Mild,Efficient, and Rapid Dehydration of Aldoximes to Nitriles Mediated by Phthalic Anhydride Under Microwave Irradiation

Summary.  Aldoximes can be efficiently and rapidly dehydrated to nitriles by treatment with phthalic anhydride under microwave irradiation. Received April 18, 2001. Accepted (revised) June 7, 2001     

Triflic Acid Mediated Cascade Cyclization of Aryldiynes for the Synthesis of Indeno[1,2‐c]chromenes: Application to Dye‐Sensitized Solar Cells

A new triflic acid (TfOH)‐mediated cascade cyclization of ortho‐anisole‐substituted aryldiynes is described for the construction of indeno[1,2‐c]chromenes. The cascade cyclization proceeds through an unusual TfOH‐induced alkyne‐alkyne cyclization followed by nucleophilic attack of the methoxy group on the benzylidene cation, which is completely different to the cyclization of ortho‐aniline‐ or ortho‐thioanisole‐substituted aryldiynes. A new class of organic dyes with the indeno[1,2‐c]chromene framework as both donor and π‐linker were synthesized. These compounds exhibit high photovoltaic performances in dye‐ sensitized solar cells (DSCs).     

Sulfamic Acid: A Mild,Efficient, and Cost-Effective Catalyst for Synthesis of Indoloquinoxalines at Ambient Temperature

A simple, cost-effective method for synthesis of indoloquinoxalines from isatin and o-phenylenediamine employing a catalytic amount of sulfamic acid at ambient temperature is reported. Moreover, the method is applicable for a variety of isatins, ninhydrin, 4-hydroxynaphthaquinone, and 1,2-diketones. The key features of the protocol include rapid reactions with good yields, simple workup procedure, and easy isolation of products.     

Erratum to: A Mild and Highly Efficient One-pot Synthesis of 1,3,5-Triaryl-2-pyrazolines

Chemistry of Heterocyclic Compounds -     

Zinc-Promoted Reduction of 1,2-Diketones: A Simple, Efficient, and Mild Approach to a-Hydroxy Ketones

Summary.  1,2-Diketones were readily converted to α-hydroxy ketones in high to excellent yields using zinc in saturated ammonium chloride solution. Received June 7, 2001. Accepted (revised) August 7, 2001     

Highly Efficient Method for Synthesis of Benzoquinones Using Hypervalent Iodine(III) Reagent and Sodium Bisulfate

A rapid, one-step, novel approach for the conversion of benzamides into benzoquinones using (diacetoxyiodo)benzene(III) and sodium bisulfate has been developed in aqueous acetonitrile at room temperature. The developed protocol is applicable to several types of substituted benzamide derivatives to get the corresponding benzoquinone products. The developed methodology offers mild reaction condition, short reaction time, and moderate to excellent yields. This is one of the most simple and environmentally benign protocols for synthesis of benzamide derivatives.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]     

Potassium Ferrate Supported on Montmorillonite K-10: A Mild and Efficient Reagent for Oxidative Deprotection of Acetals and Ketals

Summary.  A variety of acetals and ketals were oxidatively deprotected to their parent compounds using potassium ferrate(VI) supported on montmorillonite K-10 under non-aqueous conditions. Received January 23, 2001. Accepted (revised) March 14, 2001     

Reactivity of 4,5-Dichlorophthalic Anhydride towards Thiosemicarbazide and Amines: Synthesis,Spectroscopic Analysis,and DFT Study

The cyclic anhydrides are broadly employed in several fields, such as the chemical, plastic, agrochemical, and pharmaceutical industries. This study describes the chemical reactivity of 4,5-dichlorophthalic anhydride towards several nucleophiles, including thiosemicarbazide and different amines, to produce the carboxylic acid derivatives resulting from anhydride’s opening, namely, phthalimide and dicarboxylic acid (1–12) products. Their chemical structures are confirmed by NMR, IR and MS spectra analyses. Density–functional theory (DFT) studies are performed using (DFT/B3LYP) with the 6-311G(d, p) basis sets to recognize different chemical and physical features of the target compounds.     

2,6-Dicarboxypyridinium Fluorochromate: A Mild and Efficient Reagent for Oxidative Deprotection of Trimethylsilyl Ethers to Their Corresponding Carbonyl Compounds

Deprotection of trimethylsilyl ethers to their parent aldehydes and ketones in high yields has been carried out using 2,6-dicarboxypyridinium fluorochromate under mild conditions.     

A Novel and Efficient Synthesis of Pyrido[1,2‐a]‐Fused 1,3‐Diazaheterocyclic Compounds via a One‐Pot Three‐Component Reaction

An efficient one‐pot synthesis of pyrido[1,2‐a]‐fused 1,3‐diazaheterocyclic compounds by three‐component reaction of diamine, nitroketene dithioacetal (=1,1‐bis(methylsulfanyl)‐2‐nitroethene), and electron‐poor itaconic anhydride (=2‐methylidenesuccinic anhydride=2‐methylidenebutanedioic anhydride) in aqueous EtOH is reported. This protocol has the advantages of easiness, higher yields, and shorter reaction times. The structures were corroborated spectroscopically (IR, ¹H‐ and ¹³C‐NMR, and EI‐MS) and by elemental analyses. A plausible mechanism for this type of cyclization is proposed (Scheme 2).     

