Asymmetric Synthesis of Spirocyclic β‐Lactams through Copper‐Catalyzed Kinugasa/Michael Domino Reactions

The first copper‐catalyzed highly chemo‐, regio‐, diastereo‐, and enantioselective Kinugasa/Michael domino reaction for the desymmetrization of prochiral cyclohexadienones is described. In the presence of a chiral copper catalyst, alkyne‐tethered cyclohexadienones couple with nitrones to generate the chiral spirocyclic lactams with excellent stereoselectivity (up to 97 % ee, >20:1 dr). The new method provides direct access to versatile highly functionalized spirocyclic β‐lactams possessing four contiguous stereocenters, including one quaternary and one tetra‐substituted stereocenter.     

Synthesis of Optically Enriched Spirocyclic Benzofuran‐2‐ones by Bifunctional Thiourea‐Base Catalyzed Double‐Michael Addition of Benzofuran‐2‐ones to Dienones

A highly enantioselective catalytic double‐Michael addition reaction of substituted benzofuran‐2‐ones with divinyl ketones promoted by readily accessible tertiary amine–thiourea Cinchona alkaloids has been developed. A number of optically enriched spirocyclic benzofuran‐2‐ones were prepared in very good yields (up to 99 %), diastereoselectivities (up to 19:1 d.r.), and very good enantioselectivities (up to 92 % ee). Density functional theory (DFT) calculations were performed to investigate the origin of stereoselectivity.     

Formation of α‐SF5‐Enolate Enables Preparation of 3‐SF5‐Quinolin‐2‐ones, 3‐SF5‐Quinolines,and 3‐SF5‐Pyridin‐2‐ones: Evaluation of their Physicochemical Properties

This study describes, for the first time, the generation of a SF₅‐substituted ester enolate from benzyl SF₅‐acetate under soft enolization conditions, which in turn participates in aldol addition reactions in high yield. The reaction was applied in the synthesis of 3‐SF₅‐quinolin‐2‐ones, 3‐SF₅‐quinolines, and 3‐SF₅‐pyridin‐2‐ones, none of which have previously been reported. To provide guidelines for their use in drug discovery, the physicochemical properties of these building blocks were determined and compared with those of their CF₃‐ and t‐Bu‐analogues.     

Formation of α‐SF5‐Enolate Enables Preparation of 3‐SF5‐Quinolin‐2‐ones, 3‐SF5‐Quinolines,and 3‐SF5‐Pyridin‐2‐ones: Evaluation of their Physicochemical Properties

This study describes, for the first time, the generation of a SF₅‐substituted ester enolate from benzyl SF₅‐acetate under soft enolization conditions, which in turn participates in aldol addition reactions in high yield. The reaction was applied in the synthesis of 3‐SF₅‐quinolin‐2‐ones, 3‐SF₅‐quinolines, and 3‐SF₅‐pyridin‐2‐ones, none of which have previously been reported. To provide guidelines for their use in drug discovery, the physicochemical properties of these building blocks were determined and compared with those of their CF₃‐ and t‐Bu‐analogues.     

Spiro[pyrido[3,2,1‐ij]pyrimido[4,5‐b]quinoline‐7,5′‐pyrrolo[2,3‐d]pyrimidines] and Spiro[pyrimido[4,5‐b]quinoline‐5,1′‐pyrrolo[3,2,1‐ij]quinolines] Derived from 5,6‐Dihydro‐4H‐pyrrolo[3,2,1‐ij]quinoline‐1,2‐dione

Reaction of 5,6‐dihydro‐4H‐pyrrolo[3,2,1‐ij]quinoline‐1,2‐dione ( 1 ) with two equivalents of some 6‐aminouracils (or 6‐amino‐2‐thiouracil) generates spirocyclic tetrahydrobenzo[if]quinolizines ( 7 ). The one‐pot, three‐component reaction of amido ketone ( 1 ) with 6‐aminouracil (or 6‐amino‐2‐thiouracil) and a cyclic six‐membered 1,3‐diketone produces spirocyclic tetrahydropyrrolo[3,2,1‐ij]quinolinones ( 15 ).     

