Solid-phase synthesis of 2,3-disubstituted benzo[b]thiophenes and benzo[b]selenophenes

Cytotoxic and apoptotic potential of some coumarin and 2-amino-3-carbonitrile selenophene derivatives in prostate cancer

3-acetyl coumarin derivatives (1a-d) are formed as a result of condensation of salicylaldehyde derivatives and ethyl acetoacetate and were converted into coumarin-selenophene hybrid compounds (2a-d) in the basic medium by modified Gewald reaction in the presence of malononitrile and selenium. Products are characterized by nuclear magnetic resonance (NMR). The prepared compounds are screened for their anticancer activity against DU-145 cell line. In addition, selected target compounds are evaluated for apoptosis and oxidative stress on DU-145 (prostate carcinoma) cell lines.

Iodine-mediated synthesis of heterocycles via electrophilic cyclization of alkynes

Syntheses of heterocyclesvia5-exoor 6-endo-digiodocyclizations from alkynes.

Diorganyl Dichalcogenides-Promoted Nucleophilic Closure of 1,4-Diyn-3-ols: Synthesis of 2-Benzoyl Chalcogenophenes

We report here the preparation of chalcogenophene derivatives via cyclization reactions of diynols promoted by diorganyl dichalcogenides and a halogen source. Different chalcogenophenes, such as 4-halo-selenophenes, 4-butylselenyl-selenophenes, halo-thiophenes, and 4-methylthio-thiophenes, were selectively prepared in good yields from the same starting materials. The results revealed that the halogen source had a significant effect on the proportion of 4-bromo-selenophenes and 4-butylselenyl-selenophenes. The best yields of 4-iodo-selenophenes were obtained with iodine as a halogen source, while the use of NBS gave exclusively the 4-butylselenyl-selenophenes. The experiments also revealed that the cyclization reaction to form 4-halo-thiophene derivatives can also be controlled changing the ratios of reagents. The 4-iodo-thiophenes were exclusively obtained by using dimethyl disulfide (2.0 equiv) and iodine (1.5 equiv), while the 4-bromo-thiophenes were obtained when the reaction was carried out with a 1.5 molar ratio of dimethyl disulfide and a halogen source. In addition, the reaction of diynols with an excess of dimethyl disulfide in the presence of NBS gave the 4-methylthio-thiophenes as sole products. We also studied the application of chalcogenophenes obtained as starting materials in the Suzuki, Sonogashira, and Ullmann cross-coupling reactions.

Intramolecular cyclization assisted oxidative addition: synthesis of octahedral cycloplatinated methyl complexes

Cycloplatination of XMeC₆H₄CCC-(R_f) (N-4-OCH₃C₆H₄) [X = S, Se and R_f = perfluoroalkyl groups] with PtCl₂ gave a monomeric octahedral Pt(iv) complex. Emission and reactivity studies of the Pt(iv) complexes are discussed.

Scaffold-divergent synthesis of ring-fused indoles, quinolines, and quinolones via iodonium-induced reaction cascades

N-(2-Iodophenyl)imines A are readily formed from Schiff's base condensation of 2-iodoanilines with carbonyls and ketals. These imines provide useful substrates in scaffold-divergent synthesis through the attachment of an alkyne (Songashira coupling or acyl substitution of a Weinreb amide) followed by an iodonium-induced reaction cascade to give ring-fused indoles B, quinolines C, or quinolones D depending on the reaction conditions employed.

Synthesis and antidepressant-like activity of selenophenes obtained via iron(III)-PhSeSePh-mediated cyclization of Z-selenoenynes

We present here the synthesis and antidepressant-like action of a series of 2,5-disubstituted-3-(organoseleno)-selenophenes prepared by a novel synthetic route, the FeCl(3)-diorganyl dichalcogenide-mediated intramolecular cyclization of (Z)-chalcogenoenynes. The cyclized products were obtained in good yields. The results showed that 2c, 2d, 2e and 2o, evaluated in the mouse forced-swimming test, elicited an antidepressant-like activity. The studies clearly show that the phenyl group at the 2-position and an organoselenium group at the 3-position of the selenophene ring are essential for the antidepressant-like activity of selenophenes. A close inspection of the results also revealed that the fluorophenyl portion in the organoselenium group is fundamental for the antidepressant-like action of this class of organochalcogens.

The potential antioxidant activity of 2,3-dihydroselenophene, a prototype drug of 4-aryl-2,3-dihydroselenophenes

Here we present our results in palladium cross-coupling reaction of aryl boronic acids with 4-iodo-2,3-dihydroselenophene derivatives. The cross-coupled products were obtained in satisfactory yields. A dehydrogenation of 4,5-diphenyl-2,3-dihydroselenophene was activated by DDQ and the 2,3-diarylselenophene was obtained in good yield. Regarding the antioxidant activity, the selenophene derivative 3a was effective in counteracting lipid and protein oxidation as well as scavenging ABTS radical. The findings of the present study indicate that 3a is a prototype for future drug development programs to treat disorders mediated by reactive oxygen species.

