Saumen Hajra

A rapid room temperature chemical route for the synthesis of graphene: metal-mediated reduction of graphene oxide

A rapid and facile route for the synthesis of reduced graphene oxide sheets (rGOs) at room temperature by the chemical reduction of graphene oxide using Zn/acid in aqueous solution is demonstrated.

Stereoselective one-pot synthesis of oxazolines.

Treatment of alkenes with NBS, a nitrile, NaHCO3 and water in the presence of Cu(OTf)2 or Zn(OTf)2 is reported to furnish oxazolines in one pot and good yields. The reaction is equally applicable to chalcones.

Efficient Synthesis of 3,3'-Mixed Bisindoles via Lewis Acid Catalyzed Reaction of Spiro-epoxyoxindoles and Indoles.

An efficient strategy for the synthesis of 3-(3-indolyl)-oxindole-3-methanol has been developed to achieve a Lewis acid catalyzed, highly regioselective ring opening of spiro-epoxyoxindoles with indoles. The method is used for the gram-scale formal total synthesis of (±)-gliocladin C.

Catalytic enantioselective aziridoarylation of aryl cinnamyl ethers toward synthesis of trans-3-amino-4-arylchromans.

Catalytic enantioselective one-pot aziridoarylation reaction of aryl cinnamyl ethers has been demonstrated in detail. Combination of suitable copper catalyst and chiral bis-oxazoline ligand was found to be very efficient for asymmetric aziridination followed by intramolecular arylation (Friedel-Crafts) reaction to provide a general and direct method for the synthesis of trans-3-amino-4-arylchromans with high regio-, diastereo- (dr > 99:1), and enantioselectivity (up to 95% ee) with moderate yield. trans-3-Amino-4-arylchroman is an advanced intermediate for the synthesis of chromenoisoquinoline compounds such as doxanthrine, a potent and selective full agonist for the dopamine-D(1) receptor.

Organocatalytic and Enantioselective Synthesis of β-(Hydroxyalkyl)-γ-Butyrolactones

Organocatalytic cross-aldol reaction of methyl 4-oxobutyrate (2) and a variety of aldehydes 3 followed by reduction with NaBH(4) has provided a one-pot, general and efficient method for the synthesis of 4-(hydroxyalkyl)-gamma-butyrolactones 1 with high diastereo-(dr > 24:1) and enantioselectivity (ee > 99%).

Synthesis of silicon containing alanines

Abstract The synthesis of silicon containing alanines in optically pure form from an electrophilic alaninol synthon is described. The overall chemical yields for the synthesis of the novel amino acids range from 19–39%.

Synthesis of Chiral Spiro-Aziridine Oxindoles via Aza-Corey–Chaykovsky Reaction of Isatin Derived N-tert-Butanesulfinyl Ketimines

A general and direct strategy for the synthesis of chiral spiro-aziridine oxindoles has been developed via an aza-Corey-Chaykovsky reaction of isatin-derived N-tert-butanesulfinyl ketimines with excellent selectivity (dr = 98:2 to >99:1). The method is explored for the synthesis of chiral 3-substituted spiro-aziridine oxindoles with high (2S,3S)-selectivity over (2S,3R).

Visible light initiated photosensitised electron transfer (PET) reductive β-activation of α,β-unsaturated ketones for radical cyclisation: A new concept in promoting radical reactions

Abstract Photosensitised one electron reductive β-activation of α,β-unsaturated ketones for radical cyclisations are reported.

A new strategy for the construction of carbo- and oxycycles by intramolecular reductive coupling of α,β-unsaturated esters

Abstract Intramolecular coupling of α, β-unsaturated esters by photosensitised one electron reductive activation is reported to provide carbo- and oxycycles.

Design of a photosystem to harvest visible-light into electrons: Photosensitised one electron redox reactions in organic synthesis

Based on synchronous oxidation-reduction processes, analogous to photosynthetic mechanistic paradigm, a photosystem utilising Ph3P or ascorbic acid as sacrificial electron donor has been developed to halvest electrons from visible light photons. The utility of such photosystem has been demonstrated by initiating various one-electron reductive -C-C- bond formation reactions. Biologically active PGE, and C-Furanosides are synthesised employing this photosystem at a crucial step. Mimicking natural photosynthetic process or solar energy harvesting technology (refs. 1,2) in organic synthesis is of fundamental interest and vital from an ecological view point. Towards this endeavour, the past decade has witnessed substantial, multidisciplinary research efforts directed towards the conversion of solar light into chemical energy employing photoinduced electron transfer (PET) processes as key approach (ref. 3). Several new and synthetically important organic photoreactions have also been discovered that have employed electron transfer (ET) to or from the substrate in the presence of an electron rich donor or electron poor acceptor (ref. 4). Interestingly, remarkable progress has been made in PET reactions, though the chemistry of the radical cations, generated by the oxidative reactions, remains at the focus (ref. 4). Despite the great synthetic potentials of photosensitised one-electron reductions in organic synthesis, research in this area has been limited, owing to the lack of a suitable photosystem(ref. 5). Our own interests in this area(ref. 4a), have been centered on the application of PET oxidation reactions from select donors utilising cyanoarenes (ArCN) as light harvesting electron acceptors. The photosensiti- sation concept has relied on the thermodynamic feasibility of ET from ArCN-, to 0, followed by dispro- portionation of 0; as shown in Fig-1