N. Ravindranath

A mild, highly selective and remarkably easy procedure for deprotection of aromatic acetates using ammonium acetate as a neutral catalyst in aqueous medium

Ammonium acetate was found to catalyze efficiently the selective deprotection of aromatic acetates in the presence of various sensitive functionalities in aqueous methanol under neutral conditions at room temperature to yield the corresponding phenols in excellent yields. The method has been utilized for deprotection of acetates of several naturally occurring bioactive phenolic compounds and for preparation of venkatasin, a natural coumarino-lignan, from the anticancer compound cleomiscosin A.

Efficient, selective deprotection of aromatic acetates catalyzed by Amberlyst-15 or iodine

Aromatic acetates were selectively deprotected in the presence of aliphatic acetates to the corresponding phenols in excellent yields using Amberlyst-15 or iodine as catalysts in methanol at room temperature. The first catalyst can be recovered.

A simple, mild and efficient procedure for selective cleavage of prenyl esters using silica-supported sodium hydrogen sulphate as a heterogenous catalyst ☆

Prenyl esters were selectively and efficiently cleaved under slightly acidic reaction conditions using silica-supported sodium hydrogen sulfate as a heterogenous catalyst at room temperature to regenerate the parent carboxylic acids in very high yields.

Electrophilic substitution reactions of indoles with carbonyl compounds using ceric ammonium nitrate: A novel and efficient method for the synthesis of di- and tri-indolylmethanes

Ceric ammonium nitrate (CAN) is used to catalyse the electrophilic substitution reactions of indoles with carbonyl compounds at room temperature to produce di- and tri-indolylmethanes in high yields.

Pseudoguaianolides from the flowers of Parthenium hysterophorus.

Chemical investigation on the flowers of Parthenium hysterophorus has resulted in the isolation of four new pseudoguaianolides, hysterones A-D along with the known compounds, parthenin, coronopilin, 2beta-hydroxycoronopilin and tetraneurin-A. The structures of the new compounds were established by interpretation of their spectral (1D and 2D NMR) data. The X-ray crystallographic analysis of hysterones A and C was also carried out.

Charminarone, a seco-pseudoguaianolide from Parthenium hysterophorus

A novel sesquiterpenoid, charminarone, the first seco-pseudoguaianolide, has been isolated along with several known compounds from the whole plant of Parthenium hysterophorus. The structure of the new compound has been settled as 1,10-seco-dihydroisoparthenin 1,10-dione from its spectral data as well as from its conversion by reductive coupling reaction with Zn/TiCl(4) reagent to the known compound, anhydrodihydroisoparthenin. The reagent Zn/TiCl(4) has been used here for the first time to construct the seven membered ring of a pseudoguaianolide sesquiterpenoid.

A convenient and efficient one-pot conversion of ketones into amides under microwave irradiation using silica gel supported NaHSO 4 catalyst

A simple and rapid conversion of ketones into the corresponding amides in high yields has been developed by treatment with hydroxylamine hydrochloride under microwave irradiation in the presence of silica gel supported NaHSO4 catalyst.

A convenient, rapid, highly selective and eco-friendly method for deprotection of aryl acetates using silica gel supported ammonium formate under microwave irradiation

Several aryl acetates were rapidly and selectively deprotected to the corresponding phenols in excellent yields using silica gel supported ammonium formate under microwave irradiation. The process is environmentally benign.

Clerodendrone, a novel hydroquinone diterpenoid from Clerodendrum indicum

Chemical investigation of Clerodendrum indicum has resulted in the isolation of clerodendrone, a new member of hydroquinone diterpenoids (which are rare in the investigated family, Verbenaceae). The compound was characterised from its spectral (1D and 2D NMR) data and chemical reactions and was found to contain an uncommon structural pattern with beta-methyl dihydrofuran moiety.

Condensation of phenols with alkylcinnamates in the presence of FeCl31

Ferric chloride catalyses the condensation of phenols with alkylcinnamates to produce 3,4-dihydro-4-arylcoumarins.