Ambident isothiocyanatomethanide anion for regioselective synthesis of thiazoles

Under the action of methyl isothiocyanate, the ambident isothiocyanatomethanide anion, which was generated by deprotonation of methyl isothiocyanate with lithium diisopropylamide, was readily and selectively transformed to 5-methylaminothiazole-2-thiolate. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 541–542, March, 1998.     

Synthesis of trisubstituted thiazoles by ligand-free palladium-catalyzed direct 5-arylation of 2,4-disubstituted thiazoles under conventional and microwave-assisted heating

Trisubstituted thiazoles were synthesized with excellent yields using ligand-free, palladium-catalyzed, direct 5-arylation of 2,4-disubstituted thiazole and conventional or microwave-assisted heating. The palladium-catalyzed reaction yields were significantly influenced by LiCl additive, solvent, and heating method. The reaction times were reduced dramatically by employing microwave radiation instead of conventional heating. The synthetic methods can be applied to diverse 2,4,5-trisubstituted thiazoles by varying the aryl bromide and disubstituted thiazole reactants.     

Synthesis and characterization of new pyrazole-based thiazoles

A series of new 5-(heteroaryldiazenyl)thiazole incorporating pyrazole moiety have been synthesized through coupling of the thiazole with the appropriate heteroaryldiazonium salts. The newly synthesized compounds were characterized by elemental analysis, spectroscopic (IR, ¹H NMR, and Mass) data, and alternative synthesis whenever possible.     

Efficient access to 5-substituted thiazoles by a novel metallotropic rearrangement

A novel rearrangement process involving the migration of trimethylstannanyl or trimethylsilanyl groups around the thiazole ring provides access to either 2- or 5-metallated thiazoles by tuning the reaction conditions. The proposed mechanism, based on experimental evidence, is characterized by the catalytic role of thiazole bisadducts as metal-transfer agents.     

Selective synthesis of 2-substituted 4-carboxy oxazoles, thiazoles and thiazolidines from serine or cysteine amino acids

The synthesis of new 4-carboxy oxazoles, thiazoles and thiazolidines by condensation of serine or cysteine with aldehydes or acids is described. Due to the optimization of a mild and selective procedure, which takes advantage of the positive effect of microwave irradiation on the MnO₂ mediated oxidation step, the 2-substituted-4-carboxy derivatives can be obtained in multi-gram scale. Examples of coordination chemistry to Ni(II) and Co(II) are described.     

Palladium-catalyzed direct arylation of thiazoles with aryl bromides

Thiazole, 2-phenyl or -alkyl substituted one and benzothiazole are efficiently arylated with aryl bromides at the 2- and/or 5-position(s) in the presence of Pd(OAc)₂ and a bulky phosphine ligand using Cs₂CO₃ as base. 2-Phenyl-5-thiazolecarboxanilide undergoes successive diarylation at the 4- and 5-positions accompanied by decarbamoylation.     

Novel one-pot expeditious synthesis of 2,4-disubstituted thiazoles through a three-component reaction under solvent free conditions

An expeditious one pot method has been developed for the synthesis of 2,4-disubstituted thiazoles under solvent free conditions via a multicomponent approach. Substituted thiazoles were synthesized with high yields by the reaction of cyclic ketones, thiosemicarbazide, and phenacyl bromides or 3-(2-bromoacetyl)-2H-chromen-2-ones in a shorter reaction time with high purity via simple purification technique.     

NBS-mediated sequential one-pot synthesis of multifunctionalized thiazoles and thiophenes from 1,3-dicarbonyl compounds and mercaptonitrile salts

A NBS-mediated sequential one-pot synthesis of multifunctionalized thiazoles and thiophenes from 1,3-dicarbonyl compounds and mercaptonitrile salts has been developed under mild conditions. This transformation involves sequential bromination/S_N2 alkylation/Thorpe–Ziegler cyclization/regio-selective elimination of a –COR group, affording the desired products in moderate to good yields. The sequence of the leaving reactivity of –COR groups was determined and a possible mechanism was proposed.     

Synthesis of condensed thiazoles. (Review)

Data on the synthesis of thiazoles systems condensed with heterocycles are classified. The principal directions in the practical application of these substances are briefly discussed. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 167–190, February, 2006.     

A convenient synthesis of 2-acyl benzothiazoles/thiazoles from benzothiazole/thiazole and N,N'-carbonyldiimidazole activated carboxylic acids

A convenient and efficient strategy for the synthesis of 2-acyl benzothiazoles/thiazoles has been developed. The treatment of benzothiazole/thiazole with allylic Grignard reagents readily generates the corresponding 2-Grignard reagents, which is followed by a reaction with N,N'-carbonyldiimidazole activated carboxylic acids to afford various 2-acyl benzothiazoles/thiazoles products. The synthetic method is applicable to a wide array of carboxylic acids and allows easy access to 2-acyl benzothiazoles/thiazoles with considerable yields under mild reaction conditions.     

