Oxidative synthesis of benzo[1,4]oxazines from α-branched primary amines and ortho-benzoquinones

The efficient oxidative construction of benzo[1,4]oxazines from simple α-branched amines and ortho-benzoquinones is reported. The procedure pivots on a triethylamine and iodine mediated oxidative ring closure from the ketimine intermediate formed upon their condensation. This reaction was shown to tolerate a variety of α-branched benzylamines and downstream derivatization to substituted benzomorpholine structures was also demonstrated.     

Regioselective synthesis of novel imidazo[1,5-b]pyridazine derivatives from diaminoimidazoles and α-acylacrylonitriles

The heterocyclization of 1,2-diamino-4H-phenylimidazole with α-acylacrylonitriles affords cleanly 7-amino-2-R-5- phenylimidazo[1,5-b]pyridazine-3-carbonitriles. The strating α-acylacrylonitriles can be generated in situ from 3-oxo-3-(het)arylpropanenitriles and triethylorthoformate or dimethylformamide dimethyl acetal, and the products can be prepared in one pot.     

Synthesis of Spiro[benzo[h]chromene-4,3′-indoles] and Spiro[benzo[f]chromene-1,3′-indoles]

Russian Journal of Organic Chemistry - New spiro heterocycles, spiro[benzo[h]chromene-4,3′-indoles] and spiro[benzo[f]chromene-1,3′-indoles], have been synthesized in 50–60% yield...     

Synthesis of 2,3,5-trisubstituted furans from α-formylaroylketene dithioacetals

A new strategy for the synthesis of 2,3,5-trisbustituted furans from α-formylketene dithioacetals is described. The protocol involves a facile conversion of α-formylketene dithioacetals to vinylketene dithioacetals via Wittig reaction and subsequent N-bromosuccinimide-mediated cyclization to 2,3,5-trisbustituted furans. Further conversion of the 2-thioalkylfurans thus obtained to 2-aminofurans shows the potential synthetic utility of this new approach.     

Efficient Cyclization of 2‐Phenoxyalkanals to 2‐Alkylbenzo[b]furans

A new and efficient route to 2‐alkylbenzo[b]furans via acid‐catalyzed cyclization of 2‐phenoxyalkanals under mild conditions over amberlyst‐15 resin has been described.     

Photoinduced [4?+?2] cycloaddition reactions of benzo[b]thiophene-2,3-dione with alkenes

[4?+?2]-Photocycloadditions of benzo[b]thiophene-2,3-dione with electron-rich and electron-deficient alkenes have been described. Olefins preferentially add at both carbonyl groups to give the head-to-head [4?+?2] cycloadducts, i.e., dioxanes only. Comprehensive molecular orbital calculations at DFT-B3LYP level have been carried out to address the mechanism as well as regiochemical course of the reaction.     

A continuous-flow synthesis of annulated and polysubstituted furans from the reaction of ketones and α-haloketones

A synthesis of di-, tri- and tetra-substituted furans from reaction of the corresponding ketones and α-haloketones with LiHMDS is reported. Reaction under continuous-flow conditions gave increased yields and removed the need for external cooling when compared to the unoptimised batch conditions.     

Impregnated copper or palladium–copper on magnetite as catalysts for the domino and stepwise Sonogashira-cyclization processes: a straightforward synthesis of benzo[b]furans and indoles

An impregnated copper on magnetite catalyst is a versatile system for different domino Sonogashira-cyclization processes between 2-iodophenol and different alkynes to give the corresponding substituted benzo[b]furans. The catalyst could be recovered ten times without losing its activity. The related process using 2-iodoaniline was, however, better catalyzed by mixed palladium–copper on magnetite giving exclusively, in this case, the products arising from the Sonogashira coupling. The cyclization to the corresponding substituted indoles could be easily and quantitatively performed by zinc bromide treatment. This catalyst avoids the use of any type of expensive and difficult to handle organic ligand, showing excellent yields, under mild reaction conditions. The catalyst is very easy to remove from the reaction medium, just by using a simple magnet.     

Novel Stereoselective Synthesis of Densely Functionalized 2H‐Indeno[2,1‐b]furans

An easy access to densely functionalized 2H‐indeno[2,1‐b]furans is presented starting from triphenylphosphine, dialkyl acetylenedicarboxylates, alcohols (propargyl alcohol, 2,2,2‐trichloroethanol, and methanol), and ninhydrin. The stereochemistry of dimethyl 8‐oxo‐8a‐(2,2,2‐trichloroethoxy)‐8,8a‐dihydro‐2H‐indeno[2,1‐b]furan‐2,3‐dicarboxylate was established by single‐crystal X‐ray structure determination. The reaction is completely stereoselective.     

Preparation and characterization of MNPs–PhSO3H as a heterogeneous catalyst for the synthesis of benzo[b]pyran and pyrano[3,2-c]chromenes

Research on Chemical Intermediates - In this study, an efficient and novel procedure has been reported for loading sulfanilic acid on the surface of magnetite Fe3O4 nanoparticles using...     

