Synthesis, Absolute Configurations, and Biological Activities of Floral Scent Compounds from Night-Blooming Araceae

The uncommon jasmone derivatives dehydrojasmone, isojasmol, and isojasmyl acetate, floral scent compounds from night-blooming Araceae, were synthesized in a scalable synthesis employing conjugate addition with a selenoacetal as the key step. The stereoselective strategy with subsequent enzymatic kinetic resolution allowed determining the absolute configuration of the natural compounds by GC on a chiral phase. The homoterpene (E)-4,8-dimethyl-1,3,7-nonatrien-5-yl acetate, another uncommon scent compound, was obtained by α-regioselective aldehyde prenylation. The biological activities of dehydrojasmone and isojasmol were investigated in field assays, showing that these unique volatiles are able to selectively attract specific cyclocephaline scarab beetle pollinators.

Zinc-mediated α-regioselective Barbier-type cinnamylation reactions of aldehydes, ketones and esters

We report a simple, efficient, and general method for the zinc-mediated regioselective cinnamylation of aldehydes and ketones under Barbier-type conditions in a one-pot synthesis affording the corresponding α-cinnamylated alcohols in moderate to excellent yields. Compared to the literature procedures, this approach is operationally simple, uses simple reactants, and provides direct access to linear α-cinnamylated alcohols with excellent regioselectivity. Experimental results suggest that the reactions proceed through the radical pathway. In addition, the reaction was found to be scalable to the gram-scale and the one-pot protocol is also applicable to less reactive esters leading to bishomoallylic alcohols which were valuable intermediates for desymmetrizing intramolecular Heck cyclization, allowing for the elaboration to functionalized building blocks.

Highly α-regioselective neodymium-mediated allylation of diaryl ketones

The first utility of neodymium as a mediating-metal in the Barbier reaction of diaryl ketones with allyl halides is reported in this paper. This one-pot reaction was highly α-regioselective and was carried out under mild conditions.

Zinc-mediated highly α-regioselective 1,4-addition of chalcones with prenyl bromide in THF

α-Regioselective addition to chalcones was realized by use of in situ generated prenylzinc reagents from zinc and prenyl bromide in the presence of SnCl4 in a 1,4-addition fashion. The approach uses the reagent combination of prenyl bromide, zinc, and SnCl4 in THF, all of which are inexpensive, readily available, and easily removable after the reaction.