Simultaneous Electron Transfer from Free and Intercalated 4-Benzoylpyridinium Cations in Cucurbit[7]uril
摘要:
N-Substituted 4-benzoylpyridinium monocations form stable host-guest complexes with cucurbit[7]uril (CB[71) in DMSO (K-eq approximate to 0.6-1.9 x 10(3) M-1). Observation of simultaneous reversible and quasi-reversible e-transfer processes from the free and intercalated quests, respectively, is attributed to the pre-e-transfer host-guest equilibrium. The standard rate constant for Me-BP@CB[7] (k(s) = 1.0 x 10(-4) cm-s(-1)) reflects e-transfer across 5.7 angstrom, corresponding to the distance of the intercalated guest from the outmost perimeter of CB[7] (5.3 angstrom).
The First Palladium-Catalyzed Desulfitative Sonogashira-Type Cross-Coupling of (Hetero)aryl Thioethers with Terminal Alkynes
作者:Vaibhav Pravinchandra Mehta、Anuj Sharma、Erik Van der Eycken
DOI:10.1021/ol800054b
日期:2008.3.1
An unprecedented desulfitative Sonogashira-type cross-coupling protocol is exemplified by the synthesis of substituted 5-chloro-3-alkynylpyrazinones from the corresponding 5-chloro-3-(phenylsulfanyl) pyrazin-2(1H)-ones. The applicability of the method is extended to solid-phase linked pyrazin-2(1H)-ones as well as to some oxazinones, pyrazines, and phenyl thioesters.