Synthesis of Benzo[a]carbazoles through Visible Light-Induced Cycloaromatization

We report herein a synthesis of 5,6-diarylbenzo[a]carbazoles by a sequence of 6π-electrocyclization followed by β-elimination. The highly functionalized 2,3-disubstituted indoles used for this cycloaromatization process are prepared by Pd-catalyzed cyclizative cross-coupling of ortho-alkynylanilines with ortho-alkynylbenzamides. The combination of these two reactions allows us to develop a facile synthesis of benzo[a]carbazoles directly from two easily accessible internal alkynes without isolation of the indole intermediates.     

Sequential Two-Fold Claisen Rearrangement,One-Pot Ring-Closing Metathesis and Cross-Metathesis as a Route to Substituted Benzo[b]azepine-2-one,Benzo[b]azepine and Benzo[b]oxepine Derivatives

A synthetic protocol involving sequential use of three atom-economic processes viz. Claisen rearrangement, ring-closing metathesis and cross metathesis has been developed to access 7-substituted benzo[b]azepine and benzo[b]oxepine derivatives starting from appropriate aniline or phenol in good overall yield. A one-pot RCM-CM protocol has also been developed for the synthesis of benzazepine and benzoxepine derivatives.     

DABCO-Catalyzed Multicomponent Reaction for Synthesis of Benzo[a]carbazoles

DABCO (1,4-diazabicyclo[2.2.2]octane) catalyzed a multicomponent reaction using the starting precursor 2,3,4,9-tetrahydro-1H-carbazol-1-one, malononitrile, and aromatic/heteroaromatic aldehyde.     

Copper‐Catalyzed Difunctionalization of Activated Alkynes by Radical Oxidation–Tandem Cyclization/Dearomatization to Synthesize 3‐Trifluoromethyl Spiro[4.5]trienones

A copper‐catalyzed difunctionalizing trifluoromethylation of activated alkynes with the cheap reagent sodium trifluoromethanesulfinate (NaSO₂CF₃ or Langlois’ reagent) has been developed incorporating a tandem cyclization/dearomatization process. This strategy affords a straightforward route to synthesis of 3‐(trifluoromethyl)‐spiro[4.5]trienones, and presents an example of difunctionalization of alkynes for simultaneous formation of two carbon–carbon single bonds and one carbon–oxygen double bond.     

新型含苯并磷杂环戊二烯结构荧光分子的合成及性能

以三苯胺、咔唑为电子给体, 苯并磷杂环戊二烯氧化物为电子受体, 设计合成了一类新颖的D-A-D 型荧光分子, 其结构经¹H NMR, ¹³C NMR, ³¹P NMR, IR和MS确认。通过紫外可见吸收光谱和荧光光谱系统研究了不同给体和受体单元对荧光分子的紫外吸收、液体荧光、固体荧光、溶致变色及聚集诱导发光等光物理性能的影响。结果表明：合成的三种分子具有良好的液体和固体荧光性能;化合物TBN-EPIO具有显著的溶致变色效应, 在四氢呋喃-水二元溶剂体系中, 具有聚集诱导发光(AIE)效应。此外, 利用密度泛函理论计算了分子的几何构型及前线分子轨道电子云。      

Tandem Anionic oxy‐Cope Rearrangement/Oxygenation Reactions as a Versatile Method for Approaching Diverse Scaffolds

Tandem anionic oxy‐Cope rearrangement/radical oxygenation reactions provide δ,?‐unsaturated α‐(aminoxy) carbonyl compounds, which serve as convenient precursors to diverse compound classes. Functionalized carbocycles are accessible by very rare all‐carbon 5‐endo‐trig cyclizations, but also common 5‐exo‐trig radical cyclizations, based on the persistent radical effect. The tandem reactions can be further extended by highly diastereoselective allylation or reduction steps to give complex scaffolds.     

Synthesis of spiro[5.4]decenones and their transformation into bicyclo[4.4]deca-1,4-dien-3-ones by domino "elimination- double-Wagner-Meerwein-rearrangement" reactions

The [3+3] cyclization of 1,3-bis-silyl enol ethers with 1,1-diacylcyclopentanes allows a convenient synthesis of spiro[5.4]decenones. Treatment of these compounds with trifluoroacetic acid (TFA) afforded a great variety of bicyclo[4.4.0]deca-1,4-dien-3-ones containing an angular alkyl group. This core structure occurs in a number of pharmacologically relevant natural products.     

Benzo[b]tellurophene, Dibenzo[b,d]tellurophene, and Their Derivatives. (Review)

Data on the synthesis, reactions, crystal structure, and spectral characteristics of benzo[b]tellurophene, dibenzo[b,d]tellurophene, and their derivatives are reviewed and analyzed.     

Gold‐Catalyzed Cascade Reactions of Furan‐ynes with External Nucleophiles Consisting of a 1,2‐Rearrangement: Straightforward Synthesis of Multi‐Substituted Benzo[b]furans

A gold‐catalyzed cycloisomerization of silyl‐protected 2‐(1‐alkynyl)‐2‐alken‐1‐(2‐furanyl)‐1‐ols with various nucleophiles including water, alcohol, aniline, sulfonamide, and electron‐rich arene has been developed. The method provides a highly efficient access to 5,7‐disubstituted or 2,5,7‐trisubstituted benzo[b]furans with a wide diversity of substituents under mild reaction conditions, which are not easily available by other methods. Remarkably, an interesting rearrangement of the alkyl group from C2 to the C3 position of the furan ring takes place during the cyclization process. The following gold‐assisted allylic substitution enables an elaboration of benzo[b]furans on its side chain of the C5 position with a wide range of functional groups.     

