Search results
Search for "mercury(II) salts" in Full Text gives 5 result(s) in Beilstein Journal of Organic Chemistry.
1-Butyl-3-methylimidazolium tetrafluoroborate as suitable solvent for BF3: the case of alkyne hydration. Chemistry vs electrochemistry
- Marta David,
- Elisa Galli,
- Richard C. D. Brown,
- Marta Feroci,
- Fabrizio Vetica and
- Martina Bortolami
Beilstein J. Org. Chem. 2023, 19, 1966–1981, doi:10.3762/bjoc.19.147
- 1881, Kucherov identified mercury(II) salts in sulfuric acid as efficient promoters of the hydration of alkynes and this catalyst system has found applications in industrial scale synthesis [10]. However, the toxicity and the environmental issues associated with the use of mercury-based compounds have
Graphical Abstract
Figure 1: Comparison of the hydration reactions of different alkynes in BMIm-BF4 catalysed by BF3·Et2O (blue)...
Scheme 1: Anodic oxidation of tetrafluoroborate anion.
Advances in mercury(II)-salt-mediated cyclization reactions of unsaturated bonds
- Sumana Mandal,
- Raju D. Chaudhari and
- Goutam Biswas
Beilstein J. Org. Chem. 2021, 17, 2348–2376, doi:10.3762/bjoc.17.153
- cyclization reactions that are performed with Hg(II) salts. These salts are also successfully applied in stoichiometric or catalytic amounts to form complex cyclic structures and natural products. Keywords: carbocyclic; catalyzed; cyclization; heterocyclic; mercury(II) salts; Introduction The use of
- manner as reductive elimination forms during the mercury removal process (Scheme 6). Mercury(II) salts had been effectively used to synthesize five-membered furanose derivatives with high stereoselectivity. Nicotra et al. developed Hg(OAc)2-mediated cyclization of hydroxy-alkene derivative 15 to form α-ᴅ
- chromatography [68] (Scheme 21). Mercury(II) salts had also been successfully utilized in the cyclization of ether derivatives 61 to form stereoselectively trans-4,5-disubstituted oxazolidine derivatives 62 (Scheme 22) [69]. Later it was reported, when homologous allyloxycarbamate derivative 63 was cyclized with
Graphical Abstract
Scheme 1: Schematic representation of Hg(II)-mediated addition to an unsaturated bond.
Scheme 2: First report of Hg(II)-mediated synthesis of 2,5-dioxane derivatives from allyl alcohol.
Scheme 3: Stepwise synthesis of 2,6-distubstituted dioxane derivatives.
Scheme 4: Cyclization of carbohydrate alkene precursor.
Scheme 5: Hg(II)-mediated synthesis of C-glucopyranosyl derivatives.
Scheme 6: Synthesis of C-glycosyl amino acid derivative using Hg(TFA)2.
Scheme 7: Hg(OAc)2-mediated synthesis of α-ᴅ-ribose derivative.
Scheme 8: Synthesis of β-ᴅ-arabinose derivative 18.
Scheme 9: Hg(OAc)2-mediated synthesis of tetrahydrofuran derivatives.
Scheme 10: Synthesis of Hg(TFA)2-mediated bicyclic nucleoside derivative.
Scheme 11: Synthesis of pyrrolidine and piperidine derivatives.
Scheme 12: HgCl2-mediated synthesis of diastereomeric pyrrolidine derivatives.
Scheme 13: HgCl2-mediated cyclization of alkenyl α-aminophosphonates.
Scheme 14: Cyclization of 4-cycloocten-1-ol with Hg(OAc)2 forming fused bicyclic products.
Scheme 15: trans-Amino alcohol formation through Hg(II)-salt-mediated cyclization.
Scheme 16: Hg(OAc)2-mediated 2-aza- or 2-oxa-bicyclic ring formations.
Scheme 17: Hg(II)-salt-induced cyclic peroxide formation.
Scheme 18: Hg(OAc)2-mediated formation of 1,2,4-trioxanes.
Scheme 19: Endocyclic enol ether derivative formation through Hg(II) salts.
Scheme 20: Synthesis of optically active cyclic alanine derivatives.
Scheme 21: Hg(II)-salt-mediated formation of tetrahydropyrimidin-4(1H)-one derivatives.