Green synthesis of some new thiopyrano[2,3-d][1,3]thiazoles using lemon juice and their antibacterial activity

A simple green method has been developed for the synthesis of a series of new 3-phenyl-6-(substituted)-thiopyrano[2,3-d]thiazole-2,5,7(6H)-triones, 6-cyano-2-oxo-3-phenyl-thiopyrano[2,3-d]thiazoles, 3-phenyl-3,5,5a,11b-tetrahydro-2H,6H-chromeno-[4′,3′:4,5]thiopyrano[2,3-d]thiazole-2,6-dione and 5-amino-6-cyano-2-oxo-3-phenyl-3,7-dihydro-2H-thiopyrano[2,3-d]thiazoles via hetero-Diels–Alder reaction by conventional method and green method using lemon juice as natural acid. The structure of all the newly synthesized compounds was interpreted by elemental analyses and spectral data. The synthesized compounds were evaluated for their in vitro antibacterial activity against some pathogenic bacteria. This study is a platform for the future design of more potent antimicrobial agents.     

Regiocontrolled synthesis of substituted thiazoles

The regiocontrolled synthesis of 2,5-disubstituted and 2,4,5-trisubstituted thiazoles from ethyl 2-bromo-5-chloro-4-thiazolecarboxylate 1 using sequential palladium-catalyzed coupling reactions is described. [reaction: see text]     

Bromination of Enamines from Tertiary Amides Using the Petasis Reagent: A Convenient One-Pot Regioselective Route to Bromomethyl Ketones

An original one-pot synthesis of bromomethyl ketones is achived using the Petasis reagent (dimethyltitanocene) as a key for enamine generation. Several amides were used to test the limits of the procedure by changing either the alkyl chain R or the amino portion of the starting materials. The enamines generated in situ were allowed to react with bromine at low temperature followed by hydrolysis to yield bromomethyl ketones in excellent yields (85 to 95%). Mechanistic details and optimum conditions for the reaction are briefly discussed. The present approach offers several advantages such as regioselectivity in enamine formation, good yields, mild reaction conditions, and ease of experimentation.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource: Full experimental and spectral details.]     

Iodine-promoted direct sulfenylation of 2,3-dihydroimidazo[2,1-b]thiazoles with disulfides

A novel and facile method for the direct sulfenylation of 2,3-dihydroimidazo[2,1-b]thiazoles with disulfides has been developed. The transformation is promoted by iodine under metal-free conditions, providing the corresponding products in moderate to good yields.     

Novel route to the synthesis of 4-quinolyl isothiocyanates

4-Quinolyl isothiocyanates were synthesized in a regiospecific fashion from the corresponding 4-chloroquinolines and silver thiocyanate in refluxing toluene. The products were isolated in quantitative yield and high purity (>95%) by simple filtration and concentration. Reactivity and mechanism of the reaction are discussed. The new approach would provide a new mean which had been lacking for the synthesis of functionalized 4-quinolinyl isothiocyanate.     

Convenient synthetic approach to 2,4-disubstituted quinazolines

[reaction: see text] 2,4-Dialkyl or aryl quinazolines have been prepared in three steps starting from easily available anilides. A photochemically induced Fries rearrangement of the anilides gave several ortho-aminoacylbenzene derivatives that were acylated at the NH2. These acylamides underwent rapid cyclization to 2,4-disubstituted quinazolines (and benzoquinazolines) in the presence of ammonium formate under microwave activation. This procedure is compatible with different functional groups and allowed also the preparation of new quinazolines derived from naturally occurring amino acids.     

Convenient synthesis of porphine

Porphine formation from pyrrole and formaldehyde was examined in detail. Under optimized conditions, 9 mg of crystalline porphine was obtained per 1 ml of pyrrole.     

A new facile approach to N-alkylpyrroles from direct redox reaction of 4-hydroxy-l-proline with aldehydes

An unprecedented acetic acid-catalyzed efficient access to N-alkylpyrroles from reaction of 4-hydroxy-L-proline with a variety of aldehydes has been achieved in good to excellent yields under mild reaction conditions.     

A rapid, four-component synthesis of functionalized thiazoles

An efficient synthesis of 2-(dialkylamino)-4-phenyl)-1,3-thiazol-5-yl)(phenyl)methanone using acid chlorides, secondary amines, 2-bromoacethophenone and ammonium thiocyanate is described.