P. Pardasani

Recent advances in 1,4-benzoquinone chemistry

As 1,4-benzoquinonas sao encontradas em toda a natureza, podendo ser sintetizadas por diversas estrategias. Esta revisao apresenta os desenvolvimentos recentes das metodologias de sintese, das reacoes de ciclo adicao, da quimica computacional e dos estudos de pulso radiolitico. Destaca ainda a sua significância quimica e biologica e de seus compostos derivados.

STEREOSELECTIVE SYNTHESIS OF SUBSTITUTED THIAZOLIDINE DERIVATIVES

ABSTRACT Imines formed from a secondary cyclic amino acid and isatin afford thiazolo-oxazolidinone as the product via decarboxylative azomethine ylide formation. Subsequent 1,3-dipolar cycloaddition with dipolarophiles viz ethyl phenyl propiolate and methyl acrylate leads to novel spiro compounds. Structures and stereochemistry have been determined by detailed spectral and NOE studies.

Synthetic and spectral studies of novel spiro {bicyclo[3,3,0]octene-8,3′(2′H)-indol}-2′-ones obtained from indol-2,3-diones

The present article reports our approach toward the synthesis of spiro compounds via indol-2,3-diones. Thus, reaction of indol-2,3-dione derivatives with a secondary cyclic amino acid, namely, (R)-(−)-thiazolidine-4-carboxylic acid, affords a thiazolo-oxazolidinone as the main product. When the reaction is carried out in the presence of a dipolarophile, 1,3-dipolar cycloaddition to the intermediate azomethine ylide leads to a novel spiro compound. The products have been characterized on the basis of spectral studies, and the geometry of the intermediate iminium compound has been optimized by use of the semiempirical molecular orbital method.

A comprehensive approach to the photochemical synthesis of bioactive compounds by the reaction of oxazolidine, thiazolidine and pyrazolidine derivatives with indol-2,3-diones

The reactions of indol-2,3-dione derivatives with 3-phenyl-5-isoxazolone, 2-thiazoline-2-thiol, 1-phenyl-3-methyl-5-pyrazolone under photochemical conditions have been described. The UV light-induced irradiation mainly produced benzazepine and quinoline carboxylic acid derivatives. The products have been characterized on the basis of spectral data and elemental analyses.

The synthesis of epoxypiperolides and piperolides

A general synthesis of alkynyl orthoesters leads to intermediates that couple with 2-trimethylsilyloxy-4-methoxyfuran to give compounds from which epoxypiperolide and isomers are available as well as all piperolide isomers.

SYNTHESIS AND SEMIEMPIRICAL CALCULATIONS OF THIAZOLIDINONE AND IMIDAZOLIDINONE DERIVATIVES OF α-DIONES

The condensation reactions of α-diones with rhodanine and creatinine to give acenaphthylidene, isatylidene and thioisatylidene derivatives, which may act as potential bioactive compounds, are described. The synthesized compounds have been characterized by elemental analysis and spectral studies, as well as by molecular modelling using PCWIN model.

Stereoselective synthesis and antioxidant activity of azabicycloadducts derived from 9,10-phenanthrenequinone

A facile synthesis of sprio{1-aza-bicyclo-[3,3,0]-6-octene-8,1′ -phenanthrene}-2′-ones has been accomplished by [3+2] cycloaddition of azomethine ylide (amy) generated from 9,10-phenanthrenequinone and different secondary cyclic amino acids, namely, thiazolidine-4-carboxylic acid, L-pyrrolidine-2-carboxylic acid (L-proline), and piperidine-2-carboxylic acid (pipecolinic acid) with electron-deficient dipolarophiles in 67%–79% yield. AM1 calculations have been performed to understand the stereochemical course of the cycloaddition. The products have been characterized by elemental analyses and spectroscopic techniques, namely IR, 1H NMR, and 13C NMR spectroscopies as well as mass spectrometry. Some of the synthesized cycloadducts showed moderate antioxidant activity.

[3+2]-CYCLOADDITION REACTIONS OF THIOISATIN WITH L-PROLINE AND (R)-(−)-THIAPROLINE

The [3+2]-cycloaddition reactions of cyclic secondary α-amino acids viz L-proline and (R)-(−)-thiaproline with 5-methylthioisatin via azomethine ylide in the presence of dipolarophiles afford azabicyclooctane derivatives in moderate-to-good yields. The cycloadducts have been characterized by elemental analysis and spectral techniques viz IR, 1H NMR, 13C NMR, MASS. In addition, stereochemical aspects of the cycloaddition have been ascertained by MOPAC-6 calculations using AM1 hamiltonians.

Synthetic routes to the piperolides, fadyenolides, epoxypiperolides, and related compounds

Syntheses of the piperolides, the fadyenolides, epoxypiperolide, and related compounds are described. (±)-Narthogenin is also efficiently produced.

Syntheses of Indigoid Dye Precursors and Bioactive Compounds Via Condensation of 1,2- and 1,4-Diones with Thiohydantoins

The condensation of 1,2- and 1,4-diketones with thiohydantoins to give tetrahydroquinodimethane and isatylidene derivatives respectively is described which may act as potential precursors for indigoid dyes as well as bioactive compounds. The synthesized compounds have been characterized by elemental analyses, spectral studies as well as by molecular modelling using PC WIN model. In addition, the newly synthesized products have been screened for antimicrobial activity.