Novel synthesis of 2-amino-3-hetaryl-4(5H)-oxothiophenes

3-Cyano-3-hetaryl-2-oxopropyl thioacetates were obtained by the acylation of hetarylacetonitriles with acetylmercaptoacetyl chloride. Their reaction with amines led to the formation of 2-amino-3-hetaryl-4(H)-oxothiophenes. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 680–685, May, 2006.     

Intramolecular Nicholas reaction: stereoselective synthesis of 5-alkynylproline derivatives

The intramolecular Nicholas reaction of propargylic alcohols derived from N, N-acyl-diprotected omega-semialdehydes obtained from glutamic acid provided stereoselectively 5-alkynylproline derivatives. The suitable choice of the N-protecting group (tosyl or benzoyl derivative) permitted control of the stereochemistry during the ring formation. Semiempirical calculations of the species involved in the cyclization support the observed stereochemistry.     

Synthesis of some 3-EthoxycarbonyI-5-hydroxy-4-oxo-2-pyrroline derivatives from 3(2H)furanones

A number of 3-ethoxycarbonyl-5-hydroxy-2-methyl-5-or-1,5-substituted 4-oxo-2-pyrrolines have been prepared, respectively, by the action of ammonium hydroxide or primary aliphatic amines on 2-arylidene or 2-N-acetyl-N-arylaminomethylene-4-ethoxycarbonyl-5-methyl-3(2H)furanones. The structures of these prepared compounds have been determined by spectroscopic data and chemical means.     

Intramolecular (4+3) cycloadditions of nitrogen-tethered epoxy enosilanes for the synthesis of heteropolycycles

Furans bearing epoxy enolsilane units linked by a nitrogen heteroatom tether undergo intramolecular (4 + 3) cycloadditions to generate bis-heteroatomic polycyclic adducts having piperidine moieties in their frameworks. The cycloadducts, ultimately derived from furfural, a renewal chemical feedstock, are obtained with up to 4:1 dr and with ee retained from the epoxide.     

A new stereoselective synthesis of 2-amino-4,5-dihydrothiophene-3-carbonitrile derivatives

A new stereoselective method for the synthesis of trans-isomers of 2-amino-4-aryl-5-benzoyl-4,5-dihydrothiophene-3-carbonitriles was proposed. The method involves base-catalyzed reactions of phenacyl thiocyanate with 3-(het)aryl-2-cyanoprop-2-enethioamides. (4R,5S/4S,5R)-2-Amino-5-benzoyl-4-(2-chlorophenyl)-4,5-ihydrothiophene-3-carbonitrile was structurally characterized by X-ray diffraction analysis. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1379–1383, July, 2007.     

Cyclocondensation of 3-acetylfuran-2(5H)-ones with benzylidenemalononitrile. Synthesis of 3-(5-amino-4,6-dicyanobiphenyl-3-yl)furan-2(5H)-ones

Russian Journal of Organic Chemistry -     

13C and 1H NMR analysis of the nitration products of 2-amino-4-oxo-(3H)-5-trifluoromethylquinazoline and 2-amino-4-oxo-(3H)-5-fluoroquinazoline

Nitration of 2-amino-4-oxo-(3H)-5-trifluoromethylquinazoline is shown to occur exclusively at C⁶ as determined from an analysis of long range ¹H and ¹⁹F scalar couplings to ring carbons. Nitration of 2-amino-4-oxo-(3H)-5-fluoroquinazoline is found to occur both at C⁶ and C⁸ as evident from an analysis of the ¹⁹F and ¹H couplings of the ring protons.     

