Structure-property relationships of benzo[2,1-b:3,4-b’]bis[1]benzothiophenes for organic field effect transistors

A series of novel benzo[2,1-b:3,4-b’]bis[1]-benzothiophene (BBBT) derivatives with different side-chains were synthesized and characterized. And their mobility properties were evaluated based on their active layers in OFETs devices. By means of simple thermal annealing, the devices based on BBBT-4 and BBBT-6 exhibited typical p-type FETs behavior with average hole mobilities of 0.28 and 0.124?cm² V^?1?s^?1, respectively. Furthermore, the structure-property relationships of these semiconductors were also investigated by XRD and AFM.     

2-Allyl-N-benzyl substituted α-naphthylamines as building blocks in heterocyclic synthesis. New and efficient syntheses of benz[e]naphtho[1,2-b]azepine and naphtho[1,2-b]azepine derivatives

A new series of 13-acetyl-7,12-dihydro-7-ethylbenz[e]naphtho[1,2-b]azepine (4a-d) and 2-aryl-4-hydroxy-2,3,4,5-tetrahydronaphtho[1,2-b]azepine derivatives (6a-d) have been synthesized from N-allyl-N-benzyl substituted α-naphthylamines (1a-d) by utilizing aromatic amino-Claisen rearrangement, intramolecular Friedel-Crafts alkylation and intramolecular dipolar 1,3-cycloaddition nitrone-olefin reactions.     

Substituted benzoquinazolinones. Part 1: Synthesis of 6-aminobenzo[h]quinazolinones via Buchwald–Hartwig amination from 6-bromobenzo[h]quinazolinones

6-(Morpholin-4-yl)benzo[h]quinazolin-4(3H)-one derivatives 18a,b were prepared under Buchwald–Hartwig conditions by reacting 6-bromobenzo[h]quinazolin-4(3H)-ones 13a,b with morpholine in the presence of a Pd(OAc)₂/XantPhos system in 1,4-dioxane as solvent. The starting 6-bromobenzo[h]quinazolin-4(3H)-ones 13 were synthesized via condensation of the ethyl 1-amino-4-bromonaphthalene-2-carboxylate (11) with formamide (Niementowski reaction), and then reaction of the obtained benzoquinazolinone 9 with appropriates benzyl bromides. Compound 11 was prepared using a three-step procedure involving (a) metalation of the N-Boc- or N-Piv-protected 1-aminonaphthalenes with t-BuLi, followed by reaction with ethyl chloroformate, (b) bromination of the naphthalene ring of ester 3 using NBS, and next (c) deprotecion of the amine group with TFA or HCl. Biological screening of the potential cytotoxicity of compounds 8, 9, 18b on A549 and HT29 cell lines, as well as on the lymphocytes showed that compound 18b has interesting anticancer activities. The detailed synthesis, spectroscopic data, and biological assays were reported.     

Oxone®-mediated direct arylselenylation of imidazo[2,1-b]thiazoles,imidazo[1,2-a]pyridines and 1H-pyrazoles

Oxone mediated reaction of imidazo[2,1-b]thiazole, imidazo[1,2-a]pyridine and 1H-pyrazole derivatives with diaryl diselenides is presented here. The methodology represents an efficient and simple protocol for carrying out the selective synthesis of 5-arylselanyl-imidazo[2,1-b]thiazoles, 3-arylselanyl-imidazo[1,2-a]pyridines and 4-arylselanyl-1H-pyrazoles in high yields using a stable, nontoxic and cheap oxidant. The reactions were conducted at 60?°C in air using acetonitrile as solvent. Alternatively, the use of ultrasound irradiation is presented as a tool for fast and efficient energy transfer that significantly reduced the reaction time.     

DBU as a scaffold for the synthesis of [1,3]oxazolo[2’,3’ : 2,3]pyrimido-[1,2-a]azepines: annulation with aromatic cyanopropargylic alcohols

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Diversity-oriented synthesis of 1,2,3,5-tetrahydrobenzo[e][1,2,4]oxadiazepines and 2,3-dihydro-1H-benzo[e][1,2,4]triazepines by base-induced [4 + 3] annulation reactions

The base-induced formal [4 + 3] annulation reactions of N-(ortho-chloromethyl)aryl amides with nitrones or hydrazonoyl chlorides have been reported. When nitrones are used as the 1,3-dipole, the corresponding reaction afforded a series of 1,2,3,5-tetrahydrobenzo[e][1,2,4]oxadiazepine derivatives. Highly functionalized 2,3-dihydro-1H-benzo[e][1,2,4]triazepine derivatives were also synthesized via an unprecedented tandem aza-Michael addition/rearrangement aromatization between N-(ortho-chloromethyl)aryl amides and hydrazonoyl chlorides.     

