Formation of 2‐(Phenylsulfonyl)resorcinols (=2‐(Phenylsulfonyl)benzene‐1,3‐diols) from Symmetrically Substituted Maleic Anhydrides (=Furan‐2,5‐diones)

Treatment of symmetrically substituted maleic anhydrides (=furan‐2,5‐diones) 6 with lithium (phenylsulfonyl)methanide, followed by methylation of the adduct with MeI/K₂CO₃ in acetone, give the corresponding 4,5‐disubstituted 2‐methyl‐2‐(phenylsulfonyl)cyclopent‐4‐ene‐1,3‐diones 8 (Scheme 3). Reaction of the latter with lithium (phenylsulfonyl)methanide in THF (?78°) and then with 4 mol‐equiv. BuLi (?5° to r.t.) leads to 5,6‐disubstituted 4‐methyl‐2‐(phenylsulfonyl)benzene‐1,3‐diols 9 (Scheme 4).     

Two‐ and Three‐Component Reactions Leading to New Enamines Derived from 2,3‐Dicyanobut‐2‐enoates

The three‐component reactions of 1‐azabicyclo[1.1.0]butanes 1 , dicyanofumarates (E)‐ 5 , and MeOH or morpholine yielded azetidine enamines 8 and 9 with the cis‐orientation of the ester groups at the C?C bond ((E)‐configuration; Schemes 3 and 4). The structures of 8a and 9d were confirmed by X‐ray crystallography. The formation of the products is explained via the nucleophilic addition of 1 onto (E)‐ 5 , leading to a zwitterion of type 7 (Scheme 2), which is subsequently trapped by MeOH or morpholine ( 10a ), followed by elimination of HCN. Similarly, two‐component reactions between secondary amines 10a – 10c and (E)‐ 5 gave products 12 with an (E)‐enamine structure and (Z)‐oriented ester groups. On the other hand, two‐component reactions involving primary amines 10d – 10f or NH₃ led to the formation of the corresponding (Z)‐enamines, in which the (E)‐orientation of ester groups was established.     

Chemoselectivity of the Reactions of Diazomethanes with 5‐Benzylidene‐3‐phenylrhodanine

The reactions of 5‐benzylidene‐3‐phenylrhodanine ( 2 ; rhodanine=2‐thioxo‐1,3‐thiazolidin‐4‐one) with diazomethane ( 7a ) and phenyldiazomethane ( 7b ) occurred chemoselectively at the exocyclic C?C bond to give the spirocyclopropane derivatives 9 and, in the case of 7a , also the C‐methylated products 8 (Scheme 1). In contrast, diphenyldiazomethane ( 7c ) reacted exclusively with the C?S group leading to the 2‐(diphenylmethylidene)‐1,3‐thiazolidine 11 via [2+3] cycloaddition and a ‘two‐fold extrusion reaction’. Treatment of 8 or 9b with an excess of 7a in refluxing CH₂Cl₂ and in THF at room temperature in the presence of [Rh₂(OAc)₄], respectively, led to the 1,3‐thiazolidine‐2,4‐diones 15 and 20 , respectively, i.e., the products of the hydrolysis of the intermediate thiocarbonyl ylide. On the other hand, the reactions with 7b and 7c in boiling toluene yielded the corresponding 2‐methylidene derivatives 16, 21a , and 21b . Finally, the reaction of 11 with 7a occurred exclusively at the electron‐poor C?C bond, which is conjugated with the C?O group. In addition to the spirocyclopropane 23 , the C‐methylated 22 was formed as a minor product. The structures of the products (Z)‐ 8, 9a, 9b, 11 , and 23 were established by X‐ray crystallography.     

New Optically Active Bis‐Heterocycles Derived from (S)‐Proline

Enantiomerically pure bis‐heterocycles containing a (S)‐proline moiety have been prepared starting from (S)‐N‐benzylprolinehydrazide ( 2b ). The reactions with isothiocyanates or butyl isocyanate in refluxing MeOH led to the corresponding thiosemicarbazide 5 and semicarbazide 9 with a N‐benzylprolinoyl residue. The structure of the tert‐butyl derivative 5d was established by X‐ray crystallography. Base‐catalyzed cyclization of 5 and 9 led to (S)‐3‐(pyrrolidin‐2‐yl)‐1H‐1,2,4‐triazole‐5(4H)‐thiones 6 and the corresponding 5(4H)‐one 8 , respectively, whereas, in concentrated H₂SO₄, compounds 5 undergo cyclization to give (S)‐5‐amino‐2‐(pyrrolidin‐2‐yl)‐1,3,4‐thiadiazoles 7 . Furthermore, 2b reacted with hexane‐2,5‐dione in boiling ⁱPrOH to yield the (S)‐N‐(2,5‐dimethylpyrrol‐1‐yl)prolinamide 10 . In the case of the bis‐heterocycle 8 , treatment with HCOONH₄ and Pd/C in MeOH gave the debenzylated product 12 .     

