In admiration and memory of Prof. Eghert Hauinga (16. XII. 88) In a search for further synthetic routes to substituted [5.5.5.5]fenestranes, compound la, a derivative of 7-methoxyindane, was photolyzed. Two of the three photoproducts, oiz. the [3.5.5.5]fenestrane 3 a and the isomer 4 a, are formed according to the expected intramolecular meta-cycloaddition. A different mechanism is suggested for the formation of the major component 2a.

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Tphos) sec°0 -0 band,6•' sion,d•® tion,6•® Emission, d.= tion,6••'' In methyl-Compound Max, µ µ µ µ µ µ In EPA cyclohexane p-Trifluoromethylacetophenone 333 360 397 384 (383)8

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SummaryIrradiation of (RS,SR)-3-Phenyl-6-hepten-2-01 (3n) gave the photoproducts 6n-10n. Some reactions of 6n and 8n are reported. The regio-and diastereoselectivity observed in the photoreaction of substituted 5-phenylpentenes is discussed with respect to conformational preferences of the compounds to be irradiated.Introduction. -Polycyclic hydrocarbons in which four rings are annulated in such a way that they share a common C-atom are of interest for a study of the planarization of the tetracoordinate C-atom [l]. The [5.5.5.5]fenestranes ( = 'tetraquinacanes' or 'stauranes'; systematic name: tetracyclo[5.5.1 .04,13.0'",'3]tride~anes) are particularly attractive since they eventually might be transformed into a [12]annulene with a central C-atom [2]. Although a few syntheses of fenestranes have been reported [lc] [3], short and efficient routes for their preparation are still in need. We report our results of the intramolecular photocycloaddition of 3-phenyl-6-hept-en-2-01 (3n).