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Search for "thiourea" in Full Text gives 177 result(s) in Beilstein Journal of Organic Chemistry.
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
Microwave-assisted cyclizations promoted by polyphosphoric acid esters: a general method for 1-aryl-2-iminoazacycloalkanes
Beilstein J. Org. Chem. 2016, 12, 2026–2031, doi:10.3762/bjoc.12.190
- ]. Some urea and thiourea derivatives have been studied as CNS agents [7] and anthelmintic drugs [8]. This heterocyclic core therefore represents the foundation for potential bioactive agents. A few methods have been described for the synthesis of 2-iminoazacycloalkanes from acyclic precursors. One
A chiral analog of the bicyclic guanidine TBD: synthesis, structure and Brønsted base catalysis
Beilstein J. Org. Chem. 2016, 12, 1870–1876, doi:10.3762/bjoc.12.176
- reductive amination to form 18 (58%). After removal of the Boc protecting group (quant.), triamine 19 was reacted with dimethyl trithiocarbonate in refluxing nitromethane. The thiourea intermediate was activated in situ by S-alkylation with MeI. Upon further heating the final cyclization occured forming the
Rearrangements of organic peroxides and related processes
Beilstein J. Org. Chem. 2016, 12, 1647–1748, doi:10.3762/bjoc.12.162
- additional reaction step [345] (Scheme 69). The treatment of endoperoxide 232 with triethylamine in ethanol at room temperature results in the O–O-bond cleavage to form 5-hydroxytropolone (233) (Scheme 70) [346]. It is interesting to note, that a reduction of the bicyclic endoperoxide 234 with thiourea in
Multicomponent reactions: A simple and efficient route to heterocyclic phosphonates
Beilstein J. Org. Chem. 2016, 12, 1269–1301, doi:10.3762/bjoc.12.121
- (Scheme 19). 2.2.5 Pyrimidinylphosphonates: The 1,3-bi-nucleuphiles such as thiourea (82), guanidinium carbonate 84 and cyanoguanidine 86, under the above mentioned conditions afforded the pyrimidinylphosphonates 83, 85 and 87, respectively (Scheme 20). 2.2.6 Diazepinyl- and oxazepinylphosphonates: The
- this method, the one-pot reaction of isatin derivatives 301, iminophosphorane 302, and diphenyl phosphonate in the presence of Cinchona-derived thiourea as the catalyst afforded α-aminophosphonates 303 in 70–81% yields and with 70–84% ee (Scheme 62) [100]. The trans-1,5-benzodiazepines 307 bearing both
- . Three-component reaction of 6-methyl-3-formylchromone (75) with thiourea, guanidinium carbonate or cyanoguanidine in the presence of diethyl phosphonate. Three-component reaction of 6-methyl-3-formylchromone (75) with 1,4-bi-nucleophiles in the presence of diethyl phosphonate. One-pot three-component
Conjugate addition–enantioselective protonation reactions
Beilstein J. Org. Chem. 2016, 12, 1203–1228, doi:10.3762/bjoc.12.116
- thiourea catalyst 92 in high yield and modest enantioselectivity (Scheme 22) [45]. Tan and co-workers have investigated the conjugate addition–enantioselective protonation of N-arylitaconimides 95 using a C2-symmetric guanidine catalyst (Scheme 23) [24][46]. Because E- and Z-enolates can exhibit different
- (Scheme 23c). Following Tan’s work on the conjugate addition–enantioselective protonation of cyclic itaconimide 95, both the Singh and Chen groups investigated the addition of thiol nucleophiles to acyclic imides. Utilizing thiourea catalyst 102a, Singh and co-workers reported the catalytic
- ). Building on their addition of benzylic and aromatic thiols to N-acryloyloxazolidinones, Singh and colleagues demonstrated that thiourea 102b catalyzes the addition of thioacetic acid to N-acryloyloxazolidinones in high yields and enantioselectivity to provide thioester 101b [48]. In a related
Towards the total synthesis of keramaphidin B
Beilstein J. Org. Chem. 2016, 12, 1096–1100, doi:10.3762/bjoc.12.104
- pronucleophile to a substituted furanyl nitroolefin catalysed by a bifunctional cinchonine-derived thiourea has been used as the key stereocontrolling step in a new synthetic strategy to the heavily functionalised piperidine core of keramaphidin B. Keywords: bifunctional organocatalyst; enantioselective Michael
- reported cinchonine-derived bifunctional thiourea catalyst 12 afforded the addition product 13 in high yield with good levels of diastereo- and enantioselectivity (95:5 dr, 90:10 er for the major diastereomer 13). The relative stereochemical configuration of the minor diastereomeric product 14 was
- hydroxypropyl chain attached to the quaternary stereocentre, poised for further functionalisation. Having established that the cinchonine-derived bifunctional Brønsted base/thiourea organocatalyst 12 was effective for installing two stereocentres including the quaternary carbon in a model system, we next
