Highly Selective Arbuzov Reaction of α-Chlorocarbonyl Compounds with P(OEt)3 and Substituted Amino Urea

Abstract

A facile one—pot Arbuzov reaction of α-chlorocarbonyl compounds with P(OEt)₃ and substituted amino urea is described. The highly selective Arbuzov reaction of α-chlorocarbonyl compounds could take place under relatively mild conditions, giving products in high yields.     

SYNTHESIS AND THERMAL REARRANGEMENT OF 2-ALKOXYCARBONYL-3-ALKYL-4H-BENZO[b][1,4]THIAZINES

Abstract

The title compounds (4b-d) together with the benzothiazolines (5b-d) have been obtained by a reaction between 2,2′-dithiodianiline (1) and β-keto esters (2b-d). The reaction between 1 and the β-keto ester 2a gives 1,4-benzothiazine 3a in addition to the benzothiazoline 5a.

It has been established that the 1,4-benzothaizines 4b-d undergo an acid-catalysed thermal rearrangement involving a [1,3] shift of the sulfur atom, giving rise to the isomeric 1,4-benzothiazines 3b-d.     

The HSnPh3 Free Radical Mediated Cyclization of 4,9-Dioxa-1,6-dodecadien-11-yne

We report the triphenyltin hydride radical mediated cyclization of 4,9-dioxa-1,6-dodecadien-11-yne 2. The reaction proceeds under very mild conditions and in good chemical yield (59%), giving a mixture of products 5 (mixture of isomers in a 1:2 ratio) and 6 (mixture of isomers in a 1:3 ratio).     

A Two Step Synthesis of the Nucleoside Q Precursor 2-Amino-5-cyanopyrrolo[2,3-d]pyrimidin 4-one (PreQo)

PreQ_o (1) is prepared in a 70 % yield by the condensation of chloro(formyl)acetonitrile (2) with 2,6-diaminopyrimidin-4-one (3), and subsequently converted to its amide derivative 5. Isolation of the intermediate 4 in the condensation reaction was also observed giving further insight into the proposed mechanism.     

Microwave-assisted and catalyst-free sulfenylation of imidazo[2,1-b]thiazoles with sulfonyl hydrazides in water

Abstract

An efficient microwave-assisted and catalyst-free sulfenylation of imidazo[2,1-b]thiazoles with sulfonyl hydrazides has been developed in water. This method is practical and environmental friendly, and can be performed within a short reaction time. The sulfenylation reaction shows high regioselectivity, and excellent functional-group compatibility, giving the desired products in moderate to good yields.     

Access to polycyclic carbazoles from ring-fused 2-(9H-carbazol-1-yl)anilines

Abstract

Nine 2-(9H-carbazol-1-yl)anilines with rings fused at the 3,4-position were acylated at the amino group with chloroacetyl, 3-chloropropanoyl, or 4-chlorobutyryl chloride, at yields of 85–99%. The resulting ω-chloroamides were exposed to potassium tert-butoxide in THF. All nine acetamides annulated exclusively at the carbazole N atom, giving benzodiazocinocarbazoles at 76–91% overall yield. The only propanamide prepared underwent α,β-elimination, giving the corresponding acrylamide at 70% overall yield. All nine butanamides annulated exclusively at the amide nitrogen, giving pyrrolidin-2-ones at 70–94% overall yield. Additionally, the 1-indanone derived carbazolylaniline followed the same annulation pattern, but the benzylic methylene group was oxidized, giving the corresponding fluorenones. The cyclohexanone-derived carbazolylaniline was also converted into a maleimide, which participated in a Diels-Alder reaction with cyclopentadiene. Attempts to replace the amino group in the starting material via diazotization were unsuccessful. Instead, a Widman-Stoermer reaction was observed, in which the diazonium group attacked the carbazole 2-position, giving the corresponding cinnoline.     

ω,ω′-Diphospholylalkanes

Abstract

The reaction of compounds (1) with lithium or sodium can lead to different results depending on the length of the exocyclic chain : when n=1,2 or 4, we observe cleavage of both exocyclic P-C bonds, giving pure phospholyllithium or sodium.     

