P-Chirogenic α-carboxyphosphine boranes have been applied directly as pre-ligands in palladium-catalyzed asymmetric allylic alkylation and amination reactions, with in situ deprotection of the borane moiety. Using dimethylmalonate as the nucleophile afforded the alkylated product in up to 91% ee, while reaction with benzylamine gave amination in up to 94% ee. In both cases, the opposite enantiomer could be accessed in high ee by using the antipode of the ligand, easily accessible by exchanging (-)-sparteine for a (+)-sparteine mimic in the desymmetrization process used for preparing the ligands.
P-手性α-羧基膦氮
硼烷已被直接用作
钯催化下的不对称烯丙基烷基化和
氨化反应中的前
配体,并实现了
硼烷基团的原位去保护。使用
二甲基马来酸酯作为亲核试剂可获得烷基化产物,光学纯度高达91%;而与
苄胺反应则得到
氨化产物,光学纯度高达94%。在这两种情况下,通过使用
配体的对映体,可以以高光学纯度获得相对的对映体,这可以通过在制备
配体时用(+)-sparteine模拟物替换(-)-sparteine来轻松实现。