Two rigid derivatives of o-allylaniline, namely 8-allyl-2-phenyl-1,2,3,4-tetrahydroquinoline (1b) and 7-(trans-2-cinnamyl)-2-methylindoline (1c), have been chosen as suitable systems to study the potential stereoselectivity of the photocyclization process. Photolysis of 1b leads to a mixture 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 disclose whether the diastereoselectivity could be entropy dependent, photolysis of 1b and 1c has been performed at several temperatures. In both cases, linear relationships have been observed when ln(k(t)/k(c)) (the relative reaction rate constants calculated from the diastereomeric excess) is plotted against the reciprocal temperatures. However, significant entropy-controlled diastereoselectivity has only been found for the photocyclization of 1c to 4. The fluorescence spectra of 1b,c show formation of intramolecular charge-transfer exciplexes, which is in agreement with the proposed excited-state electron-transfer mechanism for photocyclization.

Photolysis of 2-allylaniline (1a) and trans-2-cinnamylaniline (2a) produced mainly the five-or the six-membered ring products 3a or 9a, respectively. Compound 1b, the N-acetyl derivative of 1a, preferentially underwent photo-Fries rearrangement of the anilide moiety, while − in contrast − the analogous compound 2b, derived from 2a, displayed competition between photocyclisation and double-bond isomerisation. The latter process, characteristic of the styrene chromophore, largely predominated in the case of 2c, the Ntrifluoroacetyl derivative of 2a, while the allyl analogue 1c was essentially unreactive. The photochemical behaviour of the cis-cinnamyl compounds 7a and 7b was analogous to that of their trans isomers 2a and 2b, although double bond isomerisation occurred to a smaller extent. Thus, the introduction of electron-withdrawing acyl groups decreased photocyclisation. The nature of the excited states involved in the

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