Scheme 22: Cyclization of ether derivatives to form stereoselective oxazolidine derivatives.
Scheme 23: Cyclization of amide derivatives induced by Hg(OAc)2.
Scheme 24: Hg(OAc)2/Hg(TFA)2-promoted cyclization of salicylamide-derived amidal auxiliary derivatives.
Scheme 25: Hg(II)-salt-mediated cyclization to form dihydrobenzopyrans.
Scheme 26: HgCl2-induced cyclization of acetylenic silyl enol ether derivatives.
Scheme 27: Synthesis of exocyclic and endocyclic enol ether derivatives.
Scheme 28: Cyclization of trans-acetylenic alcohol by treatment with HgCl2.
Scheme 29: Synthesis of benzofuran derivatives in presence of HgCl2.
Scheme 30: a) Hg(II)-salt-mediated cyclization of 4-hydroxy-2-alkyn-1-ones to furan derivatives and b) its mec...
Scheme 31: Cyclization of arylacetylenes to synthesize carbocyclic and heterocyclic derivatives.
Scheme 32: Hg(II)-salt-promoted cyclization–rearrangement to form heterocyclic compounds.
Scheme 33: a) HgCl2-mediated cyclization reaction of tethered alkyne dithioacetals; and b) proposed mechanism.
Scheme 34: Cyclization of aryl allenic ethers on treatment with Hg(OTf)2.
Scheme 35: Hg(TFA)2-mediated cyclization of allene.
Scheme 36: Hg(II)-catalyzed intramolecular trans-etherification reaction of 2-hydroxy-1-(γ-methoxyallyl)tetrah...
Scheme 37: a) Cyclization of alkene derivatives by catalytic Hg(OTf)2 salts and b) mechanism of cyclization.
Scheme 38: a) Synthesis of 1,4-dihydroquinoline derivatives by Hg(OTf)2 and b) plausible mechanism of formatio...
Scheme 39: Synthesis of Hg(II)-salt-catalyzed heteroaromatic derivatives.
Scheme 40: Hg(II)-salt-catalyzed synthesis of dihydropyranone derivatives.
Scheme 41: Hg(II)-salt-catalyzed cyclization of alkynoic acids.
Scheme 42: Hg(II)-salt-mediated cyclization of alkyne carboxylic acids and alcohol to furan, pyran, and spiroc...
Scheme 43: Hg(II)-salt-mediated cyclization of 1,4-dihydroxy-5-alkyne derivatives.
Scheme 44: Six-membered morpholine derivative formation by catalytic Hg(II)-salt-induced cyclization.
Scheme 45: Hg(OTf)2-catalyzed hydroxylative carbocyclization of 1,6-enyne.
Scheme 46: a) Hg(OTf)2-catalyzed hydroxylative carbocyclization of 1,6-enyne. b) Proposed mechanism.
Scheme 47: a) Synthesis of carbocyclic derivatives using a catalytic amount of Hg(II) salt. b) Proposed mechan...
Scheme 48: Cyclization of 1-alkyn-5-ones to 2-methylfuran derivatives.
Scheme 49: Hg(NO3)2-catalyzed synthesis of 2-methylenepiperidine.
Scheme 50: a) Preparation of indole derivatives through cycloisomerization of 2-ethynylaniline and b) its mech...
Scheme 51: a) Hg(OTf)2-catalyzed synthesis of 3-indolinones and 3-coumaranones and b) simplified mechanism.
Scheme 52: a) Hg(OTf)2-catalyzed one pot cyclization of nitroalkyne and b) its plausible mechanism.
Scheme 53: Synthesis of tricyclic heterocyclic scaffolds.
Scheme 54: HgCl2-mediated cyclization of 2-alkynylphenyl alkyl sulfoxide.
Scheme 55: a) Hg(OTf)2-catalyzed cyclization of allenes and alkynes. b) Proposed mechanism of cyclization.
Scheme 56: Stereoselective synthesis of tetrahydropyran derivatives.
Scheme 57: a) Hg(ClO4)2-catalyzed cyclization of α-allenol derivatives. b) Simplified mechanism.
Scheme 58: Hg(TFA)2-promoted cyclization of a γ-hydroxy alkene derivative.
