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Search for "thiourea" in Full Text gives 188 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
- directly by fusion of thiourea/urea with 5-aminopyrazole 126 in an oil bath at 120 °C. N-Thiocarbamoyl pyrazole derivatives 180 and 183 underwent cyclization with hydrazine hydrate to give 5-(N-triazolyl)aminopyrazole derivative 182 and hydrazinopyrazolo[3,4-d]pyrimidines 185, respectively (Scheme 51). El
Photocatalytic formation of carbon–sulfur bonds
Beilstein J. Org. Chem. 2018, 14, 54–83, doi:10.3762/bjoc.14.4
- thiourea derivative giving the Eosin Y radical anion and a thiyl radical. Aerobic oxidation closes the catalytic cycle and after hydrogen atom abstraction of the carbon-centred radical intermediate the final product is formed. Formation of 1,3,4-thiadiazoles In a second article the same concept led to the
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
- obtained (Table 1, entries 2 and 3). These results are not surprising as the substrate 1a is a weaker dinucleophile than aminopyridine and thiourea used previously [20][21][22]. However, 56% yield of 3a was obtained with KOH (Table 1, entry 4). The use of KOH as a base in the α-bromination of 1,3
Regioselective decarboxylative addition of malonic acid and its mono(thio)esters to 4-trifluoromethylpyrimidin-2(1H)-ones
Beilstein J. Org. Chem. 2017, 13, 2617–2625, doi:10.3762/bjoc.13.259
- from the group of Ma described the development of a chiral thiourea-catalyzed enantioselective decarboxylative Mannich reaction of malonic acid monoesters with 4-trifluoromethylquinazolin-2(1H)-ones as heterocyclic trifluoromethylketimine substrates for the preparation of enantioenriched 3,4
- , entries 5 and 6). Unfortunately, quinine and the chiral quinine-derived thiourea organocatalyst QT in toluene led to a mixture of racemic products along with 19% and 38% of unreacted starting material, respectively (Table 1, entries 7 and 8). As seen from the screening results, the reaction
Electron-deficient pyridinium salts/thiourea cooperative catalyzed O-glycosylation via activation of O-glycosyl trichloroacetimidate donors
Beilstein J. Org. Chem. 2017, 13, 2385–2395, doi:10.3762/bjoc.13.236
- trichloroacetimidate donors using a synergistic catalytic system of electron-deficient pyridinium salts/aryl thiourea derivatives at room temperature is demonstrated. The acidity of the adduct formed by the 1,2-addition of alcohol to the electron-deficient pyridinium salt is increased in the presence of an aryl
- thiourea derivative as an hydrogen-bonding cocatalyst. This transformation occurs under mild reaction conditions with a wide range of O-glycosyl trichloroacetimidate donors and glycosyl acceptors to afford the corresponding O-glycosides in moderate to good yields with predictable selectivity. In addition
- , the optimized method is also utilized for the regioselective O-glycosylation by using a partially protected acceptor. Keywords: cooperative catalysis; electron-deficient pyridinium salts; O-glycoside; regioselectivity; thiourea; Introduction The glycosidic linkage is the principal bond present in a
Dialkyl dicyanofumarates and dicyanomaleates as versatile building blocks for synthetic organic chemistry and mechanistic studies
Beilstein J. Org. Chem. 2017, 13, 2235–2251, doi:10.3762/bjoc.13.221
- corresponding E-1 [10] (Scheme 2). Alternatively, the same transformation can be performed with 3 and thiourea derivative 4 in a two-step reaction through intermediate 5 [11] (Scheme 2). The latter, upon treatment with Et3N, generates a carbene [:C(CN)CO2Et], which dimerizes to give E-1a albeit in low yield
Phosphonic acid: preparation and applications
Beilstein J. Org. Chem. 2017, 13, 2186–2213, doi:10.3762/bjoc.13.219
- produce compound 98 [213] (Figure 28A). A second example corresponds to the nucleophilic addition of N-heterocyclic phosphine 99 to a nitroalkene (phospho-Michael reaction) as shown in Figure 28B. The thiourea unit in 99 plays a crucial role by assuming intramolecular interaction with the nitro function
p-tert-Butylthiacalix[4]arenes functionalized by N-(4’-nitrophenyl)acetamide and N,N-diethylacetamide fragments: synthesis and binding of anionic guests
Beilstein J. Org. Chem. 2017, 13, 1940–1949, doi:10.3762/bjoc.13.188
