141170-85-6Relevant articles and documents
Nickel-catalyzed, chlorotrialkylsilane-assisted conjugate addition of alkenyltributyltin reagents to α,β-unsaturated aldehydes. Evidence for a [1-((trialkylsilyl)oxy)allyl]nickel(II) mechanism
Grisso, Bryan A.,Johnson, John R.,Mackenzie, Peter B.
, p. 5160 - 5165 (2007/10/02)
α,β-Unsaturated aldehydes R1CH=CR2CHO (R1 = H, Me, n-Pr; R2 = H, Me) react with ethenyl-, (1-ethoxyethenyl)-, (2-phenylethenyl)-, and 1-propenltrialkyltin reagents and chlorotrialkylsilanes (Me3SiCl or t-BuMe2SiCl) in the presence of Ni(COD)2 (COD = 1,5-cyclooctadiene) or 1-((trialkylsilyl)oxy)allylnickel(II) chloride catalyst precursors to afford the corresponding trialkylsilyl (E)-enol ethers in 48-79% yield. High C(3)-regioselectivities (≥15:1 crude, ≥50:1 purified) are observed when R1 = H; moderate C(3)-regioselectivities (2-12:1 crude, 2->50:1 purified) are observed when R1 = Me or n-Pr. High (E)-enol ether selectivities (5->19:1 crude, 10->50:1 purified) are observed in all cases save the addition of (1-ethoxyethenyl)tributyltin to 2-propenal, for which case a 2:1 E/Z ratio is observed. Stoichiometric model reaction and kinetic studies strongly support a Ni(0)/Nil (II) mechanism involving 1-((trialkylsilyl)oxy)allylnickel(II) intermediates and turnover-limiting alkenyl group transmetalation.
