Regioselective three‐component synthesis of novel indeno[1,2‐b]‐pyrazolo[4,3‐e]pyridines‐fused derivatives of 4‐azafluorenone alkaloid

New fused indeno[1,2‐b]pyridine derivatives have been prepared in a multicomponent reaction from benzaldehydes, indanedione and the appropriate aminoheteroaryl compound. The simple methodology permitted the syntheses of a series of indeno[1,2‐b]pyrazolo[4,3‐e]pyridines 4 from 5‐aminopyrazol 1 and modulated by the corresponding benzaldehyde 2 .     

Carbazolo[2,1‐a]carbazole derivatives via fischer indole synthesis

A series of new carbazolo[2,1‐a]carbazoles was synthesized from 4‐oxo‐1,2,3,4‐tetrahydrobenzo[a]‐carbazole derivatives.     

Synthesis of N‐pivot lariat ethers

This review covers the main strategies for the synthesis of N‐pivot lariat ethers as well as their specific syntheses.     

Fluorescent 6‐hydroxy‐ and 6,7‐dihydroxy‐4‐trifluoro‐methylcarbostyrils and formation of o‐carboxymethylated derivatives via o‐succinimide esters

Stepwise demethylation of fluorescent 6,7‐dimethoxy‐3‐trifluoromethylcarbostyrils 5 leads to 6‐hydroxy derivatives 6 and 6,7‐dihydroxyderivative 7 . Phenolate formation shifts excitation and emission maxima from 370 and 430 nm to 430 and 480 nm for the anion of 6 and as far as 500 and 580 nm for the dianion of 7 . Dependence of fluorescence quantum yield on media and polar structure, varying from 0.02 to 0.51, is discussed. O‐Alkylation of 6 with alkyl bromoacetate yields esters of type 8 in good yield. Reactive succinimidoyl (OSu) esters of type 11 were prepared after saponification to acids 9 . With amino acids or their esters, peptides and aminoglucose, linking to labeled derivatives 13 or 15 could be achieved under mild conditions in slightly basic aqueous media.     

Preparation of 5‐bromo‐6‐phenylimidazo[2,1‐b][1,3,4]thiadiazol‐2‐ylamines

The reaction of primary or secondary amines with 2,5‐dibromo‐6‐phenylimidazo[2,1‐b][1,3,4]‐thiadiazole ( 5 ) leads to a chemoselective replacement of the 2‐Br substituent. The process represents a convenient route to the corresponding 2‐ylamines 7a‐d . Hydrazine reacts in an analogous fashion ( 5 → 7e ). The structure determinations are based on an X‐ray crystal structure analysis and on one‐ and two‐dimensional NMR measurements.     

Regioselective synthesis of diazaspiro[4.4]nona‐ and tetrazaspiro[4.5]deca‐2,9‐diene‐6‐one derivatives

Several 1,2‐diazaspiro[4,4]nona‐2,8‐diene‐6‐one derivatives were synthesised via cycloaddition of nitrilimides to 3‐aryliden‐2(3H)‐furanone derivatives. The formed products react with hydrazine hydrate to give the corresponding pyrazolecarbohydrazide derivatives which undergo intramolecure cyclization upon treatment with HCl/AcOH mixture to affored 1,2,7,8‐tetrazaspiro[4.5]deca‐2,9‐diene‐6‐one derivatives. Molecular mechanics energy minimization techniques and related structural parameters for compound 8‐(4‐methylphenyl)‐1,3,4‐triphenyl‐7‐oxa‐1,2‐diazaspiro[4.4]nona‐2,8‐diene‐6‐one 5a are reported.     

