Shankar R. Thopate

Citric acid catalysed Beckmann rearrangement, under solvent free conditions

Citric acid is reported to be a highly efficient and eco-friendly catalyst for the Beckmann rearrangement under solvent free conditions.

Natural organic acids promoted Beckmann rearrangement: Green and expeditious synthesis of amides under solvent-free conditions

Naturally occurring organic acids are reported to be highly efficient promoters of the Beckmann rearrangement. Citric, oxalic, tartaric, malic, succinic, malonic, and fumaric acids efficiently promote the Beckmann rearrangement under solvent-free conditions and thermal and microwave irradiation. Tartaric acid was found to be the best promoter of the Beckmann rearrangement under conventional conditions as well as under microwave irradiation. Compared with conventional heating, microwave irradiation provides higher reaction rate and slightly higher yields.

Synthesis of 1,2-dihydro-1-oxophthalazin-4-yl trifluoromethanesulfonate and its application in the synthesis of 4-(aryl/heteroaryl/alkynyl)phthalazin-1(2H)-one

The regioselective synthesis of 1,2-dihydro-1-oxophthalazin-4-yl trifluoromethanesulfonate (3a) has been reported. The reaction of Tf2O (2a) with phthalhydrazide (1a) provides a rapid access to 3a with an excellent yield and a high level of regioselectivity. The synthetic utility of this triflate is further enhanced by carrying out the successful Suzuki and Sonogashira coupling reactions for the first time on 3a, providing a simple access to a range of biologically significant 4-aryl/heteroaryl/alkynyl phthalazinones in good yields.

One-pot synthesis and evaluation of novel 3-aryl-6-ethoxycarbonyl-4-hydroxy-2H-pyran-2-one as a potent cytotoxic agent

A series of new open chain analogs of Phelligridin J were synthesized by a clean one-pot approach. These compounds were evaluated for their in vitro cytotoxicity against normal and breast cancer cell lines. All the compounds exhibited potent cytotoxic activity in the lower micro molar range. Compound 5o exhibited the maximum cytotoxic activity with IC50 values of 12.49 and 13.76 μM, whereas compound 5a showed two-fold selectivity viz. IC50 values of 21.80 to 43.40 μM against breast cancer (MCF7) and normal fibroblast (NIH3T3) cell lines, respectively.

Chemoselective 3-O-alkylation of L-ascorbic acid under phase transfer catalysis

A detailed investigation for synthesis of chemo-selective 3-O-alkylation of L-ascorbic acid under phase transfer catalysis has been carried out. All the compounds were fully characterized by infra red (IR), NMR and microanalysis. Reaction of 5,6-O-isopropylidene-L-ascrobic acid with one equivalent of corresponding alkylating agent and tetrabutyl ammonium iodide as phase transfer catalyst in biphasic system (water:ethyl acetate, 1:1) afforded the 3-O-alkyl-5,6-O-isopropylidene-L-ascorbic acid derivatives (2a-f) in moderate to good yield as a sole product. Under this reaction condition formation of 2-Calkylated and 2,3-di-O-alkylated product was not observed. Furthermore, present protocol allowed preparation of 2,3-di-O-alkyl and differentially protected 2,3-di-O-alkyl derivatives under mild reaction conditions at room temperature in a one-pot reaction.

Crystal structure of (5R)-5-[(1S)-1,2-di-hydroxy-eth-yl]-4-meth-oxy-3-phenyl-2,5-di-hydro-furan-2-one.

In the title compound, C13H14O5, the furan ring is essentially planar [maximum deviation = 0.031 (3) Å] with a stereogenic center (R) at the sp 3 hybridized C atom. The C atom bearing the dihydroxy ethyl group is S. The absolute configuration is based on the precursor in the synthesis. The two O—H groups are in an anti conformation with respect to each other. The mean plane of the furanone group is twisted by 8.2 (4)° from that of the phenyl ring. In the crystal, molecules are linked by O—H⋯O hydrogen bonds involving furanone C=O groups and symmetry-related hydroxy groups, forming a two-dimensional network parallel to (001). Weak C—H⋯O hydrogen bonds are observed within the two-dimensional network.