Catalysis of the Reaction of Cholesteryl Acetate with 4‐Phenyl‐1,2,4‐triazoline‐3,5‐dione by Lithium Perchlorate

Abstract

The 3β‐acetoxy‐6β‐(3,5‐dioxo‐4‐phenyl‐[1,2,4]triazolidin‐1‐yl)cholest‐4‐ene structure has been assigned to a single product of the reaction of cholesteryl acetate with 4‐phenyl‐1,2,4‐triazoline‐3,5‐dione in Et₂O solution, mediated by LiClO₄.     

Synthesis of 4‐Arylthio‐3‐hydroxyphthalate by the Diels–Alder Reactionof 4‐Arylthio‐3‐hydroxy‐2‐pyrone

Treatment of 4‐arylthio‐3‐hydroxy‐2‐pyrones with acetylenedicarboxylates gave 4‐arylthio‐3‐hydroxyphthalates by the base‐catalyzed Diels–Alder reaction via a decarboxylation in good yields.     

Preparation of Microspheres by an Emulsification‐Condensation Method

Microspheres were prepared using N‐methylolurea‐dodecylamine conjugate (MU‐DOA), an emulsifiable and self‐condensaible oil. MU was prepared by reacting urea and formaldehyde at 70°C in alkali conditions and then conjugating it to DOA by a condensation reaction. The MU‐DOA conjugate was emulsified in distilled water without an emulsifier, and then the oil droplets were hardened to obtain microspheres by a self‐condensation reaction among methylols of the conjugate. The reactions of each step, e.g., the preparation of MU, the conjugation of MU and DOA, and the self‐condensation of emulsified oil, were confirmed by Fourier transform infrared (FTIR) spectra. On scanning electron microscopy (SEM), the microspheres formed by the self‐condensation of the emulsified MU‐DOA were shown as spherical and less than 30 µm in diameter. The phase transition temperatures of DOA, MU‐DOA, and MU‐DOA microspheres were 30.3°C, 21.1°C, and 20.1°C, respectively. The lower transition temperature of MU‐DOA is probably due to the bulky MU, which could reduce the intermolecular interaction of MU‐DOA. Zeta potentials of the microspheres decreased from positive to negative value as pH increased from 3.5 to 10.5. The deprotonation of the amines of MU‐DOA would be responsible for that result.     

A Method for Multiconformational Modeling of the Three‐Dimensional Shape of a Molecule

A method for multiconformational modeling of the threedimensional shape of a molecule is proposed that includes search for conformers, their optimum superposition, and analysis of spatial features of the resulting structure. The method allows one to determine features of various molecular conformations of compounds under study, to assess the contributions of conformers to particular properties of the substance, to evaluate the space occupied by the molecule, and to compare the average size of the multiconformational model of the molecule with the sizes of the most stable conformations. The potentials of the model are illustrated by density calculations for 137 organic liquids.     

Short Synthesis of 3‐Prenylcoumarins by an Unusual Prenylation

Abstract

Prenylation of coumarins that have hydroxyl or alkoxyl or halo substitution (1a–1i) using 2‐methyl‐3‐butene‐2‐ol in the presence of boron trifluoride formed 3‐prenylcoumarins (2a–2d).     

One‐Pot Synthesis of 2‐Arylthio‐2‐cyclohexenone Derivatives by the Diels–Alder Reaction of 4‐Arylthio‐3‐hydroxy‐2‐pyrones

The base‐catalyzed Diels–Alder reactions of 4‐arylthio‐3‐hydroxy‐2‐pyrones are reported. Treatment of 4‐arylthio‐3‐hydroxy‐2‐pyrones and dienophiles with triethylamine gave 2‐arylthio‐2‐cyclohexenone derivatives by the Diels–Alder reaction involving a decarboxylation in excellent to reasonable yields.     

Synthesis of 2‐Alkyl‐Substituted Benzimidazoles by Thermal Decomposition of 2‐Azidobenzenamines in thePresence of an Aldehyde

2‐Substituted benzimidazoles were prepared by reaction of 2‐azidoaminobenzenes with aldehydes under thermal conditions. The reaction probably proceeds via a sequential imine formation, azide decomposition forming a nitrene, and electrocyclization.     