- ][54][55][56][57]. Modified macrocycles with the amide fragments at the lower rim can form complexes with the anions by hydrogen bonds of the amide group with the guest. It was shown that (thia)calix[4]arene derivatives with urea and thiourea fragments at the lower rim can bind anions through hydrogen
Mechanochemical synthesis of small organic molecules
Beilstein J. Org. Chem. 2017, 13, 1907–1931, doi:10.3762/bjoc.13.186
- substituted thiourea-based organocatalysts were screened for the reaction to achieve stereoselective adducts through hydrogen bonding. Only with 2.5 mol % of thiourea-based catalyst B, α-nitrocyclohexanone and nitroalkene derivatives could undergo a Michael addition to yield up to 95% of the desired product
Influence of the milling parameters on the nucleophilic substitution reaction of activated β-cyclodextrins
Beilstein J. Org. Chem. 2017, 13, 1893–1899, doi:10.3762/bjoc.13.184
- intermediate for the preparation of 6I-S-monodeoxy-6I-monothio-β-CD [26]. Having selected the 6I-O-monotosyl-β-CD (Ts-β-CD) as the benchmark, the nucleophilic displacement of the tosylate group in the presence of azido or thiourea (TU) nucleophiles was chosen for the study under different milling conditions
- was investigated using a reaction scale of dominantly 1 mmol of substrate, in the presence of 3 equivalents of NaN3 or thiourea (TU) as nucleophiles (Scheme 1). Being the removal of the starting Ts-β-CD from the 6-monoazido-β-CD complicated due to the solubility similarities, the time to reach
- contact between balls. Unlike the reactivity in solution, under mechanochemical conditions the sulfur nucleophile (thiourea, TU) was less effective than the azide ion in the substitution reaction. A similar reversal of reactivity has been already observed for halogens [12][13][28]. The experimental
Mechanochemical synthesis of thioureas, ureas and guanidines
Beilstein J. Org. Chem. 2017, 13, 1828–1849, doi:10.3762/bjoc.13.178
- -withdrawing aryl isothiocyanates with anilines used for the synthesis of N,N'-disubstituted thioureas, thorough mixing in an agate mortar typically leads to the formation of the products in a couple of minutes. As an extension of the mechanochemical click-coupling of amines with isothiocyanates, the thiourea
- paper, the ball milling approach was then applied for a quantitative click-mechanosynthesis of thiourea-based organocatalysts and anion sensors (Scheme 5) [34]. The demonstrated efficiency of mechanochemical milling synthesis of thioureas was exploited for a quantitative transformation of
- organocatalyst design was first introduced by reacting 3,5-di(trifluoromethyl)phenyl isothiocyanate with 3,5-di(trifluoromethyl)aniline and 4-chloroaniline in a 1:1 ratio under LAG conditions using methanol as the grinding liquid. This led to quantitative formation of the Schreiner's catalyst 5 and thiourea 17
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
- , Zu Chong Zhi Road, Shanghai 201203, China University of Chinese Academy of Sciences, NO.19A Yuquan Road, Beijing 100049, China 10.3762/bjoc.13.131 Abstract The thiourea-catalyzed asymmetric synthesis of highly enantioenriched spirocyclopentaneoxindoles containing chiral amide functional groups using
- derivatives with good enantiomeric excess (ee) values, respectively. However, the utility of the reaction is limited to α,β-unsaturated aldehydes with aromatic/alkane substitutions and nitroolefins with aromatic substitutions. Additionally, Shao’s group (Scheme 1, reaction 1C) developed a one-pot thiourea
- asymmetric catalytic synthesis of saturated spirocyclopentaneoxindoles containing four consecutive stereocenters with 3-substituted oxindoles and nitrovinylacetamide using a bifunctional thiourea catalyst in good yields (up to 95%) with excellent diastereoselectivity (up to 3:97) and enantioselectivity (up
Strategies toward protecting group-free glycosylation through selective activation of the anomeric center
Beilstein J. Org. Chem. 2017, 13, 1239–1279, doi:10.3762/bjoc.13.123
- , however, they proposed that first the thiol acetate reacts with DMC to form a thiouronium ester which could be attacked by the deprotonated anomeric alcohol of the saccharide to provide the glycosyl acetate and the isolable thiourea byproduct (Scheme 27). One key advantage of this strategy is the absence
Interactions between shape-persistent macromolecules as probed by AFM
Beilstein J. Org. Chem. 2017, 13, 938–951, doi:10.3762/bjoc.13.95
