocyclopentaneoxindoles, which have been demonstrated as acceptable but still considerably limited. Organocatalytic iminium–enamine cascade reactions
Synthesis of new pyrrolidine-based organocatalysts and study of their use in the asymmetric Michael addition of aldehydes to nitroolefins
Beilstein J. Org. Chem. 2017, 13, 612–619, doi:10.3762/bjoc.13.59
- trans-β-nitrostyrene and 3-phenylpropionaldehyde promoted by OC4 (Table 4). When thioureas were used as additives the reaction was performed in toluene in order to improve the solubility. The addition of benzoic or acetic acid increased the reactivity and anti-enantioselectivity but it was detrimental
A novel method for heterocyclic amide–thioamide transformations
Beilstein J. Org. Chem. 2017, 13, 174–181, doi:10.3762/bjoc.13.20
- ) gave a broad singlet and a singlet signal at δ 13.71 and 3.87 ppm, associated with NH and OCH3 groups, respectively. The significant downfield shift of the NH proton is probably due to intermolecular hydrogen bond interactions of the type NH···S=C. All the isolated thioureas C1–13 exhibited similar 1H
- , TCT) as a desulfurylation reagent in the synthesis of carbodiimides or alkyl isothiocyanates from thioureas under mild conditions. Conclusion Several synthetic procedures related to thiation of heterocyclic amides have been reported to date. The drawback of the existing methods is the use of expensive
New approaches to organocatalysis based on C–H and C–X bonding for electrophilic substrate activation
Beilstein J. Org. Chem. 2016, 12, 2834–2848, doi:10.3762/bjoc.12.283
- studies by the Huber group and others suggest that halogen bond donors based on the bis(halobenzimidazolium) scaffold could promote other types of reactions that are typically observed with hydrogen bond donors such as thioureas [88]. Thus catalyst L23 was found to catalyze the reaction of methyl vinyl
- this review demonstrate that the catalysts based on such interactions could match or even outperform the existing O–H/N–H hydrogen bond donors such as thioureas. Several different variants of C–H hydrogen bond donors have been developed; however, the most successful designs have involved the use of
Thiazol-4-one derivatives from the reaction of monosubstituted thioureas with maleimides: structures and factors determining the selectivity and tautomeric equilibrium in solution
Beilstein J. Org. Chem. 2016, 12, 2563–2569, doi:10.3762/bjoc.12.251
- . 26, Saint Petersburg, 198504, Russia 10.3762/bjoc.12.251 Abstract 2-(Alkyl(aryl)amino)thiazol-4(5H)-ones can regioselectively be prepared from monoalkyl(aryl)thioureas and maleimides. In solution, the former heterocycles exist in a tautomeric equilibrium with 2-(alkyl(aryl)imino)thiazolidin-4-ones
- and the substituent on the exocyclic nitrogen atom governs the ratio of these tautomers. Isomers with the alkyl group in the endocyclic position can be obtained from N-methyl(ethyl)thioureas. 2D NMR spectroscopy and DFT calculations rationalize experimental results. Keywords: maleimides
- ; regioselectivity; tautomerism; thiazolidinones; thioureas; Introduction The thiazolidine core is one of the privileged scaffolds in a variety of pharmaceuticals with exclusively broad range of biological activities [1][2][3][4][5][6][7]. 2-Aminothiazolidin-4-ones can be easily prepared treating thiourea
Stereoselective amine-thiourea-catalysed sulfa-Michael/nitroaldol cascade approach to 3,4,5-substituted tetrahydrothiophenes bearing a quaternary stereocenter
Beilstein J. Org. Chem. 2016, 12, 643–647, doi:10.3762/bjoc.12.63
- affording the heterocyclic products in good yields and moderate stereoselectivities. Keywords: cascade reaction; tetrahydrothiophenes; aymmetric synthesis; amine thioureas; organocatalysis; Introduction The interest toward the development of stereoselective methodologies to prepare tetrahydrothiophenes