Reaction of γ‐Hydroxy‐N‐[1‐(dimethylcarbamoyl)ethyl]butanamides under the ‘Direct Amide Cyclization’ Conditions

The preparation of the title compounds was achieved via the ‘azirine/oxazolone method’ starting from the corresponding γ‐hydroxy acids. Upon subjecting the γ‐hydroxy‐N‐[1‐(dimethylcarbamoyl)ethyl]butanamides 4 to the so‐called ‘direct amide cyclization’ (DAC) conditions, chlorinated acids 11 or imino lactones 12 were obtained as the sole products instead of the expected cyclodepsipeptides A or their cyclodimers (Scheme 4). Variation of the substituents in 4 did not affect the outcome of the reaction and a mechanism for the formation of both products from the intermediate oxazolone 13 has been proposed. Under the acidic conditions of the DAC, the imino lactones are formed as their HCl salts 12 , which, in polar solvents or on silica gel, reacted further to give the chlorinated acids 11 . Stabilization of the imino lactones was achieved by increasing the substitution in the five‐membered ring, and their structure, in the form of the hydrochlorides, was established independently by X‐ray crystallography (Fig. 4). A derivative 15 of the imino lactone 12a was prepared by the reaction with the 2H‐azirin‐3‐amine 10a ; its structure was also established by an X‐ray crystal‐structure determination (Fig. 3). Furthermore, the structures of the ω‐chloro acids 11a and 11b were determined by X‐ray crystallography (Fig. 2).     

Reactions with 4‐Hydroxy‐2‐methylbutananilides: Unexpected Formation of a Cyclopropanecarboxamide

The successive treatment of the N,N‐disubstituted 4‐hydroxy‐2‐methylbutanamide 2a with lithium diisopropylamide (LDA) and diphenyl phosphorochloridate (DPPCl) led to the 1‐methylcyclopropanecarboxamide 10 in good yield. This base‐catalyzed cyclization offers a new approach to cyclopropanecarboxamides. Under similar conditions, the N‐monosubstituted 4‐hydroxy‐2‐methylbutanamide 2b gave the 3‐methylpyrrolidin‐2‐one 11 . The structure of the cyclopropanecarboxamide 10 was established by X‐ray crystallography.     

One‐Pot Synthesis of Highly Substituted 1H‐Pyrazole‐5‐carboxylates from 4‐Aryl‐2,4‐diketoesters and Arylhydrazines

A one‐pot synthesis of highly substituted 1H‐pyrazole‐5‐carboxylates 1 has been developed starting from easily available 4‐aryl‐2,4‐diketoesters 2 and arylhydrazine hydrochlorides 3 . More active 2‐carbonyl group of 2 was blocked with methoxyamine hydrochloride to give 2‐methoxy imine intermediates, which were then subjected to condensation cyclization with 3 in situ to provide the desired products 1 . In addition, the geometrical configuration of 1aa was unambiguously confirmed by single crystal X‐ray crystallography.     

Synthesis and characterization of a thermotropic liquid‐crystalline poly[2,5‐bis(4′‐alkoxycarbonylphenyl) styrene]