- well as the silicon AFM tip, were first functionalized by a polysiloxane monolayer bearing isothiocyanate groups, which smoothly react with amines forming stable thiourea links [48]. Monolayers of β-CD or β-CD-polymer were obtained by attachment of monoamino β-CD or amino-modified CD polymer 12
N-Propargylamines: versatile building blocks in the construction of thiazole cores
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
- iodine in ethyl acetate. Excellent yields of desired products were observed (Scheme 5). The mechanism shown in Scheme 6 was proposed for this transformation and comprises the following key steps: (i) the reaction of N-propargylamine 25 and isothiocyanate 26 forms the thiourea intermediate A, (ii
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
- hand, the presence of thiourea additives could activate nitroalkenes when used as substrates by double hydrogen bonding, which lead to improved reactivities [24]. Based on these findings, we decided to explore the effect of a Brønsted acid or an achiral thiourea as additive on the reaction between
- for the diastereoselectivity and syn-enantioselectivity. On the other hand, in the presence of trifluoroacetic acid the reaction proceeded slowly and the diastereoselectivity decreased to some extent. The presence of an achiral thiourea did not improve the results. Finally, we considered the
- possibility of accelerating the formation of the enamine intermediate and simultaneously activating the nitroalkene by using a combination of organocatalyst OC4, a Brønsted acid and an achiral thiourea. Thus the reaction was repeated in the presence of a combination of benzoic acid and N,N'-diphenylthiourea
Transition-metal-catalyzed synthesis of phenols and aryl thiols
Beilstein J. Org. Chem. 2017, 13, 589–611, doi:10.3762/bjoc.13.58
- succeeded in a Nickel catalyzed thiolation of aryl iodides with thiourea in DMF. Aryl iodides firstly reacted with thiourea in the presence of bis(triethylphosphine)nickel(II) chloride and sodium cyanoborohydride as catalyst precusor, and afforded aryl isothiuronium iodide, which could be further converted
- , the Qi group reported a similar protocol to achieve the coupling of aryl iodides and thiourea by CuI/L-proline-catalyzed reaction in the presence of Cs2CO3 as base in DMSO [98]. In 2004, the Itoh group demonstrated that Pd2(dba)3/Xantphos (L14) could catalyze the coupling of aryl halides and aryl or
- of arenes. VOSiW-catalyzed hydroxylation of arenes. Synthesis of aryl thiols using thiourea as thiol source. Synthesis of aryl thiols using alkyl thiol as thiol source. Synthesis of 1-thionaphthol using HS-TIPS as thiol source. Synthesis of aryl thiols using sodium thiosulfate as thiol source
A novel method for heterocyclic amide–thioamide transformations
Beilstein J. Org. Chem. 2017, 13, 174–181, doi:10.3762/bjoc.13.20
- heterocyclic amides attracted our attention: as a first step, we applied a chlorination of heterocyclic amides, followed by thiation via reaction with thiourea on the basis of reagent-promoted desulfurylation of isothiourea under strong basic conditions [8][9]. Aiming to continue our reseach work on the
- extra proton to II to afford the quinazoline thione C2. On the other hand the free cyclohexylamine will add to cyclohexyl isothiocyanate (4) to form the thiourea 3. Similar results were obtained by Furumoto [40], and Sun [41] reported the application of cyanuric chloride (2,4,6-trichloro-1,3,5-triazine
Synthesis of structurally diverse 3,4-dihydropyrimidin-2(1H)-ones via sequential Biginelli and Passerini reactions
Beilstein J. Org. Chem. 2017, 13, 54–62, doi:10.3762/bjoc.13.7
- , hence both reactions will be described in detail. The Biginelli reaction The Biginelli reaction is a three-component reaction between an aldehyde (in many cases aromatic aldehydes give much better results than aliphatic ones), a β-keto ester (α-acidic compound) and urea or thiourea (some mono N
- , aldehyde 1 is activated by a Lewis- or a Brønsted acid. In the next step, urea/thiourea 2 can serve as a nucleophile and react with the activated carbonyl carbon to form a heminal species. However, under acidic conditions heminals can eliminate water and form an N-acyliminium cation 3. This reactive cation
First DMAP-mediated direct conversion of Morita–Baylis–Hillman alcohols into γ-ketoallylphosphonates: Synthesis of γ-aminoallylphosphonates
Beilstein J. Org. Chem. 2016, 12, 2906–2915, doi:10.3762/bjoc.12.290
