ChemInform Abstract: Synthesis of Chiral Alkynes Having 2H or Halogen at the Secondary of Tertiary Propargylic Stereogenic Center by Hydrolysis and Halogenolysis of Optically Active Allenyltitaniums Having Axial Chirality.

ChemInform ◽  
2010 ◽  
Vol 29 (37) ◽  
pp. no-no
Author(s):  
D. K. AN ◽  
S. OKAMOTO ◽  
F. SATO
Keyword(s):  
Optically Active ◽  
Axial Chirality ◽  
Stereogenic Center

scholarly journals Trityl-Containing Alcohols—An Efficient Chirality Transmission Process from Inductor to the Stereodynamic Propeller and their Solid-State Structural Diversity

Molecules ◽  
2020 ◽  
Vol 25 (3) ◽  
pp. 707 ◽  
Author(s):  
Sylwia Górczyńska ◽  
Aleksandra Brzdonkiewicz ◽  
Maciej Jelecki ◽  
Agnieszka Czapik ◽  
Bartosz Stasiak ◽  
...  
Keyword(s):  
Crystal Engineering ◽  
Electrostatic Interactions ◽  
Structural Diversity ◽  
Optically Active ◽  
Cascade Process ◽  
Chirality Transfer ◽  
Transmission Process ◽  
Close Proximity ◽  
Cotton Effects ◽  
Stereogenic Center

The cascade process of a dynamic chirality transmission from the permanent chirality center to the stereodynamic triphenylmethyl group has been studied for series of optically active trityl derivatives. The structural analysis, carried out with the use of complementary methods, enabled us to determine the mechanism of chirality transfer. The process of chirality transmission involves a set of weak but complementary electrostatic interactions. The induction of helicity in a trityl propeller is revealed by rising non-zero cotton effects in the area of trityl UV-absorption. The presence of an additional stereogenic center in close proximity to the trityl-containing stereogenic center significantly affects the sign and, to a lesser extent, magnitude of the respective cotton effects. Despite the bulkiness of the trityl, in the crystalline phase, the molecules under study strictly fill the space. In the crystal, molecules form aggregates stabilized by OH•••O hydrogen bonds. However, the presence of two trityl groups precludes formation of OH•••O hydrogen bonding. Additionally, the trityl group seems to be responsible for the formation of the solid solutions by e.g., racemates of trans- and cis-2-tritylcyclohexanol. Therefore, the trityl group acts as a supramolecular protective group, which in turn can be used in the crystal engineering.

Control of Axial Chirality by Planar Chirality Based on Optically Active [2.2]Paracyclophane

2020 ◽  
Vol 26 (65) ◽  
pp. 14871-14877 ◽  
Author(s):  
Genki Namba ◽  
Yuki Mimura ◽  
Yoshitane Imai ◽  
Ryo Inoue ◽  
Yasuhiro Morisaki
Keyword(s):  
Optically Active ◽  
Axial Chirality ◽  
Planar Chirality

Correlation Between Optical Activity and the Helical Molecular Orbitals of Allene and Cumulenes

2020 ◽  
Author(s):  
Marc Hamilton Garner ◽  
Clemence Corminboeuf
Keyword(s):  
Electronic Structure ◽  
Optical Activity ◽  
Optical Rotation ◽  
Molecular Orbitals ◽  
Optically Active ◽  
Electronic Transitions ◽  
Frontier Molecular Orbitals ◽  
Chiral Molecules ◽  
Axial Chirality ◽  
Rotation Dispersion

<div><div><div><p>Helical frontier molecular orbitals (MOs) appear in disubstituted allenes and even-n cumulenes. Chiral molecules are optically active, but while these molecules are single-handed chiral, π-orbitals of both helicities are present. Here we computationally examine whether the optical activity of chiral cumulenes is controlled by the axial chirality or the helicity of the electronic structure. We exploit hyperconjugation with alkyl, silaalkyl, and germaalkyl substituents to adjust the MO helicity without altering the axial chirality. For the same axial chirality, we observe an inversion of the helical MOs contribution to the electronic transitions and a change of sign in the electronic circular dichroism and optical rotation dispersion spectra. While the magnitude of the chiroptical response also increases, it is similar to that of chiral cumulenes without helical π-orbitals. Overall, Helical π-orbitals correlate with the big chiroptical response in cumulenes, but are not a prerequisite for it.</p></div></div></div>

Correlation Between Optical Activity and the Helical Molecular Orbitals of Allene and Cumulenes

2020 ◽  
Author(s):  
Marc Hamilton Garner ◽  
Clemence Corminboeuf
Keyword(s):  
Electronic Structure ◽  
Optical Activity ◽  
Optical Rotation ◽  
Molecular Orbitals ◽  
Optically Active ◽  
Electronic Transitions ◽  
Frontier Molecular Orbitals ◽  
Chiral Molecules ◽  
Axial Chirality ◽  
Rotation Dispersion

<div><div><div><p>Helical frontier molecular orbitals (MOs) appear in disubstituted allenes and even-n cumulenes. Chiral molecules are optically active, but while these molecules are single-handed chiral, π-orbitals of both helicities are present. Here we computationally examine whether the optical activity of chiral cumulenes is controlled by the axial chirality or the helicity of the electronic structure. We exploit hyperconjugation with alkyl, silaalkyl, and germaalkyl substituents to adjust the MO helicity without altering the axial chirality. For the same axial chirality, we observe an inversion of the helical MOs contribution to the electronic transitions and a change of sign in the electronic circular dichroism and optical rotation dispersion spectra. While the magnitude of the chiroptical response also increases, it is similar to that of chiral cumulenes without helical π-orbitals. Overall, Helical π-orbitals correlate with the big chiroptical response in cumulenes, but are not a prerequisite for it.</p></div></div></div>

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