TY  - JOUR
A1  - Wentrup, Curt
A1  - Koch, Rainer
A1  - Kleinpeter, Erich
T1  - Twisted C=C Double Bonds with Very Low Rotational Barriers in Dioxanediones and Isoxazolones Determined by Low-Temperature Dynamic NMR Spectroscopy and Computational Chemistry
JF  - European journal of organic chemistry
KW  - NMR spectroscopy
KW  - Twisted double bonds
KW  - Push-pull effect
KW  - Density functional calculations
Y1  - 2016
U6  - https://doi.org/10.1002/ejoc.201600931
SN  - 1434-193X
SN  - 1099-0690
SP  - 4985
EP  - 4990
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Storch, Golo
A1  - Maier, Frank
A1  - Wessig, Pablo
A1  - Trapp, Oliver
T1  - Rotational Barriers of Substituted BIPHEP Ligands: A Comparative Experimental and Theoretical Study
JF  - European journal of organic chemistry
N2  - The interconversion barriers of 14 different 3,3- and 5,5-disubstituted tropos BIPHEP [2,2-bis(diphenylphosphino)-1,1-biphenyl] and BIPHEP(O) [2,2-bis(diphenylphosphoryl)-1,1-biphenyl] ligands were investigated by enantioselective dynamic high performance liquid chromatography (DHPLC) and DFT calculations using the B3LYP/6-31G* and M06-2X/6-31G* levels of theory. The experimentally determined enantiomerization barriers varied from 86.8 to 101.4 kJmol(-1) and were found to be in excellent agreement with the calculated data. The root-mean-square deviations are 7.3 kJmol(-1) for the B3LYP functional and 11.3 kJmol(-1) for the M06-2X method.
KW  - Rotational barriers
KW  - Density functional calculations
KW  - Enantioselectivity
KW  - P ligands
KW  - Biaryls
KW  - Liquid chromatography
Y1  - 2016
U6  - https://doi.org/10.1002/ejoc.201600836
SN  - 1434-193X
SN  - 1099-0690
VL  - 22
SP  - 5123
EP  - 5126
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Wessig, Pablo
A1  - Matthes, Annika
A1  - Schilde, Uwe
A1  - Kelling, Alexandra
T1  - Asymmetric synthesis of (1,5)Naphthalenophanes by Dehydro-Diels-Alder reaction
JF  - European journal of organic chemistry
N2  - An asymmetric variant of the dehydro-Diels-Alder (DDA) reaction has been developed and applied in the atropselective synthesis of various (1,5)naphthalenophanes. Whereas the suitability of the photochemically induced DDA (PDDA) was limited, the thermally induced DDA provided the desired product, depending on the chiral auxiliary used and the length of the linker, with nearly perfect stereoselectivity. Furthermore, the mechanism of the DDA was investigated by means of DFT calculations, and a stepwise mechanism involving 1,4-biradicals was suggested.
KW  - Synthetic methods
KW  - Macrocycles
KW  - Cyclophanes
KW  - Atropisomerism
KW  - Chiral auxiliaries
KW  - Density functional calculations
Y1  - 2013
U6  - https://doi.org/10.1002/ejoc.201201594
SN  - 1434-193X
IS  - 11
SP  - 2123
EP  - 2129
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Dzambaski, Zdravko
A1  - Markovic, Rade
A1  - Kleinpeter, Erich
A1  - Baranac-Stojanovic, Marija
T1  - 2-Alkylidene-4-oxothiazolidine S-oxides - synthesis and stereochemistry
JF  - Tetrahedron
N2  - A series of 5-unsubstituted and 5-substituted 2-alkylidene-4-oxothiazolidine-S-oxides were synthesized by the sulfur-oxidation with m-CPBA. The stereochemistry of 5-substituted sulfoxides was determined by means of NMR spectroscopy and DFT theoretical calculations. It was found that the thermodynamically less stable anti-isomer was initially formed in the course of the oxidation, but it underwent epimerization to the mixture enriched in the more stable syn-isomer, during the work-up process. The higher stability of syn-isomers is ascribed to the stronger hyperconjugative sigma(C-H)->sigma*(S-O) interaction versus the weaker sigma(C-C)->sigma*(S-O) delocalization in their anti-counterparts and to the existence of intramolecular 1,5-CH center dot center dot center dot C hydrogen bonds.
KW  - 2-Alkylidene-4-oxothiazolidine
KW  - Sulfoxide
KW  - Diastereoselectivity
KW  - Density functional calculations
KW  - CH center dot center dot center dot O hydrogen bonds
Y1  - 2013
U6  - https://doi.org/10.1016/j.tet.2013.05.087
SN  - 0040-4020
VL  - 69
IS  - 31
SP  - 6436
EP  - 6447
PB  - Elsevier
CY  - Oxford
ER  -