Scheme 59: Synthesis Hg(II)-salt-mediated cyclization of allyl alcohol for the construction of ventiloquinone ...
Scheme 60: Hg(OAc)2-mediated cyclization as a key step for the synthesis of hongconin.
Scheme 61: Examples of Hg(II)-salt-mediated cyclized ring formation in the syntheses of (±)-fastigilin C and (...
Scheme 62: Formal synthesis of (±)-thallusin.
Scheme 63: Total synthesis of hippuristanol and its analog.
Scheme 64: Total synthesis of solanoeclepin A.
Scheme 65: a) Synthesis of Hg(OTf)2-catalyzed azaspiro structure for the formation of natural products. b) Pro...
Synthetic accesses to biguanide compounds
- Oleksandr Grytsai,
- Cyril Ronco and
- Rachid Benhida
Beilstein J. Org. Chem. 2021, 17, 1001–1040, doi:10.3762/bjoc.17.82
Graphical Abstract
Figure 1: Tautomeric forms of biguanide.
Figure 2: Illustrations of neutral, monoprotonated, and diprotonated structures biguanide.
Figure 3: The main approaches for the synthesis of biguanides. The core structure is obtained via the additio...
Scheme 1: The three main preparations of biguanides from cyanoguanidine.
Scheme 2: Synthesis of butylbiguanide using CuCl2 [16].
Scheme 3: Synthesis of biguanides by the direct fusion of cyanoguanidine and amine hydrochlorides [17,18].
Scheme 4: Synthesis of ethylbiguanide and phenylbiguanide as reported by Smolka and Friedreich [14].
Scheme 5: Synthesis of arylbiguanides through the reaction of cyanoguanidine with anilines in water [19].
Scheme 6: Synthesis of aryl- and alkylbiguanides by adaptations of Cohn’s procedure [20,21].
Scheme 7: Microwave-assisted synthesis of N1-aryl and -dialkylbiguanides [22,23].
Scheme 8: Synthesis of aryl- and alkylbiguanides by trimethylsilyl activation [24,26].
Scheme 9: Synthesis of phenformin analogs by TMSOTf activation [27].
Scheme 10: Synthesis of N1-(1,2,4-triazolyl)biguanides [28].
Scheme 11: Synthesis of 2-guanidinobenzazoles by addition of ortho-substituted anilines to cyanoguanidine [30,32] and...
Scheme 12: Synthesis of 2,4-diaminoquinazolines by the addition of 2-cyanoaniline to cyanoguanidine and from 3...
Scheme 13: Reactions of anthranilic acid and 2-mercaptobenzoic acid with cyanoguanidine [24,36,37].
Scheme 14: Synthesis of disubstituted biguanides with Cu(II) salts [38].
Scheme 15: Synthesis of an N1,N2,N5-trisubstituted biguanide by fusion of an amine hydrochloride and 2-cyano-1...
Scheme 16: Synthesis of N1,N5-disubstituted biguanides by the addition of anilines to cyanoguanidine derivativ...
Scheme 17: Microwave-assisted additions of piperazine and aniline hydrochloride to substituted cyanoguanidines ...
Scheme 18: Synthesis of N1,N5-alkyl-substituted biguanides by TMSOTf activation [27].
Scheme 19: Additions of oxoamines hydrochlorides to dimethylcyanoguanidine [49].
Scheme 20: Unexpected cyclization of pyridylcyanoguanidines under acidic conditions [50].
Scheme 21: Example of industrial synthesis of chlorhexidine [51].
Scheme 22: Synthesis of symmetrical N1,N5-diarylbiguanides from sodium dicyanamide [52,53].
Scheme 23: Synthesis of symmetrical N1,N5-dialkylbiguanides from sodium dicyanamide [54-56].
Scheme 24: Stepwise synthesis of unsymmetrical N1,N5-trisubstituted biguanides from sodium dicyanamide [57].
Scheme 25: Examples for the synthesis of unsymmetrical biguanides [58].
Scheme 26: Examples for the synthesis of an 1,3-diaminobenzoquinazoline derivative by the SEAr cyclization of ...
Scheme 27: Major isomers formed by the SEAr cyclization of symmetric biguanides derived from 2- and 3-aminophe...
