title: Stereocontrolled synthesis of angularly fused tricyclic ring systems by means of 1-metalla-1,3,5-hexatrienes (M=Cr, W).
abstract: An efficient pathway for the stereocontrolled synthesis of functionalized, angularly fused tricyclic ring systems from readily available (1-alkynyl)carbene complexes [(OC)(5)M=C(OEt)C(triple bond)CR] (M=Cr, W; R=Ph, c-C(6)H(9)) is described. The synthesis involves the formation of a 1-metalla-1,3,5-hexatriene from the (1-alkynyl)carbene tungsten complex [(OC)(5)W=C(OEt)C(triple bond)C-c-C(6)H(9)] and a secondary amine, and its thermally induced pi-cyclization to a tetrahydroindene, which undergoes a spontaneous isomerization to another tetrahydroindene. Condensation of these tetrahydroindenes with pyran-2-ylidene complexes derived from (1-alkynyl)carbene complexes [(OC)(5)M=C(OEt)C(triple bond)CPh] (M=Cr, W) proceeds smoothly giving angularly fused tricyclic ring systems, rearrangement of which may generate spiro(cyclopentane-1,1-indanes) as side products. The synthesis is highly versatile and can be applied to the formation of various ring systems, such as steroid-type ring skeletons.
authors.affiliation: Organisch-Chemisches Institut der Universität Münster Corrensstrasse 40, 48149 Münster, Germany.
authors.forename: He-Ping
authors.initials: HP
authors.lastname: Wu
authors.forename: Rudolf
authors.initials: R
authors.lastname: Aumann
authors.forename: Roland
authors.initials: R
authors.lastname: Fröhlich
authors.forename: Birgit
authors.initials: B
authors.lastname: Wibbeling
mesh_terms: D015394:Molecular Structure; D011083:Polycyclic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism; D013256:Steroids / Q000138:chemical synthesis* / Q000737:chemistry; D014414:Tungsten / Q000737:chemistry
chemical_list: D011083:Polycyclic Compounds; D013256:Steroids; D014414:Tungsten