Aromatic Acetals Research Articles

A Cheap, Simple, and Versatile Method for Acetylation of Alcohols and Phenols and Selective Deprotection of Aromatic Acetates Under Solvent‐Free Condition

Acyclic and cyclic acetates of various alcohols and phenols were obtained in excellent yields under mild reaction conditions in the presence of a catalytic amount of sodium hydroxide under solvent–free conditions and microwave irradiation. Selective deprotection of acetate group from the corresponding phenolic compounds was carried out in the presence of LiClO4.2H2O.

Microwave-Assisted Allylation of Acetals with Allyltrimethylsilane in the Presence of CuBr

We describe the first synthesis of homoallyl ethers from acetals and allyltrimethylsilane using microwave heating and CuBr as a promoter. This method works best for aromatic acetals, giving the corresponding homoallyl ethers in good to quantitative yield.

Studies on Novel Synthetic Methodologies. Part 29. Efficient, Selective Deprotection of Aromatic Acetates Catalyzed by Amberlyst‐15 or Iodine.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Highly Efficient Deprotection of Aromatic Acetals under Neutral Conditions Using β‐Cyclodextrin in Water.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Efficient, selective deprotection of aromatic acetates catalyzed by Amberlyst-15 or iodine

Aromatic acetates were selectively deprotected in the presence of aliphatic acetates to the corresponding phenols in excellent yields using Amberlyst-15 or iodine as catalysts in methanol at room temperature. The first catalyst can be recovered.

A Mild, Highly Selective and Remarkably Easy Procedure for Deprotection of Aromatic Acetates Using Ammonium Acetate as a Neutral Catalyst in Aqueous Medium.

AbstractFor Abstract see ChemInform Abstract in Full Text.

A mild, highly selective and remarkably easy procedure for deprotection of aromatic acetates using ammonium acetate as a neutral catalyst in aqueous medium

Ammonium acetate was found to catalyze efficiently the selective deprotection of aromatic acetates in the presence of various sensitive functionalities in aqueous methanol under neutral conditions at room temperature to yield the corresponding phenols in excellent yields. The method has been utilized for deprotection of acetates of several naturally occurring bioactive phenolic compounds and for preparation of venkatasin, a natural coumarino-lignan, from the anticancer compound cleomiscosin A.

Highly efficient deprotection of aromatic acetals under neutral conditions using beta-cyclodextrin in water.

Aromatic acetals have been deprotected to the corresponding aldehydes under biomimetic conditions for the first time using beta-cyclodextrin in water under neutral conditions, thereby overcoming many of the drawbacks associated with earlier methodologies. This method, apart from being simple with regard to recycling of the catalyst, also has the potential for industrial applications.

Synthesis and cytotoxic activity of certain new arylazothiazole containing compounds

Abstract2‐Amino‐5‐arylazo‐4‐(2‐chlorophenyl)thiazoles (2a‐e) were prepared by the coupling of aryldiazonium chlorides with 2‐amino‐4‐(2‐chlorophenyl) thiazole (1). The thioureas 3a‐e were obtained by condensing the arylazothiazoles 2a‐c with the appropriate isothiocyanates. Reaction of 2d with aromatic aldehydes afforded the chalcone analogues 4a‐c. The pyridone derivatives 5a,b were synthesized by reacting the ketone 2d with different aromatic aldehydes, ethyl cyanoacetate and ammonium acetate. On the other hand, 5b was also prepared by cyclizing 4c with ethyl cyanoacetate and ammonium acetate. Furthermore, 6‐chloroimidazo[2,l‐b]‐thiazole 7 was obtained from the acid derivative 6b by treatment with POC13. While, the imidazo[2,l‐b]‐thiazolones 9a‐d were produced by the cyclization of the chloroacetyl derivatives 8a‐d with DMAP/pyri‐dine. Representative examples of the prepared compounds were tested for in vitro antitumor activity against two human tumor cell lines. Some compounds showed activity against brain tumor cell lines.

Microwave Assisted Synthesis of Pyridone Derivatives

AbstractA series of pyridone derivatives were synthesized by the reaction of aromatic aldehydes, 1,3‐dicarbonyl compounds and ammonium acetate under microwave irradiation in the absence of solvent. The reactions were completed within 3‐5 min to give the desired products in 72.4‐86.2% yields.

Synthesis and perfume characteristics of acetals containing an aromatic ring

Aromatic acetals were prepared by condensation of 2-methyl-3-(4-R-phenyl)propanals (R = Me, i-Pr, i-Bu) with ethanol, methanol, ethylene glycol, 1,2-propanediol, methyl Cellosolve, and Cellosolve. The perfume characteristics of the acetals were studied.

Reduction of acetals with samarium diiodide in acetonitrile in the presence of Lewis acids.

