TADDOLs, which contain two adjacent diarylhydroxymethyl groups in a trans relationship on a 1,3-dioxolane ring, can be prepared from acetals or ketals of tartrate esters by reaction of the latter with aromatic Grignard reagents. They are extraordinarily versatile chiral auxiliaries. Here, a historical review of the subject is followed by discussion of the preparation of TADDOLs and analogous systems, including TADDOLs with N-, P-, O-, and S-heteroatom ligands appropriate for metals. Crystal structure analysis reveals that the heteroatoms on the diarylmethyl groups are almost always in close proximity to each other, joined together by H-bonds, and predisposed to form chelate complexes in which the metallic centers reside in propeller-like chiral environments. Applications of TADDOL derivatives in enantioselective synthesis extend from utilization as stoichiometric chiral reagents or in Lewis acid mediated reactions, to roles in catalytic hydrogenation and stereoregular metathesis polymerization. Derivatives and complexes based on the following metals have so far been investigated: Li, B, Mg, Al, Si, Cu, Zn, Ce, Ti, Zr, Mo, Rh, Ir, Pd, Pt. The number of stereoselective reactions already accomplished with TADDOLs is correspondingly large. It is also easy to prepare TADDOL derivatives that are readily polymerizable and graftable, and to transform them into immobilized solid-phase catalysts. The result is catalysts, simply or dendritically immobilized in polystyrene or on silica gel and characterized by unexpected stability even after multiple use in titanium TADDOLate mediated reactions. TADDOLs show further unusual characteristics that make them useful for applications in material science and supramolecular chemistry: they are the most effective doping agents known for phase transformations of achiral (nematic) into chiral (cholesteric) liquid crystals. The TADDOL OH group that is not involved in intramolecular H-bonding shows a strong tendency to associate intermolecularly with H-bond acceptors. In the process of crystallization this leads, enantioselectively, to the formation of inclusion compounds that lend themselves to the separation of racemic mixtures not otherwise suited to the classical method of crystallization through diastereomeric salts. The high melting points of TADDOLs even make possible the resolution of racemates by distillation! Host-guest compounds formed between TADDOLs and achiral partners can serve as platforms for enantioselective photoreactions. It seems safe to predict that many more applications will be discovered for the TADDOLs and their derivatives. Supporting information for this article is available on the WWW under http://www.angewandte.com or from the author.

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TADDOLs, Their Derivatives, and TADDOL Analogues: Versatile Chiral Auxiliaries

Two chromone derivatives C11H10O3 (1) and C11H10O2 (2) have been synthesized and characterized by X-ray structural studies with a detailed analysis of the Hirshfeld surfaces and fingerprint plots facilitating a comparison of intermolecular interactions in building different supramolecular architectures. The title compounds are associated through π–stacking interactions and the linear stacking of π–π forces can be thought as the influencing agent for the organization of the title compounds into hydrogen bonded supramolecular layers and are responsible as well for the strengthening of the molecular assembly. Investigation of the intermolecular interactions and crystal packing via Hirshfeld surface analysis reveals that more than two-thirds of the close contacts are associated with weak interactions. The fingerprint plots demonstrate that these weak interactions are important for both local and crystal packing. A comparison of the Hirshfeld surface in the compounds with similar substituted chromone derivatives in the Cambridge Structural Database (CSD) has been presented.

Use of π–π forces to steer the assembly of chromone derivatives into hydrogen bonded supramolecular layers: crystal structures and Hirshfeld surface analyses

Phosphane–boranes: synthesis, characterization and synthetic applications

TADDOLe, ihre Derivate und Analoga – vielseitige chirale Hilfsstoffe

Structural bases for the inhibition of aldose reductase by phenolic compounds.

C17H14O4, M(r) = 282.30, monoclinic, P2(1)/c, a = 12.498 (4), b = 9.490 (2), c = 12.184 (2) angstrom, beta = 107.87 (2)degrees, V = 1375.4 (6) angstrom 3, Z = 4, D(x) = 1.36 g cm-3, Cu K-alpha, lambda = 1.54178 angstrom, mu = 7.98 cm-1, F(000) = 592, T = 291 K, R = 0.042 for 1848 observed reflections. The benzopyran heterocycle is planar within experimental errors (max. deviation from the best mean plane through the ten atoms 0.031 angstrom). The dihedral angle between the heterocycle and the phenyl ring is 23.5 (5)degrees. The methoxy groups are nearly coplanar with their aromatic rings (torsion angles about C(arom)-O are 4-6-degrees).

