Scheme 2.

Synthesis of trisubstituted selenophene compounds. Reagents and conditions: (a) Br₂, DMF; (b) [Pd] catalyst (Pd(dppf)Cl₂ for Series III; Pd(PPh₃)₄) for Series IV, Na₂CO₃, toluene/water (1:1), reflux, 24 h; (c) BBr₃, CH₂Cl₂, −20 °C to rt, 4 h. To simplify comparisons between compounds in closely related series, we designate locant positions of the substituents on the phenyl groups with respect to the selenophene core; for clarity, locant positions on the selenophene core itself are given by numbers in italics.