We report the synthesis and characterization of a series of novel mesogen‐jacketed liquid‐crystalline polymers, poly[2,5‐bis(4′‐alkoxycarbonylphenyl)styrene]s ( 1‐m , where m is the number of carbon atoms in the alkyl tails), along with the corresponding monomers, 2,5‐bis(4′‐alkoxycarbonylphenyl)styrenes ( 2‐m ), and their precursors, 2,5‐bis(4′‐alkoxycarbonylphenyl)toluenes ( 3‐m ). The influence of the tail length on the thermotropic properties of the two types of low‐molecular‐mass compounds and macromolecules was investigated with a combination of differential scanning calorimetry, polarized optical microscopy, and wide‐angle X‐ray diffraction techniques. Except for compound 3‐3 , which exhibited a monotropic nematic phase, all members of the low‐molar‐mass molecules developed no mesophase during both heating and cooling processes. The glass‐transition temperatures of the polymers decreased as the tail lengths increased. The 5% weight loss temperatures of all the polymers under a nitrogen atmosphere were above 360 °C, indicating quite high thermal stability. Although polymers 1‐1 and 1‐2 were non‐liquid‐crystalline, columnar nematic phases were observed for the remaining homopolymers with longer alkyl tails. The mesophases of 1‐3 to 1‐9 that developed at high temperatures remained upon cooling to room temperature, whereas those of 1‐10 to 1‐12 disappeared during the cooling process. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 830–847, 2007.     

Synthesis of Three‐, Five‐, and Six‐Membered Heterocycles Derived from New β‐Amino‐α‐(trifluoromethyl) Alcohols

Nucleophilic trifluoromethylation of α‐imino ketones 2 , derived from arylglyoxal, with Ruppert–Prakash reagent (CF₃SiMe₃) offers a convenient access to the corresponding O‐silylated β‐imino‐α‐(trifluoromethyl) alcohols. In a ‘one‐pot’ procedure, by treatment with NaBH₄, these products smoothly undergo reduction and desilylation yielding the expected β‐amino‐α‐(trifluoromethyl) alcohols 4 . The latter were used as starting materials for the synthesis of diverse trifluoromethylated heterocycles, including aziridines 5 , 1,3‐oxazolidines 8 , 1,3‐oxazolidin‐2‐ones 9 , 1,3,2‐oxazaphospholidine 2‐oxides 10 , 1,2,3‐oxathiazolidine 2‐oxides 11 , and morpholine‐2,3‐diones 12 . An optically active 5‐(trifluoromethyl)‐substituted 1,3‐oxazolidin‐2‐one 9g was also obtained.     

Mechanistic Insights into an Unexpected Carbon Dioxide Insertion Reaction through the Crystal Structures of Carbamic Diphenylthiophosphinic Anhydride and l‐[(4‐Nitrophenyl)‐sulfonyl]‐trans‐2,5‐pyrrolidinedicarboxylic Acid Methyl Ester

The crystal structures of an unexpected carbon dioxide inserted carbamidiphenylthiophosphinic anhydride and l‐[(4‐nitrophenyl) sulfonyl]‐trans‐2, 5‐pyrrolidinedicarboxylic acid methyl ester were determined by X‐ray analysis. They crystallized in the space group P2₁(#4) with a =0.9550(2), b = 0.9401(4), c= 1.2880(2) nm, β= 107.74°, V= 1.1013 (5) nm³, D_caled= 1.349 g/cm³, Z = 2 and P2₁2₁2₁(# 19) with a = 1.4666(2), b = 0.7195(2), c = 1.6339(2) nm, V = 1.7240(7) nm³, D_caled = 1.434 g/cm³, Z = 4, respectively. Through the investigation of these two crystal structures, the mechanistic insights into this unexpected carbon dioxide insertion in the reaction of trans‐2,5‐disubstituted pyrrolidine with diphenylthiophosphoryl chloride in the presence of potassium carbonate were disclosed.     

Synthesis of Acetyl and Iodo Derivatives of 4‐Hydroxy‐6‐phenyl‐6H‐pyrano[3,2‐c]pyridine‐2,5‐diones and 4‐Hydroxy‐1‐phenylpyridin‐2(1H)‐ones

A simple and efficient method has been described for the synthesis of acetyl and iodo derivatives of 4‐hydroxy‐6‐phenyl‐6H‐pyrano[3,2‐c ]pyridine‐2,5‐diones 1 and 4‐hydroxy‐1‐phenylpyridin‐2(1H )‐ones 5 . Compounds 1 with phenyl and alkyl substituent at C(7) and C(8), respectively, can be easily acetylated by refluxing in a mixture of acetic acid and polyphosphoric acid to give 3‐acetyl‐4‐hydroxy‐6‐phenyl‐6H‐pyrano[3,2‐c ]pyridine‐2,5‐diones 2 in excellent yields. Compounds 1 and 5 can be iodinated with iodine and anhydrous sodium carbonate in boiling dioxane to give 4‐hydroxy‐3‐iodo‐6‐phenyl‐6H‐pyrano[3,2‐c ]pyridine‐2,5‐diones 3 and 4‐hydroxy‐3‐iodo‐1‐phenylpyridin‐2(1H )‐ones 6 , respectively, in good yields. The structures were confirmed using infrared, nuclear magnetic resonance , and elemental analysis.     

