Prostanoids: LXXIV. 2,3-Dichloro- 4,4-ethylenedioxy-2-cyclopentenone in the Synthesis of Analogs of Marine Prostanoid

Transformations of readily accessible 2,3-dichloro-4,4-ethylenedioxy-2-cyclopentenone resulted in formation of previously unknown 2,3-dichloro-4-hydroxy-4-[(Z)-2-octenyl]-2-cyclopentenone which is a universal block synthon for analogs of marine prostanoids.     

Prostanoids: LXXXVI. Synthesis and Reductive Transformations of 2-Chloro-4,4-ethylenedioxy-3-phenylsulfanyl-2-cyclopentenone

The reduction of 2-chloro-4,4-ethylenedioxy-3-phenylsulfanyl-2-cyclopentenone with sodium tetra-hydridoborate in ethanol yields 3-chloro-4-hydroxy-2-phenylsulfanyl-2-cyclopentenone, while with the use of lithium aluminum hydride in tetrahydrofuran or the system Zn/NH₄Cl in methanol products of more profound reduction are obtained.     

Reactions of 2,3-Dichloro- and 2,3,5-Trichloro-4,4-ethylenedioxy-2-cyclopentenones with Some O-, S-, and N-Nucleophiles

2,3-Dichloro- and 2,3,5-trichloro-4,4-ethylenedioxy-2-cyclopentenones react with allyl and benzyl alcoholates and thiolates and benzylamine to give products resulting from Ad_NE substitution of the 3-chlorine atom, [1,3]-sigmatropic rearrangement, and cleavage of the C¹-C² bond.     

Photoaddition Reactions of 5-Fluoro-4,4-dimethyl-2-cyclopentenone

The photoaddition of 5-fluoro-4,4-dimethyl-2-cyclopentenone ( 4 ) to 2,3-dimethyl-2-butene leads specifically (in cyclohexane) and selectively (in acetonitrile) to the formation of the oxetanes 16 . The title compound is compared in its behaviour to the analogous 6-fluoro-4,4-dimethyl-2-cyclohexenone ( 1 ) and both α'-fluoro-4,4-dimethyl-2-cycloalkenones in turn are compared to the corresponding 2-cycloalkenones ( 6 and 3 ) and 4,4-dimethyl-2-cycloalkenones ( 5 and 2 ). The quantum yield for the addition of these enones to 2,3-dimethyl-2-butene and to cyclopentene are discussed.     

Reactions of 2,3,5-trichloro-4,4-ethylenedioxy-2-cyclopentenone with some ambident nucleophiles. Sterically loaded functionalized 6-azabicyclo[3.1.0]hex-5-enes

2,3,5-Trichloro-4,4-ethylenedioxy-2-cyclopentenone reacted with sodium azide in tetrahydrofuran to give the expected 3-azido derivative which was converted into 1,3-dichloro-4,4-ethylenedioxy-6-azabicyclo-[3.1.0]hex-5-en-2-one and 3-amino-2,5-dichloro-4,4-ethylenedioxy-2-cyclopentenone on heating in chloroform. The reaction of 2,3,5-trichloro-4,4-ethylenedioxy-2-cyclopentenone with potassium thiocyanate, depending on the conditions, afforded the corresponding 3-thiocyanato derivative or symmetric sulfide. Treatment of the title compound with hydroxylamine resulted in opening of the dioxolane ring with simultaneous formation of oxime via replacement of chlorine at the neighboring sp ²-carbon atom.Translated from Zhurnal Organicheskoi Khimii, Vol. 40, No. 10, 2004, pp. 1569–1573.Original Russian Text Copyright © 2004 by Shavaleeva, Ivanova, Usmanova, Akhmetvaleev, Miftakhov.     

Reactions of Nucleophilic Substitution in Bicyclic Nitroimidazodihydrooxazoles

This article describes numerous attempts of the S_N reaction of chlorine atom in chloromethyl group with nucleophilic compounds, such as the following: phenols, thiophenols, and amino compounds. The influences of ratios of nitroimidazodihydrooxazoles, nucleophiles and basic agent, and the polarity of solvent on the kind of formed products were established. Also, the comparison of reactivity with nucleophiles of close structural isomers of nitroimidazodihydrooxazoles has been made. The way of formation ring opening reaction products has been proposed.     

