Preparation of Partially Substituted 1-Halo- and 1,4-Dihalo-1,3-dienes via Reagent-Controlled Desilylation of Halogenated 1,3-Dienes

Depending on the desilylation reagents used, 1-halo-1,4-bis(trimethylsilyl)-1,3-butadienes afforded either
1-halo-1-trimethylsilyl-1,3-butadienes or 1-halo-4-trimethylsilyl-1,3-butadienes in excellent yields with
excellent selectivity, respectively, when treated with CF3COOH or with NaOMe. These monosilylated
1,3-butadiene products could be further desilylated to generate their corresponding halobutadienes via
the above reagent-controlled desilylation reaction. When 1,4-dihalo-1,4-bis(trimethylsilyl)-1,3-dienes were
treated with MeONa/MeOH at room temperature, desilylation of both of the two trimethylsilyl groups
took place to afford their corresponding 1,4-dihalo-1,3-dienes in excellent yields. The commonly used
desilylation reagent CF3COOH did not work for these dihalobutadienes.