in ethyl acetate Heating;

1.1: NaOMe; sulfur / methanol / 3 h 1.2: I2 / H2O 2.1: 85 percent / ethyl acetate / Heating View Scheme

1: 1-naphthalenedithiocarboxylic acid in dimethyl sulfoxide; ethyl acetate 10 h; Inert atmosphere; 2: 2,2'-azo-bisisobutyronitrile in dimethyl sulfoxide; ethyl acetate 15 h; Reflux;