Prostanoids: LXXXVII. Synthesis of 3-Hydroxy-2-phenylsulfonyl-2-cyclopentenone and Its Ethylene Acetal

By oxidation of 3-phenylmercapto-2-chloro-4,4-ethylenedioxycyclopet-2-en-1-one with H₂O₂ in AcOH (or with m-ClC₆H₄CO₃H in CH²Cl²2) was obtained 2-chloro-3-phenylsulfonyl-4,4-ethylenedioxycyclopent-2-en-1-one which on reduction with NaBH₄ or LiAlH₄ afforded respectively 3-hydroxy-2-phenylsulfonylcyclopent-2-en-1-one and its ethyleneketal.     

Reactions of 2-Chloro-4,4-ethylenedioxy-3-phenylsulfonyl-cyclopent-2-en-1-one with some hydride reducing agents and carbon-centered nucleophiles

2-Chloro-4,4-ethylenedioxy-3-phenylsulfonylcyclopent-2-en-1-one reacts with NaBH₄ and LiAlH₄ to give, depending on the conditions, 4,4-ethylenedioxy-2-chloro-3-phenylsulfonylcyclopent-2-en-1-ol and 4,4-ethylenedioxy-3-phenylsulfonylcyclopent-2-en-1-ol, as well as 4,4-ethylenedioxy-3-phenylsulfonylcyclopentan-1-ol. Reactions of the title compound with diethyl malonate under basic conditions occurs at the double-bonded carbon atoms to form a couple of the addition-elimination products at C² and C³.     

Activated Monomers and Nucleophilic Reagents in Addition and Polymerization Reactions

A number of examples of addition and polymerization reactions is presented with special emphasis on the chemical behaviors of activated monomers and/or activated nucleophilic reagents. Lithium alkoxyethanolate forms a complex with lithium alkyl. Spectroscopic studies showed this complex to possess agent-separated ion pairs. The nature of the complex is characterized by the enhanced reactivity of styrene in the copolymerization reaction with butadiene initiated by the complex. Magnesium alkyl can be sufficiently activated by magnesium alkoxyethanolate to polymerize styrene and diene. Aluminum alkyl and zinc alkyl are able to induce the anionic polymerization of vinyl ketones, but not of unsaturated esters or nitriles. Aluminum or zinc alkoxyethanolates fail to activate their corresponding metal alkyls. Bipyridyl, sparteine, triphenylphosphine, HMPT, and related Lewis bases, however, activate aluminum alkyl enough to react with carbon-carbon double bonds of the unsaturated esters and nitriles. Crotononitrile can be polymerized by the AIR₃-HMPT system to form a colorless polymer, where possible side reactions between CN and AIR₃ are prevented by HMPT. Mutual activation through complex formation is confirmed by a model system of a vinyl ketone with organozinc compounds. AIR₃-HMPT does not polymerize vinyl ketones because of a lack of complex formation. N-Carboxy-α-alanine anhydride (NCA) can be polymerized with zinc alkyl as initiator. The formation of activated NCA by proton abstraction from the NH group is shown to be the essential stage for polymerization. Zinc alkyl is also activated by conventional acid anhydrides. The propylene oxide ring can be cleaved with the ZnR₂-phthalic anhydride system, which is the initiation step in the alternate copolymerization between propylene oxide and the acid anhydride. The propagation mechanism of the CO₂-epoxide copolymerization is also discussed.     

Nucleophilic Substitution in 1,5-Benzodiazepin-2-ones

The reaction of 3-bromo-4-phenyl-2,3-dihydro-1H-1,5-benzodiazepin-2-one with cyclic amines gives 3-aminoalkyl-4-phenyl-2,3-dihydro-1H-1,5-benzodiazepin-2-one. Thiazolo[4,5-b][1,5]benzodiazepine was isolated along with the substitution product when thiourea was used.     

Some Features of Nucleophilic Substitution Reactions of N-2-Haloethyl Derivatives of 5,5-Substituted Hydantoins

Russian Journal of General Chemistry - Reaction of 5,5-dimethyl-3-(2-chloroethyl)- and 5,5-diphenyl-3-(2-bromoethyl)- hydantoins with potassium 4-aminobenzoate in dimethylformamide in the presence...     

