Terminology for Reduction of Carbonyl Compounds

Copper(I) salts catalyze the allylic oxidation of alkenes in the presence of peresters, such as tert-BuOjCOPh, to afford the corresponding allylic benzoate esters. In the case of terminal alkenes, internal allylic esters are formed in preference over the terminal isomers. The mechanism is believed to involve addition of an allylic radical to copper(II) benzoate. Rearrangement of the copper(III) intermediate then produces the product and regenerates the copper(I) catalyst. 

Asymmetric allylic oxidation of alkenes using peresters is possible when the ligand L of the Cu(III) intermediate is chiral. Copper complexes of chiral bis(pyri-dine)- and bis(oxazoline)-type ligands have been used with fert-butyl perbenzoate to obtain optically active allylic benzoates. 

A chemoselective reagent reacts selectively Vv ith one functional group in the presence of other functional groups. 

In a regioselective reaction, the reagent adds at only one of two possible regions (directions). 

A stereoselective reaction leads to the exclusive or predominant formation of one of several possible stereoisomeric products. Thus, one reaction pathway from a given substrate is favored over the other (as in nucleophilic additions to cyclic ketones or alkylations of enolate ions). 

---