Stereocontrol within confined spaces: enantioselective photooxidation of enecarbamates inside zeolite supercages.
Dye-exchanged Y zeolite is shown to be an effective medium to control the stereoselectivity in the photooxygenation of chiral oxazolidinone-functionalized Z/E-1 enecarbamates. An enantioselectivity (ee) as high as 80% was observed in the methyldesoxybenzoin (MDB) product, obtained in the methylene-blue-exchanged NaY zeolite at room temperature. The efficacy of the asymmetric induction in the MDB product depends on the Z/E geometry of the alkene, the Z-isomer being more effective than the corresponding E-isomer. The stereoselectivity is rationalized in terms of conformational effects through cationic interactions between the zeolite and the substrate.
Sivaguru
J
J
Department of Chemistry and Department of Chemical Engineering, Columbia University, 3000 Broadway, Mail Code 3119, New York, NY 10027, USA.
Poon
Thomas
T
Franz
Roberto
R
Jockusch
Steffen
S
Adam
Waldemar
W
Turro
Nicholas J
NJ