“…The synthesis is completed as in Little's route 20b by addition of methyllithium to tricyclic ketone 28 and dehydration of the resulting alcohol. The (±)-sterpurene thus obtained is identical to previously obtained material by direct comparison of 1 H and 13 C NMR spectra. ,20d 4 5 …”
(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.
“…The synthesis is completed as in Little's route 20b by addition of methyllithium to tricyclic ketone 28 and dehydration of the resulting alcohol. The (±)-sterpurene thus obtained is identical to previously obtained material by direct comparison of 1 H and 13 C NMR spectra. ,20d 4 5 …”
(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.
“…The furosesquiterpenes 144 and 145 inhibited the germination of the water cress, Lepidium sativum. 193 Formal syntheses of (±)-D (6) -protoilludene 194 and (±)-sterpurene 195 have been reported. A novel and general approach for the preparation of protoilludane sesquiterpenes has been developed.…”
Section: Himachalane Longifolane and Longipinanementioning
Synthetic Studies Towards Compounds Related to Sterpurene and Protoilludene.-As part of synthetic strategies towards the title sesquiterpenes (I) and (II), resp., the intramolecular aldol condensation of the diastereomeric cyclopentanes (XII) and (XIII) is studied. Mixtures of the cis-and trans-bicyclononenones (XIV) and (XV) with (XVI) are obtained in ratios varying from 1:1 to 12:1 depending on different acidic or basic reaction conditions. The preparation of the trans compound (XV) in ≈70% yield constitutes formally a new synthesis of (I). -(BIRKENES, O. J.; HANSEN, T. V.; M'DACHI, S.; SKATTEBOEL, L.; STENSTROEM, Y.; Acta Chem. Scand. 52 (1998) 6, 806-812; Dep. Chem., Univ. Oslo, N-0315 Oslo, Norway; EN)
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