A new donor for charge-transfer systems: synthesis and properties of 2,4,7,9-tetramethyl-1,6-dithiapyrene (TMDTP) and structure of (TMDTP)3(PF6)2·2THF and TMDTP–TCNQ

The heterocyclic donor molecule 2,4,7,9-tetramethyl-1,6-dithiapyrene (TMDTP) has been synthesized in five steps. Oxidation of TMDTP is facile (E₁^1/2 = 0.27 V and E₂^1/2 = 0.79 V vs. SCE). The charge-transfer complex, TMDTP–TCNQ, has been prepared and the salt, (TMDTP)₃(PF₆)₂·2THF, obtained by electrocrystallization. The structure of TMDTP, TMDTP–TCNQ and (TMDTP)₃(PF₆)₂·2THF has been characterized by X-ray crystallography and computationally.

The heterocyclic donor molecule 2,4,7,9-tetramethyl-1,6-dithiapyrene (TMDTP) has been synthesized in five steps. The charge-transfer complex, TMDTP–TCNQ, has been prepared and the salt, (TMDTP)₃(PF6)₂·2THF, obtained by electrocrystallization.

Rhodium-catalyzed cascade oxidative annulation leading to substituted naphtho[1,8-bc]pyrans by sequential cleavage of C(sp2)-H/C(sp3)-H and C(sp2)-H/O-H bonds

The cascade oxidative annulation reactions of benzoylacetonitrile with internal alkynes proceed efficiently in the presence of a rhodium catalyst and a copper oxidant to give substituted naphtho[1,8-bc]pyrans by sequential cleavage of C(sp(2))-H/C(sp(3))-H and C(sp(2))-H/O-H bonds. These cascade reactions are highly regioselective with unsymmetrical alkynes. Experiments reveal that the first-step reaction proceeds by sequential cleavage of C(sp(2))-H/C(sp(3))-H bonds and annulation with alkynes, leading to 1-naphthols as the intermediate products. Subsequently, 1-naphthols react with alkynes by cleavage of C(sp(2))-H/O-H bonds, affording the 1:2 coupling products. Moreover, some of the naphtho[1,8-bc]pyran products exhibit intense fluorescence in the solid state.