Synthesis, structure, and ring inversion of a trithiolane (6b,12b-epitrithioacenaphtho[1,2-a]acenaphthylene)

Reduction of 6b,12b-epipentathioacenaphtho[1,2-a]acenaphthylene 2, prepared by sulfuration of acenaphtho[1,2-a]acenaphthylene 1, with LiEt3BH, followed by air-oxidation, resulted in the desulfuration that led to 6b,12b-epitrithioacenaphtho[1,2-a]acenaphthylene 7 in 87% yield. The trithiolane ring of 7 adopts an envelope conformation both in solution at −40°C (NMR) and in crystals (X-ray). The ring inversion of the trithiolane ring is frozen at low temperature, but begins to take place as the temperature rises. Activation energy (Ea) of the ring inversion was determined to be 58 kJ mol−1, based on dynamic 13C NMR analyses.