Novel Methods for the Synthesis of 4‐Arylisoquinolinium Perchlorates and 4‐Arylisoquinolin‐1‐ones

2‐Benzylamino‐1‐phenyl‐ethanones 1 were converted to the corresponding isoquinolinium perchlorates 2 in high yields using 70% HClO₄‐FeCl₃ mixture as a cyclization and oxidation reagent. A mild and high yielding method for the oxidation of perchlorates 2 to isoquinolin‐1‐ones 3 involving the treatment of 2 with KOH and K₃[Fe(CN)₆] in THF‐H₂O two‐phase system at room temperature was developed. Compounds 2a–g were shown to be disproportionate to 3 and the corresponding 1,2‐dihydroisoquinoline 4 in the presence of base, which in turn is oxidized by K₃[Fe(CN)₆] to 2.     

Preparation of 4‐Arylcyclopentenes by Sequential Diallylation of Arylaldehydes and Ring‐Closing Metathesis

Abstract

Allylsilane diallylation of aryl aldehydes followed by ring closure metathesis leads to 4‐arylcyclopentenes in good yields.     

Practical One‐Pot Procedure for the Synthesis of 1,2,3,4‐Tetrahydroquinolines by the Imino‐Diels‐Alder Reaction

A novel‐one‐pot procedure for the synthesis of tetrahydroquinolines via the imino‐Diels‐Alder reaction is described. This procedure gives better yields and exhibits better versatility for alkene substrates than the existing hemi‐aminal based methodologies.     

Synthesis of Mesoionic 4‐(para‐substituted Phenyl‐5‐2,4‐dichlorophenyl)‐1,3‐4‐thiadiazolium‐2‐aminides by Direct Cyclization via Acylation of Thiosemicarbazides

The synthesis of ten novel mesoionic 4‐[para‐substituted (H, CH₃, OCH₃, NO₂, Cl, Br, OH, t‐C₄H₉, C₆H₅, C₄H₉) phenyl‐5‐2,4‐dichlorophenyl]‐1,3‐4‐thiadiazolium‐2‐aminides, as hydrochlorides, are described. The synthesis strategy utilized the corresponding para‐substituted isothiocyanates as starting materials to obtain the thiosemicarbazides through reaction with phenylhydrazine (61–98%), which were then submitted to acylation with 2,4‐dichloro benzoyl chloride and direct cyclization to generate the desired substituted mesoionic compounds in good yields (ca. 80%).     

Solid‐Phase Synthesis of N‐Aryl‐N′‐Carboalkoxy Guanidines by the Mitsunobu Reaction of Fmoc‐Guanidines

Abstract

A new method for the solid‐phase synthesis of N‐aryl‐N′‐carboalkoxy guanidines is described. Aromatic amines were reacted with Fmoc‐isothiocyanate to provide Fmoc‐thioureas, which were coupled with Rink amide resin to provide the corresponding resin‐bound Fmoc‐guanidines. Subsequent Mitsunobu alkylation with a variety of alcohols delivered N‐aryl‐N′ carboalkoxy guanidines in good to high purity after resin cleavage.     

One‐Pot Synthesis of 4‐Oxo‐2‐thioxohexahydropyrimidines Catalyzed by Potassium Carbonate Under Ultrasound

Abstract

The one‐pot condensation of aldehydes, ethyl cyanoacetate and thiourea catalyzed by potassium carbonate in ethanol results 4‐oxo‐2‐thioxohexahydropyrimidines in 20–90% yields under ultrasound irradiation.     

Synthesis of the Aliphatic Subunit of the Macrolide LL‐Z 1640‐2 via Vasella Ring Opening of a 6‐Iodo‐4‐deoxy‐D‐mannose

The synthesis of the aliphatic subunit 9 of the macrolide LL‐Z1640‐2 (I), starting from a 4‐deoxy‐D‐mannose derivative 2a, is described. The procedure includes the first successful application of a Vasella ring opening reaction for a 4‐deoxypyranoside. Nucleophilic addition of an alkynyllithium reagent to the aldehyde 4 led to the propargylic alcohol 7, which was converted to the advanced building block 9 in two further steps.     

