Toward 2-Thiophyne [+]

Toward 2-Thiophyne: Ketocarbene versus Hetaryne Intermediates from 2-(Trimethylsilyl)thiophen-3-yl Triflate

The reaction of 2-(trimethylsilyl)thiophen-3-yl triflate with CsF in the presence of 2,3,4,5-tetraphenylcyclopentadienone affords 4,5,6,7-tetraphenylbenzo[b]thiophene, as it would be expected from the hypothesized generation and trapping of 2-thiophyne. However, a detailed experimental and computational study discards the intermediacy of this elusive 5-membered hetaryne. Instead, a complex mechanism involving the generation of an intermediate ketocarbene, which adds to the cyclopentadienone to give an isolable tricyclic intermediate, followed by thermal rearrangements, is proposed.

Org. Lett. 2021, 23, 19, 7376–7380.