Enantioselective Copper-Catalyzed Oxy-Alkynylation of Diazo Compounds

Enantioselective
catalytic methods allowing the addition of both
a nucleophile and an electrophile onto diazo compounds give a fast
access into important building blocks. Herein, we report the highly
enantioselective oxyalkynylation of diazo compounds using ethynylbenziodoxol-(on)­e
reagents and a simple copper bisoxazoline catalyst. The obtained α-benzoyloxy
propargylic esters are useful building blocks, which are difficult
to synthesize in enantiopure form using other methods. The obtained
products could be efficiently transformed into vicinal diols and α-hydroxy
propargylic esters without loss in enantiopurity.