1-Substituted 2-Azaspiro[3.3]heptanes: Overlooked Motifs for Drug Discovery

The 2-substituted piperidine core is found in drugs (18 FDA-approved drugs), however, their spirocyclic analogues remain unknown. Described here is the synthesis of spirocyclic analogues for 2-substituted piperidines and a demonstration of their validation in drug discovery.     

“Reduced” Coumarin Dyes with an O‐Phosphorylated 2,2‐Dimethyl‐4‐(hydroxymethyl)‐1,2,3,4‐tetrahydroquinoline Fragment: Synthesis,Spectra, and STED Microscopy

Large Stokes‐shift coumarin dyes with an O‐phosphorylated 4‐(hydroxymethyl)‐2,2‐dimethyl‐1,2,3,4‐tetrahydroquinoline fragment emitting in the blue, green, and red regions of the visible spectrum were synthesized. For this purpose, N‐substituted and O‐protected 1,2‐dihydro‐7‐hydroxy‐2,2,4‐trimethylquinoline was oxidized with SeO₂ to the corresponding α,β‐unsaturated aldehyde and then reduced with NaBH₄ in a “one‐pot” fashion to yield N‐substituted and 7‐O‐protected 4‐(hydroxymethyl)‐7‐hydroxy‐2,2‐dimethyl‐1,2,3,4‐tetrahydroquinoline as a common precursor to all the coumarin dyes reported here. The photophysical properties of the new dyes (“reduced coumarins”) and 1,2‐dihydroquinoline analogues (formal precursors) with a trisubstituted C=C bond were compared. The “reduced coumarins” were found to be more photoresistant and brighter than their 1,2‐dihydroquinoline counterparts. Free carboxylate analogues, as well as their antibody conjugates (obtained from N‐hydroxysuccinimidyl esters) were also prepared. All studied conjugates with secondary antibodies afforded high specificity and were suitable for fluorescence microscopy. The red‐emitting coumarin dye bearing a betaine fragment at the C‐3‐position showed excellent performance in stimulation emission depletion (STED) microscopy.     

Synthesis and Antibacterial Activity of Some New 2,5‐Disubstituted‐1,3,4‐oxadiazole Derivatives

Synthesis of some new oxadiazole derivatives starting from 1,2,3-benzo[d]triazole-1-acetic hydrazide (1) is described. The target compounds 2-(N-substituted-aminocarbonylmethylthio)-5-(1,2,3-benzo[d]triazol-1-ylmethyl)- 1,3,4-oxadiazole (4a—4i) and 2-[2-(N-substituted-aminocarbonyl)ethylthio]-5-(1,2,3-benzo[d]triazol-1-ylmethyl)- 1,3,4-oxadiazole (5a—5i) were obtained in good yields via cyclisation of 1 and subjected to antibacterial activity test against pathogenic bacteria. The halogen containing mono- and di-substituted derivatives showed excellent antibacterial activity compared to other analogues.     

A Facile and Efficient Synthesis of 4‐Arylidene‐2‐phenyl‐5(4H)‐oxazolones and Their Antimicrobial Evaluation against Selected Human and Phytopathogens

A simple and convenient method has been developed for the synthesis of a series of 2‐(4‐substituted phenyl)‐4‐(substituted arylidene)‐1,3‐oxazol‐5‐ones ( 5a–j ) via reactions of hippuric acid with differently substituted aromatic aldehydes ( 4a–j ) in sodium acetate, potassium acetate, calcium acetate, and ammonium acetate, respectively, which were tested for their efficiency as catalysts in both conventional and microwave‐assisted synthetic methods in presence of 4 Å zeolites. The title compounds were evaluated for their antimicrobial properties against selected human pathogens (bacterial and fungal) and phytopathogens (fungal) and were compared with standard drugs. The results of the study are reported.     