Synthesis of Poly(para‐phenylene) Containing Imidazolium Cation

A novel poly(para‐phenylene) containing imidazolium cation, poly[2,5‐bis[4‐(3‐methyl‐1‐imidazolium)‐butyloxy)‐1,4‐benzene dihexafluorophosphate] (PPP‐IL), has been synthesized.     

One‐Pot,Three‐Component Synthesis of 2,3‐Dihydro‐4(1H)‐quinazolinones by Montmorillonite K‐10 as an Efficient and Reusable Catalyst

A wide range of mono‐ and disubstituted dihydroquinazolinones were synthesised via condensation of isatoic anhydride, primary amines, or ammonium salts with aromatic aldehydes in the presence of montmorillonite K‐10. The catalyst is reusable and could be recycled for several runs without any decrease in its efficiency.     

Bromination of 4‐Dichloromethyl‐4‐methylcyclohexa‐2,5‐dien‐1‐ones

Bromination of 4‐dichloromethyl‐4‐methylcyclohexa‐2,5‐dien‐1‐one and 4‐dichloromethyl‐3,4‐dimethylcyclohexa‐2,5‐dien‐1‐one has been studied. The reaction conditions required for the formation of mono‐, di‐, and tribrominated products have been optimized.     

Cucurbituril and β-Cyclodextrin as Hosts for the Complexation of Organic Dyes

The complexation of neutral organic molecules by cucurbituril and-cyclodextrin in formic acid was studied by means ofspectrophotometric titrations. In the case of -cyclodextrin thecomposition of the solvent has almost no influence upon the stability of thecomplexes formed. This situation is completely different for cucurbituril.Due to its interactions with protons the measured stability constants of thecomplexes formed with organic molecules increase with decreasing acidconcentration. At low acid concentrations cucurbituril forms more stablecomplexes with organic molecules than -cyclodextrin.     

Evaluation of the (Allyl alcohol 1,2‐butoxylate‐block‐etoxylate)‐b‐PMMA Copolymers Composition by the Dielectric Measurements

Redox initiated free‐radical polymerization of methyl methacrylate (MMA) with allyl alcohol 1,2‐butoxylate‐block‐etoxylate (AABE) was carried out to yield AABE‐b‐PMMA copolymers at elevated temperatures. The composition of the copolymers depending on the polymerization temperature was qualitatively estimated by the dielectric measurements. It has been seen that AABE segment quantity decreased and PMMA segment quantity increased with increasing the polymerization temperature. The dielectric constant and the dissipation factor of the copolymers were investigated as a function of frequency and temperature. The dielectric constant and the dissipation factor were found to be strongly affected by the polymerization temperature. The highest dielectric constant in all studied temperatures and frequencies was obtained in the case of the copolymer which was prepared at 313 K. The dipolar C‐O and OH groups of the AABE segment have the primary effect on the dielectric constant. The copolymer which was prepared at 323 K, showed the highest dissipation factor near the relaxation temperature of PMMA.     

N-Methylated Peptide Synthesis via Generation of an Acyl N-Methylimidazolium Cation Accelerated by a Brønsted Acid

The development of a robust amide-bond formation remains a critical aspect of N-methylated peptide synthesis. In this study, we synthesized a variety of dipeptides in high yields, without severe racemization, from equivalent amounts of amino acids. Highly reactive N-methylimidazolium cation species were generated in situ to accelerate the amidation. The key to success was the addition of a strong Brønsted acid. The developed amidation enabled the synthesis of a bulky peptide with a higher yield in a shorter amount of time compared with the results of conventional amidation. In addition, the amidation can be performed by using either a microflow reactor or a conventional flask. The first total synthesis of naturally occurring bulky N-methylated peptides, pterulamides I–IV, was achieved. Based on experimental results and theoretical calculations, we speculated that a Brønsted acid would accelerate the rate-limiting generation of acyl imidazolium cations from mixed carbonic anhydrides.