which r1 r2 and r3 have the above given meanings by reaction with 2 nd generation grubbs catalyst see aldrich chemistry handbook fine chemicals 2009 2010 page 1453 in the presence of cucl j org chem 2004 69 6894 6896 it was finally found out that the catalysts of formula i are suitable for the modification of butadiene acrylonitrile copolymers r1 stands for methyl or ethyl r2 stands for c6 c18 alkyl r3 stands for hydrogen or c1 c18 alkyl or stands for an electron withdrawing substituent from the series nitro and so2n c1 c18 alkyl hal stands for chlorine or bromine independently of each other lig stands for preparation of the catalyst of formula i wherein r1 me r2 c12h25 r3 no2 hal c1 lig lig1 in a schlenk apparatus the 2 nd generation grubbs catalyst 0 108 g 0 13 mmol is mixed with a solution of compound i 1 0 059 g 0 14 mmol in 5 ml dichloromethane and 25 mg of copper i chloride and was stirred for about 50 minutes to about 60 minutes at ambient temperature under an argon atmosphere the solvent was then removed under vacuum and the residue was purified by column chromatography the catalyst i was obtained as.