Structure of 7-methoxy-2-(2-methoxyphenyl)-4h-1-benzopyran-4-one (2',7-dimethoxyflavone)

C66H68O10, M(r) = 1021.2, orthorhombic, P2(1)2(1)2(1), a = 11.038(4), b = 14.183(6), c = 18.358(7)Angstrom, V = 2874(2)Angstrom(3), Z = 2, D-x = 1.18g.cm(-3), MoK alpha radiation (lambda = 0.71069 Angstrom). The final R indice is 0.080 for 1033 observed reflections

Crystal-structure of (4r,5r)-2-ethoxy-4,5-bis[(1-methoxy-1-phenyl)benzyl]-1,3-dioxolane

(2R,5S)-2-(2-Methoxyphenyl)-3-oxa-1-aza-2-phos-phabicyclo[3.3.0]octane(P-B)borane, C12H19BNO2P, is one of a series of new chiral oxazaphospholidine-borane complexes used as catalysts in the enantioselective borane reduction of ketones. The structure and the absolute configuration about the P atom were determined.

A (2R,5S)-2-o-anisyl-3-oxa-1-aza-2-phosphabicyclo[3.3.0]octane–borane complex

C20H23NO, Mr = 293.39, monoclinic, C2/c, a = 19.541(2), b = 7.159(1), c = 24.147(2)A, β = 92.65(1), V = 3374.4(5)A3, Z = 8, Dx = 1.16g.cm−3, CuKα radiation (λ = 1.54178A). The final R indice is 0.055 for 2416 observed reflections.

Crystal Structure of (2r*,3s*)‐n,n,2‐Trimethyl‐2,3‐Diphenylpent‐4‐Enamide

(I), C13H24O3S, M(r) = 260.4, orthorhombic, P2(1)2(1)2(1), a = 11.737 (2), b = 21.244 (4), c = 22.932 (3) angstrom, V = 5717.9 (1.4) angstrom 3, Z = 16, D(x) = 1.21 g cm-3, Cu K-alpha, lambda = 1.54178 angstrom, mu = 19.23 cm-1, F(000) = 2272, T = 291 K, R = 0.063 for 3245 observed reflections. (II), C14H26O3S, M(r) = 274.4, orthorhombic, P2(1)2(1)2(1), a = 8.651 (2), b = 11.920 (4), c = 14.256 (3) angstrom, V = 1470.1 (6) angstrom 3, Z = 4, D(x) = 1.24 g cm-3, Cu K-alpha, lambda = 1.54178 angstrom, mu = 18.95 cm-1, F(000) = 600, T = 291K, R = 0.056 for 1491 observed reflections. Regio- and stereo-controlled three-carbon annulation is a valuable tool for the synthesis of natural products. In a previous communication [De Lombaert, Nemery, Roekens, Carretero, Kimmel & Ghosez (1986). Tetrahedron Lett. 27, 5099-5102] we reported a novel two-step sequence yielding highly functionalized, fused cyclopentanes. The title compounds are being used to develop an enantioselective version, and were synthesized efficiently in optically pure, crystalline form from (+)-camphor. X-ray crystallography confirmed the stereochemistries shown for (I) and (II).

Structures of (2s,3r)-exo-1,7,7-trimethyl-3-propylsulfonylbicyclo[2.2.1]heptan-2-ol (i) and (2s,3r)-exo-1,3,7,7-tetramethyl-3-propylsulfonylbicyclo[2.2.1]heptan-2-ol (ii)

J. Feneau‐Dupont

Papers

Structure of 7-methoxy-2-(2-methoxyphenyl)-4h-1-benzopyran-4-one (2',7-dimethoxyflavone)

Crystal-structure of (4r,5r)-2-ethoxy-4,5-bis[(1-methoxy-1-phenyl)benzyl]-1,3-dioxolane

A (2R,5S)-2-o-anisyl-3-oxa-1-aza-2-phosphabicyclo[3.3.0]octane–borane complex

Crystal Structure of (2r,3s)‐n,n,2‐Trimethyl‐2,3‐Diphenylpent‐4‐Enamide

Structures of (2s,3r)-exo-1,7,7-trimethyl-3-propylsulfonylbicyclo[2.2.1]heptan-2-ol (i) and (2s,3r)-exo-1,3,7,7-tetramethyl-3-propylsulfonylbicyclo[2.2.1]heptan-2-ol (ii)