Ready access to 7,8‐dihydro‐ and 1,2,3,4‐tetrahydro‐1,6‐naphthyridine‐5(6H)‐ones from simple pyridine precursors

Short pathways are described for the synthesis of a representative example of each of the 7,8‐dihydro‐and 1,2,3,4‐tetrahydro‐1,6‐naphthyridine‐5(6H)‐one ring systems from simple pyridine precursors. An attempted synthesis of the related 4,6‐dihydro‐1,6‐naphthyridin‐5(1H)‐one ring system from a common intermediate was unsuccessful.     

Reactions of cephalosporin sulfones 3. Synthesis of 2‐phenylhydrazonocephem‐sulfones. A new potential entry to 2‐aminocephems

Reaction of cephem sulfones 1a‐e with aryldiazonium salts gives the 2‐azo compounds which immediately rearrange into the corresponding 2‐hydrazono derivatives 2a‐e .     

Novel derivatives of the benzo[b][1,6]naphthyridine system

An efficient synthesis of 2‐hydroxy‐6‐methylbenzo[b][1,6]naphthyridin‐1(2H)‐one was devised. The hydroxy group was alkylated, acylated and replaced by hydrogen. Electrophilic nitration, bromination and chlorosulfonation occurred readily in the 4‐position. From the last, various sulfonamide derivatives were prepared. A selection of the products was screened by the National Cancer Institute. Cytotoxicities were generally low.     

A simple and convenient method for the synthesis of 1‐dialkylaminocarbothioic acid S‐[(2,3‐epithio)propyl] esters

A simple and convenient method for the synthesis of 1‐dialkylaminocarbothioic acid S‐[(2,3‐epithio)propyl] ester was developed by the reaction of 1‐dialkylaminocarbodithioic acid‐sodium salt with 1‐chloro‐2,3‐epoxypropane in water‐methanol mixture at room temperature. An intermediate was isolated and characterized, based on which a possible mechanism was proposed.     

Convenient synthesis of N‐substituted 1‐alkyl and 1‐aryl‐3‐aminoisoquinolines

Cyclocondensation of 2‐acylphenylacetonitriles 1 with amines affords 1‐substituted 3‐aminoisoquinolines 2 in good yields.     

Synthesis of beta‐proline like derivatives and their evaluation as sodium channel blockers

A simple and convenient procedure for the preparation of beta‐proline like derivatives in their racemic and optically active forms has been reported. The compounds have been screened for their potential activity as sodium channel blockers.     

Synthesis of 2‐phenylquinolin‐4‐amines substituted with diverse amino and aminoalkyl groups

Facile synthetic approaches to 2‐phenylquinolin‐4‐amines containing an aminoalkyl group at N⁴ of the quinolin‐4‐amine and amino or aminoalkyl groups at the phenyl moiety are presented.     

One‐pot synthesis of symmetrically disubstituted 3H‐phenoxazin‐3‐ones by selective oxidative condensation with LTA

A one‐pot synthesis of some new 2,8‐disubstituted 3H‐phenoxazin‐3‐ones from 4‐substituted‐2‐aminophenols through a selective oxidative condensation by lead tetraacetate in acetic acid is described.     

Syntheses,electrochemical studies and crystal structures of new unsymmetrical tetrathiafulvalene carboxylate derivatives

A series of new unsymmetrical tetrathiafulvalene carboxylate derivatives ( 7‐11 ) were synthesized and characterized by NMR, MS, electrochemical studies and X‐ray crystal structural determination. Compound 8 showed obvious changes in redox peak potentials as the concentration of p‐toluenesulfonic acid changes.     

One pot synthesis of novel dispiro[oxindole‐thiazolidinedione/thioxo‐thiazolidinone/dihydro pyrazolone]‐pyrrolidines via 1,3‐dipolar cycloaddition reaction of azomethine ylides

A series of novel dispiro[oxindole‐thiazolidinedione]pyrrolidine, dispiro[oxindole‐thioxothiazolidinone]‐pyrrolidine, dispiro[oxindole‐dihydro‐pyrazolone]pyrrolidine were synthesized by both regio‐ and stereo‐selective 1,3‐dipolar cycloaddition reaction of azomethine ylide generated from amino acid and amino acid ester with π‐deficient alkenes in a single pot protocol in good yield. X‐ ray crystallographic studies established orthogonal disposition between spiro‐oxindole and spiro‐thiazolidinedione rings in 4a and 5a .     