3H-Pyrroles as a platform for the catalyst-free construction of dihydropyrrolo[2,1-b]oxazoles: [4 + 2]-cycloaddition vs [2 + 3]-annulation with 1-cyano-3-hydroxyalkynes

Non-aromatic pyrrole isomers, 3,3-dialkyl-2-aryl-3H-pyrroles, were reacted with 1-cyano-3-hydroxyalkynes under mild, catalyst-free conditions (20–60?°C) to regio- and stereoselectively afford (Z)-2-(dihydropyrrolo[2,1-b]oxazolylidene)acetonitriles in 62–82% yield, thus evidencing the preference for [2?+?3]-annulation over the [4?+?2]-Diels-Alder alternative. The reaction involves initial nucleophilic addition of the pyrrole moiety at the triple bond followed by tandem ring closure of an anionic intermediate.     

Synthesis of pyrazolo[3,4-b]pyrrolo[3,4-d]pyridine derivatives via Aza-Diels–Alder reaction: evaluation of torsion effect of pyrazoylimines

A modified method for the synthesis of pyrazolo[3,4-b]pyrrolo[3,4-d]pyridine was developed through an Aza-Diels–Alder reaction of pyrazoylimines with maleimides in the sealed tube. Based on the control experiment, the yields for the Aza-Diels–Alder reaction seemed proportional to the suitable torsion conformation of pyrazoylimine, which was modulated by N,N-disubstituted amidinyl moiety. The versatile sealed tube technique was also proved to promote the higher isolated yields in the Aza-Diels–Alder reaction.     

A convenient synthesis of tetrazolo[1,5-a]-α-cycloalkanones

A convenient synthesis of a series of tetrazolo[1,5-a]-α-cycloalkanones 4a-d with the carbonyl group attached at the tetrazole carbon is described. The sequence entails the formation of an exocyclic olefin at the α-methylene position and subsequent ozonolysis. The reactions proceed under mild conditions, and the tetrazole moiety is well tolerated.     

Synthesis of dihydrochromeno[4,3-b]pyrazolo[4,3-e]pyridin-6(7H)-ones involving one-pot three-component tandem Knoevenagel–Michael reaction catalyzed by n-tetrabutylammonium tribromide (TBATB)

The synthesis of dihydrochromeno[4,3-b]pyrazolo[4,3-e]pyridin-6(7H)-ones was achieved through one-pot three-component reaction from 4-hydroxycoumarin, aldehydes, and 3-amino-5-methyl-pyrazole in acetonitrile using 5 mol % TBATB as the catalyst under reflux condition. The product formation is through tandem Knoevenagel–Michael reaction followed by concomitant cyclization. Simple reaction procedure, shorter reaction time, good yields, avoidance of aqueous work-up, and column chromatographic separation are some of the salient features of the present protocol.     

Diastereoselective cascade reactions toward substituted diazaindeno[2,1-α]phenanthrenes

A cascade sequence between cyclic hemiacetals and tryptamines was developed, which provided efficient access to highly substituted diazaindeno[2,1-α]phenanthrenes in moderate to good yields with high diastereoselectivities and good to excellent enantioselectivities. Hemiacetals were prepared by asymmetric organocatalyzed conjugate addition of cyclic 1,3-diketones to α,β-unsaturated aldehydes. Hemiacetals with various R¹, both aromatic and aliphatic, were examined for the cascade sequence.     

One-pot heterocyclic ring closure of 1,1′-bi-2-naphthol to 7H-dibenzo[c,g]carbazole

An operationally simple ring closure of racemic 1,1′-bi-2-naphthol (BINOL) yielded the heterocyclic aromatic compound 7H-dibenzo[c,g]carbazole (DBC). This one-pot method gave a good conversion and is suitable for gram-scale synthesis. DBC derivatives have high thermal durability, amorphous and crystalline structures with unique morphological properties, and semi-conducting behavior with potential applications in organic electronics.     

Conversion of γ-substituted bicyclo[2.2.1] (Z)-vinylsulfones to the corresponding (E)-allylsulfones

The preparation of bicyclo[2.2.1] (E)-allylsulfones starting from the corresponding (Z)-vinylsulfones is described. Starting from 2,3-bis(phenylsulfonyl)norbornadiene 1, the Michael addition of organometallic reagents followed by the base catalyzed isomerization affords (E)-allylsulfones in high yields. The procedure allows to obtain vinylidenic norbornenes which are characteristic nuclei of valuable biologically active compounds.     

Synthesis of dipyrrolo[2,3-a:1′,2′,3′-fg]acridin-12(1H)-ones

Acylation reactions of 4,6-dimethoxyindoles with glyoxyloyl chlorides were achieved by the use of graphite powder in 1,2-dichloroethane at reflux. The products were monoketones as a result of decarbonylation, rather than the expected 1,2-diketones. Treatment of these monoketones with base led to their cyclisation and elimination of methanol to afford the novel dipyrrolo[2.3-a:1′,2′,3′-fg]acridin-12(1H)-ones.     

