Journal of Organic Chemistry
The Lewis acid-mediated Nicholas reactions of propargyl acetate–Co2(CO)6 complexes with a series of potassium alkynyltrifluoroborates and potassium alkenyltrifluoroborates are described. Alkynyltrifluoroborates directly alkynylate the intermediate propargyldicobalt cations. In contrast, alkenyltrifluoroborates proceed through one of the three modes of dominant reactivity: C-2-substituted alkenyltrifluorobrates directly alkenylate, predominantly with the retention of stereochemistry. C-1-substituted alkenyltrifluoroborates alkenylate at C-2. Potassium vinyltrifluoroborate incorporates a cyclopropane at the site propargyl to alkynedicobalt. Computational analysis of these systems explains the differential modes of reactivity of alkenyltrifluoroborates and outlines the probable mechanisms for the formation of each product.
St Onge, Brent; Taimoory, S. Maryamdokht; Battersby, Jeffrey; Trant, John F.; and Green, James R.. (2021). Reaction of Alkynyl- And Alkenyltrifluoroborates with Propargyldicobalt Cations: Alkynylation, Alkenylation, and Cyclopropanation Product Pathways. Journal of Organic Chemistry, 86 (24), 18094-18106.