Deoxygenation of pyridine N‐oxides with dimethylthiocarbamoyl chloride

Treatment of pyridine N‐oxides with dimethylthiocarbamoyl chloride in boiling acetonitrile effects chemoselective deoxygenation to pyridines.     

Studies with S‐alkylpyrimidine: New route for the synthesis derivatives of isoxazol,pyrazolo[1,5‐a]pyrimidine,pyridazine, pyridine,thieno[2,3‐b]pyridine and thiophene of potential anti‐HIV

Derivatives of thiophene, thieno[2,3‐b]pyridine, pyridine, isoxazol, pyrazolo[1,5‐a]pyridine, pyridazine linked with s‐pyrimidine derivative have been synthesized and tested for antimicrobial and antifungal activities. The structure of the newly synthesized compounds have been established on the basis of their analytical and spectral data.     

Synthesis and liquid crystalline properties of novel pyridine derivatives

The treatment of 4‐hydroxypyridine with cholestery p‐(ω‐bromoalkyloxy)benzoates in N,N‐dimethylformamide containing K₂CO₃ gave cholestery p‐[ω‐(4‐pyridyloxy)alkyloxy]benzoates, which exhibited liquid crystalline properties     

Synthesis of two potential heterocyclic amine food mutagens

The syntheses of two potential food mutagens formed during cooking, 2‐amino‐3,6,7‐trimethyl‐3H‐imidazo[4,5‐b]pyridine ( 1 ) and 2‐amino‐3,6,7‐trimethyl‐3H‐imidazo[4,5‐c]pyridine ( 2 ), are described.     

New one‐ pot synthesis of pyrazolo[3,4‐c]pyridazine and isoxazolo‐[5,4‐b]pyridine derivatives from potassium cyanoacetahydroxamate

The reaction of potassium cyanoacetohydroxamate 1 with ethyl 2‐aryl‐hydrazono‐3‐oxobutyrates 2 gave the unexpected pyrazolo[3,4‐c]pyridazines 7 and isoxazolo[5,4‐b]pyridines 10 via a one‐pot reaction. A mechanistic proof is suggested to account for the products.     

A facile rearrangement of pyrroloindoline derivative to pyrroloquinoline: A new analogues of duocarmycins

Free‐radical generated at C‐7 position of indole derivative bearing N‐(3′‐chloroallyl) group prompted a regioselective intramolecular cyclization to furnish pyrroloindoline derivative, through the more favorable 5‐exo‐trig cyclization mode. The pyrroloindoline compound smoothly rearranged to pyrroloquinoline under mild conditions.     

An efficient and greener approach to the synthesis of 3,5‐dicyanopyridin‐2(1H)‐one derivatives in aqueous media under microwave irradiation conditions

A facile and greener synthesis of a series of 3,5‐dicyanopyridin‐2(1H)‐one derivatives was accomplished via the one‐pot reaction of aldehyde, malononitrile and sodium hydroxide in aqueous media under microwave irradiation. This method had several advantages such as shorter route and time, lower cost, reduced environmental impact.     

Regioselective synthesis of polyheterocyclic scaffolds by sequential [3,3] sigmatropic rearrangements and pyridine hydrotribromide mediated heterocyclization

A number of tetracyclic polyhetero scaffolds have been regioselectively synthesised in 70‐75% yield from 4‐[(3‐aryloxy‐2‐propynyl)oxy]‐6‐methyl‐pyran‐2‐ones via thionation of the lactone carbonyl, sequential Claisen rearrangements and pyridine hydrotribromide mediated heterocyclization.     

Synthesis of new 3‐(trifluoromethyl)‐1H‐indoles by reduction of trifluoromethyloxoindoles

This work describes the synthesis of new 3‐trifluoromethylindoles. Different isatins were trifluoromethylated using (trifluoromethyl) trimethylsilane (Me₃SiCF₃) as a nucleophilic agent giving new 3‐hydroxy‐3‐(trifluoromethyl)indolin‐2‐one. Different “one‐step” procedures to transform the latter compounds into the reduced indoles were attempted, but failed. For the synthesis of the new trifluoromethylindoles the corresponding 2‐oxo‐3‐(trifluoromethyl)indoles were reduced using borane/THF complex to furnish 3‐(trifluoromethyl)indolin‐3‐ol that additionally were dehydrated using thionyl chloride in pyridine to give excellent yields of the desired products.     

Synthesis of new derivatives of thieno[2,3‐b]pyridine fused with octyl ring

Derivatives of thiophene, thieno[2,3‐b]pyridine, thieno[5′,4′:4,5]pyrimido[3,2‐a]pyridine and thiepine fused with octyl ring have been synthesized and tested for antimicrobial and antifungal activities. The structure of the newly synthesized compounds have been established on the basis of their analytical and spectral data.     

Solvent‐free one‐pot approach for synthesis of substituted 2‐aminochromenes

A solvent‐free one‐pot approach for the preparation of 2‐aminochromenes in the presence of NaHCO₃ by grinding was described. Its advantages are easy work‐up, mild reaction condition, high yield and environmental compatibility.     

