Search

Pd-catalyzed aminocarbonylation in the presence of Xantphos as a ligand was used to transform lactam-, lactone-, and thiolactone-derived triflates into N-methoxy-N-methyl or morpholine Weinreb amides. The method could also be applied to synthesize dienones in which one of the double bonds is embedded in a heterocyclic moiety, as useful substrates for Nazarov cyclization.

Three different procedures are compared to obtain properly substituted divinyl ketones in which one of the double bonds is embedded in a five-membered heterocyclic structure and therefore suitable to produce cyclopenta-fused pyrrole, derivatives by the acid-catalyzed Nazarov reaction. A convergent procedure base on the umpolung to a vinylstannane gave acceptable yields of the divinyl ketone, which forms a key intermediate in the synthesis of roseophilin.

Reporting on the torquoselectivity in the cyclization of 2-substituted five-membered azacycle and 2- and 4-substituted six-membered oxacycle derivatives. The reaction is highly diastereoselective with 2-substituted five-membered lactam derivatives 11a and 11b and leads to cis disubstituted cyclopenta-fused pyrrolines 13a and 13b, respectively.

The reaction between 1-metalated 1-ethoxy 1,3-dienes and electrophiles yields (E)-1-substituted 1-ethoxy 1,3-dienes. These alpha-substituted alkoxy dienes produce alpha, beta-unsaturated carbonyl compounds on acidic hydrolysis via a reaction pathway involving carbanionic intermediates. Use of crotonaldehyde as an electrophile produces an addition product, which on hydrolysis, yields three products depending on experimental conditions.

An approach for the synthesis of functionalized trienes and regioselective formation of medium-ring lactones is discussed. Both reactions involves intramolecular Diels-Alder reaction which generate the macrocyclic rings. The reaction is performed at varying temperature and solvents to determine both the regioselectivity and stereoselectivity of the synthetic pathway. H nuclear magnetic spectra of the reaction is discussed.

3-ethoxyhexa-3,5-dien-1-ol is prepared from a reaction between an electrophile, ethylene oxide and an alpha-metalated alkoxy diene which involves an epoxide ring opening. Synthesis of 2- and 2,6-disubstituted tetrahydro-4H-pyran-4-ones involves these alpha-substituted alkoxy dienes as intermediates. Propylene oxide yields a mixture of cis and trans compounds. 1H NMR and gas chromatography analyses are employed to calculate the cis-trans ratio.

Pd-catalyzed aminocarbonylation in the presence of Xantphos as a ligand was used to transform lactam-, lactone-, and thiolactone-derived triflates into N-methoxy-N-methyl or morpholine Weinreb amides. The method could also be applied to synthesize dienones in which one of the double bonds is embedded in a heterocyclic moiety, as useful substrates for Nazarov cyclization.

Answers to some queries such as, whether the presence of the N atom in the cyclic moiety of conjugated triene is necessary to attain electrocyclization under certain assumption are presented. Demonstration of the synthetic usefulness of the methodology, for the diasteroselective synthesis of cyclopenta-fused heterocyclic compounds, is presented.

Research has been conducted on palladium-catalyzed cross- coupling reactions of alpha-alkoxyboronates with lactam-derived vinyl triflates. The methodology developed for the preparation of azacyclic compounds is described.