Deep eutectic solvent-assisted one-pot synthesis of 2-aminothiazole and 2-aminoxazole derivatives

Choline chloride–urea-based deep eutectic solvent (DES) has been found to be a highly effective catalyst and reaction medium for the one-pot synthesis of 2-aminothiazole and 2-aminoxazole derivatives. Three-component reactions of active methylene compounds, urea or thiourea and N-bromosuccinimide NBS in deep eutectic solvent furnished structurally diverse 2-aminoxazoles and 2-aminothiazoles in good to excellent yields under mild reaction conditions and short reaction times. DES is inexpensive, biodegradable and more accessible in any laboratory and industry.     

A mild and efficient amidation of cyclic ethers catalyzed by rhodium caprylate

A small quantity of Rh₂(O₂CC₇H₁₅)₄ (2.5 mol % to 0.6 mol %) catalyzed the α-amidation of cyclic ethers under mild conditions, 35 °C, in the presence of electron-withdrawing p-chlorobenzenesulfonamide/PhI(OAc)₂ as the nitrene source, in CH₂Cl₂ for 4 h. The corresponding N-substituted amino cyclic ethers were successfully obtained in good yields (up to 87% based on 99% conversion) and compatibility with other oxidant sensitive structures in one-pot reaction.     

A novel and efficient synthesis of chiral C2-symmetric 1,4-diamines

A novel and efficient method for synthesis of (R,R)- and (S,S)-C₂-symmetric 1,4-diamines was established. The key steps are a combination of Pinacol Coupling and Corey-Winter olefination.     

A novel efficient protocol for preparation of 3-formyl-2-arylbenzo[b]furan derivatives

An efficient method for preparation of 3-formyl-2-arylbenzo[b]furan derivatives 4 from 3-chloro-2-(2-methoxyaryl)-1-arylprop-2-en-1-one 2 was developed, and the desired product was obtained in good to excellent yields. By converting 2-(2-methoxyphenyl)-3-oxo-3-phenylpropanal 1 to 2, the regioselectivity problem occurring in the reaction when using 1 as the starting material was successfully avoided. Furthermore, a one-pot procedure for the successive demethylation, cyclization, and hydrolysis was evolved, although the intermediate 3-(dibromomethyl)-2-phenylbenzo[b]furan 3a could be isolated. A plausible mechanism was proposed based on some in situ investigations.     

A novel and efficient synthesis of porphine

meso-Tetra(n-hexyloxycarbonyl)porphyrin was found to be converted into porphine, the mother compound of porphyrins, in a 77% yield when heated in aqueous sulfuric acid at 180 °C over 30 min under an inert atmosphere. The observation demonstrates that the substituted porphyrin serves as a novel and useful precursor for porphine.     

An alternative approach towards novel heterocycle-fused 1,4-diazepin-2-ones by an aromatic amidation protocol

The synthesis of new 1,4-diazepin-2-one derivatives starting from glycine or alanine aminoacids is presented. The key cyclization step includes the PIFA mediated formation of N-acylnitrenium ions and their subsequent intramolecular trapping by an (hetero)aromatic ring. The so-promoted aromatic amidation process takes place without loss of enantiomeric purity when optically pure methoxyamide precursors are employed.     

The synthesis of C-13 functionalized pleuromutilins via C-H amidation and subsequent novel rearrangement product

Multi-gram quantities of C-13 functionalized pleuromutilin intermediates were synthesized under mild conditions via C-H amidation chemistry. The initial work was performed using rhodium catalysis. However, the highest yields were achieved using silver catalysis, resulting in stereoselective oxazolidinone formation. The ring closure was performed in the presence of a C-12 vinyl group, which differentiates it from historical methods involving the saturated pleuromutilin skeleton. A highlight of this vinyl template is a unique tetracyclic rearrangement product that can be generated from its treatment with hydrochloric acid and heat.     

Graphene oxide (GO) catalyzed transamidation of aliphatic amides: An efficient metal-free procedure

Transamidation involves direct interconversion of an amide with amine, and represents an alternative to the common method of amide formation from the reaction of carboxylic acid with an amine. While the carboxamides have huge potential in biological systems and polymer industries, their formation from carboxylic acids requires activation by a suitable catalyst. A metal-free transamidation of aliphatic amide with aromatic amine catalyzed by graphene oxide (GO) has been developed and established as a general, synthetically useful and selective procedure. Graphene oxide bearing several carboxylic acids on the edges and having large surface area acts as an efficient and recyclable catalyst for transamidation.     

Selective deprotection and amidation of 2-pyridyl esters via N-methylation

The 2-pyridyl residue serves as a protecting group for various carboxylic acids. The protecting group is selectively cleaved under mild conditions via N-methylation of the pyridyl group. During the deprotection process, the various functional groups as well as the other ester moieties remain intact. The N-methylated active esters can be subsequently transformed into amides.     

5H-3-oxa-Octafluoropentanesulfonyl fluoride: a novel and efficient condensing agent for esterification, amidation and anhydridization

The use of 5H-3-oxa-octafluoropentanesulfonyl fluoride (HCF₂CF₂OCF₂CF₂SO₂F) as a novel and efficient condensing reagent for esterification of carboxylic acids with alcohols and amidation of carboxylic acids with amines in the presence of 1,3-diazabicyclo[5.4.0]-undec-7-ene (DBU) is reported. HCF₂CF₂OCF₂CF₂SO₂F cannot serve as a condensing agent for anhydridization of carboxylic acids, however, HCF₂CF₂OCF₂CF₂SO₂F/(CH₃)₃SiCN system can mediate anhydridization of some aromatic carboxylic acids.     