Synthesis and photochemical properties of trans‐2‐(2‐aryl‐ or heteroarylvinyl)‐4,5‐dichloropyridazin‐3(2H)‐ones

trans‐2‐(2‐Aryl‐ or heteroarylvinyl)‐4,5‐dichloropyridazin‐3(2H)‐ones 3 were synthesized from 4,5‐dichloropyridazin‐3(2H)‐one via 2 step. The photochemical behavior of 3 in THF, methylene chloride, acetonitrile and methanol is dependent on the kind of aryl or heterocyclic ring and the solvent polarity     

Fused polyaza‐heterocycles and 1,3,4‐thiadiazoles via a tricyano synthon

Treatment of 2‐cyano‐3‐phenyl‐2‐pentenedinitrile with some heterocyclic diazonium salts afforded the corresponding heterocyclic hydrazones. Some of the latter hydrazones were converted into fused polyaza‐heterocycles upon boiling in pyridine. Reaction of 2‐cyano‐3‐phenyl‐2‐pentenedinitrile with phenylisothiocyanate gave a tricyano‐thiole derivative which on treatment with hydrazonoyl chlorides and 1‐(benzothiazol‐2‐yl)‐2‐bromoethanone furnished 1,3,4‐thiadiazole and thiazole derivatives, respectively.     

Stereoselective synthesis of helical dihydrodipyrrolophenanthroline and hindrance hexa tert‐butyl carboxylatodipyrrolophenanthroline from reaction between 1,10‐phenanthroline and dialkyl acetylenedicarboxylates

High hindrance Hexa tert‐butoxy carbonyl dipyrrolophenanthroline and helical dihydropyrrolophen‐anthroline compounds were prepared from reactions between di tert‐butyl acetylenedicarboxylate and 1,10‐phenanthroline in polar solvents media.     

Application of the acetate of baylis‐hillman adducts in the synthesis of 3‐carbomethoxy‐2H‐thiochromenes

A new route to 2H‐thiochromenes using the tandem S_N2′ and S_NAr reaction of several Baylis‐Hillman acetates having an ortho‐substituent, such as a halogen or nitro group, with sodium sulfide in aqueous dimethyl sulfoxide has been described.     

Oxidative coupling of acridinones: Synthesis of new C2‐symmetry atropisomers

The preparation of symmetric 2,2′‐dimethoxy‐10,10′‐biacridinyl‐9,9′‐dione atropisomers were obtained by the oxidative coupling of 9(10H)‐acridinone with 1,3‐dibromo‐5,5‐dimethyl‐imidazolidine‐2,4‐dione     

Benzobis(pyrrolopyrimidopiridazines): Molecular structure and properties of the first π‐electronic analogues of dibenzo[a,o]picene

Molecular structure, aromaticity and some spectral properties of benzobis(pyrrolopyrimidopiridazines) 2 that are the first π‐electronic analogues of the still unknown dibenzo[a,o]picene are discussed.     

Synthesis of novel 5‐chlorinated 2‐aminothiophenes using 2,5‐dimethylpyrrole as an amine protecting group

A new synthetic methodology towards substituted 2‐amino‐5‐chlorothiophenes is described. Compounds of this type are important as building blocks for oligomers used in polymer research. Easily available 2‐aminothiophenes underwent Paal‐Knorr reaction to protect the free amino group before electrophilic substitution. Although the chlorination was predicted to proceed at the thiophene ring, only free positions of 2,5‐dimethylpyrrole were substituted. To direct chlorination to the thiophene ring acetamido derivative was prepared first and then chlorinated. Transamination with hexane‐2,5‐dione created a 2,5‐dimethyl pyrrole ring from the acetamido group. In the final step, after treatment with hydroxylamine dihydrochloride, the pyrrole ring is removed and a free amino group is regenerated.     

Preparation of 2‐(1H‐pyrazol‐5‐yl)benzenesulfonamides from polylithiated C(α),N‐carbo‐tert‐butoxyhydrazones and methyl 2‐(aminosulfonyl)benzoate

Select C(α), N‐carbo‐tert‐butoxyhydrazones were dilithiated with excess lithium diisopropylamide followed by condensation with methyl 2‐(aminosulfonyl)benzoate, acid cyclization, hydrolysis, and decarboxylation to afford new 2‐(1H‐pyrazol‐5‐yl)benzenesulfonamides, [NH‐pyrazolyl‐ortho‐benzene‐sulfonamides].     

