Construction of new fluorophores by Diels-Alder reaction of diacenaphthothiophenes

4 years ago

Construction of new fluorophores by Diels-Alder reaction of diacenaphthothiophenes

The Diels–Alder (DA) reaction of diacenaphtheno[1,2-b;1′,2′-d]thiophene (1a) with benzyne affords 1:1 and 1:2 adducts, 7 and 8, in 47 and 11% yields. An X-ray crystallographic analysis reveals that 8 possesses a dibenzobarrelene structure involving a rigid di(1-naphthyl)ethene moiety. Thus, the second DA reaction occurs at the central benzene ring of 7 selectively. The 1:2 adduct 8 emits intense blue fluorescence in CH2Cl2. Moreover, we examined the DA reactions of 1a and tetra-t-butyl derivative 1b with p-benzoquinone to afford acenaphtheno[1,2-j]fluoranthene 10a, and its tetra-t-butyl derivative 10b and a quinone 11b, respectively. Novel fragmentation reaction should occur to produce the acenaphthenofluoranthene frameworks of 10. An X-ray crystallographic analysis reveals a rather planar structure of 11b. The central benzene ring of 11b shows large bond alternation by the Mills-Nixon effect. The compounds 10a and 10b emit sky blue fluorescence with moderate Φ SN values. The electronic properties of new compounds are well consistent with the theoretical predictions.

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DOI: S0040402017308360