SYNTHESE VON 1-PHENYL-2,5-DIARYL(DIALKYL)-ARSOLEN; UMSETZUNG DER ARSOLE MIT ALKALIMETALLEN UND LITHIUMORGANYLEN

Article abstract of DOI:10.1016/S0022-328X(00)99433-6

The synthesis of 2,5-diaryl- and 2,5-dialkyl-1-phenylarsoles by base-catalyzed addition of phenylarsane to 1,3-diynes under ring formation is described. 1,2,5-Triphenylarsole reacts with 1 equivalent of metallic lithium or potassium under formation of the 1,2,5-triphenylarsolyl radical anion (II).With alkyl halides II reacts, probably via the 2,5-diphenylarsenide anion III, to give the 1-alkyl-2,5-diphenylarsoles IV, and with polyhalomethanes the corresponding 1-haloalkyl-2,5-diphenylarsoles are formed besides diarsolylmethanes (VIII).With trimethylchlorosilane the radical anion II reacts as an electron-transfer reagent. 1,2,5-Triphenylarsole gives with 2 equivalents lithium or potassium, probably via the dianion VI and cleavage of the arsenic-phenyl bond the 2,5-diphenylarsolyl anion III, which similarly as the anion II reacts with alkyl halides as well as with polyhaloalkanes to give the 1-alkyl-2,5-diphenylarsoles, but also diarsolylmethanes are formed in some cases. 1-Methyl-2,5-diphenylarsole forms also with 1 equivalent lithium or potassium the radical anion XII, which in comparison to II is much less stable; with excess alkalimetal cleavage occurs via the intermediate dianion XIII, to give the 2,5-diphenylarsolyl anion III.The radical anion XI reacts with alkyl halides partly via the arsenide ion III to give the 1-alkyl-2,5-diphenylarsoles and partly via an electron-transfer mechanism, by which the 1-methyl-2,5-diphenylarsole is reformed.The reaction product of 1-methyl-2,5-diphenylarsole and 2 equivalents alkali metal, the dianion XIII, reacts with alkyl halides partly via the arsenide anion III and partly via the 1-alkyl-1-methyl-λ⁵-arsolyl anion XIV, derived from the dianion XIII.The 1-alkyl-and 1-aryl-2,5-diphenylarsoles react with organolithium compounds (PhLi, t-BuLi) under formation of the 1-alkyl- and 1-aryl-2,5-diphenylarsol radical anions, respectively, which with alkyl halides give the corresponding 1-alkyl-2,5-diphenylarsoles.The electrochemical behaviour of 1-phenyl- and 1-methyl-2,5-diphenylarsole has been studied.