Stereoselective synthesis of CF3-substituted trans- and cis-enediynes via carbocupration or hydrostannation reactions of CF3-containing diyne

Trifluoromethylated Internal Alkynes: Versatile Building Blocks for the ­Preparation of Various Fluorine-Containing Molecules

“…This hydrostannation could be successfully applied for the highly stereoselective synthesis of trifluoromethyl-containing cis-enediynes as shown in Scheme 8. 20 Thus, on treating diyne 12 with n-Bu 3 SnH (1.2 equiv) in the presence of Et 3 B (20 mol%), in toluene at -78°C for one hour, the hydrostannation reaction proceeded quite smoothly to afford the corresponding vinyl stannane 16 in 75% isolated yield as the sole product. Next, 16 was converted into the corresponding vinyl iodide 17 by treatment with iodine in dichloromethane at room temperature, which underwent efficient Sonogashira cross-coupling reactions with different terminal alkynes giving rise to the corresponding stereodefined CF 3 -substituted cis-enediyne compounds 18 in 74-97% isolated yields.…”

Hydroelementation of diynes

“…Radical hydrostannation was successfully applied in the reaction with 1,3-diynes, 248 as well as diynes possessing an aryl spacer between the CRC bonds. 249 Konno et al reported selective radical hydrostannation of 5-benzyloxy-1-trifluoromethyl-5-methyl-hexa-1,3-diyne 507 with tributyltin hydride 508.…”

“…The obtained enyne 510 was generated in 75% yield and was further used in the synthesis of CF 3 -substituted (Z)-enediyne 517 compounds in iododestannylation/Sonogashira coupling reactions (Scheme 104). 248 The radical hydrostannation of various diynes and triynes 102c and 264a-e was carried out stereoselectively with tributyltin hydride 508. In the two cases, the (E)-products 521a and 521c were exclusively formed.…”

Simple Synthesis of Fluorinated Ene-Ynes via In Situ Generation of Allenes

“…19 Conjugated fluorous ene-ynes have been utilized as Michael acceptors and as intermediates towards fluorous diynes. 20,21 Additionally, the conjugated vinyl fluoride can be displaced via acetylides to give enediyne inhibitors. 22 Finally, fluorinated ene-ynes can serve as a starting material for fluorous allenes (Scheme 1B), another fluorinated functional group with rising popularity.…”

“…[23][24][25][26][27] Previous work to access vinyl-fluoride containing eneynes has largely involved palladium-catalyzed Sonogashiratype couplings of functionalized olefins (Scheme 1C, middle). 14,21,22,[28][29][30][31] Metal-free approaches to fluorinated eneynes include couplings with fluorinated sulfonates or phosponates via Julia or Horner-Wadsworth-Emmons olefination, respectively. 18,32 These methods are often limited by the multistep syntheses required to reach the requisite vinyl fluoride coupling partners.…”