- effective than tertiary amine-based thioureas [14][23], catalyst VIII, bearing a sterically demanding neopentyl group, was synthesized in order to check its impact on the stereoselectivity (Scheme 2). Catalyst VIII was easily obtained in a two-step procedure in fair overall yield. Compound VIII proved to be
Supported bifunctional thioureas as recoverable and reusable catalysts for enantioselective nitro-Michael reactions
Beilstein J. Org. Chem. 2016, 12, 628–635, doi:10.3762/bjoc.12.61
- bifunctional thioureas on sulfonylpolystyrene resins has been studied in the nitro-Michael addition of different nucleophiles to trans-β-nitrostyrene derivatives. The activity of the catalysts depends on the length of the tether linking the chiral thiourea to the polymer. The best results were obtained with
- nitro-Michael addition; supported catalysts; thioureas; Introduction The use of chiral bifunctional thioureas that allow the simultaneous activation of a electrophile, by hydrogen bonding, and a nucleophile, by deprotonation, plays a major role in the stereoselective formation of C–C bonds in different
- nanoparticles [10][11][12], inorganic solids [13][14], and different polystyrene derivatives [15][16][17][18][19][20]. Bifunctional thioureas were first supported on PEG [21], and later on different materials such as poly(methylhydrosiloxane) [16], polystyrene [18][19][20][21][22], and magnetic nanoparticles
The aminoindanol core as a key scaffold in bifunctional organocatalysts
Beilstein J. Org. Chem. 2016, 12, 505–523, doi:10.3762/bjoc.12.50
- -type acceptor, by weak hydrogen-bonding interaction between the oxygen atom of the hydroxy group and the indolic proton (Figure 5). Recently, the conjugated addition of indole derivatives to β,γ-unsaturated α-ketoesters was explored [40]. To this end, the catalytic activity of several chiral thioureas
(Thio)urea-mediated synthesis of functionalized six-membered rings with multiple chiral centers
Beilstein J. Org. Chem. 2016, 12, 462–495, doi:10.3762/bjoc.12.48
- will be summarized. Initially, the use of primary amine-thioureas as organocatalysts for the above transformation is being discussed, followed by the examples employing secondary amine-thioureas. Finally, the use of tertiary amine-thioureas and miscellaneous examples are presented. Keywords: multiple
- bonds, such as carboxylic acids, tetrazoles, thioureas, etc. The selectivity observed, when steric shielding interaction is employed, is due to the bulky group of the catalyst. This group shields one face of the enamine to provide the selectivity. The third most valuable and studied mode of activation
- organocatalysts. Review Primary amine-thioureas as organocatalysts promoting asymmetric transformations that lead to a six-membered ring As discussed earlier, except from the activation of the substrates with the formation of the corresponding enamines or iminium ions, the synthesis of enantiopure products can be
Organocatalytic asymmetric Henry reaction of 1H-pyrrole-2,3-diones with bifunctional amine-thiourea catalysts bearing multiple hydrogen-bond donors
Beilstein J. Org. Chem. 2016, 12, 295–300, doi:10.3762/bjoc.12.31
- sites, have captured tremendous attention in particular due to their unique ability of the simultaneous activation of the nucleophile and the electrophile in the same transition state [7][8][9][10][11]. Among them, chiral bifunctional thioureas bearing multiple hydrogen-bond donors have been
A quadruple cascade protocol for the one-pot synthesis of fully-substituted hexahydroisoindolinones from simple substrates
Beilstein J. Org. Chem. 2016, 12, 253–259, doi:10.3762/bjoc.12.27
- -substituted hexahydroisoindolinones was developed by using bifunctional tertiary amine-thioureas as powerful catalysts. As far as we know, there is no efficient synthetic method developed toward fully-substituted hexahydroisoindolinones. The products were obtained in good yield and diastereoselectivity. The
