The synthesis of esters, thioesters and selenoesters of dialkylarsinous acids

Abstract

Organoarsenic compounds of the type R₂AsXR' (R=alkyl, R'=alkyl or aryl and X=O, S or Se) have been reported in the literature. The methods described for the synthesis of these compounds involve multistep reactions which give very low yields. A new, more efficient method for their synthesis has now been developed which utilizes dialkyl(diethylamino)arsines as intermediates. Those compounds are prepared from dichloro(diethylamino)arsine and Grignard reagents. Dichloro(diethylamino)arsine was readily available in 90% yield by the reaction of arsenic trichloride with diethylamine in diethyl ether. Eqns. (1) and (2) describe the new reaction sequence. [Equations on PDF] We found that the yields in eqn. (2) increase as the number of carbon atoms increases. While the methyl Grignard reaction yielded 15% of dimethyl(diethylamino)arsine the propyl reaction yielded 50% of dipropyl(diethylamino)arsine. Dialkyl(diethylamino)arsines were found to react readily with alcohols, thiols and selenols. [Equation on PDF] These reactions were found to be nearly quantitative. Overall yields of between 10 and 50% of the substituted dialkyl arsine by the new method compares well with yields of about 3% reported by the use of older methods..