A highly efficient enantioselective aryl addition to aldehydes using boroxins as aryl source and conformationally restricted perhydro-1,3-benzoxazines as ligands is reported. Both enantiomeric forms of chiral arylphenylmethanols and 1,1′-disubstituted diarylmethanols are afforded with excellent yields and enantioselectivities using the same ligand by means of an appropriate combination of boroxin and aromatic aldehyde. The enantiocontrol is not significantly influenced by electronic effects or steric hindrance, even with substituted boroxins. Very homogeneous ee's are reached when substituted arylboroxins are employed, without the use of any class of additive or pre-treatment.
报道了一种高效的对映选择性芳基加成反应,利用
硼氧烷作为芳基来源,并采用构象限制的过氢-1,3-
苯并呋喃作为
配体。通过合理组合
硼氧烷和芳香醛,使用相同的
配体可以获得手性芳基
苯甲醇和1,1′-二取代二芳基
甲醇的两种对映体,具有优异的产率和对映选择性。即使在有取代的
硼氧烷存在时,对映控制也不受电子效应或空间位阻的显著影响。当使用取代芳基
硼氧烷时,可以达到非常均匀的对映体过量,并且无需任何类型的添加剂或预处理。