One-Pot Synthesis of 3,5-Disubstituted 1,2,4-Oxadiazoles Using Catalytic System NaOH‒DMSO

Russian Journal of Organic Chemistry - One-pot convenient process was developed for the production of 3,5-disubstituted 1,2,4-oxadiazoles by reaction of amidoximes with anhydrides or acyl chlorides...     

Trichloroisocyanuric Acid–KF as an Efficient Reagent for One-Pot Synthesis of Dialkylfluorophosphates from Dialkylphosphites

Trichloroisocyanuric acid–KF afforded dialkylfluorophosphates from dialkylphosphites at room temperature through a facile electrophilic–nucleophilic metathesis.     

Solid-Phase Organic Synthesis of Vinyl-Substituted 1,3,4-Oxadiazoles Using Polymer-Bound α-Selenopropionic Acid

Vinyl-substituted 1,3,4-oxadiazoles can be efficiently synthesized through acylation, cyclocondensation, and oxidation–elimination reaction from polystyrene-supported α-selenopropionic acid and acid hydrazides. This new solid-phase organic synthesis method could provide the target compounds in good yield and purity, with advantages of decreased volatility and simplification of workup procedure.     

Sulfamic Acid–Mediated,Efficient, One-Pot Synthesis of Novel 5-Substituted 1,3,4-Thiadiazol-2-ylcarbamoyl Aliphatic Amide Acid Derivatives and Facile Synthesis of Cyclic Amides

Convenient and efficient one-pot syntheses of 5-substituted-1,3,4-thiadiazol-2-ylcarbamoyl aliphatic amide acid derivatives were described and developed using sulfamic acid catalyst. Thiosemicarbazide and substituted triethylorthoester and cyclic/alicyclic anhydride were efficiently condensed using sulfamic acid to furnish 5-disubstituted-1,3,4-thiadiazol-2-ylcarbamoyl aliphatic acid and amide derivatives in fair to good yield, which exclusively get cyclized to new cyclic amide derivatives.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

One-Pot Synthesis of 2,4-Disubstituted Thiazoline from β-Azido Disulfide and Carboxylic Acid

A concise and efficient one-pot four-step synthesis of 2,4-disubstituted thiazoline via a cascade disulfide bond cleavage/thiocarbonylation/Staudinger reduction/aza-Wittig reaction is established. Treatment of various carboxylic acids with β-azido disulfides under this one-pot procedure obtained the desired thiazolines in good to excellent isolated yields.     

Suzuki–Miyaura Cross-Coupling of Bromotryptophan Derivatives at Ambient Temperature

Mild reaction conditions are highly desirable for bio-orthogonal side chain derivatizations of amino acids, peptides or proteins due to the sensitivity of these substrates. Transition metal catalysed cross-couplings such as Suzuki–Miyaura reactions are highly versatile, but usually require unfavourable reaction conditions, in particular, when applied with aryl bromides. Ligand-free solvent-stabilised Pd-nanoparticles represent an efficient and sustainable alternative to conventional phosphine-based catalysts, because the cross-coupling can be performed at considerably lower temperature. We report on the application of such a highly reactive heterogeneous catalyst for the Suzuki–Miyaura cross-coupling of brominated tryptophan derivatives. The solvent-stabilised Pd-nanoparticles are even more efficient than the literature-known ADHP-Pd precatalyst. Interestingly, the latter also leads to the formation of quasi-homogeneous Pd-nanoparticles as the catalytic species. One advantage of our approach is the compatibility with aqueous and aerobic conditions at near-ambient temperatures and short reaction times of only 2 h. The influence of different N^α-protecting groups, boronic acids as well as the impact of different amino acid side chains in bromotryptophan-containing peptides has been studied. Notably, a surprising acceleration of the catalysis was observed when palladium-coordinating side chains were present in proximal positions.     

Silica Sulfuric Acid: An Efficient and Versatile Acidic Catalyst for the Rapid and Ecofriendly Synthesis of 1,3,4‐Oxadiazoles at Ambient Temperature

A rapid and green synthesis of 2,5‐disubstituted 1,3,4‐oxadiazoles is reported. The title compounds were prepared by the reaction of different acyl hydrazides and orthoesters in the presence of silica sulfuric acid under solvent‐free conditions. In this new process, reactions were run at ambient temperature and completed in a short period of time with high yields.     

