Alkynylation of C-H Bonds via Reaction with Acetylenic Triflones

摘要

In connection with our program investigating the chemistry of the sulfone functional group, we had occasion to prepare acetylenic triflones la,b (Scheme 1) via the direct reaction of acetylenic anions with triflic anhydride. An exceptional observationattended our attempts to use THF as a solvent for the chemistry of acetylenic triflone la. Simply adding la to THF resulted in an exothermic reaction which produced α-alkynylated tetrahydrofuran in essentially quantitative yield (Table 1, entry 1). Similar reactions with five- and six-membered ethers and suffices results in the formation of α-functionalized ethers and sulfides in good to excellent yields (Table 1, entries 3--5,10--13). In contrast, anisole and phenyl isopropyl ether are recovered unchanged from the reaction. For those reactions run in solution, the best compromise solvent appears to be 1,2-dichloroethane. While even this compound undergoes alkynylation, the reaction is quite slow and most substrates are efficiently alkynylated withminimal competitive production of the propargyl chloride (Table 1, entry 14).