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.     

Enantioselective Synthesis of 3,4‐Dihydropyran‐2‐ones by Domino Michael Addition and Lactonization with New Asymmetric Organocatalysts: Cinchona‐Alkaloid‐Derived Chiral Quaternary Ammonium Phenoxides

Chiral quaternary ammonium phenoxides were readily prepared from commercially available cinchona alkaloids and proved to be useful new asymmetric organocatalysts. Among various chiral quaternary ammonium phenoxides, a cinchonidine‐derived catalyst that bears both a sterically hindered N1‐9‐anthracenylmethyl group and a strongly electron withdrawing 9‐O‐3,5‐bis(trifluoromethyl)benzyl group were found to be highly effective for the Michael addition of ketene silyl acetals (derived from phenyl carboxylates) and α,β‐unsaturated ketones followed by lactonization. Optically active 3,4‐dihydropyran‐2‐one derivatives were obtained in high yields with excellent control of enantio‐ and diastereoselectivity. This catalyst can be handled in air and stored at room temperature in a sealed bottle without decomposition for at least one month.     

Synthesis of Pyrazolo[3,4‐b]pyridin‐6‐ones

The procedures for the synthesis of substituted pyrazolo[3,4‐b]pyridine‐6‐ones and some of their properties are reviewed.     

Concurrent Asymmetric Reactions Combining Photocatalysis and Enzyme Catalysis: Direct Enantioselective Synthesis of 2,2‐Disubstituted Indol‐3‐ones from 2‐Arylindoles

The combination of photoredox and enzymatic catalysis for the direct asymmetric one‐pot synthesis of 2,2‐disubstituted indol‐3‐ones from 2‐arylindoles through concurrent oxidization and alkylation reactions is described. 2‐Arylindoles can be photocatalytically oxidized to 2‐arylindol‐3‐one with subsequent enantioselective alkylation with ketones catalyzed by wheat germ lipase (WGL). The chiral quaternary carbon center at C2 of the indoles was directly constructed. This mode of concurrent photobiocatalysis provides a mild and powerful strategy for one‐pot enantioselective synthesis of complex compounds. The experiments proved that other lipases containing structurally analogous catalytic triad in the active site also can catalyze the reaction in the same way. This reaction is the first example of combining the non‐natural catalytic activity of hydrolases with visible‐light catalysis for enantioselective organic synthesis and it does not require any cofactors.     

5‐Unsubstituted Pyrido[3,2,1‐jk]carbazol‐6‐ones: Syntheses,Substitution, and Cyclization Reactions

The synthesis of the 5‐unsubstituted pyrido[3,2,1‐jk]carbazol‐6‐one 4 can be achieved by the reaction of carbazole ( 1 ) and malonate derivatives, either in a three‐step synthesis via 5‐acetyl‐pyridocarbazolone 3 or in a one‐step reaction from 1 and malonic acid/phosphoryl chloride. The 5‐acetyl derivative 5 can be transformed via a tosylate intermediate to 4‐azido‐pyridocarbazolone 11 , which cyclizes by thermal decomposition to the isoxazolo‐pyrido[3,2,1‐jk]carbazolone 12 . The thermolysis conditions were investigated by DSC. Nitration of pyridocarbazolone 4 and subsequent introduction of azide leads to azido derivative 23 , which cyclizes on thermolysis to furazan‐oxide derivative 24 . Again, the thermolysis conditions were investigated by DSC. 5‐Chloro‐5‐nitro‐pyrido[3,2,1‐jk]carbazole‐4,6‐dione, obtained from 4 by subsequent nitration and chlorination, forms by exchange of both 5‐substituents 5,5‐dihydroxy‐pyridocarbazoledione 17 , which acylates phenol to give 5‐hydroxy‐5‐(p‐hydroxyphenyl)‐pyridocarbazoledione 20 . Acid‐catalyzed cyclodehydration of 20 forms a highly fused benzofuro‐pyridocarbazole 21 . Another C–C coupling at position 5 starts from 4‐chloro‐5‐nitro‐pyridocarbazolone 22 and diethyl malonate 2a , which forms the diethyl (nitrocarbazolyl)malonate 25 . With dimethyl malonate 2c , the intermediate dimethyl (nitrocarbazolyl)malonate gives on thermolysis the (nitrocarbazolyl)acetate 27 by loss of one ester group.     