- when K2CO3 was used as the catalyst (Table 1, entry 4). When thioureas were used as the catalysts, we also did not get the expected product (Table 1, entries 5 and 6). Since bifunctional tertiary amine-thioureas have been proved as powerful catalysts that can catalyze a variety of organocascade
- reactions, we also tested thiourea catalysts, cat-1 to cat-3. Interestingly, the thioureas cat-1 and cat-2 were able to promote the reaction (Table 1, entries 7 and 8), but we obtained an even better yield when the tertiary amine-thiourea cat-3 was used as the catalyst (Table 1, entry 9). All products were
Bifunctional phase-transfer catalysis in the asymmetric synthesis of biologically active isoindolinones
Beilstein J. Org. Chem. 2015, 11, 2591–2599, doi:10.3762/bjoc.11.279
- side did not allow us to improve the catalyst performance and a similar selectivity was obtained upon incorporation of more electron-rich aryl groups R1. The initial tests also showed that ureas are more selective than thioureas (Table 1, entry 12). Thus further optimization was carried out with ureas
Tandem cross enyne metathesis (CEYM)–intramolecular Diels–Alder reaction (IMDAR). An easy entry to linear bicyclic scaffolds
Beilstein J. Org. Chem. 2015, 11, 1486–1493, doi:10.3762/bjoc.11.161
- -bonding catalysts for Diels–Alder reactions [28]. However, in our case no influence was observed when the reaction was performed in the presence of diaryl thioureas (Table 1, entry 13). Finally, the use of benzoquinone (BQ) as an additive, which has been reported to suppress the formation of byproducts in
Sequence-specific RNA cleavage by PNA conjugates of the metal-free artificial ribonuclease tris(2-aminobenzimidazole)
Beilstein J. Org. Chem. 2015, 11, 493–498, doi:10.3762/bjoc.11.55
- . Here we report a new and mercury-free synthesis of tris(2-aminobenzimidazole) and its conjugation to PNA oligomers. In addition, the results of cleaving experiments with three different RNA substrates are presented. Results and Discussion Alternative reagents to convert thioureas into guanidines
- [18]. The reaction proceeds at ambient temperature. In contrast to ureas and thioureas formed as byproducts when using carbodiimides, the N-methylpyridine-2(1H)-thione resulting from Mukaiyama's reagent is soluble and can be easily removed by chromatography. As we were searching for a heavy metal-free
Primary-tertiary diamine-catalyzed Michael addition of ketones to isatylidenemalononitrile derivatives
Beilstein J. Org. Chem. 2014, 10, 929–935, doi:10.3762/bjoc.10.91
- been found to catalyze a variety of carbon–carbon bond-forming reactions [25][26][27][28][29][30]. Small peptides derived from acyclic amino acids, primary-secondary diamines, Cinchona-based primary amines, and thioureas with a primary amine functionality etc., have found many successful applications
Continuous flow nitration in miniaturized devices
Beilstein J. Org. Chem. 2014, 10, 405–424, doi:10.3762/bjoc.10.38
- of nitric acid per mol of toluene. The experiments using the microreactor yielded a 10% rise in the para-isomer compared with the industrial batch process. A similar approach was used for the nitration of thioureas, and the authors showed by online FTIR spectroscopy that the mechanism of the
- nitration of thioureas is based on subsequent nitrosation and nitration steps. The same group also analyzed continuous processes to perform the strongly exothermic nitration of naphthalene (47) (Scheme 14) with N2O5, both in the gas phase and in the liquid phase [49][50]. The authors reported that the
Secondary amine-initiated three-component synthesis of 3,4-dihydropyrimidinones and thiones involving alkynes, aldehydes and thiourea/urea
Beilstein J. Org. Chem. 2014, 10, 287–292, doi:10.3762/bjoc.10.25
