Diphenylphosphinodithioic acid (6b) and its triethyl ammonium salt (6a) were prepared by two new synthetic pathways, each employing cheap and readily available starting materials. These facile one-pot reactions were conducted on a kilogram scale and produced the desired products in high yield and quality, thereby surpassing all previously known routes. The synthesis of triethyl ammonium salts of 6 H-dibenzo [c, e][1, 2] oxaphosphinine-6- ...