Transformation of acetals into ethers by partial reduction using a samarium diiodide-Lewis acids-acetonitrile system is described. The reaction with aromatic acetals occurred in good yields in the presence of aluminum chloride (2 eq) whereas the corresponding aliphatic, vinylic, and alkynyl derivatives did not afford ethers under the same conditions. Beta-elimination to give an enol ether becomes predominant when aliphatic acetals that possess a hydrogen at the 2-position are treated with iodotrimethylsilane in the presence of SmI2 or SmI3.

Linear free energy relationship and conformational effects on oxidation of aromatic acetals by pyridinium fluorochromate

Linear free energy relationship and conformational effects on oxidation of aromatic acetals by pyridinium fluorochromate

Synthesis of certain benzylidene derivatives of lagochilin

Methods for preparing certain aromatic acetals of 3,15,16,18-tetrahydroxy-9,13-epoxylabdane are described. The structures of the resulting acetals are confirmed by IR and PMR spectra. Certain physicochemical constants of the compounds are presented.

Aromatic Acetals as New Initiators for Cationic Polymerization of Isobutyl Vinyl Ether

A series of aromatic acetals (1) from substituted phenols [CH3CH(OiBu)OAr; Ar = C6H5, p-CH3OC(O)C6H4, p-CH3C(O)C6H4, p-NO2C6H4, 4-NO2-2,6-di-C6H5−C6H2, o-CH3C(O)C6H4] were employed as new initiators in conjunction with Lewis acids (MtXn) for the living cationic polymerization of isobutyl vinyl ether (IBVE). Most of them were quantitatively synthesized by the addition of the corresponding phenols to IBVE. When coupled with aluminum chloride (AlCl3), 1 gave polymers with broad molecular weight distributions (MWDs), whereas the addition of ethyl acetate (10 vol %) to these systems led to the formation of controlled polymers whose number-average molecular weights (Mn) were directly proportional to monomer conversion, with relatively narrow distributions (Mw/Mn ∼ 1.2). The aromatic acetals in conjunction with tin halides (SnX4; X = Cl, Br) gave relatively high meso contents (81%) in toluene at −78 °C.

ChemInform Abstract: Aromatic Nitration under Neutral Conditions Using Nitrogen Dioxide and Ozone as the Nitrating Agent. Application to Aromatic Acetals and Acylal.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

A Novel and Convenient Synthesis of 2-Aryl-4-methylenetetrahydrofurans from 2-(Trimethylsiloxymethyl)allyltrimethylsilane and Acetals

The reaction of acetals with 2-(trimethylsiloxymethyl)allyltrimethylsilane under the influence of the combined use of a catalytic amount of tin(II) halide and acetyl halide affords the corresponding 2-aryl-4-methylenetetrahydrofurans in good yields. The reaction of aromatic acetals with 2-(trimethylsiloxymethyl)allyltrimethylsilane leads to 2-aryl-4-methylenetetrahydrofurans by tandem allylation-intramolecular cyclization.

A novel and convenient synthesis of 2-aryl-4-methylenetetrahydrofurans from 2-(trimethylsiloxymethyl)allytrimethylsilane and acetals

The reaction of acetals with 2-(trimethylsiloxymethyl)allyltrimethylsilane under the influence of the combined use of a catalytic amount of tin(II) halide and acetyl halide affords the corresponding 2-aryl-4-methylenetetrahydrofurans in good yields. The reaction of aromatic acetals with 2-(trimethylsiloxymethyl)allyltrimethylsilane leads to 2-aryl-4-methylenetetrahydrofurans by tandem allylation-intramolecular cyclization.

Aromatic Nitration under Neutral Conditions Using Nitrogen Dioxide and Ozone as the Nitrating Agent. Application to Aromatic Acetals and Acylal

Abstract Cyclic acetals derived from aromatic carbonyl compounds can be nitrated smoothly with nitrogen dioxide in ice-cooled dichloromethane or acetonitrile in the presence of ozone and magnesium oxide to give ortho- and para-nitro derivatives as the major product in good combined yields, the acetal ring as a protective group remaining almost intact. An acylal derived from benzaldehyde similarly undergoes nitration on the aromatic ring to give an isomeric mixture of three nitro compounds, in which the ortho and meta isomers predominate, while aromatic orthoesters are rapidly decomposed to give simply the parent esters. Ring nitration under neutral conditions has been interpreted in terms of a nonclassical mechanism, in which nitrogen trioxide is involved as the initial electrophile.

ChemInform Abstract: Ozone‐Mediated Reaction of Aromatic Acetals and Acylal with Nitrogen Dioxide: A Novel Methodology for the Nuclear Nitration of Acid‐ Sensitive Aromatic Compounds under Neutral Conditions.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.