- aldehydes, electron deficient alkynes and ureas/thioureas have been smoothly performed to yield a class of unprecedented 3,4-dihydropyrimidinones and thiones (DHPMs). The reactions are initiated by the key transformation of an enamine-type activation involving the addition of a secondary amine to an alkyne
- , which enables the subsequent incorporation of aldehydes and ureas/thioureas. This protocol tolerates a broad range of aryl- or alkylaldehydes, N-substituted and unsubstituted ureas/thioureas and alkynes to yield the corresponding DHPMs with specific regioselectivity. Keywords: alkynes; DHPMs; diversity
- attractiveness in biological and medicinal researches, DHPMs have also been demonstrated as quite flexible precursors for the synthesis of many other derived heterocyclic scaffolds [13]. For a rather long period, the Biginelli reaction involving the condensation of aldehydes, β-ketoesters and ureas (thioureas
Organocatalyzed enantioselective desymmetrization of aziridines and epoxides
Beilstein J. Org. Chem. 2013, 9, 1677–1695, doi:10.3762/bjoc.9.192
- including cinchona alkaloid derivatives, chiral phosphoric acids, chiral amino alcohols, chiral thioureas, chiral guanidines, and chiral 1,2,3-triazolium chlorides. In this review, the research work of enantioselective desymmetrization of meso-aziridines is organized into sections according to the employed
- yields. Interestingly, meso-N-tosylaziridines reacted sluggishly in both chloroform and toluene as the solvents under the same catalytic system, and the reason of this phenomenon is unknown. Chiral thioureas Jacobsen [50] and co-workers presented an enantioselective catalytic desymmetrization of meso-N
- -benzoylaziridines with HCl by a series of chiral thioureas (Figure 8, OC-28 to OC-44). In most of the cases, a diluted reaction mixture is necessary to obtain good enantioselectivities and OC-41 proved to be the best catalyst to provide β-chlorobenzamides (Scheme 8, 60 to 66) in high yields and enantioselectivities
Thiourea-catalyzed Diels–Alder reaction of a naphthoquinone monoketal dienophile
Beilstein J. Org. Chem. 2013, 9, 1414–1418, doi:10.3762/bjoc.9.158
- carbenes, guanidines, thioureas, amidinium ions, diols, and Brønsted acids showed their value to give densely functionalized Diels–Alder products in high selectivities [1][2][3][4][5][6][7]. In addition, some organocatalysts enabled even the formation of quaternary centers in Diels–Alder cycloadditions [3
- of one equivalent of Brønsted acid 8 had no effect (Table 2, entry 4), the addition of TADDOL (9) improved the reaction speed (Table 2, entry 5). By the use of Schreiner's catalyst 10 [7], the highest conversion speed was observed (Table 2, entry 6). After this finding, Jacobsen's thioureas 11 [13
- ] (Table 2, entry 7) and 12 [14] (Table 2, entry 8) were also tested whereby the 3,5-bis(trifluoromethyl)phenyl-substituted thiourea 12 was superior to catalyst 11. The fact that thioureas as well as diol 9 improved the reaction speed was coherent, since both catalysts are well known to catalyze the Diels
A facile, rapid, one-pot regio/stereoselective synthesis of 2-iminothiazolidin-4-ones under solvent/scavenger-free conditions
Beilstein J. Org. Chem. 2013, 9, 689–697, doi:10.3762/bjoc.9.78
- hypnotic [7][8], antitubercular [9], cardiovascular [10] and cyclooxygenase (COX) inhibitory [11] activities (Figure 1). A common strategy involved in the prevailing synthetic protocols for 2-iminothiazolidin-4-ones [12][13][14] is the cyclization of thioureas with α-halocarboxylic acids [15] or acyl
Efficient synthesis of β’-amino-α,β-unsaturated ketones
Beilstein J. Org. Chem. 2013, 9, 486–495, doi:10.3762/bjoc.9.52
- under different protocols in which the stereoselectivity of the reaction can be introduced through the use of a chiral catalyst [9][10] (Lewis acid, Brønsted acids, L-proline, Cinchona alkaloids derivatives, thioureas, etc.), or by the addition of chiral amines to α,β-unsaturated esters [11][12] or the
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