32223-12-4Relevant articles and documents
Demystifying Cp2Ti(H)Cl and Its Enigmatic Role in the Reactions of Epoxides with Cp2TiCl
Gordon, Jonathan,Hildebrandt, Sven,Dewese, Kendra R.,Klare, Sven,Gans?uer, Andreas,Rajanbabu,Nugent, William A.
, p. 4801 - 4809 (2019/01/08)
The role of Cp2Ti(H)Cl in the reactions of Cp2TiCl with trisubstituted epoxides has been investigated in a combined experimental and computational study. Although Cp2Ti(H)Cl has generally been regarded as a robust species, its decomposition to Cp2TiCl and molecular hydrogen was found to be exothermic (ΔG = -11 kcal/mol when the effects of THF solvation are considered). In laboratory studies, Cp2Ti(H)Cl was generated using the reaction of 1,2-epoxy-1-methylcyclohexane with Cp2TiCl as a model. Rapid evolution of hydrogen gas was demonstrated, indicating that Cp2Ti(H)Cl is indeed a thermally unstable molecule, which undergoes intermolecular reductive elimination of hydrogen under the reaction conditions. The stoichiometry of the reaction (Cp2TiCl:epoxide = 1:1) and the quantity of hydrogen produced (1 mol per 2 mol of epoxide) is consistent with this assertion. The diminished yield of allylic alcohol from these reactions under the conditions of protic versus aprotic catalysis can be understood in terms of the predominant titanium(III) present in solution. Under the conditions of protic catalysis, Cp2TiCl complexes with collidine hydrochloride and the titanium(III) center is less available for "cross-disproportionation" with carbon-centered radicals; this leads to byproducts from radical capture by hydrogen atom transfer, resulting in a saturated alcohol.
Unified synthesis of eudesmanolides, combining biomimetic strategies with homogeneous catalysis and free-radical chemistry
Barrero, Alejandro F.,Rosales, Antonio,Cuerva, Juan M.,Oltra, J. Enrique
, p. 1935 - 1938 (2007/10/03)
(Matrix presented) A general procedure for the synthesis of both 12,6- and 12,8-eudesmanolides has been developed. The key step is the titanocene-catalyzed radical cyclization of accessible epoxygermacrolides. The novel reagent 2,4,6-trimethyl-1-trimethylsilylpyridinium chloride, both compatible with oxiranes and capable of regenerating Cp2TiCl 2 from Cp2Ti(Cl)H and Cp2Ti(Cl)OAc, played an important role in the catalytic cycle leading to exocyclic alkenes.
Guaianolides as immunomodulators. Synthesis and biological activities of dehydrocostus lactone, mokko lactone, eremanthin, and their derivatives
Yuuya, Saori,Hagiwara, Hisahiro,Suzuki, Toshio,Ando, Masayoshi,Yamada, Atsushi,Suda, Kouji,Kataoka, Takao,Nagai, Kazuo
, p. 22 - 30 (2007/10/03)
The naturally occurring guaianolides, namely mokko lactone (1), dehydrocostus lactone (2), eremanthin (3), and related guaianolides, 16, 17, 21, 22, 28-31, 33, 36, 37, and 39, have been synthesized starting from l-α- santonin in an effort to examine their structure-activity relationship as inhibitors of the killing function of cytotoxic T lymphocytes (CTL) and the induction of intercellular adhesion molecule-1 (ICAM-1). It was observed during the present study that the guaianolides possessing an α-methylene γ- lactone moiety, i.e., 2, 3, 30, 33, 37, and 39, exhibited significant inhibitory activity toward the killing function of CTL and the induction of ICAM-1.