Synthesis and structural study of a new series of 2‐methylsulfanyl‐tetrahydropyrimidines from β‐alkoxyvinyl trihalomethyl ketones

This work describes the synthesis of a novel series of 2‐methylsulfanyl‐tetrahydropyrimidines, from the cyclocondensation reaction of β‐alkoxyvinyl trihalomethyl ketones with 2‐methyl‐2‐thiopseudourea sulfate, in good yields. A detailed ¹H‐ and ¹³C‐NMR study was performed on the 2‐methylsulfanyl‐tetrahydropyrimidines obtained and 3D structures were proposed based on AM1 calculations supported by ¹H NMR coupling constants and NOESY experiments.     

Preparation and crystal structures of two 3‐anthracenyl isoxazolyl sulfonamides

Lateral metalation and oxidation of 3‐(9′‐anthryl)‐isoxazoles ( 1 ), using Davis' oxaziridine ( 6 ), produced the desired hydroxylation ( 2 ), along with sulfonamide adduct ( 3 ), and in the case of the use of butyl lithium as base, butyl addition products ( 4 ) and ( 5 ). Structures of isoxazole sulfonamides ( 3a ) and ( 5a ), were obtained as the SR/RS‐diastereomer, however, studies indicate that this is a consequence of the crystallization process. Metalation studies with isoxazole ( 8 ) demonstrate that hydroxylation ( 9 ), can be carried out cleanly, minimizing formation of ( 10 ), using camphorsulfonyloxaziridine ( 7 ) as an electrophile.     

Synthesis of new heterocyclic compounds having 1,2,3‐triazole and isoxazole rings in a single molecule

Five series of new heterocyclic compounds of 1,2,4‐triazole Mannich bases, 1,3,4‐oxadiazole Mannich bases, 1,3,4‐oxadiazolines, 1,2,4‐triazolo[3,4‐b]1,3,4‐thiadiazines and 1,2,4‐triazolo[3,4‐b]1,3,4‐thiadiazoles, in which 1,2,3‐triazolyl and isoxazolyl have been united, were synthesized from the intermediate of 5‐methyl‐3‐(2‐phenyl‐2H‐1,2,3‐triazol‐4‐yl)isoxazole‐4‐carbohydrazide, Their structures were established by spectroscopy.     

Synthesis and structure of novel 3,4‐annelated coumarin derivatives

Condensation of 4‐chloro‐2‐oxo‐2H‐chromene‐3‐carbonitrile ( 1 ) with heteroarylamines 2a‐d in acetonitrile containing a catalytic amount of triethylamine followed by spontaneous intramolecular cyclization gave the novel coumarin derivatives 3a‐d , respectively. These compounds underwent acid hydrolysis giving the corresponding oxoderivatives 4a‐d . The structural assignments of the synthesized compounds were based on elemental, IR, ¹H and ¹³C NMR analyses.     

Claisen Condensation of N‐Methylpyrrolidinone and α‐Chloronicotinic esters

Reaction between α‐halo‐nicotinic esters and a nucleophilic source such as the N‐methylpyrrolidin‐2‐one (NMP) gave unexpected results. The presence of the halide on the pyridine gave a very interesting migration reaction. Extension to 6‐methylnicotinic ester derivatives lead to an unexpected carbanion condensation.     

1,3‐Dipolar cycloadditions of (4R*,5R*)‐1‐alkylidene‐4‐(benzoylamino)‐5‐phenyl‐3‐pyrazolidinon‐1‐azomethine imines

1,3‐Dipolar cycloadditions of azomethine imines 3a and 3b , available by acid‐catalyzed treatment of 3‐pyrazolidinone 1 with acetone ( 2a ) and butyraldehyde ( 2b ), respectively, were studied. Reactions of 3a with DMAD ( 4 ) afforded a mixture of products 9 and 10a , whilst treatment of 3b with DMAD ( 4 ) gave a mixture of compound 9 and epimeric cycloadducts 10 / 10′b . On the other hand, cycloadducts 13a,b‐16a,b were isolated as single diastereomers in 9–37% yields upon reactions of 3a,b with olefinic dipolarophiles 5–8 . The structures of cycloadducts 9, 10a, 10/10′b , and 13a,b‐16a,b were determined by ¹H nmr and NOESY spectroscopy. The structure of compound 13a was confirmed by X‐ray diffraction.