Markovnikov-addition of H-phosphonates to terminal alkynes under metal- and solvent-free conditions

Abstract

Synthesis of α-vinylphosphonates from terminal alkynes and H-phosphonates as only the Markovnikov-regioisomer under metal- and solvent-free conditions.

Preparation of Vinylphosphonates from Ketones Promoted by Tf2O

“…Previously, we reported the preparation of 3 from terminal alkynes . In this case, 5 was also detected by NMR spectrum.…”

“…The product was isolated in 64% yield and confirmed as dimethyl 1-phenyl ethenyl phosphonate (3aa). 27 The reaction condition was then optimized, and the results were summarized in Table 1. In the presence of pyridine, the yield of 3aa was increased to 71% (entry 2).…”

“…The results suggest that 5 may be the key intermediate in the reaction and the process may proceed via nucleophilic vinylic substitution. 27,30 Previously, we reported the preparation of 3 from terminal alkynes. 27 In this case, 5 was also detected by NMR spectrum.…”

“…27,30 Previously, we reported the preparation of 3 from terminal alkynes. 27 In this case, 5 was also detected by NMR spectrum. Experimental results indicated that 5 was generated via addition of triflic acid to alkyne.…”

“…In 2021, our group developed a Tf 2 O activated phosphorylation of terminal alkyne to afford vinyl phosphonates. In this case, vinyl triflate was supposed as intermediate . As vinyl triflate could be prepared from ketone and Tf 2 O in the presence of base, we examined the formation of vinyl phosphonates from ketone.…”