Synthesis, properties and application of electronically-tuned tetraarylarsonium salts as phase transfer catalysts (PTC) for the synthesis of gem-difluorocyclopropanes

Preparation of gem-difluorocyclopropane from α-methylstyrene and chlorodifluoromethane was investigated under basic two-phase conditions. Although simple tetraalkylammonium salts appeared uneffective as phase-transfer catalysts (PTC) for this purpose, tetraphenylarsonium chloride displayed moderate activity, and inspired studies of the phenomena. To improve its efficiency we synthesized set of electronically-tuned tetraarylarsonium analogues. Their preparation revealed interesting exchange process of aryl substituents on the arsonium center, whereas activity studies demonstrated a correlation of catalytic efficiency with electronic effects of the substituents. Two of the tetraarylarsonium catalysts were characterized by X-ray studies.