Cyclization/hydrosilylation of functionalized 1,6-diynes catalyzed by cationic platinum complexes containing bidentate nitrogen ligands.
A 1:1 mixture of the platinum dimethyl diimine complex [PhN[double bond]C(Me)C(Me)[double bond]NPh]PtMe(2) (4a) and B(C(6)F(5))(3) catalyzed the cyclization/hydrosilylation of dimethyl dipropargylmalonate (1) and HSiEt(3) to form 1,1-dicarbomethoxy-3-methylene-4-(triethylsilylmethylene)cyclopentane (3) in 82% isolated yield with 26:1 Z:E selectivity. Platinum-catalyzed diyne cyclization/hydrosilylation tolerated a range of functional groups including esters, sulfones, acetals, silyl ethers, amides, and hindered ketones. Diynes that possessed propargylic substitution underwent facile cyclization/hydrosilylation to form silylated 1,2-dialkylidene cyclopentanes as mixtures of regioisomers. Diynes that possessed an electron-deficient internal alkyne underwent cyclization/hydrosilylation in moderate yield to form products resulting from silyl transfer to the less substituted alkyne. The silylated 1,2-dialkylidenecyclopentanes formed via diyne cyclization/hydrosilylation underwent a range of transformations including protodesilylation, Z/E isomerization, and [4 + 2] cycloaddition with dieneophiles.
Wang
Xiang
X
P. M. Gross Chemical Laboratory, Duke University, Durham, North Carolina 27708-0346, USA.
Chakrapani
Harinath
H
Madine
James W
JW
Keyerleber
Michele A
MA
Widenhoefer
Ross A
RA
D000480:Alkynes / Q000737:chemistry*; D002384:Catalysis; D003500:Cyclization; D015195:Drug Design; D006844:Hydrocarbons, Cyclic / Q000138:chemical synthesis*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D009584:Nitrogen / Q000737:chemistry; D009944:Organoplatinum Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D012821:Silanes / Q000737:chemistry; D013237:Stereoisomerism
D000480:Alkynes; D006844:Hydrocarbons, Cyclic; D009944:Organoplatinum Compounds; D012821:Silanes; D009584:Nitrogen