1271-66-5Relevant academic research and scientific papers
Formation of fulvene and dimethylenecyclopentenyl titanium complexes from bis(η5-tetramethylcyclopentadienyl)titanium(IV) precursors
Mach, Karel,Varga, Vojtech,Hanus, Vladimir,Sedmera, Petr
, p. 87 - 95 (1991)
A mixture of isomeric (Me4C5H)(Me3C5(CH2)H)TiMe compounds was obtained by thermally induced methane elimination from (Me4C5H)2TiMe2 at 130 deg C, analogous to the formation of (Me5C5)(Me4C5(CH2))TiMe.The compound (Me5C5)(Me3C5(CH2)2)Ti was newly prepared in 27percent yield by boiling a (Me5C5)2TiCl2-LiAlH4 mixture in toluene, followed by sublimation of the soluble product.By an analogous process, (Me4C5H)(Me2C5(CH2)2H)Ti was obtained in 10percent yield.Neither type of complex was formed by either method from titanocene derivatives with fewer methyl groups at cyclopentadienyl ligands.
Total Synthesis of Bis-anthraquinone Antibiotic BE-43472B
Yamashita, Yu,Hirano, Yoichi,Takada, Akiomi,Takikawa, Hiroshi,Suzuki, Keisuke
, p. 2490 - 2515 (2018)
This is a full account of our synthetic endeavor on the total synthesis of bis-anthraquinone antibiotic BE-43472B, an unusual octacyclic aromatic polyketide with a bis-anthraquinone scaffold. Three key steps enabled a facile access to the anthraquinone unit corresponding to the ABCF rings; (1) cyclo-condensation or -addition of benzonitrile oxides with cyclic enone derivatives, (2) benzoin cyclization for the stereoselective ring fusion with an angular hydroxy group, and (3) pinacol rearrangement for stereoselective installation of the angular aryl group. Other keys for the success include, (4) diastereoselective methylation of a lactol derivative, and (5) late-stage installation of the C3 hydroxy group through stereoselective oxirane ring formation via halohydrin derivatives. Whereas oxidation of the double bond in the enone with an adjacent 1,3-diketone moiety failed, the projected oxidation was achieved with the alkene keeping the isoxazole moiety intact as a 1,3-diketone equivalent. In the racemic total synthesis, X-ray crystal structure analysis of the target was achieved, proving the three-dimensional architecture for the first time. The asymmetric total synthesis was also achieved by exploiting a cycloadduct of the nitrile oxide and the enantiomerically pure cyclohexenone, which was convertible to the common intermediate via dehydrogenation followed by alkoxycarbonylation.
1H and 13C NMR spectroscopic study of titanium(IV) species formed by activation of Cp2TiCl2 and [(Me4C5)SiMe2NtBu]TiCl2 with methylaluminoxane (MAO)
Bryliakov, Konstantin P.,Talsi, Evgenii P.,Bochmann, Manfred
, p. 149 - 152 (2004)
Using 13C and 1H NMR spectroscopy, the products of the reaction of Cp2TiCl2 with methylaluminoxane (MAO) at Al:Ti ratios of 5:1 to 300:1 have been identified as Cp2TiMeCl, Cp2TiMe2, [Cp2TiMe(μ-Cl)Cp2-TiCl]+[Me-MAO]- (II1), [Cp2TiMe(μ-Cl)Cp2TiMe]+[Me-MAO]- (II2), [Cp2TiMe(μ-Me)Cp2TiMe]+[Me-MAO]- (II3), the heterobinuclear ion pair [Cp2Ti(μ-Me)2AlMe2]+[Me-MAO] - (III), and a zwitterion-like intermediate, formulated as Cp2TiMe+←Me-Al-≡MAO (IV). In contrast, [(Me4C5)SiMe2NtBu]TiCl2/M AO gives only zwitterion-like, not heterobinuclear, species.
Azulichlorins and Benzocarbachlorins Derived Therefrom
Noboa, Mario A.,Abusalim, Deyaa I.,Lash, Timothy D.
, p. 11649 - 11664 (2019)
Acid-catalyzed condensation of azulidipyrrane aldehydes with a dihydrodipyrrin carbaldehyde afforded the first examples of azulichlorins. These macrocyclic products were isolated in a monoprotonated form, and the free bases proved to be somewhat unstable. The monocations were strongly diatropic, and proton NMR spectroscopy showed the internal C-H at ca. -2 ppm. Addition of TFA gave the related dications, but these exhibited significantly reduced aromatic ring currents. Reaction of an azulichlorin with tert-butyl hydroperoxide and KOH in dichloromethane/methanol gave a benzocarbachlorin and two related aldehydes. The UV-vis spectrum for the benzocarbachlorin showed a split Soret band at 414 and 430 nm, together with a strong chlorin-like absorption at 684 nm. The proton NMR spectrum indicated that the carbachlorin is strongly aromatic and the internal C-H was observed at -4.64 ppm. Addition of TFA afforded a C-protonated dication with a significantly increased diatropic ring current. The proton NMR spectrum, NICS calculations, and AICD plots indicated that the system favors a 22πelectron delocalization pathway that runs through the fused benzo unit. Addition of TFA to the benzocarbachlorin aldehydes primarily led to the formation of monocations, and the generation of C-protonated dications was no longer favored due to the presence of electron-withdrawing formyl moieties.
