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 ImBHi3 (11) and ImBF3 (18). With Mel and CH3C(O)Cl the imidazolium salts ImMe+ (19) and ImC(O)Me+ (20) are obtained. CS2 gives the zwitterionic compound ImCS2 (24) which is transformed into the cationic thiocarboxylic ester ImC(S)SCH2Cl+ on treatment with CH2Cl2. 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 ImSiR2Cl+ (29; R = Me, Ph) are obtained from 5 and the silanes R2SiCl2. The neutral adduct ImSnPh2Cl2 (32) is formed in the reaction of 5 with Ph2SnCl2. Iodine reacts with 5 to give the charge-transfer adduct Iml2 (35), which can be further transferred into the imidazolium salt Iml+I- 3 (36).