Occurrence, Biogenesis, and Synthesis of Biologically Active Carbazole Alkaloids

Cross-coupling reactions using samarium(II) iodide.

Treatment of 2-aryl- and 2-heteroarylindoles with propargyl ethers in the presence of a catalytic amount of indium nonafluorobutanesulfonate [In(ONf)3] gave aryl- and heteroaryl-annulated[a]carbazoles in good yields. The synthetically attractive feature is reflected by its applicability to a wide range of 2-aryl- and 2-heteroarylindoles. In the annulation reaction, propargyl ethers act as C3 sources (HC≡C−CH2OR). Among these, two carbon atoms are incorporated into the product as members of a newly constructed aromatic ring and the remaining carbon atom forms a methyl group on the aromatic ring, where the methyl group is always located next to the C3 position of the indole nucleus. The methyl group can be easily removed through SeO2 oxidation followed by decarbonylation with RhCl(CO)(PPh3)2−Ph2P(CH2)3PPh2 as a catalyst. The new annulation strategy is applicable also to symmetrical dimers such as bithiophene and bifuran derivatives. Mechanistic studies suggest that the first step is addition reaction initia...

Indium-catalyzed annulation of 2-aryl- and 2-heteroarylindoles with propargyl ethers: concise synthesis and photophysical properties of diverse aryl- and heteroaryl-annulated[a]carbazoles.

Recent progress in the chemistry and applications of indolocarbazoles

Playing the sax: The enantioselective total syntheses of (-)- and (+)-decarbamoyloxysaxitoxin (doSTX) and (+)-saxitoxin (STX) are reported. A new methodology was developed for the synthesis of STXs, featuring discriminative reduction of the nitro group and N-O bond in nitroisoxazolidine. Enantioselective total syntheses of (-)- and (+)-decarbamoyloxysaxitoxin (doSTX) and (+)-saxitoxin (STX) were achieved. The characteristic spiro-fused cyclic guanidine structure of STX was constructed by oxidation at the C4 position with IBX via an alpha-iminium carbonyl intermediate and acid-promoted cyclization of guanidine at the C5 position. A second-generation methodology was developed for the synthesis of STX, featuring discriminative reduction of the nitro group and N-O bond in nitroisoxazolidine. This approach provides efficient access to the key diamine intermediate for STXs.

Total Synthesis of (−)- and (+)-Decarbamoyloxysaxitoxin and (+)-Saxitoxin

1,3-dipolar cycloadditions. Part XII - selective cycloaddition route to 4-nitroisoxazolidine ring systems†

A straightforward, easy and smooth process of synthesizing indolo[2,3-a]carbazoles, which can frequently serve as a nucleus of several natural products is reported. The process involves only two st...

A new route to the synthesis of indolo[2,3-a]carbazoles

1,3-Dipolar cycloadditions: Investigation of cycloadditions of c-aryl-n-(4-chlorophenyl) nitrones to n-cinnamoyl piperidines

Remarkable stereocontrol in 1,3-dipolar cycloaddition of acyclic nitrones: Investigation of the cycloaddition of C,N-diaryl nitrones to methyl cinnamate under different reaction conditions

An investigation regarding the synthesis of 2H-thiopyran compounds from substituted benzaldehydes with sodium sulfide (Na2S·10H2O) in aqueous ethanol was carried out. The structural elucidation of the products was performed by spectroscopic methods and in one example as X-ray crystallographic analysis. A plausible mechanistic pathway is also proposed that is entirely different from an earlier report.

Pizush Kanti Biswas

Papers

1,3-dipolar cycloadditions. Part XII - selective cycloaddition route to 4-nitroisoxazolidine ring systems†

A new route to the synthesis of indolo[2,3-a]carbazoles

1,3-Dipolar cycloadditions: Investigation of cycloadditions of c-aryl-n-(4-chlorophenyl) nitrones to n-cinnamoyl piperidines

Remarkable stereocontrol in 1,3-dipolar cycloaddition of acyclic nitrones: Investigation of the cycloaddition of C,N-diaryl nitrones to methyl cinnamate under different reaction conditions

Synthetic Studies on 2H-Thiopyran Compounds: A Reinvestigation of the Reaction Between Benzaldehydes and Sodium Sulfide