TY  - JOUR
A1  - Fudickar, Werner
A1  - Linker, Torsten
T1  - Imaging by sensitized oxygenations of photochromic anthracene films
BT  - Examination of effects that improve performance and reversibility
JF  - Chemistry - a European journal
N2  - The aliphatic anthracene compound 1 and the oligomeric anthracene 2 were synthesized. Thin films of 1 and 2 mixed with the sensitizers tetraphenylporphyrin (TPP) and methylene blue (MB) were irradiated with visible light in air. Upon formation of singlet oxygen, the anthracene units were converted quantitatively to the corresponding endoperoxides. Heating of the irradiated samples afforded the parent anthracenes with high yields. Here, we demonstrate that the kinetics and reversibility of this reaction strongly depend on the microenvironment of the anthracene groups in the two compounds. The photooxidation of thin films of I is accompanied by interesting changes in the morphology of the film and allows the first application of 1 as a nondestructive negative-tone photo-resist for lithography and as an oxidizing ink. The morphology of 2 remained unchanged after photooxidation as a result of the stabilizing oligomer backbone. This stabilizing effect significantly improves the photochromic performance of 2. The reversibility of the photooxidation is very high (> 90%) for oligomeric films of 2 after several cycles of irradiation and beating. Decomposition of the anthracene and a loss of the activity of the sensitizer diminish slightly the performance of the monomeric species.
KW  - anthracenes
KW  - lithography
KW  - photochromism
KW  - singlet oxygen
KW  - thin films
Y1  - 2006
U6  - https://doi.org/10.1002/chem.200600387
SN  - 0947-6539
VL  - 12
SP  - 9276
EP  - 9283
PB  - WILEY‐VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Fudickar, Werner
A1  - Vomdran, Katja
A1  - Linker, Torsten
T1  - Auxiliary controlled singlet-oxygen ene reactions of cyclohexenes
JF  - Tetrahedron
N2  - The photooxygenation of homochiral cyclohexene ketals, which are easily available from 2-cyclohexenone and L-tartrates, affords hydroperoxides and after reduction the corresponding allylic alcohols in good yields and high regioselectivities. This can be rationalized by electronic repulsions in a perepoxide intermediate and provides evidence for unfavorable 1,3 diaxial interactions with a dioxolane oxygen atom. Only low stereoselectivities were observed, due to the flexibility of the cyclohexene ring. However, the diastereomers could be separated and after cleavage of the auxiliary, 4-hydroxy-2-cyclohexen-1-one was isolated in enantiomerically pure form, which can serve as a building block for natural product synthesis.
KW  - singlet oxygen
KW  - auxiliary control
KW  - regioselectivity
KW  - stereoselectivity
Y1  - 2006
U6  - https://doi.org/10.1016/j.tet.2006.07.104
SN  - 0040-4020
VL  - 62
IS  - 46
SP  - 10639
EP  - 10646
PB  - Elsevier
CY  - Oxford
ER  -