| Abstract
| - Two rigid derivatives of o-allylaniline, namely8-allyl-2-phenyl-1,2,3,4-tetrahydroquinoline (1b) and 7-(trans-2-cinnamyl)-2-methylindoline (1c), have been chosen assuitable systems to study the potential stereoselectivity ofthe photocyclization process. Photolysis of 1b leads to amixture of diastereomeric lilolidines 4 (trans/cis), while 1cproduces a mixture of 4 (trans/cis) and the tetrahydropyrrolo[3,2,1-hi]indole derivatives 5 (trans/cis). To disclosewhether the diastereoselectivity could be entropy dependent,photolysis of 1b and 1c has been performed at severaltemperatures. In both cases, linear relationships have beenobserved when ln(kt/kc) (the relative reaction rate constantscalculated from the diastereomeric excess) is plotted againstthe reciprocal temperatures. However, significant entropy-controlled diastereoselectivity has only been found for thephotocyclization of 1c to 4. The fluorescence spectra of 1b,cshow formation of intramolecular charge-transfer exciplexes,which is in agreement with the proposed excited-stateelectron-transfer mechanism for photocyclization.
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