Synthesis of 4‐hydroxyquinolin‐2(1H)‐one analogues and 2‐substituted quinolone derivatives

A versatile synthetic method for preparing 4‐hydroxyquinolone and 2‐substituted quinolone compounds from simple benzoic acid derivatives was demonstrated. The synthetic strategies involve the use of well known ethyl acetoacetate synthesis, malonic ester synthesis and reductive cyclization. The key intermediates were keto esters 4a‐e , which could be transformed to 4‐hydroxyquinolones 5a,b or 2‐substituted quinolone ethyl esters 6a‐c depending on the reaction conditions. 4‐Hydroxyquinolone analogues were prepared and investigated for N‐methyl‐D‐aspartate (NMDA) activity in vitro. Among these derivatives, 6,7‐difluoro‐3‐nitro‐4‐hydroxyquinolin‐2(1H)‐one ( 9 ) exhibited moderate activity.     

Photocycloaddition Reactions of Alkyl and Aryl 2‐Thioxo‐3H‐benzoxazole‐ 3‐carboxylates to Alkenes

The photochemical reactions of alkyl and aryl 2‐thioxo‐3H‐benzoxazole‐3‐carboxylates 1 have been examined. Irradiation of 1 in the presence of tetra‐ and trisubstituted alkenes 2a and 2b , 2‐methylprop‐2‐ene nitrile 2e , and dienes 2f and 2g gave [2+2] cycloadducts of the CS bond of 2‐thioxobenzoxazoles and the CC bond of alkenes, spiro[benzoxazole‐thietanes] 3, 4, 8 – 13, 15, 18, 20, 23 – 26 in moderate‐to‐good yields. The photoaddition reactions proceed in a regiospecific manner. The spirocyclic compounds obtained are indefinitely stable at room temperature. Irradiation of 1a in the presence of 1,1‐ and 1,2‐disubstituted alkenes 2c and 2d yielded the products 5 – 7 of oxazole‐ring cleavage. Compound 1d also underwent photoaddition with alkenes to yield spiro[benzoxazole‐thietanes] and/or 2‐substituted benzoxazoles and/or iminothietanes, depending on the nature of the substituents present in the alkenes. On intramolecular [2+2] photoadduct, tetracyclic 27 , was obtained, when ethenyl 2‐thioxobenzoxazole‐3‐carboxylate 1e was irradiated.     

Asymmetric Synthesis of 1,3‐Butadienyl‐2‐carbinols by the Homoallenylboration of Aldehydes with a Chiral Phosphoric Acid Catalyst

Asymmetric C(sp)? C(sp²) bond formation to give enantiomerically enriched 1,3‐butadienyl‐2‐carbinols occurred through a homoallenylboration reaction between a 2,3‐dienylboronic ester and aldehydes under the catalysis of a chiral phosphoric acid (CPA). A diverse range of enantiomerically enriched butadiene‐substituted secondary alcohols with aryl, heterocyclic, and aliphatic substituents were synthesized in very high yield with high enantioselectivity. Preliminary density functional theory (DFT) calculations suggest that the reaction proceeds via a cyclic six‐membered chairlike transition state with essential hydrogen‐bond activation in the allene reagent. The catalytic reaction was amenable to the gram‐scale synthesis of a chiral alkyl butadienyl adduct, which was converted into an interesting optically pure compound bearing a benzo‐fused spirocyclic cyclopentenone framework.     

Synthesis and Analysis of the Conformational Preferences of 5‐Aminomethyloxazolidine‐2,4‐dione Scaffolds: First Examples of β2‐ and β2, 2‐Homo‐Freidinger Lactam Analogues

Constrained peptidomimetic scaffolds are of considerable interest for the design of therapeutically useful analogues of bioactive peptides. We present the single‐step cyclization of (S)‐ or (R)‐α‐hydroxy‐β²‐ or α‐substituted‐α‐hydroxy‐β^{2, 2}‐amino acids already incorporated within oligopeptides to 5‐aminomethyl‐oxazolidine‐2,4‐dione (Amo) rings. These scaffolds can be regarded as unprecedented β²‐ or β^{2, 2}‐homo‐Freidinger lactam analogues, and can be equipped with a proteinogenic side chain at each residue. In a biomimetic environment, Amo rings act as inducers of extended, semi‐bent or folded geometries, depending on the relative stereochemistry and the presence of α‐substituents.     

