A singlet aryl-CF3 carbene: 2-benzothienyl(trifluoromethyl)carbene and interconversion with a strained cyclic allene.

Matrix-isolated 2-benzothienyl(trifluoromethyl)carbene was generated by irradiation of the corresponding diazirine, and characterized by IR and UV/vis spectroscopy, in situ trapping, and DFT modeling. Experiments and calculations indicate that the carbene is a ground-state singlet, in contrast to previously characterized aryl(trifluoromethyl)carbenes. The carbene could be interconverted photochemically with a ring-opened thioquinomethide and a highly strained cyclic allene.