Manas Chakrabarty

Dry reaction of indoles with carbonyl compounds on montmorillonite K10 clay: a mild, expedient synthesis of diindolylalkanes and vibrindole A

Abstract Dry reaction of indoles 1a – c with aldehydes 2a – i , ketones 2j – o and an acetal 2p on M. K10 clay at room temperature furnished 3,3′-diindolylalkanes (DIAs: 3a – h , j – r ). The novel formation of tris(3-indolyl)methane 4 from 2i through tandem reactions and of the DIAs 6 and 8 from 1d through Plancher rearrangements were also observed.

Application of sulfamic acid as an eco-friendly catalyst in an expedient synthesis of benzimidazoles

Sulfamic acid, an eco-friendly and zwitterionic solid, proved to be a very efficient catalyst for the reaction of ortho-phenylenediamine with aryl aldehydes in ethanol at room temperature to furnish both 1-arylmethyl-2-aryl- and 2-arylbenzimidazoles in very good to excellent overall yields.

Carbazole alkaloids from Murraya koenigii

Two new alkaloids, 9-carbethoxy-3-methylcarbazole and 9-formyl-3-methylcarbazole, and a known metabolite, 3-methyl-carbazole were isolated from the roots of Murraya koenigii. All three compounds were identified by detailed spectral analyses including 2D NMR studies and their structures confirmed by synthesis. Of the two new metabolites, the 9-formyl compound displayed weak cytotoxicity against both mouse melanoma B16 and adriamycin-resistant P388 mouse leukemia cell lines.

Novel clay-mediated, tandem addition–elimination-(Michael) addition reactions of indoles with 3-formylindole: an eco-friendly route to symmetrical and unsymmetrical triindolylmethanes

Abstract Dry reaction of 3-formylindole ( 1 ) with indole ( 2a ) on Montmorillonite K10 clay at room temperature furnished within minutes tris(indol-3-yl)methane ( 3a ) in high yield. The reaction of 1 with other mono- and dialkylindoles ( 2b–c , skatole, 8a–c ) under similar conditions yielded either or both of symmetrical ( 3b–c , 9 ) and unsymmetrical ( 4b–c , 5b–c , 10 , 11a–c ) triindolylmethanes.

Microwave-assisted Michael reactions of 3-(2′-nitrovinyl)indole with indoles on TLC-grade silica gel. A new, facile synthesis of 2,2-bis(3′-indolyl)nitroethanes

Abstract 3-(2′-Nitrovinyl)indole reacted with indole and 1- and 2-alkylindoles on TLC-grade silica gel under microwave irradiation to furnish in 7–10 min bis(indolyl)nitroethanes in high yields (70–86%). The same products were also obtained in 69–84% yields without microwave irradiation, but the reactions required 8–14 h for completion. Skatole was inert under both sets of conditions.

A sojourn in the synthesis and bioactivity of diindolylalkanes

The different synthetic routes to diindolylalkanes (DIAs), an important class of synthetic and natural products, their merits and demerits and the properties of the bioactive DIAs have been presented in this review which is the first of its kind in this field. The synthesis of the bioactive DIAs (3), streptindole (4), vibrindole A (6), 10 and 11 has also been included in this review.

Phaseoloidin, a homogentisic acid glucoside from Entada phaseoloides

Abstract The structure of phascoloidin isolated from the seeds of Entada phaseoloides has been determined as homogentisic acid 2- O -β- d -glucopyranoside by chemical and spectral means.

A New Method of Nitration of Carbazoles Using Ceric Ammonium Nitrate (CAN)

Abstract A convenient procedure for the mononitration of carbazole and 9-alkylcarbazoles using CAN in CH3CN in presence of SiO2 is reported. The results with 9-acetyl, 9-benzoyl and 9-benzenesulphonylcarbazoles are also discussed.

Mild Deprotection of tert‐Butyl Carbamates of NH‐Heteroarenes under Basic Conditions

Abstract Aqueous methanolic potassium carbonate under reflux has been demonstrated to be a highly effective deprotective agent for the tert‐butyl carbamates of indoles, indazoles, carbazole, thiazoloindole, and pyrrole. The method is a mild one and is particularly expeditious for NH‐heteroarenes bearing electron‐withdrawing groups.

First General Solvent‐Free Synthesis of Symmetrical Triindolylmethanes Using Acid‐Washed Montmorillonite Clay

Abstract Dry reaction of indoles and alkylindoles (1a–h) with triethyl orthoformate (2.5 equiv.) on acid‐washed montmorillonite K10 clay at room temperature afforded in <5 min–4 hr the respective symmetrical TIMs (2a–h) in good to high yields along with the formylindole 3 and the formyl‐TIM 4 from 1g and 1h, respectively.