The evaluation of solution- and solid-phase approaches to the divergent synthesis cinnoline and phenanthrene ring systems: SCS-09 special issue-combinatorial approaches to discovery

Cinnoline and phenanthrene ring systems have been synthesized from a set of readily available substrates using functional group tolerant reactions. This approach proved successful in both solution- and solid-phase synthesis for phenanthrenes but was limited to solution-phase synthesis for cinnolines. The described approaches to these ring systems complements related approaches to other scaffolds that can be readily accessed from the same substrates using slight variations in the applied chemistry.

Iodine/palladium approaches to the synthesis of polyheterocyclic compounds

A simple, straightforward strategy for the synthesis of polyheterocyclic compounds (PHCs) is reported, which involves iterative cycles of palladium-catalyzed Sonogashira coupling, followed by iodocyclization using I(2) or ICl. A variety of heterocyclic units, including benzofurans, benzothiophenes, indoles, and isocoumarins, can be efficiently incorporated under mild reaction conditions. In addition, variations of this strategy afford a variety of linked and fused PHCs.

A simple and mild synthesis of 1H-isochromenes and (Z)-1-alkylidene-1,3-dihydroisobenzofurans by the iodocyclization of 2-(1-alkynyl)benzylic alcohols

A variety of iodo-substituted isochromenes, dihydroisobenzofurans, and pyranopyridines are readily prepared in good to excellent yields under mild conditions by the iodocyclization of readily available 2-(1-alkynyl)benzylic alcohols or 2-(1-alkynyl)-3-(hydroxymethyl)pyridines. Reactions are carried out in MeCN at 25 degrees C with 3 equiv of I(2) as the iodine source and NaHCO(3) (3 equiv) as the base. The regiochemical outcome of the reaction strongly depends on the substitution pattern of the starting material. In particular, the 5-exo-dig cyclization mode, leading to dihydroisobenzofurans, is observed in the case of substrates bearing a tertiary alcoholic group, owing to the gem-dialkyl effect, while the 6-endo-dig cyclization mode, leading to isochromene or pyranopyridines, is the usually preferred pathway in the case of substrates bearing a primary or secondary alcoholic group.

Synthesis of 3-sulfenyl- and 3-selenylindoles by the Pd/Cu-catalyzed coupling of N,N-dialkyl-2-iodoanilines and terminal alkynes, followed by n-Bu(4)NI-induced electrophilic cyclization

3-Sulfenyl- and 3-selenylindoles are readily synthesized by a two-step process involving the palladium/copper-catalyzed crossing coupling of N,N-dialkyl-ortho-iodoanilines and terminal alkynes and subsequent electrophilic cyclization of the resulting N,N-dialkyl-ortho-(1-alkynyl)anilines with arylsulfenyl chlorides or arylselenyl chlorides. The presence of a stoichiometric amount of n-Bu(4)NI is crucial to the success of the electrophilic cyclization. A variety of 3-sulfenyl- and 3-selenylindole derivatives bearing alkyl, vinylic, aryl, and heteroaryl substituents have been prepared in good to excellent yields (up to 99%). By employing N,N-dibenzyl-ortho-iodoanilines, a 3-sulfenyl-N-H-indole has been successfully prepared. In addition, 3-sulfonyl- and 3-sulfinylindoles have also been successfully prepared by facile oxidation of the corresponding 3-sulfenylindoles.

Competition studies in alkyne electrophilic cyclization reactions

The relative reactivity of various functional groups toward alkyne electrophilic cyclization reactions has been studied. The required diarylalkynes have been prepared by consecutive Sonogashira reactions of appropriately substituted aryl halides and competitive cyclizations have been performed using I(2), ICl, NBS and PhSeCl as electrophiles. The results indicate that the nucleophilicity of the competing functional groups, polarization of the alkyne triple bond, and the cationic nature of the intermediate are the most important factors in determining the outcome of these reactions.

Parallel synthesis of a multi-substituted benzo[b]furan library

The solution-phase parallel synthesis of a 121-member library of multi-substituted benzo[ b]furans is described. 2,3,5-Trisubstituted benzo[ b]furans have been prepared by the palladium-catalyzed substitution of 3-iodobenzofurans by Suzuki-Miyaura, carbonylative Suzuki, Sonogashira, Heck, and carboalkoxylation chemistry. The 3-iodobenzofurans are readily prepared in good to excellent yields by the palladium/copper-catalyzed cross-coupling of various o-iodoanisoles and terminal alkynes, followed by electrophilic cyclization with ICl.