Synthesis of 2,2-functionalized benzo[1,3]dioxoles

Highly functionalized catechol ketals exhibiting either a tert-butyl moiety or a spiro center in position 2 are synthesized by ketalization and functionalized in a sequence of subsequent transformations. By a specific ketalization protocol catechol ketals of enolizable β-keto esters can be prepared. With the succeeding steps these compounds incorporate moieties, which are not compatible and accessible by direct ketalization of catechol.     

Synthesis of 1,3-disubstituted benzo[c]thiophene analogs containing benzo[b]thiophene/benzo[b]pyrrole

The synthesis of 1,3-disubstituted benzo[c]thiophene analogs incorporating benzo[b]thiophene/benzo[b]pyrrole units is described.     

Isoquinoline-mediated S-vinylation and N-vinylation of benzo[d]oxazole-2-thiol and benzo[d]thiazole-2-thiol

An effective route to 5-vinylated and N-vinylated benzo[d]oxazole-2(3H)-thiones and benzo[d]thiazole-2(3H)-thiones is described via reaction of acetylenic esters and benzo[d]oxazole-2-thiol and benzo[d]thiazole-2-thiol in the presence of 15 mol%of isoquinoline.     

Theophylline as a new and green catalyst for the one-pot synthesis of spiro[benzo[a]pyrano[2,3-c]phenazine] and benzo[a]pyrano[2,3-c]phenazine derivatives under solvent-free conditions

A green, convenient, high yielding and one-pot procedure for the synthesis of novel spiro[benzo[a]pyrano[2,3-c]phenazine] derivatives by domino multi-component condensation reaction between 2-hydroxynaphthalene-1,4-dione, benzene-1,2-diamines, ninhydrine, and malononitrile in the presence of a catalytic amount of 1,3-dimethyl-7H-purine-2,6-dione (theophylline) as an expedient, eco-friendly and reusable solid base catalyst under thermal, microwave irradiation and solvent-free conditions. This procedure has also been applied successfully for the synthesis of benzo[a]pyrano[2,3-c]phenazines.     

Synthesis of a linear benzo[3]phenylene-[60]fullerene dyad

The synthesis of a new linear benzo[3]phenylene-[60]fullerene dyad 1 is achieved over 10 steps in 15% overall yield by using an efficient sequence combining a double cobalt(I)-mediated cyclotrimerization with a Bingel reaction.     

Synthesis of 1,3-diaryl benzo[c]thiophenes

An array of 1,3-diarylbenzo[c]thiophenes has been synthesized via the ring opening of lactones followed by thionation using Lawesson’s reagent.     

Nitrogen is a requirement for the photochemical induced 3-azabicyclo[3.3.1]nonane skeletal rearrangement!

Specific 3-azabicyclo[3.3.1]nonane derivatives undergo skeletal cleavage when subjected to light or Lewis acidic conditions affording novel heterotricycles, which is in stark contrast to 3-oxabicyclo[3.3.1]nonanes.     

Regioselective synthesis of C-prenylated flavonoids via intramolecular [1,3] or [1,5] shift reaction catalyzed by acidic clays

Prenyl side chain and dihydropyrano skeleton exists in many natural and synthetic biologically active flavonoids. A highly efficient and regioselective method for the synthesis of C-prenylated flavonoids via intramolecular [1,3] or [1,5] shift reaction of 5-O-prenylflavonoids catalyzed by Florisil or Montmorillonite clays is described. Florisil catalyzes intramolecular [1,5] shift reaction of 5-O-prenylflavonoids to obtain 8-C-prenylated flavonoids exclusively, Montmorillonite K10 exhibits the superior selectivity to promote intramolecular [1,3] shift reaction to obtain 6-C-prenylated flavonoids compared with Florisil and Montmorillonite KSF. This method provides a practical process to regioselective synthesize biologically important C-prenylated flavonoids in good yields using commercially available and inexpensive catalyst under mild conditions.     

[C]Lithium trimethylsilyl ynolate: a new [C] precursor and its application in heterocyclic synthesis

[¹¹C]Lithium trimethylsilyl ynolate was characterized to be a new precursor in carbon-11 chemistry. It was obtained from [¹¹C]carbon monoxide and lithiated silyldiazomethane. The new precursor might be of high potential for the incorporation of carbon 11 into heterocyclic ring systems for which labeling methods are not well developed. More examples will certainly follow if other researchers will apply this useful method.     

Synthesis and Characterization of [1,2,4,6]Thiatriazino[2,3-a][1,3]benzimidazol-1(2H)-one and [1,3,5]Thiadiazino[3,4-a][1,3]benzimidazol-2-imine

Abstract

The reaction of thionyl chloride with amidines 2, derived from N-benzimidazol-2-yl imidates 1, leads to [1,2,4,6]thiatriazino[2,3-a][1,3]benzimidazol-1(2H)-one 3 in good yields. [1,3,5]Thiadiazino[3,4-a][1,3]benzimidazol-2-imine 4 was prepared by condensation of NaSCN with benzimidazol-2-yl imidate 1. The isolated compounds 3 and 4 were identified by spectroscopic methods including IR, ¹H NMR, and ¹³C NMR as well as elemental analyses and MS of 3d and 4b.

GRAPHICAL ABSTRACT      

An efficient synthesis of benzo[b]benzofurano[2,3-e]-[1,6]naphthyridine-8-ones

An efficient method for the synthesis of benzo[b]benzofurano[2,3-e][1,6]naphthyridine-8-one derivatives has been developed via Pictet-Spengler reaction of 4-(3-aminobenzofuran-2-yl)quinoline-2-ones,which could be obtained from alkylation of 4-bromomethylquinoline-2-ones with salicylonitrile and subsequent Thorpe-Ziegier isomerization,with aromatic aldehydes under p-TsOH as catalyst in good yields.     

