Uc. Yoon et al., A solvent effect that influences the preparative utility of N-(silylalkyl)phthalimide and N-(silylalkyl)maleimide photochemistry, J ORG CHEM, 64(12), 1999, pp. 4411-4418
The photochemistry of selected N-silylalkyl-substituted phthalimides and ma
leimides has been investigated with the aim of exploring the generality and
preparative consequences of an intriguing solvent effect on excited-state
reaction chemoselectivities and quantum efficiencies. An example of this ef
fect is found in the photochemistry of N-[(trimethylsilyl)butyl]phthalimide
10, where irradiation in MeCN leads to production of a mixture of four pro
ducts that arise by excited-state intramolecular hydrogen-atom abstraction.
In contrast, the benzoindolizidine 15 is the sole product produced by a si
ngle electron transfer (SET)-desilylation pathway upon irradiation of 10 in
35% H2O-MeCN. Another example of this solvent effect is found in the photo
chemistry of the N-silylpropyl-maleimide 17. Irradiation in MeCN results in
the production of the 2+2-dimer 19 whereas the pyrrolizidine 18 is generat
ed exclusively by irradiation of 17 in 35% H2O-MeCN. The results of fluores
cence and triplet sensitization experiments suggest that the solvent effect
has multiple sources including the control of the nature, reactivity, and
intrinsic lifetimes of singlet and triplet excited states of the phthalimid
e and maleimide systems. The exploratory studies have clearly demonstrated
the generality of this solvent effect and how it can be used to enhance the
preparative utility of the photochemistry of N-(silylalkyl)phthalimides an
d N-(silylalkyl)maleimides.