1-Acylamino-2-Chlorovinylphosphonium Salts as Versatile Reagents for Preparation of 1,3-Azole Derivatives

Abstract

The substituted vinylphoephonium salts (I) were obtained by the reaction of readily available N-(1,2,2-trichloro-ethyl)carboxamides with triphenylphosphine. These salts are active electrophilic reagents suitable for syntheeie of novel typee of phosphorylated aldehydes (11), mesome-ric ylides-betainee (111) and enamides (IV,V) All those compound8 undergo intramolecular cyclizations leading to different azolylphoephonium salte (VI-IX).     

Low-Dentate Reagents as Titrants in Complexometry: Selection of Promising Reagents

An approach was proposed to the selection of promising titrants using computer databases. The approach takes into account the absolute and relative stabilities of complexes formed in the titration and also the competing protolysis reactions. Thirty-two low-dentate reagents were selected for determining five transition metals. Under certain conditions, these reactions give clear jumps in logarithmic titration curves. With the selected reagents, we obtained potentiometric procedures equally precise and more selective than the procedures using EDTA.     

New Method for the Synthesis of 2-Acylamino-1-benzothiophene-3-carboxamide Derivatives from the Corresponding Esters

An unusual chemical method has been applied for the preparation of 1-benzothiophene-3-carboxamide derivatives from esters by reaction with lithium amide in tetrahydrofurane.     

2-Aminothiophene. Heterocyclization of benzylthionitriles

Synthesis of unstable 2-aminothiophene by way of its hydrochloride salt has been achieved in excellent yield. The key reaction in the scheme involves a novel heterocyclization of benzylthionitriles, which would appear to have general utility. Spectral and physical properties are tabulated and a possible mechanism is proposed.     

Synthesis and Heterocyclization of 3-Arylaminothiocrotonanilides

Reactions of acetylthioacetanilide with arylamines in acetic acid in the presence of sodium acetate give 3-arylaminothiocrotonanilides in good yields. When treated with -bromoacetophenone in acetone, these products are converted to substituted 4-hydroxy-²-thiazolinium bromides, one of which was dehydrated to obtain the corresponding thiazolium bromide. The structure of the heterocyclization products was confirmed by single crystal X-ray diffraction and NMR study of 2-acetonylidene-3,4-diphenyl-2,3-dihydrothiazole formed by dehydration of the corresponding ²-thiazolinium salt with simultaneous hydrolysis.     

Heterocyclization Reactions of 2-(2-Propynylthio)-4(1H)-quinazolinone Derivatives when Treated with Electrophilic and Nucleophilic Reagents

Reaction of the potassium salt of 2-thioquinazolin-4-one with propargyl halides leads to formation of 2-propargylthioquinazolin-4-one derivatives, which undergo heterocyclization when they are treated with electrophilic or nucleophilic reagents and, depending on the nature of the cyclization agent, leads to formation of tricyclic systems with angular or linear structure.     

Studies on Spiroheterocycles,Part II: Heterocyclization of the Spiro Compounds Containing Cyclohexanone and Thiobarbituric Acid with Different Bidentate Nucleophilic Reagents

The reaction of thiobarbituric acid with different diarylidene ketones 1a–c yields the spiro compounds 2a–c. The diarylidene derivatives 3a–c are synthesized by the condensation of spiro compounds 2a–c with different aldehydes. A series of spiro heterocycles compounds 4a–l, 5a–l, 6a–l, 7a–l, 8a–l, and 9a–l are synthesized from the diarylidene compounds. The structures of the compounds are ascertained from their analytical and spectral data. Some of the compounds are screened for their biological activities.     

Polycondensation of (NPCl2)3 with Bifunctional Reagents

Abstract

The reaction of hexachlorocyclotriphosphazene and hydroquinone in the two-phase solvent system tetrahydrofuran/aqueous NaCl-NaOH solution leads in the beginning of the polycondensation to a mixture of oligomers with formula N₃P₃Cl₅-[P-OC₆H₄O)-N₃P₃Cl₄]_n-(p-OC₆H₄)-N₃P₃Cl₅. The first compound (n=0) in this series could be isolated in a pure state. Two others have been identified by spectroscopic methods. As expected, the addition of a phase-transfer catalyst (Bu₄NBr) accelerates the polymerization reaction. In addition to the oligomers mentioned before two isomers with formula N₃P₃Cl₄-(p-OC₆H₄O)₂-N₃P₃Cl₄ were formed in the reaction mixture together with large amounts of polymeric material. One of these isomers was obtained as a pure compound in a very low yield. The X-ray crystal structures of N₃P₃Cl₅-(P-OC₆H₄O)-N₃P₃Cl₅ and N₃P₃Cl₄-(P-OC₆H₄O)₂-N₃P₃Cl₄ will be compared. The structural data in combination with ³¹P NMR data of various reaction mixtures provide some clues for the structure of the polymers, formed ultimately. The reaction pathway during the polycondensation will be discussed and compared with that of the polycondensation of (NPCl₂)₃ with p-phenylenediamine.     