Selective Synthesis of 1,2‐Diarylpyrrolo[3,4‐b]pyridine‐5,7‐diones via Cyclization Reaction of β‐Enamino Imides with Cinnamaldehydes

The novel 1,2‐diaryl substituted pyrrolo[3,4‐b]pyridine‐5,7‐diones were selectively synthesized in high yields by the base catalyzed cyclization reaction of 3‐arylamino‐1‐methyl‐1H‐pyrrole‐2,5‐diones with cinnamaldehyde and its derivatives in acetonitrile at room temperature. However, when piperidinium trifluoroacetate was employed as catalyst, the reaction afforded a mixture of 1,2‐diaryl and 1,4‐diaryl substituted pyrrolo[3,4‐b]pyridine‐5,7‐diones in comparable yields.     

Report on an Unusual Cascade Reaction between Azulenes and 2,3‐Dichloro‐5,6‐dicyano‐1,4‐benzoquinone (=4,5‐Dichloro‐3,6‐dioxocyclohexa‐1,4‐diene‐1,2‐dicarbonitrile; DDQ)

The oxidation of 1‐(3,8‐dimethylazulen‐1‐yl)alkan‐1‐ones 1 with 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (=4,5‐dichloro‐3,6‐dioxocyclohexa‐1,4‐diene‐1,2‐dicarbonitrile; DDQ) in acetone/H₂O mixtures at room temperature does not only lead to the corresponding azulene‐1‐carboxaldehydes 2 but also, in small amounts, to three further products (Tables 1 and 2). The structures of the additional products 3 – 5 were solved spectroscopically, and that of 3a also by an X‐ray crystal‐structure analysis (Fig. 1). It is demonstrated that the bis(azulenylmethyl)‐substituted DDQ derivatives 5 yield on methanolysis or hydrolysis precursors, which in a cascade of reactions rearrange under loss of HCl into the pentacyclic compounds 3 (Schemes 4 and 7). The found 1,1′‐[carbonylbis(8‐methylazulene‐3,1‐diyl)]bis[ethanones] 4 are the result of further oxidation of the azulene‐1‐carboxaldehydes 2 to the corresponding azulene‐1‐carboxylic acids (Schemes 9 and 10).     

Synthesis and Hill Inhibitory Activity of New Substituted 3‐Aryl‐5‐cyano‐6‐methylthio Pyrimidine‐2, 4‐diones

Novel substituted derivatives of 3‐aryl‐5‐cyano‐6‐methylthiopyrimidine‐2, 4‐diones were synthesized by the reaction of ethyl 2‐cyano‐3,3′‐dimethylthioacrylate with arylureas in good yields. The structures of all title compounds were evaluated by elemental analyses and ¹H NMR spectra and compound 2c was also confirmed by X‐ray diffraction. Hill reaction inhibitory activity of title compounds was assayed.     

Reactions of 2‐Unsubstituted 1H‐Imidazole 3‐Oxides with 2,2‐Bis(trifluoromethyl)ethene‐1,1‐dicarbonitrile: A Stepwise 1,3‐Dipolar Cycloaddition

The reaction of 1,4,5‐trisubstituted 1H‐imidazole‐3‐oxides 1 with 2,2‐bis(trifluoromethyl)ethene‐1,1‐dicarbonitrile ( 7 , BTF) yielded the corresponding 1,3‐dihydro‐2H‐imidazol‐2‐ones 10 and 2‐(1,3‐dihydro‐2H‐imidazol‐2‐ylidene)malononitriles 11 , respectively, depending on the solvent used. In one example, a 1 : 1 complex, 12 , of the 1H‐imidazole 3‐oxide and hexafluoroacetone hydrate was isolated as a second product. The formation of the products is explained by a stepwise 1,3‐dipolar cycloaddition and subsequent fragmentation. The structures of 11d and 12 were established by X‐ray crystallography.     

