1,3,4,5-Tetramethyl-2-methylenimidazolin - ein Olefin mit Ylid-artigen Eigenschaften [1] / 1,3,4,5-Tetramethyl-2-methylenimidazoline - an Olefin with Ylidic Properties [1]

Abstract

A facile synthesis of l,3,4,5-tetramethyl-2-methylenimidazoline 5 (Im) starting from the pentamethylimidazolium ion (8) and KH is described. Boranes react with 5 to give the adducts ImBHi 3 (11) and ImBF 3 (18). With Mel and CH 3 C(O)Cl the imidazolium salts ImMe + (19) and ImC(O)Me + (20) are obtained. CS 2 gives the zwitterionic compound ImCS 2 (24) which is transformed into the cationic thiocarboxylic ester ImC(S)SCH 2 Cl + on treatment with CH 2 Cl 2 . Reaction with chlorotrimethylsilane gives the imidazolium ion ImSiMe + 3 (26) which may be transferred into the disilylated imidazolium ion 28 via deprotonation and subsequent silylation, the silylated olefin 27 being the intermediate. Similarly, the cations ImSiR 2 Cl + (29; R = Me, Ph) are obtained from 5 and the silanes R 2 SiCl 2 . The neutral adduct ImSnPh 2 Cl 2 (32) is formed in the reaction of 5 with Ph 2 SnCl 2 . Iodine reacts with 5 to give the charge-transfer adduct Iml 2 (35), which can be further transferred into the imidazolium salt Iml + I - 3 (36).