Catalytic asymmetric synthesis of biologically important 3-hydroxyoxindoles: an update
Beilstein J. Org. Chem. 2016, 12, 1000–1039, doi:10.3762/bjoc.12.98
- , heterocyclic groups and aliphatic groups. A plausible mechanism was proposed as shown in Scheme 29. The thiourea NH moieties and the tertiary amino group of the catalyst activated the carbonyl groups of isatin and the α-protons of gem-diols, respectively through hydrogen bond interactions. The α-proton of gem
- same group reported the organocatalytic asymmetric addition reactions of isatins with electron-rich aromatics sesamols using the cinchona alkaloid-derived thiourea catalyst (cat. 17) under mild conditions. In the presence of 10% catalyst, sesamols reacted with isatins smoothly in tert-butyl ether at
- of the bifunctional thiourea catalyst (cat. 24, 10 mol %), affording the E-adducts in high yields (up to 95%) and with moderate to good enantioselectivities (up to 99% ee). Different allyl ketones were examined under these conditions, affording the corresponding products in good yields, especially
1H-Imidazol-4(5H)-ones and thiazol-4(5H)-ones as emerging pronucleophiles in asymmetric catalysis
Beilstein J. Org. Chem. 2016, 12, 918–936, doi:10.3762/bjoc.12.90
- -alkylation. The starting thiohydantoins, in turn, are obtained by heating a mixture of the corresponding N-substituted amino acid or its methyl ester 3 and thiourea at 195 °C [59] (Scheme 1b). Following this protocol different 1H-Imidazol-4(5H)-ones have been prepared in good yields. 1.2 1H-Imidazol-4(5H
- acceptors in reactions promoted by bifunctional Brønsted bases. 1.2.1 Nitroalkenes as acceptors. Investigation of the base-catalyzed Michael addition reaction of 2-thio-1H-imidazol-4(5H)-ones 4 to nitroalkenes 5 [55] revealed that cinchona alkaloids such as quinine, (DHQ)2Pyr or even thiourea tertiary amine
- (Scheme 8) [85]. This catalyst belongs to a new subclass of bifunctional Brønsted bases, which was developed on the basis of Takemoto’s model [86]. This model is featured by three different moieties: a basic site, a urea (thiourea) function and a 3,5-bis(trifluoromethyl)phenyl group, all three elements
Asymmetric α-amination of 3-substituted oxindoles using chiral bifunctional phosphine catalysts
Beilstein J. Org. Chem. 2016, 12, 725–731, doi:10.3762/bjoc.12.72
- (diethyl azodicarboxylate, 2a) was selected as the model reaction for the evaluation of chiral phosphine catalysts (Table 1). Using bifunctional thiourea catalysts 4a and 4b, the reaction proceeded smoothly at room temperature to afford the product 3a in good yields, albeit with low enantiomeric excesses
- (ee) (Table 1, entries 1 and 2). When the thiourea moiety in the catalysts were replaced by amides, the enantioselectivities were greatly improved (Table 1, entries 3–6). The examination of catalysts 4c–f with further fine-tuning on the acyl group revealed 4d as the optimal catalyst for this
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
- nitroalkenes and commercially available 1,4-dithiane-2,5-diol to 3,4,5-substituted tetrahydrothiophenes, bearing a quaternary stereocenter, is presented. A secondary amine thiourea derived from (R,R)-1,2-diphenylethylamine was found to be the most effective catalyst when using trans-β-methyl-β-nitrostyrenes
- - and enantioselectivity (Table 1, entries 1–5). Thiourea catalyst VII afforded the best result, leading to products 5/6 in a ratio of 72/28 although with low ee values (Table 1, entry 6). Reacting trisubstituted olefin 2a with compound 4, led to three isomers with modest diastereocontrol when using
- catalysts (I–VII). Among the catalysts tested, compound VII proved to be the most active and enantioselective, giving the major diastereoisomer 7a with 44% ee (Table 1, entry 13). Taking into account that amine thiourea VII, bearing a sterically hindered secondary amine moiety, was significantly more
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
- the thiourea derived from (L)-valine and 1,6-hexanediamine. The catalysts can be used in only 2 mol % loading, and reused for at least four cycles in neat conditions. The ball milling promoted additions also worked very well. Keywords: bifunctional organocatalysts; organocatalysis; stereoselective
- thiourea I [30] onto sulfonylpolystyrene resin leading to catalysts II–V (Figure 1), which differ in the length of the diamine linker or in the substitution pattern of the nitrogen in the sulfonamide. These materials, and the related unsupported thiourea VI, have been previously tested as excellent
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