Flash-photolytic generation of dienols and dienolates from alpha,beta-unsaturated esters and kinetics of their amine-catalyzed ketonization in nonaqueous media.

Dienols of alpha,beta-unsaturated esters were generated and observed by flash photolysis and their decay rates in acetonitrile and in hexane solutions were measured in the presence of amines or aminoalcohols. In acetonitrile, 1 ratio 1 ammonium dienolate transient intermediates were observed. In hexane, no dienolate could be detected and two moles of the inductor participated in the rate-determining step for tautomerization.

Synthesis of C8 alkyl glycosides via palladium-catalyzed telomerization of butadiene with O-benzylated aldoses.

Conditions of the butadiene telomerization with benzylated aldoses with a free anomeric hydroxyl, which efficiently furnish the corresponding octadienyl compounds have been determined. Deprotection and hydrogenation of the telomers over Pd/C led to the octyl glycosides.

Titanium-mediated [4 + 1] assembly of 1,3-dienes and nitriles: formation of 3-cyclopentenyl amines and cyclopentenones.

In the presence of Ti(OiPr)4 and iPrMgCl, dienes couple with nitriles to afford the title products in good yields.

Coating alginate microspheres with a serum albumin-alginate membrane: application to the encapsulation of a peptide.

Calcium alginate gel microspheres coated with a human serum albumin (HSA)-alginate membrane were prepared adapting a transacylation method previously applied to large beads. The procedure involved emulsification of an aqueous solution of sodium alginate and propylene glycol alginate (PGA) in an oily phase, followed by addition of CaCl(2). The resulting gel microspheres were transferred in an aqueous solution of HSA.

Mechanistic insights into the palladium-induced domino reaction leading to ketones from benzyl beta-ketoesters: first characterization of the enol as an intermediate.

The monitoring by UV spectroscopy of the Pd-catalyzed hydrogenolysis in acetonitrile of 2-methyl-2-benzyloxycarbonyl-1-indanone and 2-methyl-2-benzyloxycarbonyl-1-tetralone showed the successive formation of corresponding beta-ketoacids and enols to deliver finally the ketones. Some factors which influence the stability of the intermediates are determined. In contrast to the above benzyl beta-ketoesters, the enol was not detected from benzyl (2-methylinden-3-yl) carbonate.

Palladium-catalyzed oxidation of benzylated aldose hemiacetals to lactones.

Benzyl protected sugar hemiacetals are oxidized to the corresponding lactones in excellent yields using bromobenzene, K(2)CO(3) and the Pd(OAc)(2)/PPh(3) catalytic system.

Substituent effects on two-center three-electron bonds and hydrogen bonds involving unsaturated organic functional groups and an ammonia radical cation--the resonance contribution.

A theoretical investigation of the substituent effects on the two-center, three-electron (2c-3e) bond involved between unsaturated functional groups and an amine nitrogen is presented. The competitive hydrogen-bonded complexes are also studied. In both cases, the bond energies are found to be in the range of 20-30 kcal mol(-1).