Chiral sulfoxides as activators of allyl trichlorosilanes in the stereoselective allylation of aldehydes.

Chiral aryl methyl sulfoxides proved to be efficient activators in the asymmetric allylation of aldehydes with allyl trichlorosilanes. High enantioselectivity was found in the case of electron-poor aldehydes. The high levels of diastereoselectivity and the detection of nonlinear effects have allowed the elucidation of some mechanistic aspects of the reaction.

Absolute configuration assignment of norcamphor-derived furyl hydroperoxide using density functional theory calculations of optical rotation and vibrational circular dichroism.

Density functional theory (DFT) calculations of sodium d line specific rotation and of vibrational circular dichroism (VCD) have been used to assign the absolute configuration of a recently prepared (1S,4R)-norcamphor-derived furyl hydroperoxide, (+)-3, introduced as a stereoselective oxidant. Both approaches give the same absolute configuration to the newly generated stereogenic carbon at position 2, i.e., (1S,2S,4R)-(+)-3, thus providing a confident assignment in a case made difficult by the large conformational flexibility and the small difference between the computed optical rotations of the two possible diastereoisomers. Although the computed IR absorption spectra of (1S,2S,4R)-3 and (1S,2R,4R)-3 are practically indistinguishable, a number of significant differences in the VCD spectra of these two nonmirror-image isomers can be observed, which allows the structural identification of the synthesized compound. This is clearly shown here for the first time.

Asymmetric Friedel-Crafts alkylation of indole with chalcones catalyzed by chiral phosphoric acids.

The reaction of indole with chalcones, to give Michael-type adducts, was found to occur with good efficiency (up to 98% yield) and moderate enantioselectivity (up to 52% e.e.) in the presence of a chiral BINOL-based phosphoric acid. Furthermore, the alkylation products can be obtained in much higher e.e.s after one only crystallization.

Easy approach to chiral Michael adducts by Eu+3-catalyzed conjugate addition.

Michael addition of enantiopure N-acetoacetyl-oxazolidin-2-ones is shown to take place in the presence of catalytic amounts of Eu(+3) salts and complexes in high yields, very reduced reaction times, and moderate diastereoselectivity. The level of diastereoselectivity can be significantly enhanced by the suitable exploitation of the easy epimerization of the adducts in the presence of silica gel.

Renewable camphor-derived hydroperoxide: synthesis and use in the asymmetric epoxidation of allylic alcohols.

Renewable enantiopure tertiary furyl hydroperoxide has been easily synthesized in two steps starting from low cost (+)-(1R)-camphor and it has been used in the asymmetric epoxidation and kinetic resolution of allylic alcohols (enantioselectivities up to 46%).

Novel highly regioselective VO(acac)2/TBHP mediated oxidation of o-alkenyl phenols to o-hydroxybenzyl ketones.

A novel mild methodology for the preparation of o-hydroxybenzyl ketones is described starting from o-alkenyl phenols and based on the VO(acac)(2)/TBHP (2 mol %/1.2 equiv) system. VO(acac)(2) first catalyzes the epoxidation of o-alkenyl phenols and then the rearrangement of the epoxyphenols to ketones via the selective benzylic C-O cleavage and 1,2 hydride migration. The protocol has also been applied to set up a useful and easy one-pot conversion of o-alkenyl phenols to benzo[b]furans by means of the sequential addition of TFA, after the generation of the intermediate o-hydroxybenzyl ketones.