Search

Allyl, dimethylallyl, crotyl, and prenyl ethers of various aromatic ortho-hydroxy carbonyl compounds undergo a tandem sequence of Claisen rearrangement, carbonyl olefination, and cyclization upon microwave irradiation in the presence of a stabilized ylide. The products are multiply substituted 6- or 8-allylated or prenylated coumarins (2H-chromen- 2-ones). [ABSTRACT FROM AUTHOR]

Total synthesis of anticonvulsant amino acid, lacosamide, is reported. The key step is stereospecific allyl cyanate-to-isocyanate rearrangement, which proceeds with chirality transfer. The enantiopure starting material for the rearrangement step was accessed from ethyl I-lactate. [ABSTRACT FROM AUTHOR]

The mechanism of the palladium-catalyzed synthesis of allylic silanes and boronates from allylic alcohols was investigated. ¹H, 29Si, 19F, and 11B NMR spectroscopy was used to reveal key intermediates and byproducts of the silylation reaction. The tetrafluoroborate counterion of the palladium catalyst is proposed to play an important role in both catalyst activation as well as the transmetalation step. We propose that BF3 is generated in both processes and is responsible for the activation of the substrate hydroxyl group. An (η³-allyl)palladium complex has been identified as the catalyst resting state, and the formation of (η³-allyl)palladium complexes directly from allylic alcohols has been studied. Kinetic analysis provides evidence that the turnover limiting step is the transmetalation, and insights into notable similarities between the borylation and the silylation reaction mechanisms enabled us to considerably improve the stereoselectivity of the borylation. [ABSTRACT FROM AUTHOR]

Chiral ion pairs play a key role in modern enantioselective synthesis, though little is known about their properties. We have now used the special features of unsymmetrically substituted allyl derivatives to obtain unprecedented insight into ion pair dynamics. By employing chiral high-performance liquid chromatography, it was possible to follow the time-dependent concentrations of all four isomeric esters (two regioisomeric pairs of enantiomers) and all four isomeric alcohols generated during the hydrolysis of enantiopure 1-(4-chlorophenyl)-3-phenylallyl and 3-(4-chlorophenyl)-1-phenylallyl 4-nitrobenzoates. Combination of these results with the directly measured rate constant for the reaction of the laser-flash photolytically generated 1-(4-chlorophenyl)-3-phenylallyl cation with water provided a complete mechanistic scheme for allyl carboxylate solvolysis. It is demonstrated that solvolysis and internal return can be explained by the same intermediates. The correlation equation log k = sN(N + E) was used to elucidate the variable importance of external and internal return in the solvolysis reactions. This information will be crucial for the interpretation of the ultrafast dynamics of ion pairs generated by femtosecond laser pulses. [ABSTRACT FROM AUTHOR]

The article focuses on the synthesis of the 1-allyl-3,5-dimethyl-1H-pyrazole-4-carbaldehyde (I) and propane-1,3-diselenol (II) in the presence of Me3SiCl catalyst. It says that the preparation of propane-1,3-diselenol (II) was performed by reductive cleavage of the Selenium bond in polytrimrthylene diselenide in the N2H4·H2O—KOH. It states that the reaction accompanied with heat evolution was completed in five minutes.

The oxidation reactions are effectively and economically performed under mild conditions. [ABSTRACT FROM AUTHOR]