Synthesis,spectral characterization,and biological evaluation of imidazole‐substituted pyridine‐2‐amine and benzo‐substituted imidazole‐2‐amine

A series of new imidazole‐substituted pyridine‐2‐amine and benzo‐substituted imidazol‐2‐amine 3 – 12 were synthesized by treating various amines 1(a – d) with alkyl/aryl isothiocyanate 2(a‐c) at 60–90°C in isopropyl alcohol without using any catalyst with high yields. The structures of all the newly synthesized compounds were characterized using IR, NMR (¹H, ¹³C), mass, and elemental analyses. All the newly synthesized compounds were screened for their in vitro antioxidant and antimicrobial activities to understand their biological potency. All the title compounds exhibited good antioxidant and antimicrobial activities in vitro when compared to the standard drugs.     

On the Reactions of Furan‐2,3‐diones with Oxindole (=1,3‐Dihydro‐2H‐indol‐2‐one) and Lawesson Reagent. Synthesis of New 1,3‐Dihydro‐2H‐indol‐2‐ones,Bis‐furanones,and Bis‐pyrrolones

Lactone analogues of 3‐substituted oxindoles (=1,3‐dihydro‐2H‐indol‐2‐ones) and nonbenzoid oxa‐analogous isoindigoid or nonbenzoid isoindigoid dyes were prepared by the reactions of furan‐2,3‐diones with oxindole and Lawesson reagent (Schemes 1 and 3), respectively. So, new derivatives of 2‐oxobutanoic acid, bis‐furanone, and bis‐pyrrolone, which are potentially biologically active compounds, were synthesized for the first time.     

Optical Activity 1,5‐Substituted‐1,3,5‐hexahydrotriazine‐2‐N‐nitroimines: Synthesis and Insecticidal Activity

Twelve novel neonicotinoid analogues 1‐(2‐furfuryl)‐5‐substituted‐1,3,5‐hexahydrotriazine‐2‐N‐nitroimines 3a , 3b , 3c , 3d , 3e , 3f , 3g , 3h , 3i , 3j , 3k , 3l were synthesized. Their structures were characterized by ¹H NMR, IR, and elemental analysis. The preliminary bioassay tests showed that all the title compounds gave ≥90% mortality against Nilaparvata lugen 500 mg/L.     

Photoaddition Reactions of Benzoxazole‐2(3H)‐thiones to Cycloalkenes and Heteroaromatics

Photoaddition reactions of benzoxazole‐2‐thiones 1 with cycloalkenes 2 and heteroaromatics 3 were examined. Irradiation of N‐acylbenzoxazole‐2‐thiones 1a and 1b , and 3‐(methoxycarbonyl)‐ and 3‐(phenoxycarbonyl)benzoxazole‐2(3H)‐thiones ( 1f and 1h , resp.) in the presence of cycloalkenes 2a – 2c , cyclohexa‐1,4‐diene ( 2d ), and indene ( 2e ) yielded 2‐substituted benzoxazoles 4 – 13, 18 and 19 , and iminothietanes 14 – 17 , by intramolecular trapping of the acyl or MeOCO and PhOCO groups by thiolate anion of the zwitterionic intermediate I and by the phenolate anion of the zwitterionic intermediate II , respectively, derived from the spirocyclic amino‐thietanes AT formed by [2+2] cycloaddition of the C?S bond of 1 and C?C bond of 2 . Irradiation of 1 in the presence of heteroaromatics 3 gave the 2‐substituted benzoxazoles 20 – 33 exclusively.     

