5549-09-7Relevant articles and documents
Murahashi et al.
, p. 4197 (1973)
Vinyl Carbocations Generated under Basic Conditions and Their Intramolecular C-H Insertion Reactions
Wigman, Benjamin,Popov, Stasik,Bagdasarian, Alex L.,Shao, Brian,Benton, Tyler R.,Williams, Chloé G.,Fisher, Steven P.,Lavallo, Vincent,Houk,Nelson, Hosea M.
supporting information, p. 9140 - 9144 (2019/06/08)
Here we report the surprising discovery that high-energy vinyl carbocations can be generated under strongly basic conditions, and that they engage in intramolecular sp3 C-H insertion reactions through the catalysis of weakly coordinating anion salts. This approach relies on the unconventional combination of lithium hexamethyldisilazide base and the commercially available catalyst, triphenylmethylium tetrakis(pentafluorophenyl)borate. These reagents form a catalytically active lithium species that enables the application of vinyl cation C-H insertion reactions to heteroatom-containing substrates.
Cycloisomerization and [2 + 2]cyclodimerization of 1,5-cyclooctadiene catalyzed with the Ni(COD)2/BF3·OEt2 system
Saraev,Kraikivskii,Matveev,Bocharova,Petrovskii,Zelinskii,Vilms,Klein, Hans-Friedrich
scheme or table, p. 231 - 238 (2010/05/12)
The catalytic system Ni(COD)2/BF3·OEt2 has been studied in conversions of 1,5-cyclooctadiene under argon and ethylene atmosphere. It has been demonstrated that the catalytic system formed under argon exhibits a high effectiveness in cycloisomerization of 1,5-COD surpassing in this characteristic all known nickel complex catalysts (selectivity to bicyclo-[3.3.0]-octene-2 is up to 99.5% at 100% conversion). In the case of ethylene atmosphere the system produces mainly dimers (yield of cyclodimers above 70%). It has been shown that the catalytic system Ni(COD)2/BF3·OEt2 has the feature of "a living catalyst" consisting in resuming the initial activity with a new portion of 1,5-COD added when the monomer was fully exhausted. The main and side products of the 1,5-COD conversion have been identified with GC-MS and preparative liquid chromatography combined with NMR and IR spectroscopy. Based on EPR and IR spectroscopic data a mechanism for the catalytic performance of the Ni(COD)2/BF3·OEt2 system in argon or ethylene atmospheres is suggested. It has been shown that Ni(0) is oxidized by the Lewis acid to Ni(I) which is stabilized by substrate molecules in a mononuclear form without involvement of conventional organoelement entities. Three sorts of paramagnetic nickel species have been found: ionic complexes containing π-coordinated COD ligands; ionic complexes σ-bonded to COD; complexes as intimate pairs with BF4- counter ions. A mechanism for the catalytic conversion of 1,5-cyclooctadiene is proposed.
Carbacyclin compounds; pharmaceutical compositions and method of use
-
, (2008/06/13)
Compounds of formula (Ic): STR1 having valuable platelet-aggregation inhibitory activities useful for the prophylaxis and treatment of such diseases as thrombosis and pharmaceutical compositions containing said compounds.