Synthesis of stable 1-ethoxy-2,3-diferrocenylcyclopropenylium tetrafluoroborate and its reactions with lithium reagents

1-Ethoxy-2,3-diferrocenylcyclopropenylium tetrafluoroborate selectively reacts with MeLi, n-BuLi, sec-BuLi with formation of the 3,3-dialkyl-1,2-diferrocenylcyclopropenes, while with tert-BuLi both 2-tert-butyl-1,3-diferrocenylcyclopropene and 1,3-di-tert-butyl-2,3-diferrocenylcyclopropene are obtained. The structures of 3,3-dimethyl-, 3,3-dibutyl-1,2-diferrocenyl and 2-tert-butyl-1,3-diferrocenylcyclopropenes were confirmed by X-ray crystallographic analysis.

Treatment of 1,2-diferrocenylcyclopropenone with triethyloxonium tetrafluoroborate gives highly stable 1-ethoxy-2,3-diferrocenylcyclopropenylium tetrafluoroborate storage-stable at room temperature in the crystalline state. Its reactions with alkyllithium reagents afford stable 1,2,3, substituted cyclopropenes and products of opening small cycle.Figure optionsDownload as PowerPoint slide