Efficient and Facile Synthesis of Substituted Aminothiadiazolylhydrazonoindolin‐2‐ones

New series of substituted aminothiadiazolylhydrazonoindolin‐2‐ones were prepared in high yields (89–94%) via the cyclocondensation of thiocarbonohydrazides ( 1a , 1b , 1c , 1d ) with 3‐(dicyanomethylene)‐2‐indolone in (ethanol/piperidine) at room temperature. Explanations of these conversations involve the nucleophilic addition on the dicyanomethylene carbon atom. The structures were established by spectroscopic data and single crystal X‐ray crystallography.     

A General and Facile Synthesis of Novel Polysubstituted Quinazolin‐4(3H)‐ones

A simple and efficient approach to synthesize novel polysubstituted quinazolin‐4(3H)‐ones has been developed, and the key step is a sequential procedure involved iron‐mediated reduction and acid‐catalytic cyclization. The present method provides a convenient and practical strategy for the synthesis of quinazolin‐4(3H)‐one derivatives.     

Facile synthesis of 2‐alkylthio‐5‐phenylmethylene‐4H‐imidazol‐4‐ones

2‐Alkylthio‐5‐phenylmethylidene‐4H‐imidazol‐4‐ones 4 were synthesized by S‐alkylation of 2‐thioxo‐3‐alkyl(aryl)‐4‐imidazolidinones 3 , which were obtained via cyclization of isothiocyanates 2 with aliphatic(aromatic) primary amines. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:348–351, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10160     

Ultrasound‐Assisted Facile Synthesis and Antimicrobial Studies of Alkanediyl‐bis‐thiazolidin‐4‐ones and Alkanediyl‐bis‐thiazinan‐4‐ones

Alkanediyl‐bis‐2‐aryl‐thiazolidin‐4‐one and alkanediyl‐bis‐2‐aryl‐1,3‐thiazinan‐4‐one derivatives have been congregated in a single step reaction of diaminoalkanes, aryl aldehydes, and sulfanyl acids in the presence of coupling agent N,N′‐dicyclohexylcarbodiimide under ultrasonic conditions. This method of constructing 4‐keto derivatives of thiazolidine and thiazinane is quick and clean besides yielding the products in quantitative yields. The spectral techniques corroborated the structures of the isolated products. Biological assay of the synthesized products has also been reported.     

Synthesis of Novel Thiazolidin‐4‐ones and Thiazinan‐4‐ones Analogous to Rosiglitazone

This work reports the synthesis of thiazolidin‐4‐ones and thiazinan‐4‐ones analogous to rosiglitazone, a potent antidiabetic drug. The desired compounds were synthesized with moderate to good yields by one‐pot reactions between different primary amines, mercaptoacetic or mercaptopropionic acids, and the 4‐(2‐(methyl(pyridin‐2‐yl)amino)ethoxy)benzaldehyde. The cyclocondensation reactions were carried out for 20 h, and all the products were characterized by ¹H and ¹³C nuclear magnetic resonance spectroscopy, mass spectrometry, and one example by X‐ray diffraction.     

A Facile Synthesis of 2‐Imino‐4‐methylene‐1,3‐dithiolanes

A one‐pot synthesis of 2‐imino‐4‐methylidene‐1,3‐dithiolanes via a three‐component reaction of propargyl bromide (=3‐bromoprop‐1‐yne), primary amines, and carbon disulfide (CS₂) is described.     

The Synthesis and Antibacterial Activity of Novel 4‐Pyrrolidin‐3‐cyanopyridine Derivatives

2‐Bromo‐4‐(pyrrolidin‐1‐yl)pyridine‐3‐carbonitrile obtained from 2‐(1,3‐bis(pyrrolidin‐1‐yl)allylidene)malononitrile has been used as a substrate for the synthesis of new cyanopyridine derivatives: 2‐methoxy, 2‐phenoxy, 2‐aminoethylthio, and 2‐thioxo. 4‐(Pyrrolidin‐1‐yl)‐2‐thioxo‐1,2‐dihydropyridine‐3‐carbonitrile 7 in reaction with suitable alkyl and aminoalkyl halides gave respective sulfides. All synthesized compounds were evaluated for their antimicrobial activity against 26 aerobic and anaerobic bacteria. Determined minimal inhibitory concentration values ranged from 6.2 to 100 µg/mL. Derivatives 1 , 3 , 4 , 6 , and 12 were the most active compounds.     