Synthesis of Benzo[b]thiophene Substituted Carbamates,Ureas, Semicarbazides,and Pyrazoles and Their Antimicrobial and Analgesic Activity

2-Azidocarbonyl-3-chlorobenzo[b]thiophene 3 was obtained from 3-chloro-benzo[b]thiophene-2-carbonyl chloride 1 and 3-chloro-benzo[b]thiophene-2-carboxy hydrazide 2 . The compound 3 on Curtius rearrangement with various alcohols, amines, and hydrazines afforded the corresponding carbamates 4a–b , ureas 5a–j , and semicarbazides 6a–g , respectively. Compound 2 was also utilized for the synthesis of pyrazoles 7a–c by treatment with various chalcones. The structures of the newly synthesized compounds were elucidated on the basis of IR, ¹ H NMR, and mass spectral data and have been screened for antimicrobial and analgesic activities.     

Furyl(aryl)methanes and Their Derivatives. 23. Simple Synthesis of Benzo[b]furan Derivatives from 2-Alkylfurans

New derivatives of benzo[b]furan were obtained during successive bromination and dehydrobromination of alkanones containing a gem-difurylmethyl fragment. A mechanism is proposed for the transformations that occur.     

Synthesis of [b]-Fused Benzo[d]furano Heterocycles

In the reactions of 3,4,6,7-tetrachloro-2,5-dihydroxy-2,3-dihydrobenzo[b]furan with 4-methyl and 4-phenyl thiosemicarbazides, dithizone and sodium N,N-diethyldithiocarbamate the [b]fused benzo[d]furano heterocycles have been synthesized.     

[a]-Anellated carbazoles with antitumor activity: Synthesis and cytotoxicity

Summary The cycloadducts3,5, and7, readily available from methoxy-substituted 3-vinylindoles1 and2, were dehydrogenated withDDQ to the coplanar [a]-anellated carbazoles4,6, and8. Compound4a, also characterized by X-ray structural analysis, shows significant cytotoxicity against K562 und RXF393 human tumor cell lines.

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[a]-Anellierte Carbazole mit Antitumoraktivität: Synthese und Cytotoxizität

Zusammenfassung Die aus den methoxysubstituierten 3-Vinylindolen1 und2 zugänglichen Cycloaddukte3,5 und7 lassen sich mitDDQ zu den coplanar-anellierten Carbazolen4,6 und8 dehydrieren. Verbindung4a, die auch durch eine Röntenstrukturanalyse charakterisiert wurde, zeigt signifikante Cytotoxizität gegen Humantumor-Zellinien (K562 und RXF93).

     

Tandem Acid/Pd-Catalyzed Reductive Rearrangement of Glycol Derivatives

Herein, we describe the acid/Pd-tandem-catalyzed transformation of glycol derivatives into terminal formic esters. Mechanistic investigations show that the substrate undergoes rearrangement to an aldehyde under [1,2] hydrogen migration and cleavage of an oxygen-based leaving group. The leaving group is trapped as its formic ester, and the aldehyde is reduced and subsequently esterified to a formate. Whereas the rearrangement to the aldehyde is catalyzed by sulfonic acids, the reduction step requires a unique catalyst system comprising a Pd^II or Pd⁰ precursor in loadings as low as 0.75 mol % and α,α′-bis(di-tert-butylphosphino)-o-xylene as ligand. The reduction step makes use of formic acid as an easy-to-handle transfer reductant. The substrate scope of the transformation encompasses both aromatic and aliphatic substrates and a variety of leaving groups.     

基于苯并[b]萘并[1,2-d]噻吩的可见光驱动光环化荧光turn-on型二芳基乙烯的合成与性能研究

可见光驱动光环化的荧光turn-on型二芳基乙烯分子开关是超分辨显微成像的理想材料, 但目前关于该类型分子的报道仍较少. 本工作合成了一种基于苯并[b]萘并[1,2-d]噻吩(BNTP)的405 nm可见光驱动光环化的荧光turn-on型二芳基乙烯分子BNTP-BTTO4, 同时系统研究了该分子的光物理性能与稳定性, 并借助密度泛函理论(DFT)计算厘清了分子实现可见光驱动光环化及荧光turn-on原因. 另外, 本研究发现BNTP引入后分子表现出比参比分子Ph-BTTO4更优异的抗疲劳性、热稳定性和光稳定性, 尤其是在历经200 min 405 nm可见光照射后, BNTP-BTTO4(c)吸收强度只下降4%, 光稳定性大幅提升. 本研究为设计开发性能优异的可见光驱动光环化的荧光turn-on型二芳基乙烯提供了新的思路.     

Palladium‐Catalyzed Three‐Component Cascade Cyclization Reaction of Bisallenes with Propargylic Carbonates and Organoboronic Acids: Efficient Construction of cis‐Fused Bicyclo[4.3.0]nonenes

A bicycle built for two : The title reaction affords cis‐fused bicyclo[4.3.0]nonenes from readily available 1,5‐bisallenes with structurally diverse propargylic carbonates and arylboronic acids (see scheme; X=NTs, C(E¹)₂ with E¹=CO₂Bn, SO₂Ph, dba=trans,trans‐dibenzylidenacetone). The reaction may involve a sequential oxidative addition, two different types of three carbopalladations, and a Suzuki‐type coupling.