Scheme 28: Lewis acid-catalyzed synthesis of 8H-pyrrolo[3,2-g]quinazoline-2,4-diamine [63].
Scheme 29: Synthesis of [1,2,4]oxadiazoles by the addition of hydroxylamine to dicyanamide [49,64].
Scheme 30: Principle of “bisamidine transfer” and analogy between the reactions with N-amidinopyrazole and N-a...
Scheme 31: Representative syntheses of N-amidino-amidinopyrazole hydrochloride [68,69].
Scheme 32: First examples of biguanide syntheses using N-amidino-amidinopyrazole [66].
Scheme 33: Example of “biguanidylation” of a hydrazide substrate [70].
Scheme 34: Example for the synthesis of biguanides using S-methylguanylisothiouronium iodide as “bisamidine tr...
Scheme 35: Synthesis of N-substituted N1-cyano-S-methylisothiourea precursors.
Scheme 36: Addition routes on N1-cyano-S-methylisothioureas.
Scheme 37: Synthesis of an hydroxybiguanidine from N1-cyano-S-methylisothiourea [77].
Scheme 38: Synthesis of an N1,N2,N3,N4,N5-pentaarylbiguanide from the corresponding triarylguanidine and carbo...
Scheme 39: Reactions of N,N,N’,N’-tetramethylguanidine (TMG) with carbodiimides to synthesize hexasubstituted ...
Scheme 40: Microwave-assisted addition of N,N,N’,N’-tetramethylguanidine to carbodiimides [80].
Scheme 41: Synthesis of N1-aryl heptasubstituted biguanides via a one-pot biguanide formation–copper-catalyzed ...
Scheme 42: Formation of 1,2-dihydro-1,3,5-triazine derivatives by the reaction of guanidine with excess carbod...
Scheme 43: Plausible mechanism for the spontaneous cyclization of triguanides [82].
Scheme 44: a) Formation of mono- and disubstituted (iso)melamine derivatives by the reaction of biguanides and...
Scheme 45: Reactions of 2-aminopyrimidine with carbodiimides to synthesize 2-guanidinopyrimidines as “biguanid...
Scheme 46: Non-catalyzed alternatives for the addition of 2-aminopyrimidine derivatives to carbodiimides. A) h...
Scheme 47: Addition of guanidinomagnesium halides to substituted cyanamides [90].
Scheme 48: Microwave-assisted synthesis of [11C]metformin by the reaction of 11C-labelled dimethylcyanamide an...
Scheme 49: Formation of 4-amino-6-dimethylamino[1,3,5]triazin-2-ol through the reaction of Boc-guanidine and d...
Scheme 50: Formation of 1,3,5-triazine derivatives via the addition of guanidines to substituted cyanamides [92].
Scheme 51: Synthesis of biguanide by the reaction of O-alkylisourea and guanidine [93].
Scheme 52: Aromatic nucleophilic substitution of guanidine on 2-O-ethyl-1,3,5-triazine [95].
Scheme 53: Synthesis of N1,N2-disubstituted biguanides by the reaction of guanidine and thioureas in the prese...
Scheme 54: Cyclization reactions involving condensations of guanidine(-like) structures with thioureas [97,98].
Scheme 55: Condensations of guanidine-like structures with thioureas [99,100].
Scheme 56: Condensations of guanidines with S-methylisothioureas [101,102].
Scheme 57: Addition of 2-amino-1,3-diazaaromatics to S-alkylisothioureas [103,104].
Scheme 58: Addition of guanidines to 2-(methylsulfonyl)pyrimidines [105].
Scheme 59: An example of a cyclodesulfurization reaction to a fused 3,5-diamino-1,2,4-triazole [106].
Scheme 60: Ring-opening reactions of 1,3-diaryl-2,4-bis(arylimino)-1,3-diazetidines [107].
Scheme 61: Formation of 3,5-diamino-1,2,4-triazole derivatives via addition of hydrazines to 1,3-diazetidine-2...
Scheme 62: Formation of a biguanide via the addition of aniline to 1,2,4-thiadiazol-3,5-diamines, ring opening...
Figure 4: Substitution pattern of biguanides accessible by synthetic pathways a–h.