Dynamic Kinetic Resolution of 2,3-Dihydrobenzo[b]furans: Chemoenzymatic Synthesis of Analgesic Agent BRL 37959

An efficient asymmetric synthesis of (S)-2,3-dihydrobenzo[b]furan-3-carboxylic acid (8?a) and (S)-5-chloro-2,3-dihydrobenzo[b]furan-3-carboxylic acid (8?b) was established. Key to the success was the highly stereoselective enzymatic kinetic resolution of the corresponding methyl or ethyl esters that was further developed into a dynamic process. As a reliable and fast tool for analysing the enantiomeric excess, HPLC coupled with a CD detector was utilized. The route was completed by a Friedel-Crafts acylation of ethyl (S)-5-chloro-2,3-dihydrobenzo[b]furan-3-carboxylate (7?c) followed by saponification leading to (S)-5-chloro-2,3-dihydrobenzo[b]furan-3-carboxylic acid (2), an analgesic agent.     

Theophylline as a new and green catalyst for the one-pot synthesis of spiro[benzo[α]pyrano[2,3-c]phenazine]and benzo[α]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[α]pyrano[2,3-c]phenazine]derivatives by domino multi-component condensation reaction between 2-hydroxynaphthalene-l,4-dione,benzene-l,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[α]pyrano[2,3-c]phenazines.     

Synthesis of novel benzo[h][1,6]naphthyridine derivatives from 4-aminoquinoline and cyclic β-ketoester

This paper describes the synthesis of 2,8-dichloroquinolin-4-amine 4 and 4,5,7-trichloro-3-(2-chloroethyl)-2-methylbenzo[h][1,6]naphthyridine 8 as novel class of building blocks. Also describes the regioselective S_NAr reactions of 2,4,8-trichloroquinoline 2 on C₂ and C₄ positions with azide, similarly S_NAr reactions of benzo[h][1,6]naphthyridine 8 at C₄, C₅ positions, and S_N2 reactions on C₃-(2-chloroethyl) side chain with nucleophiles such as primary aromatic amines, methoxide/ethoxide, and azide at different temperatures.     

Silver-Catalyzed Highly Regioselective Synthesis of α-Carbonyl Furans from Enynones

A general and efficient method for the synthesis of a wide range of α-carbonyl furans is described here. The cyclization of enynone is catalyzed by AgBF₄ in a fluorous biphasic system of perfluorodecalin and N,N-dimethylformamide. A variety of chain ketone and cyclic ketone substrates were used to investigate the scope of the reactions.     

Tetrabutylammonium fluoride-promoted α-[C]methylation of α-arylesters: a simple and robust method for the preparation of C-labeled ibuprofen

Tetrabutylammonium fluoride-promoted α-[¹¹C]methylation of α-arlylesters was developed. The method was amenable to the remote-controlled synthesis of ¹¹C-labeled ibuprofen.     

The preparation of optically active α-amino 4H-[1,2,4]oxadiazol-5-ones from optically active α-amino acids

Optically active α-amino 4H-[1,2,4]oxadiazol-5-ones (oxadiazolones) were prepared from optically active α-amino acids in five synthetic steps. The oxadiazolone moiety serves as a bioisosteric replacement for the carboxylic acid. Incorporation of an α-amino oxadiazolone into a representative dipeptide mimic is described.     

Synthesis of substituted naphthalenes from α-substituted ketones and 1,2-bis(halomethyl)benzenes including a rearrangement aromatization of benzo[c]oxepine

An efficient and practical method for the synthesis of cyano, sulfonyl and phosphoryl substituted naphthalene derivatives via the rearrangement aromatization of benzo[c]oxepine has been developed. The system holds the advantages of metal catalysts free, and mild reaction conditions.     

CuI catalyzed domino coupling–cyclization of 2-iodo-phenols and 1-alkynes to the synthesis of 2-substituted benzo[b]furans/furo-pyridines

CuI/proline-catalyzed coupling reaction of 2-iodo-phenols with terminal alkynes and the following cyclization process is carried out successively in DMSO at 80?°C. Under this tandem process, 2-substituted benzo[b]furans/furo-pyridines were synthesized in good to excellent yields with a great diversity.     

Facile preparation of two tetrols from permethylated α-cyclodextrin and unambiguous NMR analysis

An unprecedented straightforward approach wherein an excess of diisobutylaluminum hydride is able to strip off in reasonable yield (45%) and in a regioselective manner four methyl groups from permethylated α-cyclodextrin, to provide a symmetric tetrol (2) in one chemical step from a commercially available material is described. An asymmetric tetrol (3) was also isolated from the reaction as a minor product (19%). Both compounds are unambiguously characterized by ¹H NMR, ¹³C NMR, COSY, HSQC and HRMS.