Rhodium-catalyzed silylcarbocyclization (SiCaC) and carbonylative silylcarbocyclization (CO-SiCaC) reactions of enynes.
The reaction of a 1,6-enyne with a hydrosilane catalyzed by Rh(acac)(CO)(2), Rh(4)(CO)(12), or Rh(2)Co(2)(CO)(12) under ambient CO atmosphere or N(2) gives 2-methyl-1-silylmethylidene-2-cyclopentane or its heteroatom congener in excellent yield through silylcarbocycization (SiCaC) process. The same reaction, but in the presence of a phosphite such as P(OEt)(3) and P(OPh)(3) under 20 atm of CO, affords the corresponding 2-formylmethyl-1-silylmethylidene-2-cyclopentane or its heteroatom congener with excellent selectivity through carbonylative silylcarbocycization (CO-SiCaC) process. The SiCaC reaction has also been applied to a 1,6-enyne bearing a cyclohexenyl group as the alkene moiety and a 1,7-enyne system. The functionalized five- and six-membered ring systems obtained by these novel cyclization reactions serve as useful and versatile intermediates for the syntheses of natural and unnatural heterocyclic and carbocyclic compounds. Possible mechanisms for the SiCaC and CO-SiCaC reactions as well as unique features of these processes are discussed.
Ojima
Iwao
I
Department of Chemistry, State University of New York at Stony Brook, Stony Brook, New York 11794-3400, USA. iojima@notes.cc.sunysb.edu
Vu
An T
AT
Lee
Seung-Yub
SY
McCullagh
James V
JV
Moralee
Andrew C
AC
Fujiwara
Masaki
M
Hoang
Tram H
TH
D002248:Carbon Monoxide / Q000737:chemistry; D002384:Catalysis; D003500:Cyclization; D007202:Indicators and Reagents; D009682:Magnetic Resonance Spectroscopy; D012238:Rhodium / Q000737:chemistry*; D012821:Silanes / Q000737:chemistry*
D007202:Indicators and Reagents; D012821:Silanes; D002248:Carbon Monoxide; D012238:Rhodium