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Abstract.A novel trifunctional epoxy resin 4-(3, 3-dihydro-7-hydroxy-2, 4, 4-trimethyl-2H-1-benzopyran-2-yl)-1, 3-benzenediol glycidyl (shorted as TMBPBTH-EPOXY) was synthesized in our lab to improve thermal performance. Its curing behavior and performance were studied by using 4, 4′-diaminodiphenyl sulfone (DDS) as hardener with the mass ratio of 100:41 of TMBPBTH-EPOXY and DDS. The curing activation energy was investigated by differential scanning calorimetry (DSC) to be 64.0 kJ/mol estimated by Kissinger's method and 68.7 kJ/mol estimated by Flynn-Wall-Ozawa method respectively. Thermogravimetric analyzer (TGA) was used to investigate the thermal decomposition of cured compounds. It was found that when curing temperature was lower than 180°C, the thermal decomposition temperature increased with the rise of curing temperature and curing time. On the other hand, when the curing temperature was higher than 180°C, the thermal decomposition temperature went down instead with the increase of curing time that might be the over-crosslinking of TMBPBTH-EPOXY and DDS hardener. The glass transition temperature (Tg) of cured TMBPBTH-EPOXY/DDS compound determined by dynamic mechanical thermal analysis (DMTA) is 290.1°C.

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Diels-Alder Reactions of α,β-Unsaturated Thioesters and α,β-Unsaturated Selenoesters.-The regio-and exo/endo-selectivity of Diels-Alder reactions of thio-and selenoesters (II) with dienes is investigated. In general, thermal reactions show only low selectivities as expected. The selectivity improves upon use of soluble Lewis acid promotors such as EtAlCl 2 and TiCl 4 . -(BYEON, C.-H.; CHEN, C.-Y.; ELLIS, D. A.; HART, D. J.; LI, J.; Synlett (1998) 6, 596-598; Dep. Chem., Ohio State Univ., Columbus, OH 43210, USA; EN)

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Applications of Organosulfur Chemistry to Organic Synthesis: Total Synthesis of (+)-Himbeline and (+)-Himbacine.-The total synthesis of himbeline (IXa) and himbacine (IXb) involves the preparation of sulfone (VI) and aldehyde (VII) as single enantiomers followed by coupling of these compounds using a Julia-Lythgoe olefination. -(HART, D. J.; LI, J.; WU, W.-L.; KOZIKOWSKI, A. P.; J. Org. Chem. 62 (1997) 15, 5023-5033; Dep. Chem., Ohio State Univ., Columbus, OH 43210, USA; EN)