Practical and efficient synthesis of N-halo compounds

A practical and efficient synthesis of N-halo compounds is described. Treatment of primary and secondary amines or amides with sodium hypohalite in the presence of tert-butanol and acetic acid afforded N-halo compounds in 90-100% yield.     

A mild and efficient one-pot synthesis of 2-dihydroimidazoles from aldehydes

The reactions of various aldehydes and 1,2-diamines followed by NXS treatment proceed at 0 °C-rt to give the corresponding dihydroimidazoles in high yields. The reaction is mild, and many functional groups such as halogens, nitriles, and esters can exist.     

An efficient synthesis of 4,5-dihydronaphtho[2,1-b]furan through a novel ring transformation of 2H-pyran-2-one

An innovative route for the synthesis of substituted naphtho[2,1-b]furan has been delineated through a ring transformation reaction of suitably functionalized 2H-pyran-2-ones by reaction with 6,7-dihydro-5H-benzofuran-4-one, in good yield.     

A one-pot efficient synthesis of highly functionalized 5,6-dihydronaphthalenes from 2H-pyran-2-one

A one-pot efficient synthesis of highly functionalized 5,6-dihydronaphthalenes has been delineated through carbanion-induced ring transformation of 2H-pyran-2-ones by 2-cyclohexenone.     

An efficient microwave assisted synthesis of novel class of Rhodanine derivatives as potential HIV-1 and JSP-1 inhibitors

(Z)-5-(2-(1H-Indol-3-yl)-2-oxoethylidene)-3-phenyl-2-thioxothiazolidin-4-one (7a-q) derivatives have been synthesized by the condensation reaction of 3-phenyl-2-thioxothiazolidin-4-ones (3a-h) with suitably substituted 2-(1H-indol-3-yl)-2-oxoacetaldehyde (6a-d) under microwave condition. The thioxothiazolidine-4-ones were prepared from the corresponding aromatic amines (1a-e) and di-(carboxymethyl)-trithiocarbonyl (2). The aldehydes (6a-h) were synthesized from the corresponding acid chlorides (5a-d) using HSnBu₃.     

A concise synthesis of novel naphtho[a]carbazoles and benzo[c]carbazoles

Starting from simple indole precursors the synthesis of naphtho[a]carbazoles and benzo[c]carbazoles is described. Key steps include the use of the Suzuki-Miyaura reaction to afford 2- or 3-aryl substituted indoles, as well as a potassium t-butoxide and light assisted aromatic ring-forming reaction.     

A novel route for the synthesis of highly congested aryl-tethered 2-aminobenzylamines through ring transformation of 2-pyranones

An innovative and efficient synthesis of highly congested 2-amino-3-aminomethyl-5-methylsulfanyl/sec-aminobiphenyl-4-carbonitriles 4 has been delineated through base catalyzed ring transformation of 6-aryl-4-methylsulfanyl/sec-amino-2H-pyran-2-one-3-carbonitriles 1 with Boc-protected 1,3-diamino-2-propanone 2, followed by TFA catalyzed hydrolysis of the intermediate [3-tert-butoxycarbonylaminomethyl-4-cyano-5-methylsulfanyl/sec-aminobiphenyl-2-yl]carbamic acid tert-butyl ester 3 in moderate yields as the TFA salts.     

Synthesis and characterization of novel optically active poly(amide-imide)s via direct amidation

N,N′-Pyromelliticdiimido-di-l-methionine (3) was prepared from the reaction of pyromellitic dianhydride (1) with l-methionine (2) in glacial acetic acid and pyridine solution at refluxing temperature. The direct polycondensation reaction of the monomer diimide-diacid (3) with 1,3-phenylenediamine (4a), 1,4-phenylenediamine (4b), 2,6-diaminopyridine (4c), 3,5-diaminopyridine (4d), 4,4′-diaminodiphenylether (4e) and 4,4′-diaminodiphenylsulfone (4f) was carried out in a medium consisting of triphenyl phosphate, N-methyl-2-pyrolidone, pyridine and calcium chloride. The resulting poly(amide-imide)s having inherent viscosities 0.45-0.53 dl g⁻¹ were obtained in high yields and are optically active and thermally stable. All of the above compounds were fully characterized by IR spectroscopy, elemental analyses and specific rotation. Some structural characterization and physical properties of these new optically active poly(amide-imide)s are reported.     

A novel and efficient approach for the amidation of C-terminal peptides

A highly efficient and practical synthesis of C-terminal amidated peptides has been developed. According to this approach, amidation of the C-terminus of peptides was carried out using NH₄Cl, alkylammonium chloride (RNH₃Cl) and semicarbazide hydrochloride in the presence of TBTU as a coupling reagent and a tertiary amine as the base at room temperature in good to high yields. Some opioid peptides such as enkephalin derivatives were synthesized according to this novel method.     

H_2SO_4-SiO_2:Highly efficient and novel catalyst for the Ferrier-type glycosylation

<正>Sulfuric acid immobilized on silica gel is designed as a very useful catalyst for synthesis of 2,3-unsaturated glycopyranosides. This handy,metal-free,environment friendly transformation provides high yields andα-stereoselectivities in a very few amount (0.02 eq.) of catalyst and in short reaction times(10 min).