Synthesis of 2‐Aryl‐5‐oxo‐4‐[2‐(phenylmethylidene)hydrazino]‐2,5‐dihydro‐1H‐pyrrole‐3‐carboxylates by the Reaction between Hydrazones,Acetylenedicarboxylates, and 1‐Aryl‐N,N′‐bis(arylmethylidene)methanediamines

An efficient approach for the preparation of functionalized 2‐aryl‐2,5‐dihydro‐5‐oxo‐4‐[2‐(phenylmethylidene)hydrazino]‐1H‐pyrroles is described. The four‐component reaction between aldehydes, NH₂NH₂?H₂O, dialkyl acetylenedicarboxylates, and 1‐aryl‐N,N′‐bis(arylmethylidene)methanediamines proceeds in EtOH under reflux in good‐to‐excellent yields (Scheme 1). The structures of 4 were corroborated spectroscopically (IR, ¹H‐ and ¹³C‐NMR, and EI‐MS, and, in the case of 4f , by X‐ray crystallography). A plausible mechanism for this type of reaction is proposed (Scheme 2).     

Synthesis and Structures of Two Isomeric 4‐Diazo‐2,3,4,5‐tetrahydrofuran‐3‐ones

The two regioisomeric 4‐diazo‐2,3,4,5‐tetrahydrofuran‐3‐ones 6 and 7 were prepared via the common intermediate 2,3,4,5‐tetrahydro‐2,2‐dimethyl‐5,5‐diphenylfuran‐3‐one ( 8 ). Diazo transfer with 2,4,6‐triisopropylbenzenesulfonyl azide yielded 6 , whereas 7 was obtained via oxidation of the monohydrazone 12 , which was prepared selectively from tetrahydrofuran‐3,4‐dione 11 . The crystal structures of 6 and 7 have been established by X‐ray crystallography.     

Synthesis and molecular structure of novel 4‐aryloctahydropyrido‐[1,2‐c]pyrimidine derivatives

A series of new 4‐aryloctahydropyrido[1,2‐c]pyrimidine‐1,3‐diones 6a,b,d‐h and j were synthesized by intramolecular cyclization of α‐aryl‐α‐(1‐ethoxycarbonyl‐2‐piperidyl)‐acetamide derivatives 5a,b,d‐h and j . The structures of compounds were determined by ¹H and ¹³C nmr spectroscopy. Nmr and X‐ray diffraction data indicate that the configuration at the C4, C4a stereocenters constitute RR and SS pair.     

Synthesis of 1,3‐Selenazol‐2(3H)‐imines

The reaction of N,N′‐diarylselenoureas 16 with phenacyl bromide in EtOH under reflux, followed by treatment with NH₃, gave N,3‐diaryl‐4‐phenyl‐1,3‐selenazol‐2(3H)‐imines 13 in high yields (Scheme 2). A reaction mechanism via formation of the corresponding Se‐(benzoylmethyl)isoselenoureas 18 and subsequent cyclocondensation is proposed (Scheme 3). The N,N′‐diarylselenoureas 16 were conveniently prepared by the reaction of aryl isoselenocyanates 15 with 4‐substituted anilines. The structures of 13a and 13c were established by X‐ray crystallography.     

Synthesis,Structure of Zwitterionic 2‐Amino‐N′‐(imidazolidin‐2‐ylidene)benzohydrazides,and Their Transformation into 3‐(Imidazolidin‐2‐ylideneamino)quinazolin‐4(1H)‐one Derivatives

The reaction of 2‐chloro‐4,5‐dihydroimidazole ( 5 ) with 2‐aminobenzohydrazides 6a–e led to the formation of 2‐amino‐N′‐(imidazolidin‐2‐ylidene)benzohydrazides as zwitterions 7a–e , which on treatment with carbon disulfide in the presence of triethylamine afforded 3‐(imidazolidin‐2‐ylideneamino)‐2‐thioxo‐2,3‐dihydroquinazolin‐4(1H)‐ones 8a–e . Compounds 8a–d were further converted into the corresponding 3‐(imidazolidin‐2‐ylideneamino)quinazoline‐2,4(1H,3H)‐diones 9a–d using hydrogen peroxide–sodium hydroxide solution. The structures of the compounds prepared were established by elemental analyses, IR and NMR spectra as well as X‐ray crystallographic analyses of 7e and 9a .