HFO-1234yf as a CF3-Building Block: Synthesis and Chemistry of CF3-Ynones

Reaction of low cost, readily available 4(th)generation refrigerant gas 2,3,3,3-tetrafluoropropene (HFO-1234yf) with lithium diisopropylamide (LDA) leads to formation of lithium 3,3,3-trifluoropropynide, addition of which to a range of aldehydes formed CF3-alkynyl alcohol derivatives on multigram scale, which were oxidised using Dess-Martin periodinane (DMP) to give substituted CF3-ynones with minimal purification required. Michael-type additions of alcohol and amine nucleophiles to CF3-ynones are rapid and selective, affording a range of CF3-enone ethers and enaminones in excellent yields with high stereoselectivity for theZ-isomer. By analogous reactions with difunctional nucleophiles, a wide range of CF3-substituted pharmaceutically relevant heterocyclic structures can be accessed, exemplified in the simple synthesis of the anti-arthritis drug celecoxib from HFO-1234yf in just three steps.