ChemInform Abstract: REAKTIONEN MIT DERIVATEN AUS DER (CH)8CH2‐REIHE, DER DIRIGIERENDE EINFLUSS VON SUBSTITUENTEN BEI DER PHOTOLYSE EINIGER CIS‐3A,7A‐DIHYDROINDENE

Abstract

are transformed to the cis-dihydroindenes I I, 13. 15a, b, 17. As determined by the reaction halflives at 120 and 153"C, respectively, the thermal stability of the starting compounds decreases in the order 14b > 14a 2 16 > 12 > 10; steric reasons are discussed as a possible explanation for this sequence. Cycloaddition reactions of 11, 13,15a, b (17 is unreactive) with maleic anhydride and 4-phenyl-1,2,4-triazoline-3,5-dione, respectively, yield the adducts 21(21')a, b, 22a, b, 24 and 25 for which the endo-configuration of the carbocyclic five-membered ring with respect to the C-8/C-9 double bond is unambiguously proven at least in the case of 22a, b by formation of the cagephotoproducts 23a, b. Irradiation of the dihydroindenes involves different pathways: while excitation of 13 leads back to the tricyclic diene 12 the tetraesters 15a, bare converted to the intramolecular cyclization products 28a, b, and the diphenyl-compound 17 undergoes phenyl migration affording the di-x-methane isomer 30; all reactions proceed in a specific manner and only under direct irradiation conditions. Die zahlreichen thermischen, photochemischen und metall-katalysierten Umwandlungen von Verbindungen des Typs (CH),CH, haben -iihnlich wie in der (CH),,-Reihe -vielGiltige Wecliselbe~ielitingen L M ischcn dcn Isomwen erkennen lasmi. Dcr /cnli-alen ' I L. 7: Scott und M . J o J w s ,~~. , Chem. Rev. 72, 181 (1972).