PHOTOADDITION OF STYRENE ON CERTAIN BETA- POLYKETONES

The irradiation of 1,5-diphenylpentane-1,3,5-trione 1 and 1-phenylhexa ne-1,3,5-trione 2 at lambda > 290 nm with styrene gives, products of d ouble photo-addition : 1,2,6,9-tetraphenylnonane-1,5,9-trione 5 and 1, 2,6-triphenyldecane-1,5,9-trione 6, respectively. Under the same condi tions with lambda > 220 nm, 2-(3-oxo-3-phenylpropionyl)indane-1,3-dion e 3 and 2-(3-oxobutyryl)indane-1,3-dione 4 give only products of simpl e photoaddition: enylpropionyl)-2-phenylbenzocycloheptane-1,5-dione 7 and -(3-oxobutyrl)-2-phenylbenzocycloheptane-1,5-dione 8, respectively . The regiospecificity previously observed with the beta-diketones [1] is not a general rule for these beta-triketones. The phenyl group in position 6 (products 5 and 6) is not in the a-position of the benzoyl group. The delta-triketones obtained are characterized using beta-dike tonic models, which are prepared by a simple sequence. Observations of products 7 and 8 show that styrene reacts with the cyclic enol only. This work may be considered as a model study for the prediction of the behavior of triketones 1, 2, 3 and 4 in the side chain of polymeric c ompounds.