Iodine-mediated hydration of alkynes on keto-functionalized scaffolds: mechanistic insight and the regiospecific hydration of internal alkynes
- Zachary Lee,
- Brandon R. Jones,
- Nyochembeng Nkengbeza,
- Michael Phillips,
- Kayla Valentine,
- Alexis Stewart,
- Brandon Sellers,
- Nicholas Shuber and
- Karelle S. Aiken
Beilstein J. Org. Chem. 2019, 15, 2747–2752, doi:10.3762/bjoc.15.265
- ; regiospecific hydration; Findings The Kucherov reaction is one of the most well-known approaches for the hydration of alkynes. This reaction, originally published in 1881, requires the use of mercury(II) salts in catalytic quantities [1][2]. Countless studies have shown that mercury-based compounds are
Graphical Abstract
Scheme 1: Proposed mechanism for the iodine-mediated hydration of terminal alkynes 1 [15].
Figure 1: 1H NMR investigations on the iodine-mediated hydration of 8 (the range of 1.75–5.25 ppm is displaye...
Figure 2: 1H—13C HSQC spectrum for α-iodo intermediate 9 in CD3CN in the range of 0.90–5.00 ppm (for 1H NMR s...
Scheme 2: Possible outcomes of the iodine-mediated hydration of asymmetric, internal alkynes with neighboring...
Scheme 3: Iodine-mediated hydration of asymmetric, internal alkynes 11a–e.
A reductive coupling strategy towards ripostatin A
- Kristin D. Schleicher and
- Timothy F. Jamison
Beilstein J. Org. Chem. 2013, 9, 1533–1550, doi:10.3762/bjoc.9.175
- alternative promoters were investigated to avoid the use of mercury(II) salts in the ketal deprotection (including MeI, H2O2, AgClO4/I2); however, these generally led to concomitant removal of the TBS groups. Ketone 19 was converted to the α,β-unsaturated ester 20 using the Peterson olefination [32
Graphical Abstract
Figure 1: Structures of the ripostatins.
Figure 2: Retrosynthesis of ripostatin A.
Scheme 1: Nickel-catalyzed reductive coupling of alkynes and epoxides.
Figure 3: Proposed retrosynthesis of ripostatin A featuring enyne–epoxide reductive coupling and rearrangemen...
Scheme 2: Potential transition states and stereochemical outcomes for a concerted 1,5-hydrogen rearrangement.
Scheme 3: Rearrangements of vinylcyclopropanes to acylic 1,4-dienes.
Scheme 4: Synthesis of cyclopropyl enyne.
Scheme 5: Synthesis of model epoxide for investigation of the nickel-catalyzed coupling reaction.
Scheme 6: Nickel-catalyzed enyne–epoxide reductive coupling reaction.
Scheme 7: Proposed mechanism for the nickel-catalyzed coupling reaction of alkynes or enynes with epoxides.
Scheme 8: Regioselectivity changes in reductive couplings of alkynes and 3-oxygenated epoxides.
Scheme 9: Enyne reductive coupling with 1,2-epoxyoctane.
Figure 4: Initial retrosynthesis of the epoxide fragment by using dithiane coupling.
Scheme 10: Synthesis of dithiane by Claisen rearrangement.
Scheme 11: Deuterium labeling reveals that the allylic/benzylic site is most acidic.
Scheme 12: Oxy-Michael addition to δ-hydroxy-α,β-enones.
Figure 5: Revised retrosynthesis of epoxide 5.
Scheme 13: Synthesis of functionalized ketone by oxy-Michael addition.
Figure 6: Retrosynthesis by using iodocylization to introduce the epoxide.
Scheme 14: Synthesis of ketone 57 using thiazolidinethione chiral auxiliary.
Figure 7: Retrosynthesis involving decarboxylation of a β-ketoester.
Scheme 15: Synthesis of β-ketoester 61.
Scheme 16: Decarboxylation of 61 under Krapcho conditions.
Scheme 17: Improved synthesis of 63 and attempted iodocyclization.
Figure 8: Retrosynthesis utilizing Rychnovsky’s cyanohydrin acetonide methodology.
Scheme 18: Synthesis of cyanohydrin acetonide and attempted alkylation with epoxide.
Scheme 19: Allylation of acetonide and conversion to aldehyde.
Scheme 20: Synthesis of the epoxide precursor by an aldol−decarboxylation sequence.