Synthesis and Acid–Base Properties of β-Octabromo-Substituted Unsymmetrical Nitrophenylporphyrins

Russian Journal of Organic Chemistry - The bromination of [5-(4-nitrophenyl)-10,15,20-triphenylporphyrinato]cobalt(II) and [5,10,15-tris-(4-nitrophenyl)-20-phenylporphyrinato]cobalt(II) with...     

One-Pot Synthesis of Tri-Acetalated Aldohexoses with 1,1-Dialkoxycyclohexane–p-Toluenesulfonic Acid

Abstract

2-Deoxy-d-arabino-hexose (1), 2-acetamido-2-deoxy-d-glucose (2), and 2-deoxy-2-trifluoroacetamido-d-glucose (3) were each treated with 1,1-dimethoxycyclohexane or 1,1-dibenzyloxycyclohexane in 1,4-dioxane in the presence of p-toluenesulfonic acid. The major products were the 1,1-dimethyl or 1,1-dibenzyl acetals (4-9) of 3,4:5,6-di-O-cyclohexylidene-2-deoxy-aldehydo-d-arabino-hexose, and of 2- (acylamino)-3,4:5,6-di-O-cyclohexylidene-2-deoxy-aldehydo-D-glucose. The dibenzyl acetal derivatives were converted, by hydro-genolysis, into the corresponding, acyclic aldehydes (10-12) in good yields.     

One-Pot Synthesis of 2,5-Furandicarboxylic Acid from 2-Furoic Acid by a Pd-catalyzed Bromination–Hydroxycarbonylation Tandem Reaction in Acetate Buffer

The one-pot synthesis of 2,5-furandicarboxylic acid from 2-furoic acid with a yield of 57 % was achieved for the first time using a Pd-catalyzed bromination-hydroxycarbonylation tandem reaction in HOAc-NaOAc buffer. This synthetic protocol shows major improvements compared to previously reported methods, such as using biomass-based 2-furoic acid as low-cost raw material, one-pot synthesis without isolation of intermediate products, and no need for an acidification procedure. Experiments indicate that the involved Xantphos-modified Pd-catalyst and the buffer solution play significant promoting roles for each individual reaction whereas Br₂ (as the brominating reagent) had a negative effect on the second hydroxycarbonylation step, while CO was deleterious for the first bromination step. Hence, in this practical one-pot synthesis, Br₂ should be consumed in the first bromination step as fully as possible, and CO is introduced after the first bromination step has been completed.     

An Efficient Solid Acid Promoted Synthesis of Quinoxaline Derivatives at Room Temperature

Quinoxaline derivatives have been synthesized in a very short time with excellent yields by the condensation of 1,2-diamines with aliphatic or aromatic 1,2-dicarbonyl compounds or benzilmonoxime in the presence of silica sulfuric acid as a very inexpensive solid acid catalyst at room temperature. The recovery and reuse of the catalyst are also satisfactory.     

Propanephosphonic Acid Anhydride–Mediated Cyclodehydration of Maleic Acid Monoamides

Propanephosphonic acid anhydride (T3P) has been proposed as a novel reagent for the preparation of maleic acid isoimides from the corresponding monoamides. A series of substituted aromatic and aliphatic isoimides have been prepared in good yields. The main advantage of this synthetic method is the use of environmentally benign, cost-efficient reagents and solvents, which are also safer to handle than the ones employed previously.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

Synthesis, Mesogenic and Spectroscopic Properties of 2,5-Disubstituted Thiophene Derivatives

Two series of 2,5-disubstituted thiophene derivatives （series 1： 2,5-bis（p-alkoxyphenylethynyl）thiophene and series 2： 2,5-bis[p-（p-alkoxyphenylethynyl）（phenylethynyl）]thiophene） were synthesized and characterized by ^1H NMR, ^13C NMR, HRMS and elemental analysis. The relationship between the structure and the mesogenic and spectroscopic properties has been discussed. The results show that compounds 1a-1f all exhibited an enantiotropic nematic mesophase, which was confirmed by the polarized optical microscopy （POM）, differential scanning calorimeter （DSC） and variable temperature powder X-ray diffraction （PXRD）. In contrast, the extended conjugated analogues 2a-2b had no liquid crystal properties. As for the spectroscopic properties, incorporating more phenylethynyl units results in red-shifted absorption and emission spectra, greatly enhanced quantum efficiency.     

