Intramolecular C-H insertion reactions of (eta(5)-cyclopentadienyl)dicarbonyliron carbene complexes: scope of the reactions and application to the synthesis of (+/-)-sterpurene and (+/-)-pentalenene.
(eta(5)-Cyclopentadienyl)dicarbonyliron carbene complexes, [(eta(5)-C(5)H(5))(CO)(2)Fe=CHR](+)BF(4)(-), are generated as reactive intermediates from thioether derivatives, (eta(5)-C(5)H(5))(CO)(2)FeCH(R)SPh, by S-alkylation with trimethyloxonium tetrafluoroborate and loss of thioanisole. The carbene complexes undergo intramolecular C-H insertion into appropriately situated side chains to form cyclopentane derivatives. The reaction has been developed into a general procedure employing cycloalkanones as scaffolds bearing the iron carbene moieties and the side chains at C(2) and C(3), respectively. The products of the intramolecular insertion reactions are substituted bicyclo[n.3.0]alkanones. The scope and limitations of the reaction are described. The reaction is applied to a total synthesis of sterpurene and to a formal synthesis of pentalenene. Overall, this approach to cyclopentane annulation complements the related metal-catalyzed insertion reactions of diazocarbonyl compounds, which are also believed to occur via metal carbene complexes.
Ishii
S
S
Department of Chemistry and Biochemistry, 251 Nieuwland Science Hall, University of Notre Dame, Notre Dame, IN 46556, USA.
Zhao
S
S
Mehta
G
G
Knors
C J
CJ
Helquist
P
P
D003517:Cyclopentanes / Q000138:chemical synthesis / Q000737:chemistry*; D005658:Fungi / Q000737:chemistry; D006838:Hydrocarbons; D007501:Iron; D008697:Methane / Q000031:analogs & derivatives* / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D012717:Sesquiterpenes / Q000138:chemical synthesis
C442378:(eta(5)-cyclopentadienyl)dicarbonyliron carbene; D003517:Cyclopentanes; D006838:Hydrocarbons; D009942:Organometallic Compounds; D012717:Sesquiterpenes; C030011:carbene; C024646:pentalenene; D007501:Iron; D008697:Methane