Resolution and Rotational Barriers of Quinolinone and Acridone Sulfenamide Derivatives:  Demonstration of the S−N Chiral Axis

Governing higher-order stereogenicity is a long-standing goal in stereoselective catalysis, because it allows to achieve selectivity for more than a twofold number of stereoisomers per stereogenic unit. Current methods warrant control over the power of two stereoisomers and the configurations are routinely assigned using the descriptors ( R ) and ( S ), or related binary codes. In contrast, conformational analysis ranges beyond this dualistic treatment of stereoisomerism, which constitutes an unmet challenge for catalyst stereocontrolled processes. Herein, we now report that sixfold stereogenicity can be governed by stereoselective catalysis. By controlling a configurationally stable stereogenic axis with six large rotational barriers, a catalytic [2+2+2]-cyclotrimerization selectively governs the formation of one out of six stereoisomers with up to 0:0:2:98:0:0 stereocontrol. The underpinnings of conformational analysis and stereoselective catalysis are thereby conceptually reunited. Novel molecular architectures featuring distinct chemical topologies and unexplored chemical designs are anticipated from catalystcontrol over higher-order stereogenicities

Download Full-text

The Nature of S-N Bonding in Sulfonamides and Related Compounds: Insights into π-Bonding Contributions from Sulfur K-Edge XAS

10.26434/chemrxiv.13204985.v1 ◽

2020 ◽

Author(s):

Tulin Okbinoglu ◽

Pierre Kennepohl

Keyword(s):

Density Functional ◽

Chemical Properties ◽

Functional Theory ◽

Rotational Barriers ◽

Td Dft ◽

Nitrogen Bonds ◽

X Ray Absorption ◽

Related Compounds ◽

And Chemical Properties

Molecules containing sulfur-nitrogen bonds, like sulfonamides, have long been of interest due to their many uses and chemical properties. Understanding the factors that cause sulfonamide reactivity is important, yet their continues to be controversy regarding the relevance of S-N π bonding in describing these species. In this paper, we use sulfur K-edge x-ray absorption spectroscopy (XAS) in conjunction with density functional theory (DFT) to explore the role of S<sub>3p</sub> contributions to π-bonding in sulfonamides, sulfinamides and sulfenamides. We explore the nature of electron distribution of the sulfur atom and its nearest neighbors and extend the scope to explore the effects on rotational barriers along the sulfur-nitrogen axis. The experimental XAS data together with TD-DFT calculations confirm that sulfonamides, and the other sulfinated amides in this series, have essentially no S-N π bonding involving S<sub>3p</sub> contributions and that electron repulsion and is the dominant force that affect rotational barriers.

Download Full-text

Conformational stabilities, rotational barriers, and vibrational spectra of 2-pyrrolecarboxaldehyde and 3-pyrrolecarboxaldehyde calculated using density functional theory

Журнал структурной химии ◽

10.26902/jsc_id39178 ◽

2019 ◽

Vol 60 (2) ◽

Keyword(s):

Density Functional Theory ◽

Vibrational Spectra ◽

Density Functional ◽

Functional Theory ◽

Rotational Barriers

Download Full-text

Structural Parameters and Internal Rotational Barriers of tert-Butylammonium Ion: AM1 and ab initio Calculations

Zeitschrift für Naturforschung A ◽

10.1515/zna-1992-1215 ◽

1992 ◽

Vol 47 (12) ◽

pp. 1255-1256

Author(s):

Hiroyuki Ishida ◽

Yoshihiro Kubozono ◽

Setsuo Kashino ◽

Ryuichi Ikeda

Keyword(s):

Ab Initio Calculations ◽

Ab Initio ◽

Internal Rotation ◽

Barrier Height ◽

Structural Parameters ◽

Mo Calculations ◽

Ab Initio Mo Calculations ◽

Rotational Barriers ◽

Ab Initio Mo ◽

Internal Rotational Barriers

Semiempirical and ab initio MO calculations were performed to estimate the structural parameters of tert-butylammonium ion and its potential energies for the internal rotation of the CH3 and NH3+ groups. The barrier height for the rotation of NH3+ was found to be lower than for that of CH3 , corresponding to the C - N bond being longer than the C - C bond.

Download Full-text