109005-04-1Relevant articles and documents
A Chemical, Spectroscopic, and Theoretical Assessment of the Lewis Acidity of LiClO4 in Diethyl Ether
Pagni, Richard M.,Kabalka, George W.,Bains, Satinder,Plesco, Miechelle,Wilson, Jennifer,Bartmess, John
, p. 3130 - 3133 (1993)
Moderate diastereoselectivity is observed in the reaction of cyclopentadiene with dimethyl maleate and optically active dimenthyl fumarate in LiClO4/diethyl ether.Moderate regioselectivity is also seen in the reaction of isoprene and methyl acrylate in the same medium.NMR experiments and MNDO calculations, in conjunction with published work on Li(1+) in the gas phase, demonstrate that the strong, intrinsic Lewis acidity of Li+ is moderated in ether by complexation to the solvent and the counterion.
Enantioselective Construction of Modular and Asymmetric Baskets
Badji?, Jovica D.,Finnegan, Tyler J.,Gunther, Michael J.,Pavlovi?, Radoslav Z.,Wang, Xiuze
supporting information, p. 25075 - 25081 (2021/10/25)
The precise positioning of functional groups about the inner space of abiotic hosts is a challenging task and of interest for developing more effective receptors and catalysts akin to those found in nature. To address it, we herein report a synthetic methodology for preparing basket-like cavitands comprised of three different aromatics as side arms with orthogonal esters at the rim for further functionalization. First, enantioenriched A (borochloronorbornene), B (iodobromonorbornene), and C (boronorbornene) building blocks were obtained by stereoselective syntheses. Second, consecutive A-to-B and then AB-to-C Suzuki–Miyaura (SM) couplings were optimized to give enantioenriched ABC cavitand as the principal product. The robust synthetic protocol allowed us to prepare (a) an enantioenriched basket with three benzene sides and each holding either tBu, Et, or Me esters, (b) both enantiomers of a so-called “spiral staircase” basket with benzene, naphthalene, and anthracene groups surrounding the inner space, and (c) a photo-responsive basket bearing one anthracene and two benzene arms.
Preparation and Structural Analysis of Several New α,α,α',α'-Tetraaryl-1,3-dioxolane-4,5-dimethanols (TADDOL's) and TADDOL Analogs, Their Evaluation as Titanium Ligands in the Enantioselective Addition of Methyltitanium and Diethylzinc Reagents to Benzaldehyde, and Refinement of ...
Ito, Yoshio N.,Ariza, Xavier,Beck, Albert K.,Bohac, Andrej,Ganter, Camille,et al.
, p. 2071 - 2110 (2007/10/02)
Preparation and screening of twenty new ligands, all analogs of α,α,α',α'-tetraaryl-1,3-dioxolane-4,5-dimethanol (TADDOL), for the Ti-catalyzed asymmetric addition of methyltri(isopropoxy)titanium and diethylzinc to benzaldehyde are described.These ligands have the dioxolane ring of the TADDOL's replaced by cyclobutane, cyclopentane, cyclohexene, cyclohexane, bicycloheptene and -heptane and bicyclooctene and -octane moieties; several have H-atoms or alkyl groups in place of the aryl groups, and nine of them have C2 symmetry.X-Ray crystallography and molecular mechanics are used to analyze the structure of the ligands, and two structural features appear to correlate with selectivity: i) the torsion angle for the chelating O-atom and the ortho-C-atom of the axial Ph group (a small, ca. 19 deg, angle is optimum, Fig. 8) and ii) the "degree of perpendicularity" of the axial Ph group (Fig. 9).Competition experiments indicate that TADDOL 1a catalyzes both the methyltitanium and diethylzinc additions >/= 50 times faster than the related dioxolane analogs 12a, 12c, and 12e (Scheme 7), indicating that both axial and equatorial aryl groups (see Footnote 6) are necessary for ligand-accelerated catalysis of these reactions.A refined mechanistic hypotesis is presented (Fig. 10) to explain the selectivities observed for these new ligands.Our analysis suggests that a combination of structural features appear necessary for good catalytic efficiency and high selectivity.These features, especially the rather subtle conformational effects, appear to be optimized (among the ligands tested) in the TADDOL's.
