Greener synthesis using hydrogen peroxide in ethyl acetate of alicyclic ring-fused benzimidazoles and anti-tumour benzimidazolequinones

Environmentally-friendly and cost effective hydrogen peroxide in ethyl acetate was used to prepare in high yields pyrrolo[1,2-a]benzimidazoles from commercial o-(pyrrolidin-1-yl)anilines without the requirement for organic-aqueous extraction and chromatography. Six, seven and eight membered ring-fused analogues were similarly obtained in high yields with methanesulfonic acid required for the pyrido[1,2-a]benzimidazole. Anti-tumour benzimidazolequinone derivatives were obtained in high yield via the cyclization of 3,6-dimethoxy-2-(cycloamino)anilines.     

Preparation of selenofunctionalized heterocycles via iodosobenzene-mediated intramolecular selenocyclizations of olefins with diselenides

An intramolecular selenocyclizations of olefins mediated by a commercially available hypervalent iodine(III) reagent, PhIO, was developed. This method provided access to a wide range of selenenylated heterocycles under ambient conditions. The striking advantages of this protocol over all previous methods include mild reaction conditions, easy operation, good yields, high levels of functional group compatibility, large–scale application and suitability for the late-stage functionalization of complex molecules of biological importance.     

Bench‐Stable Electrophilic Indole and Pyrrole Reagents: Serendipitous Discovery and Use in C–H Functionalization

The development of reagents allowing the reversal of the standard reactivity (Umpolung) of small building blocks is an important field of research in chemistry, as it allows increasing the flexibility of organic synthesis. Indoles and pyrroles are ubiquitous heterocycles in natural products and drugs. They are usually functionalized making use of their high nucleophilicity. In contrast, only few methods are based on the use of electrophilic indole and pyrrole synthons, as the needed reagents are highly unstable or can be used only with a very narrow scope. Herein, we report the serendipitous discovery and first use in the C–H functionalization of arenes of IndoleBX and PyrroleBX, new thermally highly stable benziodoxol(on)e hypervalent iodine reagents. IndoleBX and PyrroleBX could be obtained in one step from the corresponding heterocycles and acetoxy benziodoxolone using a Lewis acid catalyst. The mild reactions conditions allowed the introduction of a broad range of functional groups, including ethers, halogens and boronic esters. The new reagents could then be used in the rhodium‐ and ruthenium‐catalyzed C–H heteroarylation of arene rings bearing heterocyclic or benzamide directing groups. Such transformations could not be realized using previously reported C–H functionalization procedures.     

Concise synthesis and characterization of novel seco-steroids bearing a spiro-oxetane instead of a metabolically labile C3-hydroxy group

Two novel stereoisomeric analogues of 1,25-dihydroxyvitamin D₃ bearing a spiro-oxetane at the C3 position of the A-ring have been designed and synthesized in a convergent manner. The absolute configuration at the C1 position of the synthesized compounds was determined by the circular dichroism exciton chirality method using the corresponding C1-allylic benzoates. The replacement of the C3-hydroxy group with a spiro-oxetane provided an advantageous conformational preference for the parent seco-steroids, which would facilitate the formation of a stable receptor complex.     

Synthesis of 4‐Alkyl‐1(2H)‐phthalazinones and 4‐Alkyl‐2,3‐benzoxazin‐1‐ones via Ring Cleavage of 3‐Substituted N‐Alkylated‐3‐hydroxyisoindolin‐1‐ones

Abstract

N‐Alkyl (Me, Et, i‐Pr, t‐Bu)‐substituted phthalimdes 5a–d were easily transformed to 1(2H)‐phthalazinones 8d–i and 2,3‐benzoxazin‐1‐ones 9d, f, and j via a one‐pot addition–decyclization–cyclocondensation process.     

Copper on iron promoted one-pot synthesis of β-aminoenones and 3,5-disubstituted pyrazoles

The reaction of hydroximoyl chlorides with acetylenes in the presence of a copper on iron bimetallic system leads to β-aminoenones via reductive ring opening of isoxazole intermediates. The valuable β-aminoenone building blocks can be isolated or transformed into pyrazoles with the addition of hydrazine in a straightforward one-pot procedure.     

Lithium-1,3-Benzazaphospholides: Structure and Reactivity

The formation, structure and electrophilic substitution reactions at phosphorus or nitrogen of N -lithium-1,3-benzazaphospholides is reported.     

High Stability of a Phosphenium Ion Allows Umpolung of P--H Bonds

The high intrinsic stability of 1,3,2-diazaphospholenium cations enhances ionic polarization of covalent P--X bonds in P -halogeno- and P -hydrido-diazaphospholenes. The physical properties of the latter suggest a hydridic nature of the P--H bond, and their reactivities display an "Umpolung" as compared to known reaction patterns of phosphines.     

Novel 1,2,4-Triphosphole, 1,2,3-Triphosphetene and Azaphospholene Derivatives from N -Heterocyclic Carbenes and Phosphaalkynes

The stable singlet carbenes N,N '-bis(2,2-dimethylpropyl)-benzimidazolin-2-ylidene 1 and 1,3,4,5-tetramethylimidazol-2-ylidene 2 react with phosphaalkynes P L C-- t Bu ( 3a ) or P L C--N i Pr 2 ( 3b ) regioselective to give the aromatic 1,2,4-triphosphole derivatives ( 1 or 2 + 3a M 6a or 6b , respectively) or 1,2,3-triphosphetene ( 1 + 3b M 7 ) or azaphospholene ( 2 + 3b M 9 ) in almost quantitative yields. The mechanisms of the surprising formation of compound 9 under C--H-activation was studied by quantum chemical DFT calculations.