1,4-Dimethyl-2,3-diphenylfulvene: A convenient precursor to heteroatom-substituted-1-methyl-2,5-dimethyl-3,4-diphenylcyclopentadienyl transition metal complexes

Reaction of 2,5-dimethyl-3,4-diphenylcyclopent-2-enone ( 1 ) with Ph 3 PCH 2 in THF gave 2,5-dimethyl-3,4-diphenylcyclopent-2-enel-ylidene ( 2 ) in 75% yield. Treatment of 2 with one equivalent Br 2 , followed by twp equivalents of triethylamine gave 1,4-dimethyl-2,3-diphenylfulvene ( 3 ) in 60% overall yield. Treatment of 3 with LiCH 3 and LiC 6 H 5 followed by FeCL 2 gave [ η 5 -1-CH 3 CH 2 -2,5-(CH 3 ) 2 -3,4-(C 2 H 5 ) 2 -3,4-(C 6 H 5 )C 2 ] 2 Fe and [ η 5 -1-C 6 H 5 CH 2 -2,5-(CH 3 ) 2 -3,4-(C 6 H 5 ) 2 C 5 ] 2 Fe, respectively, in good yield. Treatment of 3 with LiNHC(CH 3 ) 3 and LiP(C 6 H 5 ) 2 followed by FeCl 2 gave [ η 5 -1-(CH 3 ) 3 CNHCH 2 -2,5-(CH 3 ) 2 -3,4-(C 6 H 5 ) 2 -3,4-(C 6 H 5 ) 2 C 5 ] 2 Fe and [ η 5 -1-(C 6 H 5 ) 2 PCH 2 -2,5-(CH 3 ) 2 -3,4-(C 6 H 5 ) 2 C] 2 Fe, respectively, in good yield. Treatment of 3 with (R)-LiNHCH(CH 3 )C 6 H 5 followed by FeCl 2 gave the corresponding enantiomerically pure ferrocene complex (R,R)-[ η 5 -1-C 6 H 5 CH(CH 3 )NHCH 2 -2,5-(CH 3 ) 2 -3,4-(C 6 H 5 ) 2 C 5 ] 2 Fe in 44% yield.