2-Oxocephems. Synthesis and Properties of 7-Acylamino-2-oxocephem-4-carboxylic Acids

A synthesis of (6 R, 7 R)-7-acylamino-2-oxocephem-4-carboxylic acids from penicillins is reported based on the formation of the 2-oxocephem system in an intramolecular Wittig condensation. An interesting steric effect of the acylamino grouping on the course of this key step was used to advantage. Some physical and biological properties of this new type of Δ³-cephem are described.     

Heterocyclization of Orthoaminoester and Orthoamino-nitrile-thieno[2, 3-c]pyridine: The Facile Synthesis of Fused Pyridothienopyrimidines

A highly efficient and versatile synthetic approach to the synthesis of pyrido[4′, 3′: 4]thieno[2,3-d]pyrimidines (4, 14, 15, 21) and their heterofused (e.g., triazolo-, triazino-, imidazo-, and tetrazolo-,) pyridothienopyrimidines (5–9, 16, 17, 22–24) is described utilizing 2-amino-3-cyano-4,5,6,7-tetrahydro-thieno[2,3-c]pyridine-6-carboxylic acid ethyl ester ( 2 ) and diethyl 2-isothio-cyanate-4,5,6,7-tetrahydrothieno[2,3-c]pyridine-3,6-dicarboxylate ( 10 ) as starting materials.     

Regioselective Heterocyclization of 3-(Cyclohex-2′-enyl)-4-hydroxy-6-methylpyran-2-one

Summary.  Regioselective heterocyclization of 3-(cyclohex-2′-enyl)-4-hydroxy-6-methyl pyran-2-one with various reagents afforded different heterocycles. With N-iodosuccinimide in acetonitrile at 0–5°C it gave 6-methyl-9′-iodo-2′-oxabicyclo[3.3.1]nonano[3,2-c]pyran-2-one, with C₅H₅NHBr₃ or C₆H₁₂N₄HBr₃ in CHCl₃ at 0–5°C it furnished 6-methyl-9′-bromo-2′-oxabicyclo[3.3.1]nonano[3,2-c]pyran-2-one. Cold concentrated H₂SO₄ lead to 6-methyl-2′-oxabicyclo[3.3.1]nonano[3,2-c]pyran-2-one, whereas PdCl₂(PhCN)₂ in C₆H₆ at 80°C afforded 9-methyl benzofuro[3,2-c]pyran-2-one. Corresponding author. E-mail: kcm@klyuniv.ernet.in Received December 27, 2001. Accepted (revised) March 1, 2002     

Stable and Storable N(CF3)2 Transfer Reagents

Fluorinated groups are essential for drug design, agrochemicals, and materials science. The bis(trifluoromethyl)amino group is an example of a stable group that has a high potential. While the number of molecules containing perfluoroalkyl, perfluoroalkoxy, and other fluorinated groups is steadily increasing, examples with the N(CF₃)₂ group are rare. One reason is that transfer reagents are scarce and metal-based storable reagents are unknown. Herein, a set of Cu^I and Ag^I bis(trifluoromethyl)amido complexes stabilized by N- and P-donor ligands with unprecedented stability are presented. The complexes are stable solids that can even be manipulated in air for a short time. They are bis(trifluoromethyl)amination reagents as shown by nucleophilic substitution and Sandmeyer reactions. In addition to a series of benzylbis(trifluoromethyl)amines, 2-bis(trifluoromethyl)amino acetate was obtained, which, upon hydrolysis, gives the fluorinated amino acid N,N-bis(trifluoromethyl)glycine.     

Heterocyclization of acetylketeneN,S-acetals with benzoyl cyanamide

N-Unsubstituted mono- and diacetylketeneN,S-acetals undergo cyclization with benzoyl cyanamide to form 2-amino-4-methylthiopyrimidine derivatives. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2073–2075, November, 1997.