Polyphosphoric Acid–Mediated,One-Pot,Novel Reactions to Build Polymethoxyarylnaphthalene Lignans

The one-pot reaction of succinic anhydride with 1,2-dimethoxybenzene furnished two structurally complicated polymethoxyarylnaphthalene lignans, polymethoxyarylnaphthol 1 as the minor product and polymethoxynaphtho[1,2-b]oxacycloheptatrienone 2 as the major product, in the presence of a small amount of polyphosphoric acid (PPA) as catalyst at 140°C and yielded 2 as a single product in good yield when a large amount of PPA as solvent was employed at 60–80°C. The novel structures of 1 and 2 were elucidated from ¹H NMR, ¹³C NMR, infrared (IR), and Electrospray ionization–mass spectrometry (ESI-MS) and further confirmed by x-ray diffractions. The possible mechanisms for the formation of 1 and 2 were also proposed.     

Convenient One‐Pot Synthesis of Sulfonamides from Thiols using Trichloroisocyanuric Acid

A convenient synthesis of sulfonamides from thiols is described. In situ preparation of sulfonyl chlorides from thiols is accomplished by oxidation with trichloroisocyanuric acid (TCCA), benzyltrimethylammonium chloride and water (2.5 equiv). The sulfonyl chlorides are then further allowed to react with excess amine in the same reaction vessel. Triethylamine can be optionally added as acid scavenger.     

Pinacol Formation and Reduction of Aromatic Carbonyls with Magnesium–Methanol at Ambient Temperature

Summary. A simple and inexpensive procedure for the pinacol formation of aromatic aldehydes and reduction of aromatic ketones to the corresponding alcohols with magnesium in dry methanol at ambient temperature is reported. The pinacol formation and reduction are proposed to be proceeding by SET from magnesium.Received November 26, 2002; accepted (revised) March 7, 2003 Published online September 25, 2003     

Synthesis of 2,5-disubstituted 1,3,4-oxadiazoles by visible-light-mediated decarboxylation–cyclization of hydrazides and diketones

A visible-light-induced synthesis of 2,5-disubstituted 1,3,4-oxadiazoles from simple diketones and hydrazides with the assistant of the photocatalyst eosin Y catalyzed decarboxylation and cyclization under mild conditions has been discovered. The reaction tolerates a wide range of functional groups and gives a variety of valuable 1,3,4-oxadiazoles in moderate to good yields. Finally, a plausible reaction mechanism was proposed.     

CeCl3·7H2O-Catalyzed One-Pot Synthesis of Hantzsch 1,4-Dihydropyridines at Room Temperature

An efficient synthesis of a series of 1,4-dihydropyridines was accomplished at room temperature by the reaction of aldehydes with ammonium acetate and ethyl acetoacetate catalyzed by CeCl₃·7H₂O.     

A Convenient Synthesis of Unsymmetrical N,N′-Disubstitutedα,ω-Diaminoalkanes

A general procedure is described for regiospecific construction of unsymmetrical N-alkyl (or aralkyl)-N′-aryl-α,ω-diaminoalkanes 3 (n=2,3,4) by reduction of N-(ω -arylaminoalkyl)amides 2 with borane. Compounds 2 are readily obtained by condensation of N-(ω-haloalkyl)amides 1 with aromatic amines.     

o-Iodoxy Benzoic Acid–Mediated Synthesis of 3,5-Diarylisoxazoles and Isoxazole-3-carboxylic Acids

A new, convenient, ecofriendly synthesis of 3,5-diarylisoxazoles is reported from α,β-unsaturated ketoximes. Similarly, a novel synthesis of isoxazole carboxylic acids is also reported. Both the methods use efficient, environmentally friendly, and nontoxic iodoxybenzoic acid (IBX) as an oxidative cyclizing reagent. Easy procedure, environmentally benign reaction conditions, and nontoxicity are advantages to the methodology.