Pd(II)-catalyzed dehydrogenative Heck olefination of selenophenes with a broad olefinic substrate scope and high functional group tolerance is demonstrated. Carbonyl-substituted and phenyl-substituted olefins with electron-donating (D) and electron-accepting (A) groups can be regioselectively installed at C2 of the selenophene. The 2-olefinated selenophenes can subsequently undergo a second oxidative olefination to rapidly produce a new class of symmetrical D−π−D or unsymmetrical D−π−A 2,5-diolefinated selenophene materials.
We discovered a unique synthetic
route to construct 2H-pyran-containing
tetracyclic dithienocyclopentapyran (DTCP) and dibenzocyclopentapyran
(DBCP) architectures. The synthesis involves an acid-induced dehydration
cyclization followed by a [1,5] hydride-shift isomerization to form
a cyclopentanone moiety which was converted to the pyran-embedded
tetracyclic products by a CuI-catalyzed intramolecular C–O
bond formation in good yield. DTCP was used as a building block to
prepare an acceptor–donor–acceptor (A–D–A)
type n-type material DTCP-BC leading to a solar cell efficiency of
9.32%.
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