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Reactions of organo-metal compounds O 0350Tributyl (3,3,3-trifluoro-1-propynyl)stannane as an Efficient Reagent for the Preparation of Various Trifluoromethylated Heterocyclic Compounds. -Title compound (III), synthesized from propene (I) and chlorobutylstannane (II) is used in 1,3-dipolar cycloadditions with diazomethane (IV), phenylazide (XI) and acetonitrile oxide (VIII) to afford the tributylstannyl substituted heterocycles (V), (XII) and (IX)/(X) in good yields, respectively. These heterocyclic compounds are proved to be useful building blocks for the regioselective introduction of a functional group such as an aryl group or iodine. -(HANAMOTO*, T.; HAKOSHIMA, Y.; EGASHIRA, M.; Tetrahedron Lett. 45 (2004) 41, 7573-7576; Dep. Chem. Appl. Chem., Fac. Sci. Eng., Saga Univ., Honjo, Saga 840, Japan; Eng.) -M. Paetzel 02-055

Photophysical and photochemical features of [3n]cyclophanes (3nCPs) (n = 2-6) in solution were investigated by emission and transient absorption measurements. The studied 3nCPs show excimer fluorescence without locally excited fluorescence whereas some of them emit excimer phosphorescence in rigid glass at 77 K. The probability of excimeric phosphorescence from transannular π-electron systems was shown to strictly depend on the symmetric molecular structures. A feature of intersystem crossing from an excimeric fluorescence state to the excimeric triplet state was observed. Transient absorption spectra obtained upon laser flash photolysis of 3nCP revealed formation of the triplet excimer states. Triplet sensitization of 33CP using xanthone as the sensitizer demonstrated formation of triplet 33CP via triplet energy transfer whereas from the xanthone ketyl radical formation, it was inferred that triplet xanthone undergoes H atom abstraction from 32CP, providing a benzylic 32CP radical as the counter species. Based on kinetic and spectroscopic data obtained upon laser flash photolysis, differences in photochemical reactions of triplet xanthone between 32CP and 33CP were discussed.