Efficient Atropodiastereoselective Access to 5,5′‐Bis‐1,2,3‐triazoles: Studies on 1‐Glucosylated 5‐Halogeno 1,2,3‐Triazoles and Their 5‐Substituted Derivatives as Glycogen Phosphorylase Inhibitors

Whereas copper‐catalyzed azide–alkyne cycloaddition (CuAAC) between acetylated β‐D ‐glucosyl azide and alkyl or phenyl acetylenes led to the corresponding 4‐substituted 1‐glucosyl‐1,2,3‐triazoles in good yields, use of similar conditions but with 2 equiv CuI or CuBr led to the 5‐halogeno analogues (>71 %). In contrast, with 2 equiv CuCl and either propargyl acetate or phenyl acetylene, the major products (>56 %) displayed two 5,5′‐linked triazole rings resulting from homocoupling of the 1‐glucosyl‐4‐substituted 1,2,3‐triazoles. The 4‐phenyl substituted compounds (acetylated, O‐unprotected) and the acetylated 4‐acetoxymethyl derivative existed in solution as a single form (d.r.>95:5), as shown by NMR spectroscopic analysis. The two 4‐phenyl substituted structures were unambiguously identified for the first time by X‐ray diffraction analysis, as atropisomers with aR stereochemistry. This represents one of the first efficient and highly atropodiastereoselective approaches to glucose‐based bis‐triazoles as single atropisomers. The products were purified by standard silica gel chromatography. Through Sonogashira or Suzuki cross‐couplings, the 1‐glucosyl‐5‐halogeno‐1,2,3‐triazoles were efficiently converted into a library of 1,2,3‐triazoles of the 1‐glucosyl‐5‐substituted (alkynyl, aryl) type. Attempts to achieve Heck coupling to methyl acrylate failed, but a stable palladium‐associated triazole was isolated and analyzed by ¹H NMR and MS. O‐Unprotected derivatives were tested as inhibitors of glycogen phosphorylase. The modest inhibition activities measured showed that 4,5‐disubstituted 1‐glucosyl‐1,2,3‐triazoles bind weakly to the enzyme. This suggests that such ligands do not fit the catalytic site or any other binding site of the enzyme.     

Asymmetric Decarboxylative 1,4‐Addition of Malonic Acid Half Thioesters to Vinyl Sulfones: Highly Enantioselective Synthesis of 3‐Monofluoromethyl‐3‐Arylpropanoic Esters

An asymmetric decarboxylative 1,4‐addition of malonic acid half thioesters (MAHTs) to 2‐aryl‐substituted vinyl sulfones has been developed, yielding adducts with excellent enantioselectivity (up to 97 % ee). In view of tuning pK_a values, a quinine‐based benzyl‐substituted thiourea was designed and demonstrated as the most efficient catalyst. The enantioselective synthesis of 3‐monofluorinated analogues of 3‐methyl indanone and (+)‐turmerone has been accomplished from decarboxylative 1,4‐addition adducts with satisfactory results.     

Synthesis,Modification, and Anticonvulsant Activity of 3′‐R1‐Spiro[indoline‐3,6′‐[1,2,4]triazino[2,3‐c]quinazolin]‐2,2′(7′H)‐diones Derivatives

Previously unknown 3′‐R¹‐5‐R²‐spiro[indoline‐3,6′‐[1,2,4]triazino[2,3‐c]quinazoline]‐2,2′‐(7′H)‐diones and their N‐substituted analogues were obtained via reaction of 6‐R¹‐3‐(2‐aminophenyl)‐1,2,4‐triazin‐5‐ones with isatin and its substituted derivatives. It was shown that alkylation of 3′‐R¹‐5‐R²‐spiro[indoline‐3,6′‐[1,2,4]triazino[2,3‐c]quinazolin]‐2,2′‐(7′H)‐diones by N‐R³‐chloroacetamides or chloroacetonitrile in the presence of а base proceeds by N‐1 atom of isatin fragment. The spectral properties (¹H and ¹³C NMR spectra) of synthesized compounds were studied, and features of spectral patterns were discussed. The high‐effective anticonvulsant and radical scavenging agents among 3′‐R¹‐5‐R²‐spiro[indoline‐3,6′‐[1,2,4]triazino[2,3‐c]quinazolin]‐2,2′(7′H)‐diones and their N‐substituted derivatives were detected. It was shown that compounds 2.2 , 2.8 , and 3.1 exceed or compete the activity of the most widely used in modern neurology drug—lamotrigine on the pentylenetetrazole‐induced seizures model. The aforementioned fact may be considered as a reason for further profound study of synthesized compounds using other pathology models.