BF3-promoted annulation of azonaphthalenes and ynamides for synthesis of benzo[e]indoles

A novel BF₃-promoted [3+2] annulation of azonaphthalenes and ynamides is described.This protocol provides a modular and efficient entry to functionalized amino benzo[e]indole derivatives smoothly.     

A straightforward preparation of benzo[f]naphtho[b][1,4]oxazepines from TNT

2,4,6-Trinitrotoluene readily reacts with 1-nitroso-2-naphthol to afford 9,11-dinitrobenzo[f]naphtho[2,1-b][1,4]oxazepine. The nitro groups of the latter undergo displacement by O- and S-nucleophiles with preferential substitution of the 11-NO₂ (peri-nitro group). The structures of the substitution products are confirmed by X-ray diffraction and ¹H NMR NOE experiments.     

Alkoxide-Accelerated [1,3] Sigmatropic Shift of Bicyclo[3.2.1]oct-6-en-2-ols to 8-endo-Hydroxybicyclo[3.3.0]oct-2-en-4-ones

Bicyclo[3.2.1]oct-6-en-2-ols 6 are shown to undergo [1,3] sigmatropic shift to afford 8-endo-hydroxy-bicyclo[3.3.0]oct-2-en-4-ones 8 under the influence of potassium hydride.     

Synthesis and characterization of benzo[c]thiophene analogs incorporating benzo[b]thiophene/1-hexylindole/benzo[b]furan

Synthesis of 1,3-disubstituted benzo[c]thiophene analogs incorporating heterocycles such as benzo[b]thiophene/1-hexylindole/benzo[b]furan and thiophene units is described. Optical and electrochemical studies of the benzo[c]thiophene analogs are also reported.     

Preparation of benzo[4,5]thiazolo[3,2-a]chromeno[4,3-d]pyrimidin-6-one derivatives using MgO-MgAl2O4 composite nano-powder

MgO-MgAl₂O₄ nanocomposite was prepared from the co-precipitation of Mg(NO₃)₂ and Al(NO₃)₃ salts, characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS) and fourier transform infrared spectroscopy (FTIR) techniques and evaluated in the synthesis of thirty five derivatives of benzo[4,5]thiazolo[3,2-a]chromeno[4,3-d]pyrimidin-6-ones (d₁-d₃₄) via the multi-component reaction of 4-hydroxycoumarins, aldehydes, and 2-aminobenzothiazole derivatives under solvent free condition. The catalytic activity of MgO-MgAl₂O₄ nanocomposite and the synthesis of the above mentioned compounds were investigated under thermal solvent free (times: 1.4–3 h; yields: 75–95%), ultrasonic irradiation (US) conditions (times: 1–2.5 h; yields: 69–97%) and using high-speed ball milling (HSBM) technique (times: 0.7–2.5 h; yields: 67–97%). In all cases, the products were obtained in excellent yields. Nuclear Magnetic Resonance (NMR) and MASS spectroscopy were used to characterize the structure of the desired product. The mechanism for the preparation of compounds d₁-d₃₄ was proposed and confirmed by ¹H NMR investigations.     

Synthesis and Ring Transformation of Pyrrolo[2,3-d][1,3]oxazine to Pyrrolo[2,3-d]Pyrimidines

A convenient route is reported for the synthesis of fused pyrrolo[2,3-d][1,3]oxazine and pyrrolo[2,3-d]-pyrimidine derivatives from 2-amino-1-benzyl-3-t-butoxycarbonyl]-4,5-dimethylpyrrole.     

Versatile strategies for the solid phase synthesis of small heterocyclic scaffolds: [1,3,4]-thiadiazoles and [1,3,4]-oxadiazoles

New robust protocols for the solid phase synthesis of 5-alkylthio-, 5-alkyl/aryl-, and 5-acylamino-2-alkylamino-[1,3,4]-thiadiazoles are described based on a common resin bound thiosemicarbazide. A protocol for the solid phase synthesis of 2-alkyl/aryl-amino-5-alkylamino-[1,3,4]-oxadiazoles from a resin bound semicarbazide is likewise reported. The protocols have been verified by the preparation of four small libraries that all gave products in good to excellent yields and purity.     

Synthesis of benzo[g]indeno[2,1-b]quinoline derivatives via four-component and one-pot synthesis in presence of 3-methyl-1-sulfonic acid imidazolium hydrogen sulfate

A simple and facile synthesis of 12-arylbenzo[g]indeno[2,1-b]quinoline-6,11,13-trione deriv-atives was accomplished by the one-pot condensation of 2-hydroxynaphthalene-1,4-dione, aryl aldehydes, 2H-ind...     

Skeletal isomerism within 1,3-disilabicyclo[1.1.0]butane and 2,3-disilabuta-1,3-diene derivatives

A bis-adamantane-spiro-fused 1,3-bis(triisopropylsilyl)-1,3-disilabicyclo[1.1.0]butane equilibrates with the corresponding 2,3-bis(triisopropylsilyl)-1,3-disilabuta-1,3-diene with a ratio of 1:19. The 1,3-disilabuta-1,3-diene was fully characterized by a combination of multinuclear NMR and UV-VIS spectroscopies, elemental analysis, and single-crystal X-ray diffraction analysis.