Synthesis of Novel Heterocycles Derived from 4‐Arylmethylene‐2‐phenyl‐1,3‐oxazole‐5(4H)‐ones

The acid hydrazide derivatives 2 were converted into pyrazolone, triazinone, and schiff bases. However, the reaction of Schiff base 12 with malononitrile or thioglycolic acid gives the pyrazolotriazinone or thiazolidinone derivative, respectively. The structures of the newly synthesized compounds were established on the basis of IR, ¹H‐NMR, mass spectral data, and elemental analyses. The antimicrobial activities of the synthesized compounds were examined against two types of bacteria and two types of fungi. Some of the tested compounds showed promising activities.     

Synthesis of 3‐arylazo‐6‐oxopyridazin‐5‐carbonitriles: A versatile precursor for condensed arylazopyridazin‐6‐ones

1‐[2‐Phenyl‐1‐diazenyl]‐1‐[2‐phenylhydrazono]acetone or 1‐[‐2‐(4‐methylphenyl)‐1‐diazenyl]‐1‐[‐2‐(4‐methylphenyl)hydrazono]‐butan‐2‐one were produced via coupling the (E) 2‐oxopropanal‐1‐phenyl‐hydrazone or (E) 2‐oxobutanal‐1‐(4‐methylphenyl)hydrazone with aromatic diazonium salts. These formazanes condensed readily with ethyl cyanoacetate to yield 5‐methyl‐3‐oxo‐2‐phenyl‐6‐phenylazo‐2,3‐dihydropyridazine‐4‐carbonitrile compound ( 9a ), 5‐ethyl‐3‐oxo‐2‐p‐tolyl‐6‐p‐tolylazo‐2,3‐dihydro‐pyridazine‐4‐carbonitrile and/or 5‐ethyl‐3‐oxo‐2,6‐di‐p‐tolyl‐2,3‐dihydropyridazine‐4‐carbonitrile that reacted with sulphur in presence of piperidine to yield the aminothienopyridazinones. The latter reacted with electron poor olefins and acetylenes to yield aminophthalazines. Compound ( 9a ) reacted also with benzylidenemalononitrile to yield the arylazophthalazinone.     

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.     

Multicomponent Reactions of Furan‐2,3‐diones: Synthesis and Characterizations of Furo[3,2‐c]pyran‐4‐ones

Furo[3,2‐c]pyran‐4‐ones, which possess a natural‐product skeleton, are synthesized via a simple, one‐pot, three‐component reaction of furan‐2,3‐diones with dialkyl acetylenedicarboxylates and Ph₃P.     

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.     

Synthesis of 1‐[(pyrazol‐3‐yl)methyl]pyridazin‐6‐ones

This paper presents the synthesis of 1‐[(pyrazol‐3‐yl)methyl]pyridazin‐6‐ones from ethyl 4‐(4,5‐dichloro‐6‐oxopyridazin‐1‐yl)‐3‐oxobutanoate.     

Synthesis and Photochromic Behavior of Novel Annelated 2H‐Chromenes Derived from Hydroxy‐9H‐xanthen‐9‐ones

The synthesis of four novel pyrano‐xanthenones derived from hydroxy‐9H‐xanthen‐9‐ones is described, and their photochromic properties in solution are reported. All compounds synthesized exhibit a good colorability, making them good potential dyes. The presence of the chromone system fused in the 7,8‐position seems to lead to more stabilized colored forms.