Facile Synthesis and Properties of 2‐λ5‐Phosphaquinolines and 2‐λ5‐Phosphaquinolin‐2‐ones

Treatment of 2‐ethynylanilines with P(OPh)₃ gives either 2,2‐diphenoxy‐2‐λ⁵‐phosphaquinolines or 2‐phenoxy‐2‐λ⁵‐phosphaquinolin‐2‐ones under transition‐metal‐free conditions. This reaction offers access to an underexplored heterocycle, which opens up the study of the fundamental nature of the N?P^V double bond and its potential for delocalization within a cyclic π‐electron system. This heterocycle can serve as a carbostyril mimic, with application as a bioisostere for pharmaceuticals based on the 2‐quinolinone scaffold. It also holds promise as a new fluorophore, since initial screening reveals quantum yields upwards of 40 %, Stokes shifts of 50–150 nm, and emission wavelengths of 380–540 nm. The phosphaquinolin‐2‐ones possess one of the strongest solution‐state dimerization constants for a D–A system (130 M ^?1) owing to the close proximity of a strong acceptor (P?O) and a strong donor (phosphonamidate N? H), which suggests that they might hold promise as new hydrogen‐bonding hosts for optoelectronic sensing.     

Synthesis and reactions of 2‐hetero‐4H‐3,1‐benzoxazin‐4‐ones

The present review covers the synthesis and reactions of 2‐hetero‐4H‐3,1‐benzoxazin‐4‐ones which include oxygen, sulfur and nitrogen substituents. Literature coverage includes publications primarily from the mid 1960's to December 1999.     

Facile Heterocyclic Synthesis and Antibacterial Activity of Substituted Isoxazol‐5(4H)‐ones

An efficient, simple, and green procedure for the synthesis of isoxazol‐5(4H)‐one derivatives are described here through a convenient one‐pot, three‐component reaction at room temperature. The title compounds are isolated in high to excellent yields and after short reaction times, and are characterized by various spectroscopic methods such as IR, ¹H NMR, and ¹³C NMR. The synthesized compounds 4a–c and 4e–i were tested for their in vitro activity against a panel of Gram‐positive and Gram‐negative bacteria, demonstrating their ability to inhibit microorganisms with a zone of inhibition ranging from 15 to 30 mm, minimum inhibitory concentration between 250 and 900 μg/mL, and minimum bacterial concentration between 700 and 1000 μg/mL.     

Facile Synthesis of Diastereoisomerically and Optically Pure 2‐Substituted Hexahydro‐1H‐pyrrolizin‐3‐ones

We report a short synthetic route that provides optically active 2‐substituted hexahydro‐1H‐pyrrolizin‐3‐ones in four steps from commercially available Boc (tert‐but(oxy)carbonyl))‐protected proline. Diastereoisomers (−)‐ 11 and (−)‐ 12 were assembled from the proline‐derived aldehyde (−)‐ 8 and ylide 9 via a Wittig reaction and subsequent catalytic hydrogenation (Scheme 3). Cleavage of the Boc protecting group under acidic conditions, followed by intramolecular cyclization, afforded the desired hexahydro‐1H‐pyrrolizinones (−)‐ 1 and (+)‐ 13 . Applying the same protocol to ylide 19 afforded hexahydro‐1H‐pyrrolizinones (−)‐ 25 and (−)‐ 26 (Scheme 5). The absolute configuration of the target compounds was determined by a combination of NMR studies (Figs. 1 and 2) and X‐ray crystallographic analysis (Fig. 3).     

Synthesis of 3‐Fluoropyrrolidines and 4‐Fluoropyrrolidin‐2‐ones from Allylic Fluorides

Various 3‐fluoropyrrolidines and 4‐fluoropyrrolidin‐2‐ones were prepared by 5‐exo‐trig iodocyclisation from allylic fluorides bearing a pending nitrogen nucleophile. These bench‐stable precursors were made accessible upon electrophilic fluorination of the corresponding allylsilanes. The presence of the allylic fluorine substituent induces syn‐stereocontrol upon iodocyclisation with diastereomeric ratios ranging from 10:1 to > 20:1 for all N‐tosyl‐3‐fluoropent‐4‐en‐1‐amines and amides. The sense and level of stereocontrol is strikingly similar to the corresponding iodocyclisation of structurally related allylic fluorides bearing pending oxygen nucleophiles. These results suggest that the syn selectivity observed upon ring closure involves I₂–π complexes with the fluorine positioned inside.     

