Sankuratri Nagaraju

Application of microwave heating technique for rapid synthesis of γ,δ-unsaturated esters

The use of microwave heating technique for the acceleration of ortho ester Claisen rearrangement (a three step transformation) is described. Irradiation of a DMF solution of the allyl alcohol 5, triethyl orthoacetate and propionic acid (catalytic) in an Erlenmeyer flask for 10 minutes in a microwave oven generated the ester 8 in 83% yield. Analogously, ortho ester Claisen rearrangement of a variety of allyl and propargyl alcohols (9, 12-22) were achieved. The formation of the diester 10 from 2-butyne-1,4-diol (9) via the ortho ester Claisen rearrangement of two allyl alcohol moieties (involving sh steps) in 15 minutes, demonstrates the versatility of the microwave heating technique.

A stereoselective total synthesis of bakkenolide-A (fukinanolide)

A highly stereoselective synthesis of bakkenolide-A (fukinanolide. 1a) employing the radical mediated spirannulation methodology is described.

Enantioselective synthesis of both (+)- and (-)-derivatives of bicyclo[4.3.0]nonan-8-one and 3,8-diones from R-carvone

Enantioselective synthesis of both the enantiomeric forms of the hydrindane derivatives mentioned in the title, potential chiral precursors in terpenoid synthesis, starling from R-carvone employing two different cyclopentannulation methodologies is described.

A radical cyclisation strategy to α-spiro-β-methylene-γ-butyrolactones. Total synthesis of (±)-norbakkenolide-A

The 5-exo-dig radical cyclisation reaction of the bromoacetals 9, obtained from the enol ethers 8, and treatment of the resulting hemiacetal 10 with Jones′ reagent transforms the cyclic ketones 7 and 12 into α-spiro-β-methylene-γ-butyrolactones 11 and norbakkenolide-A 2.

A stereoselective synthesis of (±)-homogynolide-B

A highly stereoselective formal total synthesis of homogynolide-B via the ketoketals 4 and the ketospirolactone 3a starting from Hagemanns eater 2 is described.

Sonochemical Acceleration of Conversion of 2-Alkoxytetrahydrofurans to γ-Butyrolactones Synthesis of (±)-Quercus Lactone-A

Effect of sonochemical irradiation on the conversion of 2-alkoxytetrahydrofurans to γ-butyro-1actores by Jones reagent, and its extension to the highly stereoselective synthesis of quercus lactone a, is reported.

Chiral Synthons from Monoterpenes.1 Stereoselective Syntheses of (-)5S, 6S, 9R-6-Isopropyl-9-Methyl-2-Oxaspiro[4.4]Nonan-3-One and (-) 3aR, 6R, 7aR-3a-Methyl-6-Isopropenylhexahydrobenzofuran-2-One

Highly stereoselective syntheses of two C-12 chiral synthons 3 and 9, mentioned in the title, starting from the monoterpenes R-1 imonene and R-carvone, using radical cyc 1 sation as key reaction, are described.

Regio- and stereospecific construction of vicinal quaternary carbons: total synthesis of (±)-albene

A regiospecific and stereoselective total synthesis of the trisnorsesquiternene (±)-albene, via a prochiral precursor is described. The ortho ester Claisen rearrangement of the allyl alcohol, obtained in two regiospecific reactions from a Diels-Alder adduct, followed by hydrolysis of the resultant ester furnished an ene acid in a highly stereoselective manner. Anhydrous copper sulphate catalysed intramolecular cyclopropanation reaction of the diazo ketone derived from the ene acid, generated a cyclopropyl ketone. The regiospecific reductive cleavage of this cyclopropyl ketone resulted in a prochiral ketone. Finally, Shapiro reaction on the tosylhydrazone, derived from the latter ketone, furnished (±)-albene.

Isomerisation of 1-methylene-2-methyl-2-(2-oxopropyl)-cyclohexanes to 2-methylene-1-methyl-1-(2-oxopropyl)-cyclohexanes by ene and retro-ene reaction

Thermal activation of the normal Claisen products, the enones 4, 7 and 14 in the presence of a catalytic amount of propionic acid generated the isomeric enones 6, 9 and 15 via the sequential intramolecular ene-reaction of the enol tautomer followed by 1,5-hydrogen transfer (or retro ene-reaction) of the resultant acetyl cyclopropane intermediate. Conversion of the enones 9 and 15 into the corresponding cyclohexenones 10 and 16 established the structures of the rearrangement products.

Stereospecific total synthesis of (±)-albene via a prochiral precursor

The total synthesis of racemic albene 2 via the prochiral precursor 3, using a stereoselective Claisen rearrangement and an intramolecular diazoketone cyclopropanation as key reactions, is described.