94012-65-4Relevant academic research and scientific papers
Novel, stereoselective tricyclization of a dienyne by titanium aryloxide centers
Himes, Richard A.,Fanwick, Phillip E.,Rothwell, Ian P.
, p. 18 - 19 (2007/10/03)
Titanium centers supported by aryloxide ligation mediate the tricyclization of a dienynevia intramolecular insertion of an olefin into the titanium-vinyl bond of a titanacyclopent-2-ene.
Generation and trapping of allene oxides: An approach to chiral, nonracemic α-alkoxyketones
Shipman, Michael,Thorpe, Heidi R.,Clemens, Ian R.
, p. 14265 - 14282 (2007/10/03)
Epoxy mesylates 5 react with a variety of sodium alkoxides to produce the corresponding α-alkoxyketones in good yields. Evidence is presented for the involvement of transient allene oxides in these reactions. Enantiomerically enriched epoxy mesylates (2R,3S)-5a-c were prepared using the Sharpless asymmetric epoxidation reaction as the key step. These precursors rearrange to α-alkoxyketones without significant racemisation under modified reaction conditions (ROK, 18-crown-6, THF, -78°C). The reactions are shown to proceed with stereochemical inversion at the epoxide centre.
Development of a titanocene-catalyzed enyne cyclization/isocyanide insertion reaction
Berk, Scott C.,Grossman, Robert B.,Buchwald, Stephen L.
, p. 8593 - 8601 (2007/10/02)
The first early transition metal-catalyzed enyne cyclization reaction is described. The system converts enyne substrates to bicyclic iminocyclopentenes through the use of 10 mol % of Cp2Ti(PMe3)2 in the presence of a silyl cyanide. Subsequent hydrolysis produces the corresponding bicyclic cyclopentenones in good overall yield. The cyclization reaction is tolerant of polar functional groups such as ethers, amines, and esters and is diastereoselective with certain chiral enyne substrates.
Novel Bicyclization of Enynes and Diynes Promoted by Zirconocene Derivatives and Conversion of Zirconabicycles into Bicyclic Enones via Carbonylation
Negishi, Ei-ichi,Holmes, Steven J.,Tour, James M.,Miller, Joseph A.,Cederbaum, Fredrik E.,et al.
, p. 3336 - 3346 (2007/10/02)
Enynes and diynes react with "ZrCp2" (where Cp = η5-C5H5) generated by treating Cl2ZrCp2 with Mg and HgCl2 or 2 equiv of an alkyllithium, such as n-BuLi, or a Grignard reagent, such as EtMgBr, and can produce in excellent yields zirconabicycles represented by 2 (M = Zr) and 8, respectively.Their protonolysis can provide the corresponding exocyclic alkenes and conjugated dienes 9, respectively.Iodinolysis of 2 (M = Zr) can give the corresponding diiodides in high yields, while carbonylation of 2 (M = Zr) can produce bicyclic enones 3 (Y = O) in moderate to goodyields.Although the bicyclization reaction fails with terminal alkyne containing substrates, various types of substituents on the alkyne moiety, such as alkyl, alkenyl, aryl, trialkylsilyl, and trialkylstannyl groups, can be accommodated.Investigation of the n-BuLi-Cl2ZrCp2 reaction has revealed that is gives first (n-Bu)2ZrCp2 at -78 deg C, which then decomposes to give Cp2Zr(CH2=CHEt), identified as its PMe3 complex 11.The PMe3-stabilized complex reacts with diphenylacetylene to produce a crystalline compound which has been identified as a zirconacyclopropene, 36a.This demonstrated, for the first time, the feasibility of converting alkynes into zirconacyclopropenes.The reaction of preformed, three-membered zirconacycles with alkynes gives five-membered zirconacycles.The reaction of diphenylacetylene is ca. 150 times as fast as that of (E)-stilbene.These results support a mechanism involving formation of a zirconacyclopropene intermediate followed by its intramolecular carbometalation with the alkene moiety of enynes for the Zr-promoted bicyclization of enynes.