A Convenient Synthesis of Imidazolidin‐4‐ones via Domino Reactions

A series of imidazolidin‐4‐one derivatives was synthesized via a domino reaction of aldiminoesters and dialkylzinc. Chiral ligands were also examined in this reaction to obtain optically active products.     

Synthesis of derivatives of 1,3,2‐diazaphospholidin‐4‐ones and the corresponding 2‐sulfides

Aromatic‐substituted derivatives of 1,3,2‐diazaphospholidin‐4‐ones 2a–g were readily prepared from 1,3‐diaryl glycinamides 1 by the reaction with hexaethylphosphoric triamide. Their chemical transformation was selectively effected with different thionation reagents to afford thionated products at the phosphorus atom to give 3a–g and at the carbonyl group to give 4a . An oxidation reaction at phosphorus to produce 5a was effected with 10% hydrogen peroxide. Preliminary bioassays revealed that some of the title compounds, 2a–g and 3a–g possess selective herbicidal activity against rape. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:497–500, 2001     

A Simple Synthesis of Polyfunctionalized 4‐Aminopyrazolidin‐3‐ones as ‘Aza‐deoxa’ Analogs of D‐Cycloserine

A simple five‐step synthesis of fully substituted (4RS,5RS)‐4‐aminopyrazolidin‐3‐ones as analogs of D ‐cycloserine was developed. It comprises a two‐step preparation of 5‐substituted (4RS,5RS)‐4‐(benzyloxycarbonylamino)pyrazolidin‐3‐ones, reductive alkylation at N(1), alkylation of the amidic N(2) with alkyl halides, and simultaneous hydrogenolytic deprotection/reductive alkylation of the primary NH₂ group. The synthesis enables an easy stepwise functionalization of the pyrazolidin‐3‐one core with only two types of common reagents, aldehydes (or ketones) and alkyl halides. The structures of products were elucidated by NMR spectroscopy and X‐ray diffraction.     

Functionalization of Quinazolin‐4‐ones Part 1: Synthesis of Novel 7‐Substituted‐2‐thioxo Quinazolin‐4‐ones from 4‐Substituted‐2‐Aminobenzoic Acids and PPh3(SCN)2

4‐(Nitro, amino, acetylamino)‐2‐aminobenzoic acid were allowed to react with PPh₃(SCN)₂ and gave the crossholding 7‐nitro, 7‐acetylamino‐ and 7‐amino‐2‐thioxo quinazolin‐4‐ones respectively. The nature of the substituent at position 4 of the 2‐aminobenzoic acids has significant influence on the outcome of the cyclisation reaction with PPh₃(SCN)₂. Similarly, the nature of the substituent at position 7 of the 2‐substituted quinazolin‐4‐ones significantly affected the ease with which alkylation reactions could be performed. The alkylation selectivity of the 7‐ substiuted‐2‐thioxo quinazolin‐4‐ones was found to depend on the nature of the alkyl halide and the nature of the substituent at position 2.     

Syntheses of Enantiomerically Pure 2‐Substituted Pyrrolidin‐3‐ones via Lithiated Alkoxyallenes – An Auxiliary‐Based Synthesis of both Enantiomers of the Antibiotic Anisomycin

The hydrochlorides of both enantiomers of the antibiotic anisomycin were prepared starting with the ‘diacetone‐fructose’‐substituted allene 1 and the N‐Boc‐protected imine precursor 2a . Addition of an excess of lithiated 1 to 2a provided a 2 : 1 mixture 3a of diastereoisomers, which were cyclized to 4a under base promotion (Scheme 2). The two diastereoisomers of 4a were separated and converted into enantiomerically pure pyrrolidin‐3‐ones (2R)‐ 5a and (2S)‐ 5a . A similar sequence yielded the N‐Tos‐protected compounds (2R)‐ 5b and (2S)‐ 5b . Compounds 5a were converted into silyl enol ethers 6 and by subsequent regio‐ and stereoselective hydroboration into pyrrolidine derivatives 7 (Scheme 3). Straightforward functional‐group transformations led to the hydrochlorides 9 of anisomycin (Scheme 3). The (2R) series provided the hydrochloride (2R)‐ 9 of the natural occurring enantiomer, whereas the (2S) series furnished the antipode (2S)‐ 9 . The overall sequence to the natural product involved ten steps with eight purified intermediates and afforded an overall yield of 8%. Our stereochemically divergent approach to this type of hydroxylated pyrrolidines is highly flexible and should easily allow preparation of many analogues.