Synthesis of azaphenanthridines via anionic ring closure

A new and convergent synthesis of azaphenanthridines via an anionic ring closure is reported. Ortho-lithiation/in situ borylation of cyanopyridines produces the corresponding cyanopyridylboronic esters, which undergo a Suzuki-Miyaura cross-coupling to give the key intermediates. Addition of lithium morpholide produces the azaphenanthridines.     

Condensation of o -benzoquinone with 4-hydroxy coumarins: A new synthesis of 3 aryl-4-hydroxy coumarins and coumestans

The 4-hydroxy coumarins have been reacted witho-benzoquinone, in acetone in the absence of the oxidant potassium ferricyanide. The products were found to be 3-aryl-4-hydroxy coumarins which were cyclised to the corresponding 11,12-dihydroxy coumestans. The structure of 11,12-dihydroxy coumestan has been confirmed by an unambiguous synthesis. The structures of other compounds were confirmed on the basis of their analytical, chemical and spectral data.     

Synthesis and activities of new 4-hydroxy benzoxazolone derivatives

<正>A series of new 4-substituted benzoxazolone derivatives were synthesized according to a convenient method,their anti-inflammatory and analgesic activities in vivo were evaluated.All of them were new compounds,the structures of all the synthesized compounds were confirmed by ~1H NMR,~(13)C NMR,ESI-MS and HR-MS.Most of the compounds exhibited anti-inflammatory activity.     

Synthesis of cytisine derivatives of coumarins

New substituted 4-chloromethylcoumarins that were used as alkylating agents to modify cytisine were synthesized by Pechmann condensation. A series of 4-(12-cytisylmethyl)coumarins containing pharmacophores of the natural heterocycles coumarin and cytisine in a single molecule was prepared. The alkylation gave the best results if diisopropylethylamine was used as the base. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 485–488, September–October, 2007.     

Synthesis of C3-dihydrofuran substituted coumarins via multicomponent approach

An efficient method was developed for the synthesis of dihydrofuran substituted coumarin from a one-pot, four-component reaction of 2-hydroxy aromatic aldehydes, 6-methyl, 4-hydroxy pyranone, aromatic aldehyde, and pyridinium ylide in the presence of tri-ethylamine under microwave irradiation. The reaction proceeds under solvent-free conditions to afford C3-dihydrofuran substituted coumarin in a diastereoselective manner in good yields (71–89%).     

Synthesis of benzo[b]furans via CuI-catalyzed ring closure

A wide variety of benzo[b]furans were synthesized efficiently via a CuI-catalyzed ring closure of 2-haloaromatic ketones. The methodology was tolerant to various functional groups, affording benzofurans in 72-99% yields.     

Electrochemical study of catechol and some 3-substituted catechols in the presence of 4-hydroxy coumarin: application to the electro-organic synthesis of new coumestan derivatives

Electrochemical oxidation of catechol (1d), 3-methylcatechol (1a), 3-methoxycatechol (1b) and 2,3-dihydroxybenzoic acid (1c) in the presence of 4-hydroxycoumarin as nucleophile in aqueous solution has been studied using cyclic voltammetry and controlled-potential coulometry. The results indicate that (1a–1d) participating in a 1,4 (Michael) addition reaction convert to coumestan derivatives (5a–5d). The electrochemical synthesis of 5a–5d has been successfully performed in an undivided cell in good yield and purity.     

Synthesis of substituted quinolines from N-aryl-N-(2-alkynyl)toluenesulfonamides via FeCl3-mediated intramolecular cyclization and concomitant detosylation

A series of substituted quinolines have been synthesized in moderate to good yields (55–81%) from easily available substrates N-aryl-N-(2-alkynyl)toluenesulfonamides via FeCl₃-mediated intramolecular cyclization and concomitant detosylation.     

Synthesis of 4,5-dihydro-1,4-benzothiazepine derivatives via ring expansion

Basic treatment in methanol of a chloro-β-lactam fused with dihydrobenzothiazine led to the corresponding 1,4-benzothiazepine derivative via a new ring expansion. The structure of the product, deduced from IR and ¹H NMR data, was confirmed by X-ray measurements.     

Synthesis of some 1-hydroxy derivatives of 4- and 6-azaindole analogues

1-Hydroxy-4-azaindole and 1-hydroxy-4-(and 6)-azaindol-2(3H)-one derivatives are novel compounds and a facile synthesis by the reductive cyclisation of substituted 3-nitropyridines is described. Problems associated with the catalytic hydrogenation of the parent nitro compounds are also discussed.     