Efficient regioselective synthesis of 6-amino-5-benzoyl-1-substituted 2(1H)-pyridinones

[Reaction: see text]. A regioselective and efficient approach toward 6-amino-5-benzoyl-1-substituted 2(1H)-pyridinones by reaction of acyclic ketene aminals with propiolic acid ester was developed. The effect of the solvent and temperature on the regioselectivity of the reaction and the compatibility of the target compounds to functional group manipulations was examined. Substrates with an ortho substituent build atropisomers due to the restricted rotation around the C-N bond. The enantiomers were separated, and the barrier of rotation was determined experimentally. Quantum chemical calculations allowed a ranking of the barrier heights, and a new mechanism of rotation by deformation of the central pyridinone moiety is proposed.     

Concise synthesis of 2-amino-4(3H)-quinazolinones from simple (Hetero)aromatic amines

A novel and simple method of preparation of 2-alkylaminoquinazolin-4-ones with fused heteroaromatic rings from easily accessible (hetero)aromatic amines is described. The method is very efficient, and the 2-alkylaminoquinazolinone derivatives are obtained in three steps without chromatographic purification. The key step is the ring closure of the N-protected guanidine intermediates by intramolecular Friedel-Craft's type substitution.     

Synthesis of 5-alkoxy-4-amino-3-bromo-2(5H)-furanones containing benzene rings

Using KF as base and THF as solvent, different 5-alkoxy-3,4-dibromo-2(5H)-furanones were reacted with amines containing a benzene ring structure by Michael addition–elimination reaction at room temperature or 40 °C to give twenty-three 5-alkoxy-4-amino-3-bromo-2(5H)-furanones containing benzene rings, with yields of 21–86 % (mostly over 64 %). The structures of all the newly synthesized compounds were elucidated and confirmed by FTIR, UV, ¹H NMR, ¹³C NMR, and mass spectroscopy, elemental analysis, and X-ray single-crystal diffraction. This rapid synthesis of the series of 2(5H)-furanones derivatives with different bioactive units is not only an important synthetic strategy for 2(5H)-furanone derivatives but also a basis for synthesis of potential drug molecules for activity testing.     

A simple one-step synthesis of 3-amino-2,4(1H,3H)quinazolinediones

Anthranilic acids and alkyl carbazates in refluxing quinoline give high yields of 3-arnino-2,4(1H,3H)-quinazolinediones.     

Application of the Blaise reaction: stereoselective synthesis of (4R)-tert-butyl 3-amino-4-trimethylsilyloxy-2-alkenoates from (R)-cyanohydrins

O-Trimethylsilyl protected (R)-cyanohydrins 3 react with Reformatsky reagents from tert-butyl 2-bromoesters 4 and zinc dust (Blaise reaction) to give the corresponding addition products in high yields. Workup with an aqueous solution of NH₄Cl at low temperature gives (4R)-tert-butyl 3-amino-4-trimethylsilyloxy-2-alkenoates (R)-5 without racemization. Hydrogenation of the alkenoates 5 to the corresponding tert-butyl β-amino-γ-hydroxyalkanoates 6, resulting in a mixture of two diastereoisomers, was only possible under special hydrogenation conditions. With HCl in dichloromethane compounds 6 cyclize to the corresponding β-amino-γ-hydroxybutyrolactones 8.     

A simple synthesis of 5-substituted-thiophene-2 (3H)-thiones

Treatment of 1-alkyne and allene derivatives successively with two equivalents of n-Buli, one equivalent of CS₂ and then an electrophile yielded novel 5-substituted-thiophene-2 (3H)-thiones $\text{4}$.     

First stereoselective synthesis of (4aS,5R)-4,4a,5,6,7,8-hexahydro-4a,5-dimethyl-2(3H)-naphthalenone

The synthesis of enantiomerically pure (4aS,5R)-hexahydro-4a,5-dimethyl-2(3H)-naphthalenone (−)-1 is described for the first time. The synthesis starts from (R)-3-methylcyclohexanone and involves the preparation of Piers enol lactone 6 in its enantiopure form as the key intermediate. Treatment of (+)-6 with methyl lithium followed by an intramolecular aldol reaction gives the bicyclic enone (−)-1.