Study on the new synthetic reactions using organozirconium

Abstract

A convenient synthetic method for the preparation of 1-phenylseleno-1, 3-butadiene derivatives were studied. It was performed by transmetalation of symmetrical and unsymmetrical 5-membered zirconacycles using phenylselenenyl bromide. The reactions proceeded in chemo-and stereospecific manner. 1,4-Bis(phenylseleno)-1,3-butadiene derivatives were also prepared using 2 equivalent of phenylselenenyl bromide via transmetalation of zirconacyclopentadiene derivatives. Also studied were the rearrangement of bromobenzyl zirconocenes. The unusual intramolecular rearrangement of alkyl and alkenyl group from zirconocene to benzylic carbon withsimultaneous breaking of the C-Br bond occurred. The mechanism study indicated that the rearrangement could occur more than once. Vinylcyclopropane derivatives were propared by the rearrangement of vinyl moiety from zirconocene to cyclopropane with simultaneous breaking of the C-Br bond of bromocyclopropane in $Cp_2Zr[CH(Br)CH_2CH(Ph)][CH = C(H)R]$. Also successful was the preparation of 1-phenylseleno-1-vinylcyclopropane derivatives by the quenching of the zirconocene intermediates using phenylselenenyl bromide. 1-Cyclopropyl-1-vinylcyclopropane could be prepared via double rearrangement. This carbone-carbone bond forming reaction via rearrangement is further applied to intramolecular rearrangement to yield cyclized product. 5-Bromo-5-phenyl-1-pentene was cyclized to phenyl-cyclopentane mediated by $Cp_2ZrHCl$.