Intramolecular allylation of the azo group of 2-(allylsilyl)azobenzenes and its photocontrol
Pentacoordinate allylsilanes bearing an azobenzene moiety were synthesized and their structures were elucidated. The reaction of allyldifluorosilane (E)-7a with BF3 · OEt2 did not proceed, but (E)-7a was allowed to react with a fluoride ion to give tetrafluorosilicate 8a via intramolecular allyl-migration from the silicon atom onto the azo group. Activation of both the nucleophilic and electrophilic parts by the Si?N interaction was found to be important for promotion of the allyl-migration reaction. The azobenzene moiety of the allylsilane was reversibly isomerized by photoirradiation. The (Z)-7a formed by photoirradiation of (E)-7a is in a tetracoordinate state in contrast to the (E)-7a, and it did not react with a fluoride ion at all under the conditions where (E)-7a reacted quantitatively. The reactivity was successfully controlled without changing any conditions other than the change of the coordination number of the silicon atom induced by photoirradiation.
Reversible photoswitching of the coordination numbers of silicon in organosilicon compounds bearing a 2-(phenylazo)phenyl group
Several organosilicon compounds bearing a 2-(phenylazo)phenyl group were synthesized from the corresponding chlorosilanes and 2-lithioazobenzene prepared by halogen-lithium transmetalation of 2-iodoazobenzene. Their structures were determined by 1/s