Braj B. Lohray

A short synthesis of oxazolidinone derivatives linezolid and eperezolid: a new class of antibacterials

Oxazolidinone derivatives such as Linezolid and Eperazolid, which are a new class of antibacterials, have been synthesized from 1,2,5,6-dianhydro-3,4-isopropylidine-D-mannitol in good yield.

Enantioselective epoxidation of olefins catalyzed by polymer-bound optically active Mn(III)-salen complex

The synthesis of the first polymeric chiral Mn(III)-salen complex is reported along with its application as a recyclable asymmetric catalyst for enantioselective epoxidation of unfunctionalized olefins.

Polymeric catalysts for chemo‐ and enantioselective epoxidation of olefins: New crosslinked chiral transition metal complexing polymers

Polymeric analogs of well-known chiral Mn(III)-salen complexes were synthesized and were used as recyclable catalysts for asymmetric epoxidation of olefins. For this purpose two different monomers, 2 and 3, bearing chiral Mn(III)-salen moieties were synthesized. The monomer 3 carries a bulky substituent closer to the Schiff base moiety, while monomer 2 lacks such a substituent. These metal complexed chiral monomers were subsequently copolymerized with ethylene glycol dimethacrylate producing insoluble crosslinked functional matrices that possess macroporous morphology. Chemo- and enantioselective catalytic activities of these two polymers were evaluated for epoxidation of olefins. Both polymers catalyzed the epoxidation of a variety of olefins at room temperature in the presence of iodosylbenzene (PhIO) as the terminal oxidant with yields comparable to the homogenous system. In terms of their enantioselective catalytic activity, polymer P-2 (obtained from 3) performed better than polymer P-1 (obtained from 2). Unfortunately, while the homogeneous systems are reported to offer over 80% enantioselectivity, with the present polymeric catalysts, enantioselectivity to a maximum of 30% were observed. Unlike the homogeneous system, use of an external nitrogenous donor played a very insignificant role in influencing enantioselectivity.

Asymmetric catalytic dihydroxylation of alkenes on polymer support: Scope and limitation

Abstract Osmium catalyzed asymmetric dihydroxylation of alkenes has been reported using dihydroquinidine (DHQD) and dihydroquinine (DHQ) on a polystyrene support. Effect of other oxidants and additives has been examined.

Polymer supported transition metal complexes for catalytic epoxidation of olefins

Abstract Catalytic epoxidation of different alkenes has been reported using polymer supported Mn(III)-Salen complex in the presence of iodosylbenzene as terminal oxidant.

Unprecedented reactivity and selectivity in heterogeneous asymmetric catalytic dihydroxylation of alkenes

Abstract An unprecedented selectivity and reactivity in heterogeneous asymmetric catalytic dihydroxylation (AD) of olefins has been achieved using 3,6-(9- O -bisdihydroquinyl) pyridazine and 3,6-(9- O -bisdihydroquinidyl)pyridazine immobilized on ethyleneglycol dimethacrylate polymer backbone.

Catalytic asymmetric dihydroxylation of alkenes using silica gel supported cinchona alkaloid

Abstract Immobilization of 3,6-bis(9-O-dihydroquinyl)pyridazine and 3,6-bis(9-O-dihydroquinidyl) pyridazine on silica gel support has been reported. The use of immobilized auxiliary has lead to comparable rate with that of the homogeneous catalytic AD of alkenes, however with lower ee.

Synthesis of highly diastereo- and enantiomerically enriched tetracarbonyl(η3-allyl)iron(1+) complexes for allylic substitutions with silyl enol ethers and silyl ketene acetals

The preparation of highly diastereo- and enantiomerically enriched alkoxycarbonyl-substituted tetracarbonyl (η3-allyl)iron(1+) complexes 2a–d (2a–c: 20–53%, de > 90- ⩾ 95% or greater; 2d: 31–40%, ee ⩾ 99%) by means of an auxiliary controlled complexation (aux. = 8-phenylmenthyl) of diastereo- or of enantiopure (E)-configuration enoates 1 as starting materials is reported. The nucleophilic addition of various silyl enol ethers or silyl ketene acetals 3a–e to the complexes 2a–d followed by oxidative cleavage of the carbonyliron fragment offers an efficient access to 6-oxoenoates 4 in moderate to excellent yields (five steps, 5–72%) with diastereomeric or enantiomeric excesses ranging from de > 90- ⩾ 95% (4a–f) or ee ⩾ 96- ⩾ 99% (4g–k) with retention of the (E)-double bond geometry. The reaction proceeds with virtually complete chirality transfer from C-O via C-Fe to C-C with retention (double inversion) of stereochemistry of the stereogenic centre with respect to the starting material 1. It has been proven that a uniform configuration of the carbon atom bearing the leaving group in 1 is essential for controlling the absolute stereochemistry during the formation of complexes of type 2 with a definite absolute configuration at the allylic position.

Novel indole containing thiazolidinedione derivatives as potent euglycemic and hypolipidaemic agents

Abstract Several thiazolidinediones having indol as heterocyclic moiety have been synthesized and evaluated for euglycemic properties. A few of them have been found to be superior to troglitazone.

Novel euglycemic and hypolipidemic agents: Part-2. Antioxidant moiety as structural motif.

Several thiazolidinediones having antioxidant moities in their structural motif have been synthesised and evaluated for their euglycemic and hypolipidemic activities. A few of them have been found to be superior to troglitazone.