Rhodium-catalyzed cycloisomerization of 1,6-enynes with an intramolecular halogen shift: reaction scope and mechanism.
The rhodium(I)-species-catalyzed cycloisomerization reaction of a wide spectrum of 1,6-enynes with an unusual intramolecular halogen shift was investigated. This Rh-catalyzed enyne cyclization reaction represents a new process for the synthesis of stereodefined alpha-halomethylene-gamma-butyrolactones, lactams, tetrahydrofurans, pyrrolidines, and cyclopentanes. Coordinatively unsaturated rhodium species ([Rh(COD)Cl](2) + dppb + AgSbF(6)) only catalyzes the reaction with enyne substrates bearing a Z-form double bond, while neutral rhodium species (RhCl(PPh(3))(3)) could catalyze enyne substrates bearing a Z- or E-form double bond to form the desired products and has a wider substrate scopes. The mechanism of the reaction was studied by the employment of control experiments with different enyne isomers, and a pi-allyl rhodium intermediate was suggested to explain the formation of the cyclic products with an intramolecular halogen shift.
Tong
Xiaofeng
X
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Road, Shanghai 200032, China.
Li
Dao
D
Zhang
Zhaoguo
Z
Zhang
Xumu
X
D000480:Alkynes / Q000138:chemical synthesis*; D002384:Catalysis; D003500:Cyclization; D006219:Halogens / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D012238:Rhodium / Q000737:chemistry*; D013237:Stereoisomerism
D000480:Alkynes; D006219:Halogens; D012238:Rhodium