Spectrofluorimetric Determination of Nitrite with Pyridoxal-5-Phosphate-2-Pyridylhydrazone

Abstract

The nitrite ion oxidizes pyridoxal-5-phosphate-2-pyridyl-hydrazone in acid medium giving a fluorescent product (λ_ex 325 nm, λ_em 420 nm). This redox reaction is used to developed a spectrofluorimetric method for the determination of nitrite. The calibration graph is liner in the 0.1 ? 1.0 μg mL^?1 range. The interference levels, stoichiometry and nature of the reaction have been studied. The method is applied to determine nitrite in water and soil samples     

Synthesis and Reactions of 4-Oxiranylmethylfuro[3,2-b]pyrroles and Their Benzo Derivatives

Methyl 4-oxiranylmethyl-4H-furo[3,2-b]pyrrole-5-carboxylates 2a-c and methyl 1-oxiranylmethyl-1H-benzo[4,5]furo[3,2-b]pyrrole-2-carboxylate (2d) were prepared by reaction of the appropriate starting compounds 1a-d with excess chloromethyloxirane. The compounds 2a-d undergo oxirane ring opening by heterocyclic amines (morpholine, pyrrolidine, piperidine or 4-methylpiperazine) giving N-2-hydroxy-3-heteroaminopropyl-substituted compounds 3a-f or substituted 4,5-dihydrofuro[2',3':4,5]pyrrolo[2,1-c][1,4]oxazin-8-ones 4a-e.     

Intramolekulare Cyclisierung von Aminofluorsilanen

Aminofluorosilanes react with lithiated amines undergoing LiF-elimination and substitution (1). The acyclic silicon-nitrogen-compound2 is isolated in the reaction with a difluorosilane after renewed lithiation.2 is cyclisated in the reaction with butyllithium by butane- and LiF-elimination (3). Aminofluorosilanes with bulky (4) or mesomeric stabilized (5) ligands form stable lithioaminofluorosilanes, which react with fluorosilanes giving substitution products (6, 7).6 and7 react with the lithium salt oftert-butylamin in a molar ratio of 12 to give8 and9 by intramolecular cyclisation.—The mass,¹H and¹⁹F nmr spectra of the compounds are reported.     

1,6-Anhydrofuranosen,XVIII. Wahlweise Cyclisieruhg Eines D-Allose-Deriyates Zur 1,6-Anhydrofuranose Oder Zum Furanoiden 1,6′:1,6-Dianhydrid

Abstract

Depending on reaction conditions 1,2-Di-O-acetyl-3,5,6-tri-O-benzyl-D-allofuranose (2b) can be cyclized with SnCl₄ either giving the monomeric 1,6-anhydrohexofuranose derivative 3a, as was already reported in a patent procedure, or by changing the solvent from methylene chloride to toluene giving the 1,6′:1′,6-dianhydride 4a mainly. The dimeric structure of compounds 4 was proved by CI-mass spectrometry. The ¹H-n.m.r. spectrum of the acetate 4d allowed us to deduce the conformation preferentially adopted by these dianhydrides.     

Succinimide-N-Sulfonic Acid: A Mild,Efficient, and Reusable Catalyst for the Chemoselective Trimethylsilylation of Alcohols and Phenols

Abstract

Succinimide-N-sulfonic acid (SuSA) is easily prepared by the reaction of succinimide with chlorosulfonic acid. This reagent is able to efficiently catalyze the chemoselective trimethylsilylation of alcohols and phenols with hexamethyldisilazane (HMDS). All reactions were performed under mild reaction conditions, giving excellent yields.

GRAPHICAL ABSTRACT      

Synthese de O-Glycosides d'Alcenyles Catalysée par les Complexes du Palladium(0)

Abstract

Allylic carbonates reacted with carbohydrates having a free anomeric hydroxyl group in the presence of a catalytic amount of palladium(0) giving the unsaturated O-glycosides under neutral conditions with excellent yields. In the mannofuranose and ribofuranose series, the reaction was stereospecific leading only to the α and the β anomers respectively, although a mixture of α and β anomers was obtained in the glucopyranose series.     

FORMATION OF THIADIAZOLE AND THIAZOLE RINGS FROM HETEROCYCLES WITH A THIOAMIDE SIDE CHAIN

Abstract

Substituted or unsubstituted thioureido heterocycles can be successfully used for the formation of a new thiadiazole or thiazole ring. For example, a fused thiadiazolo ring is formed either from carbethoxythioureido- or carbethoxymethylthioureido-heterocycles (I). The reaction proceeds by oxidative cyclization and can be performed in the presence of various oxidizing agents. On the other hand, some reducing agents convert II back into I. A particular case represents the reaction between 2-chloro-3-aminopyridine and carbethoxy isothiocyanate giving directly III (R = = COOEt), although the reaction must proceed via an intermediate like I (n = O).     

