Studies in the Cycloproparene Series: The Generation and Trapping of 1H-Cyclopropa[l]phenanthrene

Abstract

1H- Cyclopropa [l] phenanthrene (4a) has been generated and trapped with furan as cycloadducts (16) and (17). The route to (4a) involves highly regioselective formation of la- methylselenodihydrocyclopropa [I] phenanthrene (60) (80%) by addition of methaneselenolate to 1aH-cyclopropa [I] phenanthrene (7a). Methylation of (60) to give the tetrafluoroborate salt (6p)and subsequent base treatment affords (4a) via the methylselenonium methylide (6q). The non-aromatic laH-cyclopropaphenanthrene (7a) is easily obtained by removal of the elements of chlorotrimethylsilane from chlorides (6m,n). These latter compounds result from half-reduction of the dichlorocarbene adduct (61) of 9-trimethylsilylphenanthrene (51).