P. Yella Reddy

Porphyrin-rhodanine dyads for dye sensitized solar cells

A series of four new porphyrin-rhodanine dyads were synthesized having the rhodanine acetic acid group either at the meso- or the pyrrole-β position of a free-base/zinc porphyrin. These dyads were fully characterized by UV-visible, 1 H NMR, MALDI-MS and fluorescence spectros- copies and cyclic voltammetry. Both the Soret and Q-bands were red-shifted in the case of pyrrole- β substituted dyads. The redox potentials of all four dyads were altered in comparison with their individual constituents. The dyads were tested in dye sensitized solar cells and the zinc metalated dyads gave a better performance in comparison with the corresponding free-base dyads. Copyright

Regioselective generation of iminium cation by PET processes: Its in situ trapping by intramolecular nucleophiles and synthesis of some biologically active heterocycles.☆

Abstract Efficient, mild and direct route for regiospecific iminium cation is developed by sequential two electron oxidation of several N-alkylated tertiary amines by photoinduced electron transfer processes. The regiospecificity of iminium cation arises from the deprotonation step of amine radical cation to generate α-amino radical which depends on the stereoelectronic factor subject to kinetic acidity of amine radical cation. Iminium cation is efficiently trapped insitu by internal nuleophiles to give cyclic compounds 14–18 and 22a–c. Stereoselective synthesis of cis α,α′-dialkylated piperidines and pyrrolidines 30a–c is achieved by nucleophilic opening of tetrahydro-1,3-oxazines 22a–c.

Regiocontrolled set promoted photocyclisation of 2-alkyl-1-piperidine and pyrrolidine propanols : stereoselective synthesis of cis-α,α'-dialkyl piperidines and pyrrolidines via tetrahydro-1,3-oxazines

Abstract Photocyclisation of amino alcohols (1a-c) to (4a-c) via insitu generated iminium cation by photoinduced SET reaction and their utility in the stereoselective synthesis of cis-α-α′-dialkyl piperidines and pyrrolidines is described.

Microwave-Assisted, Rapid, Solvent-Free Aza-Michael Reaction by Perchloric Acid Impregnated on Silica Gel

Abstract Highly efficient solvent-free aza-Michael additions of a variety of amines to α,β-unsaturated carbonyl compounds under microwave-irradiation conditions catalyzed by perchloric acid impregnated on silica gel (HClO4/SiO2) is reported. The reactions are completed within 2–7 min in a microwave oven to produce the corresponding adducts in excellent yields, and the catalyst can be recovered and reused.

Synthesis and utilization of a novel glycine derived chiral precursor, based on a recyclable L-Prolinol auxiliary, for the enantioselective preparation of α-amino acids and their N-methyl derivatives

Abstract α-Amino Acids and their N-Methyl derivatives are synthesised in fairly high optically purity employing a new glycine derived template based on a recyclable L-Prolinol chiral auxiliary.

Durable Unsymmetrical Zinc Phthalocyanine for Near IR Sensitization of Nanocrystalline TiO2 Films with Non-Volatile Redox Electrolytes

We are presenting our results based on unsymmetrical zinc phthalocyanine by adopting ‘push-pull’ concept for the nanocrystalline dye-sensitized solar cells. Using this sensitizer in combination with nonvolatile organic-solvent-based electrolytes, we obtained a photovoltaic efficiency of 1.52% under standard global AM 1.5 sunlight and compared the results with volatile organic-solvent based electrolyte. These devices exhibit admirable stability when subjected to continuous thermal stress at 60 oC for 1000 h. The sensitizer is thermally stable up to 150 oC and can be useful for roof top applications.

Highly Efficient Microwave‐Assisted Synthesis of Subphthalocyanines

Abstract A novel, highly efficient, single‐step synthesis of subphthalocyanines using microwave irradiation of phthalonitrile and boron trichloride in 1‐chloronaphthalene was accomplished for the first time. This provides a new preparative method for the synthesis of subphthalocyanines with reduced reaction times and improved yields.

Photoinduced Electron Transfer (PET) Promoted Oxidative Activation of 1-(N-Benzyl-N-methylglycyl)-(S)-prolinol: Development of Novel Strategies Towards Enantioselective Syntheses of α-Amino Acids, Their N-Methyl Derivatives and α-Hydroxy Acids Employing (S)-Prolinol as aRecyclable Chiral Auxiliary

PET activation of 1-(N-benzyl-N-methylglycyl)-(S)-prolinol (1) in dry acetonitrile, utilizing 1,4-dicyanonaphthalene (DCN) as a light-harvesting electron-acceptor and methyl viologen (MV ++ ) as an electron-transfer mediator, leads to the formation of 3-[benzyl(methyl)amino]perhydropyrrolo[2,1-c][1,4]oxazin-4-one (3). When this photolysis is carried out in aqueous acetonitrile, exclusively 3-hydroxyperhydropyrrolo[2,1-c][1,4]oxazin-4-one (4) is produced. The formation of 3 can be rationalized in terms of intramolecular cyclization of the in situ generated iminium cation intermediate (2) by the OH moiety of (S)-prolinol, while 4 is generated by hydrolysis of 2 followed by acetalization. Nucleophilic alkylation of 3 and 4, using Grignard reagents and allyltrimethylsilane/TiCl 4 , provides 12a-d & 15 and 17a-c & 21, respectively, in a highly stereoselective manner. Hydrolysis of the resultant amides (12, 15, 17, and 21) provides α -amino acid derivatives (14) and α -hydroxy acids, respectively, in optically active form, along with the recovered (S)-prolinol chiral auxiliary in its recyclable form.