Synthesis and calming activity of 2-amino-4-(4-<Emphasis Type="Italic">β</Emphasis>-d-allopyranoside-phenyl)-6-3(4)-substituted phenylpyrimidines

Using helicid as starting material, E-4-β-D-allopyranoside-cinnamic-4-substituted phenylketones (1a–1h) containing the structure of chalcones were synthesized; then these chalcones were reacted with guanidine hydrochloride through a 1,4-Michael reaction, giving 2-amino-4-(4-β-D-allopyranoside-phenyl)-6-3(4)substituted phenylpyrimidines (2a–2h), which were characterized by IR, ¹H NMR, and HR-MS. The target compounds were evaluated by the spontaneous locomotor activity test, showing that all of them had good calming activity; compound 2f was found to have the greatest.     

Eco-Friendly Synthesis and Insecticidal Activity of Some Fluorinated 2-(N-Arylamino)-4-Arylthiazoles

A series of fluorinated 2-(N-arylamino)-4-arylthiazoles (3) was synthesized by the condensation of appropriate arylthioureas (2) with corresponding α-bromoacetophenones (1) by using “green chemistry” techniques, viz. mechanochemical mixing and microwave or ultrasonic irradiation. Compared with conventional procedures, the reaction can be carried out under milder conditions, requiring a shorter reaction time and giving higher yields following the green chemistry methodology. All the synthesized compounds were characterized on the basis of elemental analyses and spectral data (IR, ¹H NMR, and mass spectrometry). Representative compounds were also evaluated for their insecticidal activity against Helicoverpa armigera, and some of them showed promising activity.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Flow-Injection Biamperometry of Phenol

ABSTRACT

A simple and rapid method determination of phenol is described, using a bromination reaction and biamperometric detection. The method is based on measurements of the intensity of current passing through two identical inert electrodes giving the concentration of phenol in samples. The sample is injected into a stream of carrier and merged with a stream of acidic bromine solution which brominates phenol in the reaction coil. A linear relationship between peak height and phenol concentration is observed in the range of 0.05 to 8 μg ml^?1 of phenol. The relative standard deviation was 2.8% for analysis of 5μg ml^?1 phenol and the sampling rate was 70 h^?1     

Chemo-enzymatic Synthesis of Novel Oligo-N-acetyllactosamine Derivatives having a β(1-4)–β(1-6) Repeating Unit by Using Transition State Analogue Substrate

Chitinase-catalyzed hydrolytic and transglycosylating behavior of 1,2-oxazoline derivative of N-acetyllactosamine (LacNAc-oxa) 1 has been investigated. An extremely rapid hydrolysis (ring-opening of the oxazoline moiety) could be observed, suggesting that 1 behaves as a transition state analogue substrate for chitinase A1 (Bacillus circulans WL-12). This disaccharide monomer 1 was found to polymerize under basic conditions, giving rise to novel oligosaccharides having a β(1-4)–β(1-6) repeating unit in the main chain. The degree of polymerization of the resulting oligosaccharides was up to 5. This is the first example of enzymatic glycosylation reaction forming a β(1-6) bond catalyzed by chitinase.     

Intramolecular Radical,Knoevenagel, or SN2′ Cyclization of Carbohydrate Derivatives for Access to Enantiomerically Pure 2-Oxospiroalkanes

Abstract

Intramolecular radical cyclization of D-glucose-derived substrate, (2R,3R,4R,5S)-2, 3-(isopropylidenedioxy)-5-[(1R)-l, 2-(isopropylidenedioxy)ethyl]-4-[3-bromo-3, 3-bis(methoxycarbonyl)propyl]-4-vinyltetrahydrofuran, 7 proceeded in a 6-endo-trig mode to give a derivative of 2-oxaspiro[4.5]decane 8 exclusively. Intramolecular Knoevenagel-like reaction of substrate 9 afforded derivatives of 2-oxaspiro-[4.4]nonane 10 as a 3:1 diastereomeric mixture. Intramolecular SN²′ displacement of substrate 22 proceeded highly stereoselectively giving a derivative of 2-oxaspiro-[4.4]decane 23.     

The formation of mesitylphosphine and dimesitylphosphine in the reaction of organonickel σ-complex [NiBr(Mes)(bpy)] (Mes = 2,4,6-trimethylphenyl,bpy = 2,2′-bipyridine) with phosphine PH3

Abstract

The reactivity of the previously reported organonickel σ-complex [NiBr(Mes)(bpy)], where Mes = 2,4,6-trimethylphenyl, bpy = 2,2′-bipyridine, toward phosphine PH₃ was investigated. The reaction leads to primary mesitylphosphine MesPH₂ as the main product and dimesitylphosphine Mes₂PH as secondary product with the nickel complex as transmetalating agent. The formed MesPH₂ reacts with an excess of the complex giving Mes₂PH as the major product.