Nucleophilic arsenic reagents were prepared in situ from a nonvolatile cyclooligoarsine. As-As bond cleavage of the cyclooligoarsine readily proceeded with anion sources. Various kinds of organoarsenic compounds were easily constructed in high yields by selecting anion sources and electrophiles. In comparison with conventional methods of As-C bond formation, a wide variety of organoarsenic compounds were safely and easily synthesized by using this method.