パラジウムまたはルテニウム触媒存在下,ジシラン類または(トリメチルシリル)トリブチルスタンナンを用いる塩化シンナミルのシリル化と生成物の立体選択性

The palladium-catalyzed dechlorinative silylations of cinnamyl chloride with hexamethyldisilane, chloropentamethyldisilane, fluoropentamethyldisilane or (trimethylsilyl) tributylstannane were examined to shed light on its selectivities. The reaction of the disilanes was conducted under similar conditions (170℃, catalyst : palladium-phosphine complex) to those in previously reported palladium-catalyzed reactions of disilanes with allyl chloride. Both selectivities and product yields were found to be low under these conditions. So, several catalysts were examined in the reactions in order to find an active one, and the following results were obtained; (1) in the reaction of hexamethyldisilane, Pd (OAc)_2-PPh_3 showed a good catalytic activity to give transcinnamyltrimethylsilane, cis-cinnamyltrimethylsilane and (1-phenyl-2-propenyl)trimethylsilane in 35%, 30% and 16% yields, respectively, (2) Pd_2 (dba)_3-P (OCH_2)_3CEt worked well as a catalyst in the reaction of chloropentamethyldisilane to afford cis-cinnamylchlorodimethylsilane and (1-phenyl-2-propenyl) chlorodimethylsilane in 5% and 70% yields, and (3) in the reaction of fluoropentamethyldisilane, Pd_2 (dba)_3 showed a good catalytic activity to give trans-cinnamylfluorodimethylsilane, cis-cinnamylfluorodimethylsilane and (1-phenyl-2-propenyl) fluorodimethylsilane in 24%, 8% and 45% yields, respectively. Consequently, yields of the dechlorinative silylation producs were successfully improved, but trans-selectivities were not. Especially, the reactions of chloro- and fluoropentamethyldisilane gave a thermodynamically stable (1-phenyl-2-propenyl)silane as a major product. The reaction of (trimethylsilyl) tributylstannane with cinnamyl chloride proceeded, even at room temperature in the presence of tris (dibenzylideneacetone) dipalladium (0), to afford cinnamyltrimethylsilane and (1-phenyl-2-propenyl)trimethylsilane in 15% and 48% yields, respectively. It should be emphasized that carbon-tin bond forming products were not detected at all. Dichlorotris (triphenylphosphine)ruthenium (II) also effected the reaction to afford trans -cinnamyltrimethylsiland and (1-phenyl-2-propenyl)trimethylsilane in 30% and 43% yields, respectively.