- , without any additive, provided, after thermal Arbuzov rearrangement, a variety of diethyl allylphosphonates (Scheme 1, reaction 3) [18]. Moreover, the asymmetric allylic substitution of MBH carbonates with diphenyl phosphonate using chiral thiourea phosphite as catalyst, afforded the related
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
- substrates, and chiral products were obtained in good yields and selectivities. Remarkably, the performance of tetrakistriazoles was found to be comparable (or in some cases superior) to the well-established thiourea- and squaramide-based catalysts developed for similar transformations. Quaternary
- observed under mild conditions with L11. The activity of catalysts L11 was found to be comparable to the activity of common thiourea-based hydrogen bond donors, and double-charged catalyst DABCO-Me2·2X was found to be one of the most active catalysts. As before [53], the activity of ammonium salts L11 was
- demonstrated by Schreiner in a detailed study of hydrogen-bonding thiourea organocatalysts containing a 3,5-bis(trifluoromethyl)phenyl group as the privileged motif [56][57][58]. A recent example of utilizing such interactions in catalysis was demonstrated by Bibal and co-workers [58]. In this study, Bibal and
Continuous-flow synthesis of primary amines: Metal-free reduction of aliphatic and aromatic nitro derivatives with trichlorosilane
Beilstein J. Org. Chem. 2016, 12, 2614–2619, doi:10.3762/bjoc.12.257
- obtained in quantitative yield as a clean product with no need for purification. We also investigated the continuous-flow reduction of nitro ester 5, which can be conveniently prepared in one step through the organocatalyzed addition of diethyl malonate to trans-β-nitrostyrene promoted by a chiral thiourea
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
- ; 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
- for this transformation was postulated. It includes a nucleophilic attack of the thiourea sulfur atom on the C=C bond of the maleimide followed by a proton transfer and nucleophilic attack of the thiourea nitrogen atom on one of the two carbonyl groups; the latter step is considered rate determining
- -phenylmaleimide providing thiazolidine with the exocyclic position of the phenyl group, whereas an isomer with the phenyl group on the endocyclic nitrogen atom was obtained from the same thiourea and N-ethylmaleimide (Scheme 1) [9]. This behavior has not been explained and there is lack of more recent information
Efficient mechanochemical synthesis of regioselective persubstituted cyclodextrins
Beilstein J. Org. Chem. 2016, 12, 2364–2371, doi:10.3762/bjoc.12.230
- impurities, could be performed. Isolation and purification processes could also be simplified. Considerably lower alkylthiol/halide ratio were necessary to reach the complete reaction in comparison with thiourea or azide reactions. While the presented mechanochemical syntheses were carried out on the
- well as solvent impurities increase synthesis and purification costs and time. Selectively per-6-thiolated CDs are also used in gold nanoparticle chemistry, particularly in electrochemical sensors [17]. Thiourea (TU) is one of the best precursors of those CDs because as the halogen is exchanged to the
Highly chemo-, enantio-, and diastereoselective [4 + 2] cycloaddition of 5H-thiazol-4-ones with N-itaconimides
Beilstein J. Org. Chem. 2016, 12, 2293–2297, doi:10.3762/bjoc.12.222
- . Results and Discussion Our studies were initiated by examining a model reaction between 5H-thiazol-4-one 1a and N-phenyl itaconimide 2a (Table 1). The reaction was first evaluated in toluene at 25 °C and using L-tert-leucine-based thiourea−tertiary amine I as the catalyst (Table 1, entry 1), with
- chemoselectivity and thus the moderate yield. When the H-bond donor was changed from thiourea to urea (catalyst II), it did not provide better results (Table 1, entry 2) [17][19]. In the [4 + 2] annulation of 5H-thiazol-4-ones with nitroalkenes, dipeptide-based thiourea−amide−tertiary amine III (DP-TAA) was
- dipeptide-based tertiary amine for this type of reaction. By modifying the thiourea moiety of III to urea lead us to catalyst DP-UAA IV, which could further increase the enantioselectivity (Table 1, entry 4). Subsequently, we screened the solvent effect with IV as the catalyst (Table 1, entries 5–7), and
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