Using triethynylphosphine ligands bearing bulky end caps to create a holey catalytic environment: application to gold(I)-catalyzed alkyne cyclizations.
The synthesis, properties and catalytic uses of phosphinoalkynes bearing bulky end caps at the alkyne termini, that is, tris[(triarylsilyl)ethynyl]phosphines are reported. The most salient feature of the new phosphines is the holey molecular shape possessing a deep and large-scale metal-binding cavity. The holey phosphines displayed remarkable rate enhancement in the gold(I)-catalyzed six- and seven-membered ring forming cyclizations of acetylenic keto esters and 1,7-enynes. It is proposed that the cavity in the ligand forces a nucleophilic center (enol or alkene) of the acetylenic compounds close to the gold-bound alkyne, making ring-closing anti attack feasible.
Ochida
Atsuko
A
Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan.
Ito
Hideto
H
Sawamura
Masaya
M
D000114:Acetylene / Q000031:analogs & derivatives* / Q000737:chemistry; D000480:Alkynes / Q000138:chemical synthesis* / Q000737:chemistry; D002384:Catalysis; D003500:Cyclization; D006046:Gold / Q000737:chemistry*; D008024:Ligands; D015394:Molecular Structure; D010720:Phosphines / Q000737:chemistry*; D016062:Porosity; D013237:Stereoisomerism
D000480:Alkynes; D008024:Ligands; D010720:Phosphines; C516921:triethynylphosphine; D006046:Gold; D000114:Acetylene