D2-symmetric chiral

ENANTIOSELECTIVE EPOXIDATION OF ( >(i-METHYLSTYRENE BY D2-SYMMETRIC CHIRAL TRANS-DIOXORUTHENIUM(VI) PORPHYRINS... 

The asymmetric epoxidation of /i-alkenes and terminal alkenes proved to be more difficult, though a recent finding, describing the use of a modified salen complex to epoxidize ( )-0-methylstyrene to form the corresponding epoxide in 83% ee, represents another important step forward. Alternatively, chiral (D2-symmetric) porphyrins have been used, in conjunction with ruthenium or iron, for efficient asymmetric oxidation of trans- and terminal alkenes[92]. 

In the second step, the chiral D2 -symmetric structure 51-D2 is the kinetic product, which may be irreversibly converted to its achiral C2h-symmetric diastereomer 51-C2h (Fig. 15.19). Mechanistic studies indicated that oxidation of achiral diamine... 

Recently, Wong and coworkers reported a series of rod-like D2 -symmetric, enantiopure molecules, based on Pt(II) complexes of homochiral tetraphenylenes (R)-63, (R)-64 and (R)-BINAP. The highest homolog of such chiral rod had an estimated length of 4.8 nm [112]. 

Absolute Configuration in Two Molecules with Chiral Axes by Vibrational Circular Dichroism A C2-symmetric Annelated Heptafhiophene and a D2-symmetric Dimer of 1,T-Binaphfhyl, J. Phys. Chem. A 2003, 107, 7692-7696. 

A. Rajca, H. Wang, P. Bolshov, S. Rajca, Greek Cross Dodecaphenylene Sparteine-mediated Asymmetric Synthesis of Chiral D2-Symmetric Jt-Conjugated Tetra-o-phenylenes, Tetrahedron 2001,... 

Fig. 28.3 A D2 symmetric octaalkyl substituted porphyrin as chirality sensor and memory. (Reproduced with permission from Chemical and Engineering News, 1997.)...

Furusho, Y., Kimurat, T., Mizuno, Y. and Ada, T. (1997) Chirality-memory molecule a D2-symmetric fully substituted porphyrin as a conceptually new chirality sensor. J. Am. Chem. Soc. 119 5267-5268. 

After the potential occurrence of chiral fullerenes and nanotubes could be inferred from the structural principles of fullerenes [35-37], these carbon spheroids became of practical interest for the first time with the isolation and characterization of D2-symmetrical Cyg by Diederich and coworkers [1]. Obeying the IPR (isolated pentagon rule) and having a closed electronic shell with a fully occupied HOMO (highest occupied molecular orbital), its structure had been theoretically predicted shortly before to be the only stable form of [76]fuUerene... 

In a continuation of the study on chiral tetraphenylenes, Wong reported a series of rod-like, D2-symmetric, enantiopure molecules and chiral hehcal macrocycles based on metal coordination with homochiral tetraphenylenes [48, 51]. From optically pure tetrahydroxytetraphenylene 98, two useful chiral budding blocks, namely, l,8,9,16-tetrakis(diphenylphosphino)tetraphenylene (104) and 1,8,9,16-tetraethynyltetraphenylene (105), were synthesized (Scheme 5.24). 

Simeonov, K. S., Amsharov, K. Y, 8c Jansen, M. (2007). Connectivity of the chiral D2-symmetric isomer of Cyg through a crystal-structure determination CygClis TiCU. Angewandte Chemie-International Edition, 46(44), 8419-8421. 

A single calixarene consisting of two different phenolic units A and B in alternating order ABAB is (time averaged) C2v-symmetric. Consequently, its homodimer is chiral (D2-symmetry) without the directionality of the hydrogen-bonded belt, just by... 

If the spirobifluorene core in low-molecular-weight compounds is totally symmetrically substituted, the point group of the molecules is D2d comprising an S4 improper rotation axis, and chirality cannot be observed. The symmetry can be broken by bridging the 2 and 2 positions, and the 7 and 7 positions, respectively. Resulting chiral molecules with the point group D2, the vespirenes (Fig. 48), have been synthesized and characterized by Haas and Prelog [25]. 

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