1,3,4,5-TETRAMETHYL-2-METHYLENIMIDAZOLINE - AN OLEFIN WITH YLIDIC PROPERTIES

A facile synthesis of 1,3,4,5-tetramethyl-2-methylenimidazoline 5 (Im) starting from the pentamethylimidazolium ion (8) and KH is described. Boranes react with 5 to give the adducts 1mBH(3), (11) and ImBF(3) (1 8). With Mel and CH3C(O)Cl the imidazolium salts ImMe(+) (19) and ImC( O)Me(+) (20) are obtained. CS2 gives the zwitterionic compound ImCS(2) (24) which is transformed into the cationic thiocarboxylic ester ImC( S)SCH2Cl+ on treatment with CH2Cl2. Reaction with chlorotrimethylsilan e gives the imidazolium ion ImSiMe(3)(+) (26) which may be transferred into the disilylated imidazolium ion 28 via deprotonation and subsequ ent silylation, the silylated olefin 27 being the intermediate. Simila rly, the cations ImSiR(2)Cl(+) (29; R = Me, Ph) are obtained from 5 an d the silanes R(2)SiCl(2). The neutral adduct ImSnPh(2)Cl(2) (32) is f ormed in the reaction of 5 with Ph(2)SnCl(2). Iodine reacts with 5 to give the charge-transfer adduct ImI(2) (35), which can be further tran sferred into the imidazolium salt IMI(+)I(3)(-) (36).