Synthesis and mutagenic potency of structural isomers of 2‐amino‐1‐methyl‐6‐phenylimidazo[4,5‐b]pyridine

Synthesis of 2‐amino‐1‐methyl‐6‐phenylimidazo[4,5‐b]pyridine (PhIP), three structural isomers, and two desphenyl PhIP congeners has been carried out. Mutagenic potency was evaluated using S. typhimurium strain TA98 in the Ames test. Mutagenic potency increased in relation to structural features in these heterocyclic amines that allow extended resonance between the phenyl and imidazo[4,5‐b]pyridine N²‐amino substituents. By contrast, PhIP isomers, whose substitution disallows involvement of the phenyl group in their aminoimidazo resonance hybrids, and desphenyl congeners were from 86‐ to 234‐fold less mutagenic than PhIP.     

Synthesis of some novel 2‐substituted‐N‐aryl‐benzoxazole‐5‐carboxamides using cobalt dipyridine dichloride as a catalyst

An efficient synthesis of some novel 2‐substituted‐N‐aryl‐benzoxazole‐5‐carboxamides from 2‐substituted — 5‐carbomethoxy benzoxazole on treatment with different substituted anilines promoted by cobalt dipyridine dichloride as a catalyst is described. This new approach has the advantage of excellent yields (90%) and short reaction times 1‐2 h.     

Syntheses of oxazolo[4,5‐c]pyridine and 6‐azaindole

The preparation of oxazolo[4,5‐c]pyridine and 6‐azaindole from 4‐bromo‐3‐pivaloylaminopyridine ( 8 ) is reported. The oxazolopyridine 2‐tert‐butyl‐oxazolo[4,5‐c]pyridine ( 9 ) was successfully prepared from 8 in 78% yield by a new base/TBAB promoted non‐catalyzed microwave cyclisation strategy (10 min) or, alternatively, in 54% yield by conventional heating (48 hrs) and CuI catalysis. The 6‐azaindole 2‐phenyl‐1‐(trimethylacetyl)‐6‐azaindole ( 13 ) was prepared from 8 in a two step procedure, including a Sonogashira coupling reaction.     

Phase transfer catalyzed synthesis of 3‐methyl‐4h‐pyrazolo[3,4‐d]isoxazole from 3,5‐dimethyl‐4‐isoxazolyldiazonium tetrafluoroborate

Reaction of 3,5‐dimethyl‐4‐isoxazolyl‐diazonium tetrafluoroborate ( 2 ) with two equivalents of potassium acetate and five mole percent of 18‐crown‐6 in ethanol‐free chloroform produce 3‐methyl‐4H‐pyrazolo[3,4‐d]isoxazole ( 3 ) in good to excellent yield. Pyrazole ( 3 ) was subjected to acylation/aroylation to afford the corresponding 4‐N‐acetyl/aroyl derivatives by reaction with CH₃COCl/ArCOCl in Et₃N.     

Dimethylformamide dimethyl acetal in heterocyclic synthesis: Synthesis of polyfunctionally substituted pyridine derivatives as precursors to bicycles and polycycles

Polysubstituted pyridines 11a,c and 12 were prepared by the reaction of benzoylacetone with dimethylformamide dimethyl acetal followed by treatment with cyanothioacetamide 9a , cyanoacetamide 9b and the anion of malononitrile dimmer 9c in dry DMF. When the reaction was carried out in ethanol as a solvent and piperidine as a base afforded 14a,b . Thienopyridines 16a,b were prepared by the reaction of pyridinethiones 11a and 14a with 2‐chloro‐N‐p‐tolyl‐acetamide ( 15 ). Further reaction of thienopyridines 16a,b with either DMFDMA or nitrous acid to gave 17a,b and 18a,b respectively. The reaction of pyridine derivative 11c with hydrazine and phenylhydrazine afforded the tricyclic compounds 19a,b .     

An interesting cyclization of N‐methyl‐3‐phenyl‐N‐(2‐(Z)‐phenylethenyl)‐cis‐oxiranecarboxamide

Under Lewis acid condition, N‐methyl‐3‐phenyl‐N‐(2‐(Z)‐phenylethenyl)‐cis‐oxiranecarboxamide undergoes elegant double cyclizations to give interesting products.     

Synthesis and antifungal activity of spiro[cyclopropane‐1,4′‐pyrazol‐3‐one] derivatives

A series of new spiro[cyclopropane‐1,4′‐pyrazol‐3‐one] derivatives 3a‐h were synthesized by the reaction of 4‐arylidene‐3H‐pyrazol‐3‐one 1 with secondary and tertiary carbanions derived from a methylene and methine group bearing both a leaving group and electron‐withdrawing group, e.g. methyl chloroacetate, ethyl chloroacetate, isopropyl chloroacetate, tert‐butyl chloroacetate, chloroacetonitrile, 2‐chloro‐N,N‐diethylacetamide, methyl 2‐chloropropionate and 2‐chloropropionitrile, in the presence of sodium hydride. All the synthesized compounds 3a‐h were active against Candida albicans with MIC ≤ 25 μg/mL in vitro.