A practical and inexpensive one-pot synthesis of bis(indenyl) dimethyltitanium with aqueous workup procedure
Ross, Jan H.,Preuss, Till,Brahms, Christian,Doye, Sven
, p. 118 - 121 (2014)
A simple, reliable, and reproducible procedure for the multi-gram synthesis of highly pure bis(indenyl)dimethyltitanium is presented. The procedure relies on a one-pot conversion of inexpensive indene, methyllithium, and titanium tetrachloride to [Ind2TiMe2] and a convenient and quick aqueous workup protocol. Overall, quantities of several grams of [Ind 2TiMe2] can be synthesized within a few hours. The procedure can also be used for the synthesis of [Cp2TiMe2] from cyclopentadiene, methyllithium, and titanium tetrachloride.
Preparation of (+)-nemorensic acid and approaches to nemorensine using the partial reduction of electron deficient furans
Donohoe, Timothy J.,Guillermin, Jean-Baptiste,Walter, Daryl S.
, p. 1369 - 1375 (2002)
Starting from a commercially available furoic acid, the synthesis of (+)-nemorensic acid is described in nine steps, and in 32% overall yield. Key steps in our sequence are a chiral auxiliary controlled, stereoselective, Birch reduction of 3-methyl-2-furo
New molecular design for blue BODIPYs
Wu, Zhiyuan,Fujita, Hikaru,Magdaong, Nikki Cecil M.,Diers, James R.,Hood, Don,Allu, Srinivasarao,Niedzwiedzki, Dariusz M.,Kirmaier, Christine,Bocian, David F.,Holten, Dewey,Lindsey, Jonathan S.
, p. 7233 - 7242 (2019)
Diverse dihydrodipyrrins are available as precursors in the de novo synthesis of bacteriochlorins and chlorins. Each dihydrodipyrrin contains one pyrrole and one pyrroline (3,4-dihydropyrrole) ring joined at the respective α-positions via a methylene unit as well as a geminal-dimethyl group at one of the pyrroline β-positions. Complexation of the dihydrodipyrrin ligands occurs smoothly upon treatment with Bu2B-OTf or BF3·OEt2 in dichloromethane containing triethylamine at room temperature. Six such dihydrodipyrrinatoboron complexes have been prepared and are examined here. The complexes with -BF2 or -BBu2 absorb in the blue region (λabs ~ 400 nm) and fluoresce (λem ~ 500 nm) with large Stokes shift (~100-150 nm), almost no absorption-fluorescence spectral overlap, and high fluorescence quantum yield (Φf ~ 0.4-0.9). The spectral features are rather insensitive to substituents in the pyrrole nucleus (carboethoxy, bromo, and p-tolyl) and the presence of a 1-naphthalenyl group at the meso-position. In one case examined, the spectral properties including Φf value were almost identical in toluene and acetonitrile. The blue BODIPYs may be useful as broadband photosensitizers upon violet-laser excitation.
ATTRACTANT COMPOSITION FOR THE SPECIES DELOTTOCOCCUS ABERIAE, METHODS FOR THE MONITORING, DETECTION AND/OR CONTROL OF THE PEST
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Paragraph 0045; 0048, (2022/01/12)
The present invention relates to the compound (4,5,5-trimethyl-3-methylenecyclopent-1-en-1-yl)methyl acetate and to an attractant composition for insects of the species Delottococcus aberiae comprising said compound. The present invention also relates to an attractant device for Delottococcus aberiae comprising said compound or said composition, and to a method for the control and/or monitoring of the populations of insects of the species Delottococcus aberiae.
Oxidation Under Reductive Conditions: From Benzylic Ethers to Acetals with Perfect Atom-Economy by Titanocene(III) Catalysis
Funk, Pierre,Richrath, Ruben B.,Bohle, Fabian,Grimme, Stefan,Gans?uer, Andreas
supporting information, p. 5482 - 5488 (2021/02/03)
Described here is a titanocene-catalyzed reaction for the synthesis of acetals and hemiaminals from benzylic ethers and benzylic amines, respectively, with pendant epoxides. The reaction proceeds by catalysis in single-electron steps. The oxidative addition comprises an epoxide opening. An H-atom transfer, to generate a benzylic radical, serves as a radical translocation step, and an organometallic oxygen rebound as a reductive elimination. The reaction mechanism was studied by high-level dispersion corrected hybrid functional DFT with implicit solvation. The low-energy conformational space was searched by the efficient CREST program. The stereoselectivity was deduced from the lowest lying benzylic radical structures and their conformations are controlled by hyperconjugative interactions and steric interactions between the titanocene catalyst and the aryl groups of the substrate. An interesting mechanistic aspect is that the oxidation of the benzylic center occurs under reducing conditions.
Reductive C-O, C-N, and C-S Cleavage by a Zirconium Catalyzed Hydrometalation/β-Elimination Approach
Matt, Christof,K?lblin, Frederic,Streuff, Jan
supporting information, p. 6983 - 6988 (2019/09/09)
A zirconium catalyzed reductive cleavage of Csp3 and Csp2 carbon-heteroatom bonds is reported that makes use of a tethered alkene functionality as a traceless directing group. The reaction is successfully demonstrated on C-O, C-N, and C-S bonds and proposed to proceed via a hydrozirconation/β-heteroatom elimination sequence of an in situ formed zirconium hydride catalyst. The positional isomerization of the catalyst further enables the cleavage of homoallylic ethers and the removal of terminal allyl and propargyl groups.
