Asymmetric C(sp)–H Addition of Terminal Alkynes to Cyclopropenes by a Chiral Gadolinium Catalyst

We
herein report the diastereo- and enantioselective C­(sp)–H
addition of terminal alkynes to cyclopropenes by a chiral half-sandwich
gadolinium catalyst. This protocol constitutes the first example of
asymmetric hydroalkynylation of cyclopropenes with terminal alkynes
and offers a straightforward and 100% atom-efficient route for the
synthesis of a wide range of enantioenriched alkynylcyclopropane derivatives
in high yields (65–96%) and excellent stereoselectivity (>20:1
dr; 90–99% ee). Elaboration of some of the alkynylcyclopropane
products through selective transformation of the CC moiety
has also been demonstrated to give further diversified chiral cyclopropane
derivatives which are otherwise difficult to access.