A Simple and Efficient Method for the Synthesis of α,β‐Unsaturated Acyl Azo Compounds with NaNO2‐Acetic Anhydride Under Mild Conditions

In this paper, eight aryl substituted α, β‐unsaturated acyl hydrazides undergo efficient oxidation to α,β‐unsaturated acyl azo compounds using NaNO₂‐acetic anhydride under mild conditions with excellent yields.     

Novel,Mild, and Highly Efficient Method for the Synthesis of 2-Arylbenzothiazoles by the Oxidation of 2-Arylbenzothiazolines with Silicon Lewis Acids

Oxidation of structurally diverse 2-arylbenzothiazolines to give the corresponding 2-arylbenzothiazoles has been carried out in benzene using dimethyldichlorosilane and trimethylchlorosilane. Short reaction times, mild reaction conditions, easy and quick isolation of the products, and excellent yields are the main advantages of this procedure.     

Silica-Supported LiHSO4 as a Highly Efficient,Mild, Heterogeneous,and Reusable Catalytic System for the Solvent-Free Synthesis of Bis(indolyl)methanes

Silica-supported LiHSO₄ (LiHSO₄/SiO₂) is used as a green, cheap, and efficient catalytic system for the synthesis of bis(indolyl)methanes via the condensation of indoles with carbonyl compounds under solvent-free conditions. The reactions proceed rapidly at room temperature, and the title compounds are obtained in high to excellent yields.     

A Mild and Efficient CH2‐Extrusion Reaction for the Enantiospecific Synthesis of Highly Configurationally Stable Tröger Bases

A novel CH₂‐extrusion reaction leading to the transformation of ethano‐Tröger bases into disubstituted methano derivatives is reported (yields up to 93 %). Under mild and metal‐free oxidative conditions, a loss of CH₂ and a ring contraction are provoked. Despite two bond cleavages at stereogenic nitrogen and carbon centers and a temporary rupture of the bicyclic structure, a very high enantiospecificity (es≥98 %) is observed for this unusual reaction.     

Ni Nanoparticles: Mild and Efficient Catalyst for the Chemoselective Synthesis of 2-Arylbenzimidazoles, 2-Arylbenzothiazoles,and Azomethines

A new and efficient method has been developed for the synthesis of biologically significant 2-arylbenzimidazoles, 2-arylbenzothiazoles, and azomethines using recyclable and inexpensive polyvinyl pyrrolidone (PVP)–stabilized Ni nanoparticles in ethylene glycol at room temperature in excellent yields.     

Tin(II) Chloride Dihydrate Catalyzed Groebke Condensation: An Efficient Protocol for the Synthesis of 3-Aminoimidazo[1,2-a]pyridines

The ability of tin(II) chloride dihydrate as a catalyst to promote the three-component condensation reaction from a diversity of aromatic aldehydes, 2-aminopyridines and isonitriles at room temperature is described. This methodology affords a number of 3-aminoimidazo[1,2-a]pyridines in the presence of tin(II) chloride dihydrate as a new and mild Lewis acid catalyst in the multi-component reaction in reasonable yields and short reaction time without any significant optimization of the reaction conditions.     

Benzyltriphenylphosphonium Chlorochromate: A Mild and Novel Reagent for Oxidation of Benzylic and Allylic Alcohols Under Non-Aqueous and Aprotic Conditions or Microwave Conditions

This paper describes the oxidation of benzylic and allylic alcohols under non-aqueous and aprotic conditions or microwave conditions using benzyltriphenylphosphonium chlorochromate (1) PhCH₂PPh₃CrO₃.HCl which has been prepared by mixing an aqueous solution of benzyltriphenylphosphonium chloride with CrO₃ in 6 N HCl at room temperature. This reagent is stable orange powder which may be stored for months without loss of its activity. This compound is readily soluble in organic solvents such as acetonitrile, chloroform and dichloromethane and slightly soluble in carbon tetrachloride, ether and hexane. the oxidation under microwave conditions is much more faster.     

Synthesis of Novel Phthalazino[1,2‐b]quinazolinedione Derivatives: Efficient and Practical Reaction of 2‐Amino‐N′‐Arylbenzohydrazides and 2‐Formylbenzoic Acids

This work reported the synthesis of novel phthalazino[1,2‐b]quinazolinedione derivatives through the reaction of 2‐amino‐N′‐arylbenzohydrazides and 2‐formylbenzoic acids in the presence of TsOH in EtOH under reflux conditions.