1,2-Adducts of 5-Allyl-2,3,5-trichloro-4,4-dimethoxy-2-cyclopentenone with Ethyl Acetate Lithium Salt and Their Reactions with Iodine

The condensation of 5-allyl-2,3,5-trichloro-4,4-dimethoxy-2-cyclopentenone with ethyl acetate lithium salt generated in situ in THF at -78°C gave adducts at the carbonyl group, the corresponding cis- and trans-chlorohydrins. The steric structure of the products was determined by involving them into reaction with iodine. From the trans-adduct the expected bicyclic compound was obtained, while the cis-chlorohydrin underwent anomalous deacetalization to iodomethoxycyclopentenone. Spectral parameters of the adducts were discussed. Unusual diastereotopicity was observed for the remote methylene groups in the ester moiety.     

Nucleophilic Reactions of Osmanaphthalynes with PMe3 and H2O

Members of a new class of complexes, 2 (CF₃), 2 (H), 2 (Br), 2 (I), and 2 (OCH₃), have been synthesized in a one-pot method involving the treatment of osmanaphthalynes bearing corresponding substituents ( 1 (CF₃), 1 (H), 1 (Br), 1 (I), and 1 (OCH₃)) with trimethylphosphine (PMe₃) and water. The main reaction process involves two steps, namely a ligand-exchange with trimethylphosphine and nucleophilic addition of water to the Os≡C bond of the osmanaphthalyne. The substituents have a significant influence on the rate of the reaction, as befits a nucleophilic addition. Fortunately, the key intermediate [ 1 (OCH₃)]′ could be successfully captured, and the detailed reaction mechanism has been explored with the aid of density functional theory (DFT) calculations, which were in excellent agreement with the experimental findings. All of the target complexes have been fully characterized by ¹H, ³¹P{¹H}, and ¹³C{¹H} NMR spectroscopy, high-resolution mass spectrometry, and elemental analysis.     

Enhanced Reactivity in Nucleophilic Acyl Substitution Ion/Ion Reactions Using Triazole-Ester Reagents

The acyl substitution reactions between 1-hydroxy-7-aza-benzotriazole (HOAt)/1-hydroxy-benzotriazole (HOBt) ester reagents and nucleophilic side chains on peptides have been demonstrated in the gas phase via ion/ion reactions. The HOAt/HOBt ester reagents were synthesized in solution and ionized via negative nano-electrospray ionization. The anionic reagents were then reacted with doubly protonated model peptides containing amines, guanidines, and imidazoles in the gas phase. The complexes formed in the reaction cell were further probed with ion trap collision induced dissociation (CID) yielding either a covalently modified analyte ion or a proton transfer product ion. The covalent reaction yield of HOAt/HOBt ester reagents was demonstrated to be higher than the yield with N-hydroxysuccinimide (NHS) ester reagents over a range of equivalent conditions. Density functional theory (DFT) calculations were performed with a primary amine model system for both triazole-ester and NHS-ester reactants, which indicated a lower transition state barrier for the former reagent, consistent with experiments. The work herein demonstrates that the triazole-ester reagents are more reactive, and therefore less selective, than the analogous NHS-ester reagent. As a consequence, the triazole-ester reagents are the first to show efficient reactivity with unprotonated histidine residues in the gas phase. For all nucleophilic sites and all reagents, covalent reactions are favored under long time, low amplitude activation conditions. This work presents a novel class of reagents capable of gas-phase conjugation to nucleophilic sites in analyte ions via ion/ion chemistry.

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Reactions of Electrophilic and Nucleophilic Substitution in Flavonoid Series Involving Amino Acids and Their Derivatives

Reactions of catechin and dihydroquercetin flavonoids with amino acids containing primary amino groups have been conducted. Amino acids can be used in both electrophilic substitution (Mannich aminomethylation) and electrophilic substitution (acylation) reactions.     

Significantly Enhanced Reactivities of the Nucleophilic Substitution Reactions Induced by Microwaves in Ionic Liquid

The reaction rate of nucleophilic substitution can be dramatically enhanced by microwave irradiation using the ionic liquid [Bmim]BF4 as a solvent. Nucleophilic reagents (anilines, thiophenol) react with ethoxymethylene isopropylidene malonate to give corresponding products in 5–10 min in good yields.     

β‐Cyclodextrin Immobilized onto Dowex Resin: A Unique Microvessel and Heterogeneous Catalyst in Nucleophilic Substitution Reactions

The catalytic activity of β‐cyclodextrin immobilized on Dowex resin as an efficient solid‐liquid phase transfer catalyst was developed for the synthesis of alkyl thiocyanates and phenacyl derivatives in water. The nucleophilic substitution reactions were performed under mild reaction condition and gave the products in excellent yields. Furthermore, the catalyst could be recycled by facile separation without any loss of activity.