One-pot synthesis of pyrano[4,3-b]quinolinones from 2-alkynyl-3-formylquinolines via oxidative 6-endo-dig ring closure

A new regioselective one-pot procedure to synthesize pyranoquinolinones from readily available 2-alkynyl 3-formylquinolines under mild NaClO₂/H₂O₂ conditions in good yields has been explored. This reaction sequence, involving oxidation followed by regioselective electrophilic 6-endo-dig cyclization is more efficient over the traditional Pd(0)-mediated synthesis. When scavenger-free conditions were used, unusual chlorinated furoquinolinone derivatives were obtained.     

Plant coumarins: VI. Synthesis of 3-vinylfurocoumarin derivatives based on oreoselone

Palladium-catalyzed Heck reaction of oreoselone trifluoromethanesulfonate with various terminal alkenes (methyl acrylate, styrene, vinylpyridines, N-vinylpyrrole, and N-vinyl-1,2,4-triazole) led to the formation of the corresponding (E)-3-vinyl-7H-furo[3,2-g]chromen-7-ones. The yield was found to depend on the catalytic system and initial olefin structure.     

FeCl3-mediated synthesis of polysubstituted tetrahydroquinolines via domino Mannich/Friedel-Crafts reactions of aldehydes and amines

A useful method to construct highly substituted tetrahydroquinolines has been developed through an iron(III) chloride-mediated domino Mannich and intramolecular Friedel-Crafts alkylation followed by intermolecular Friedel-Crafts alkylation reactions of aliphatic aldehydes with aromatic amines.     

Synthesis of RHPS4 via an anionic ring closing cascade

A new and convergent synthesis of the potent telomerase inhibitor RHPS4 is presented. The key step is the construction of the pentacyclic framework via an anionic ring closing cascade in which two new rings are formed.     

Synthesis of 3H-pyrazol-3-one derivatives containing a 9H-thioxanthene ring

2,4-Dihydro-5-methyl-2-phenyl-4-(9H-thioxanthen-9-yl)-3H-pyrazol-3-one ( 3 ) was prepared by condensing 9H-thioxanthen-9-ol ( 1 ) with 2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-one ( 2 ), or by cyclizing ethyl α-acetyl-9H-thioxanthene-9-acetate ( 4 ) with phenylhydrazine. 2,4-Dihydro-5-methyl-2-phenyl-4-(9H-thioxan- then-9-yl)-3H-pyrazol-3-one 10,10-dioxide ( 8 ) was prepared by cyclizing ethyl α-acetyl-9H-thioxanthene-9-acetate 10,10-dioxide ( 7 ) with phenylhydrazine. Compound 8 was also obtained by oxidizing 3 with hydrogen peroxide in acetic acid. 5-Amino-2,4-dihydro-2-phenyl-4(9H-thioxanthen-9-yl)-3H-pyrazol-3-one ( 10 ) was obtained by condensing 1 with 5-amino-2,4-dihydro-2-phenyl-3H-pyrazol-3-one ( 9 ).     

Synthesis of robustin and related 4-hydroxy-3-phenyl coumarins and isoflavones

Robustin (31a) occurring in the roots of Derris robusta has been synthesised from mono-O-methylphloroglucinol (20) as follows. Hoesch condensation with homopiperonitrile (21) gave 2,4-dihydroxy-6-methoxyphenyl 3,4-methylenedioxybenzyl ketone (22) which on reaction with 2-hydroxy-2-methyl-3-butene in the presence of borontrifluoride-etherate afforded 5-C-(24) and 3-C-(23) prenyl derivatives. These on cyclodehydrogenation with DDQ followed by coumarin condensation with ethyl chloroformate yielded robustin (31a) and isorobustin (32) respectively. Model experiments with nuclear prenylation of 2,4-dihydroxy-6-methoxy-phenyl benzyl ketone (1), followed by oxidative cyclisation and either courmarin or isoflavone condensation have yielded new isopentenylated 4-hydroxy-3-phenylcourarins or isoflavones.     

若干D环带硝基的小檗因衍生物的光环化合成

通过酰烯胺的光环化反应, 合成了六个D环带硝基的小檗因类化合物。在酰烯胺的制备中, 还得到了几个非预期的副产物, 阐明了它们的结构。