Chemoselective one-pot access to benzo[e]indole-4,5-diones and naphtho[2,1-b]thiophene-4,5-diones via copper-catalyzed oxidative [3 + 2] annulation of α-oxoketene N,S-acetals/β-ketothioamides with α-/β-naphthols

An operationally simple and efficient one-pot method for the synthesis of 1-aroyl (or alkanoyl)-2-thioalkyl-3-aryl (or alkyl)-3H-benzo[e]indole-4,5-diones and naphtho[2,1-b]thiophene-4,5-diones has been devised by copper-catalyzed cross-coupling of α-oxoketene N,S-acetals/β-ketothioamides with α-/β-naphthols in open air for the first time. The key to the success of this transformation is the room temperature oxidation of α-/β-naphthol to 1,2-naphthoquinone as a reactive species, which undergoes formal [3 + 2] annulation with α-oxoketene N,S-acetals/β-ketothioamides via cascade sequence of Michael addition/tautomerization/oxidation/cyclization/aromatization reactions, enabling addition of a pyrrole/thiophene ring onto naphthoquinone moiety. Further, benzo[e]indole-4,5-diones were transformed to pentacyclic fused phenazine derivatives under solvent-free conditions. Based on our experimental outcomes, a tentative mechanistic rationale for this chemoselective protocol is proposed, which is well validated and supported by the control experiments.     

Synthesis of new 10,11-dihydrodibenzo[a,d]cycloheptene S-thiocarbamate derivatives via a benzylic Newman–Kwart rearrangement

New S-thiocarbamates possessing a 10,11-dihydro-5H-dibenzo[a,d]cycloheptene moiety were obtained unexpectedly in the process of preparing new O-thiocarbamates starting from 5-dibenzosuberol (10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5-ol) and aroyl-isothiocyanates. These compounds were obtained via a benzylic Newman–Kwart rearrangement mechanism. The structures of the new thiocarbamates were confirmed by elemental analysis, IR, and NMR spectroscopy and by X-ray crystallography.     

A mild method for the synthesis of bis-pyrazolo[3,4-b:4′,3′-e]pyridine derivatives

A mild and efficient method for the synthesis of bispyrazolo[3,4-b:4′,3′-e]pyridines from 5-aminopyrazoles and aromatic aldehydes using an inexpensive FeCl₃ catalyst is reported. The reaction temperature was reduced from 220–250?°C to 130?°C compared to conventional methods. A large proportion of the products precipitated directly from the mixture at room temperature. Aliphatic and α,β-unsaturated aldehydes selectively resulted in formation of the corresponding 1H-pyrazolo[3,4-b]pyridine derivatives. A possible domino reaction mechanism was also proposed. Several aryl alkynyl groups were introduced to these tricyclic molecules via the Sonogashira coupling reaction.     

Chromeno[2,3-c]pyrroles by one-pot multicomponent domino addition–amination reaction

A new aspect concerning chromone chemistry leading to the one-pot synthesis of chromeno[2,3-c]pyrroles is described. The synthesis involves a multicomponent reaction of 3-formylchromones with isocyanides and azodicarboxylates, whereupon novel chromeno[2,3-c]pyrrole derivatives were formed in good yields. The structures of the products were elucidated by 1D and 2D NMR experiments and were unambiguously confirmed by the use of crystal X-ray diffraction analysis. Full assignment of all ¹H and ¹³C NMR chemical shifts has been achieved. A plausible mechanistic scheme is proposed.     

Improved synthesis of (S)-7-amino-5H,7H-dibenzo[b,d]azepin-6-one, a building block for γ-secretase inhibitors

An improved synthesis of (S)-7-amino-5H,7H-dibenzo[b,d]azepin-6-one (1), involving a selective crystallization of epimeric menthylcarbamates for the resolution step followed by simultaneous cleavage of the carbamate and the lactam protecting group is described. Epimerization conditions of the undesired epimer have also been determined.     

Oxidation of thiazolo[3,2-a]pyrimidin-3(2H)-ones with DMSO and Lawesson’s reagent

2,2′-Dimers with a central double bond were prepared by the oxidation of 5,6-disubstituted 7-methyl-5H-[1,3]thiazolo[3,2-a]pyrimidin-3(2H)-ones with DMSO and Lawesson’s reagent at room temperature. The role of DMSO as an oxidizing reagent was confirmed by NMR spectroscopy. The E-configuration of the central CC bond for the two diastereomers of compound 8m was proven by single crystal X-ray data. The dimeric thiazolopyrimidines were orange or red colored and absorption bands at 283–330 and 459–476?nm were observed in the UV spectra.