TY  - JOUR
A1  - Matic, Aleksandar
A1  - Schlaad, Helmut
T1  - Thiol-ene photofunctionalization of 1,4-polymyrcene
JF  - Polymer international
N2  - 1,4-Polymyrcene was synthesized by anionic polymerization of -myrcene and was subjected to photochemical functionalization with various thiols (i.e. methyl thioglycolate, methyl 3-mercaptopropionate, butyl 3-mercaptopropionate, ethyl 2-mercaptopropionate and 2-methyl-2-propanethiol) using benzophenone/UV light as the radical source. The yield of thiol addition to the trisubstituted double bonds of 1,4-polymyrcene decreased in the order 1 degrees thiol (ca 95%) > 2 degrees thiol (ca 80%) > 3 degrees thiol (<5%), due to the reversibility of the thiol-ene reaction. Remarkably, thiol addition to the side-chain double bonds was 8 - 10 times (1 degrees thiol) or 24 times (2 degrees thiol) faster than to the main-chain double bonds, which can be explained by the different accessibility of the double bonds and steric hindrance. Despite the use of a 10-fold excess of thiol with respect to myrcene units, the thiol-ene addition was accompanied by chain coupling reactions, which in the extreme case of 3 degrees thiol (or in the absence of thiol) resulted in the formation of insoluble crosslinked material. As an example, a methyl-thioglycolate-functionalized 1,4-polymyrcene was saponified/crosslinked to give submicron polyelectrolyte particles in dilute alkaline solution. (c) 2018 Society of Chemical Industry
KW  - polymyrcene
KW  - thiol-ene
KW  - photochemistry
KW  - regioselectivity
Y1  - 2018
U6  - https://doi.org/10.1002/pi.5534
SN  - 0959-8103
SN  - 1097-0126
VL  - 67
IS  - 5
SP  - 500
EP  - 505
PB  - Wiley
CY  - Hoboken
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  - 
TY  - JOUR
A1  - Bauch, Marcel
A1  - Böttcher, Dominique
A1  - Bornscheuer, Uwe T.
A1  - Linker, Torsten
T1  - Enzymatic Cleavage of Aryl Acetates
JF  - ChemCatChem : heterogeneous & homogeneous & bio- & nano-catalysis ; a journal of ChemPubSoc Europe
N2  - Seven enzymes have been screened for the cleavage of aryl acetates. Phenyl and naphthyl acetates react with lipases and esterases, whereas the sterically demanding anthracene acetate gave a conversion only with porcine liver esterase and esterase 2 from Bacillus subtilis (BS2). These two enzymes have been employed on a preparative (0.5 mmol) scale and afforded cleavage products in 91 and 94% yields, even for anthracene acetate. Thus, this method is superior to chemical cleavage with catalytic amounts of sodium methoxide (Zemplen conditions), which gave only low conversions. Finally, regioselectivity has been achieved with an anthracene bisacetate, in which an ethyl group controls the cleavage of the first acetate. This indicates that steric interactions play a crucial role in the enzymatic cleavage of aryl acetates, which might be interesting for future applications or the development of enzyme inhibitors.
KW  - arenes
KW  - enzyme catalysis
KW  - regioselectivity
KW  - steric hindrance
KW  - substituent effects
Y1  - 2016
U6  - https://doi.org/10.1002/cctc.201600678
SN  - 1867-3880
SN  - 1867-3899
VL  - 8
SP  - 2853
EP  - 2857
PB  - Wiley-VCH
CY  - Weinheim
ER  -