Furan ring opening ‐ indole ring closure: Synthesis of furo[2′,3′:3,4]‐cyclohepta[1,2‐b]indolium chlorides

A new synthetic approach to furo[2′,3′:3,4]cyclohepta[1,2‐b]indolium chlorides is elaborated starting from 2‐acetylaminoaryldifurylmethanes or 2‐aminoaryldifurylmethanes under treatment with methanolic HCl solution. The reaction proceeds in three steps: recyclization, intramolecular cyclization, and disproportionation. In this case the furan ring takes part in building up both pyrrole and seven‐membered rings. The same salts can be obtained directly from 2‐acetylaminobenzaldehydes and 2‐methylfuran under similar conditions without isolation of corresponding 2‐acetylaminoaryldifurylmethanes.     

Selective synthesis of some 4,5‐dihydro‐2H‐benzo[g]indazoles and 8,9‐dihydro‐2H‐benzo[e]indazoles via the vilsmeier‐haack reaction under thermal and microwave assisted conditions

A selective and easy method is described for the synthesis of 4,5‐dihydro‐2H‐benzo[g]indazoles and 8,9‐dihydro‐2H‐benzo[e]indazoles by the Vilsmeier‐Haack reaction of various tetralone phenylhydrazones under thermal and microwave irradiation conditions.     

Thermal decomposition reactions of n‐alkylated 2‐aminobiphenyls to carbazole and phenanthridine

Thermal cyclization reactions were examined by passing vapors of N‐alkylated 2‐aminobiphenyls 1a‐c and 2 over calcium oxide at 450‐600°C under nitrogen carrier gas. The reactions yielded 9‐methylcarbazole 3 , carbazole 4 , phenanthridine 5 and phenanthrene 6. The major product for the reactions of 1a, 1b and 2 was phenanthridine 5 while that of 1c was carbazole 4.     

New access to thiazolo[4,5‐d]pyrimidine derivativess

4‐Amino‐5‐bromo‐2‐substituted‐aminopyrimidines are readily obtained from the newly prepared 5‐bromo‐2,4‐dichloro‐6‐methylpyrimidine by sequential treatment with ethanolic ammonia and secondary amines. These compounds were successfully reacted with various isothiocyanates in the presence of sodamide in DMF to form the new thiazolo[4,5‐d] pyrimidine derivatives.     

Synthesis of novel substituted flavonoids

Eighteen substituted chalcones, flavones and 3‐flavonols were synthesized and characterized using ¹H‐NMR, IR and elemental analysis. The substitution pattern includes two halogen atoms, nitro and methyl groups in ring A as well as two or three methoxy groups in ring B.     

Δ2‐Isoxazolines from β,γ‐unsaturated oximes

3,5‐Disubstituted Δ²‐isoxazolines can be prepared using the palladium‐mediated nucleometalation / methoxycarbonylation of β,γ‐unsaturated oximes. This novel route to this class of compounds is tolerant of a wide variety of functionality in the starting material, and provides a rapid route to highly functionalized isoxazolines.     

Electron impact studies. CVII—Negative ion mass spectra of the oxime group. Monoximes derived from α-dicarbonyl systems

Specific losses of water are observed from the molecular anions of monoximes of α-diketones. Labelling studies, kinetic energy release values and the +E spectra of ions have been used to aid in the elucidation of the fragmentation pathways. It is proposed that the majority of ions have α-keto nitrile structures.     

An efficient synthesis of new thiazolopyrimidinones under microwave irradiation

7‐Chloromethyl‐6‐nitro‐5H‐thiazolo[3,2‐a]pyrimidin‐5‐one ( 2 ) is obtained by cyclocondensation of 2‐aminothiazole with ethyl 4‐chloroacetoacetate. This product was shown to react with various nitronate or malonate anions under microwave irradiation to give potentially bioactive 6‐nitro‐5H‐thiazolo[3,2‐a]pyrimidin‐5‐ones. Extension to other anions centered on S atom allows for the generalization this synthetic procedure.     

Synthesis of some new 4‐substituted‐3, 5‐bis(2‐pyridyl)‐1h‐pyrazole

Several 4‐substituted‐3, 5‐bis(2‐pyridyl)‐1H‐pyrazoles, where the substituent is chloro, bromo, iodo, nitro, diazo, were synthesized under mild reaction conditions in high yields. The structures of the products were characterized by ¹H NMR, ¹³C NMR, ESI‐MS, IR and elemental analyses.     

The convenient synthesis of benzimidazole derivatives catalyzed by I2 in aqueous media

In the presence of catalytic amount of iodine, in THF‐H₂O, the condensation of aldehydes with 1,2‐phenylenediamine gave the benzimidazole derivatives under mild conditions in good yields. The method can be used for the synthesis of 2‐substituted benzimidazoles or 1,2‐disubstituted benzimidazoles.