1: in tetrahydrofuran T=60°C; Grignard reaction; 2: With tin(ll) chloride in tetrahydrofuran T=60°C; Further stages.;

[1,3-bis(diphenylphosphino) propane] dichloronickel(II); 2,3-dichloro-1,3-butadiene 1.) -78 deg C to r.t., 2.) r.t., 6 h;