Design of a Chiral Mesoporous Silica and Its Application as a Host for Stereoselective Di-π-methane Rearrangements
作者:Miriam Benitez、Gerhard Bringmann、Michael Dreyer、Hermenegildo Garcia、Heiko Ihmels、Michael Waidelich、Kathrin Wissel
DOI:10.1021/jo047878j
日期:2005.3.1
A chiral periodic mesoporous organosilica (ChiMO) was prepared, in which a 1,2-bis-(ureido)cyclohexyl linker (38 wt %) is introduced into the walls of the hybrid organic−inorganic material. This silica was used as a host for 11-formyl-12-methyldibenzobarrelene (2), and the stereoselectivity of the di-π-methane rearrangement of 2 within this host−guest complex was studied. At low conversions, the only
制备了手性周期性介孔有机硅(ChiMO),其中将1,2-双-(脲基)环己基连接基(38 wt%)引入到杂化有机-无机材料的壁中。该二氧化硅用作11-甲酰基-12-甲基二苯并戊烯(2)的主体,并研究了该主体-客体复合物中2的二-π-甲烷重排的立体选择性。在低转化率下,唯一的产物是相应的二苯并半bullvalvalene。使用ChiMO作为宿主,在11%的转化率下对映体过量为24%。这些值与使用基于常规八面沸石(LiY和NaY)的系统作为手性助剂的宿主所获得的值相当。我们测试了S-苯甘氨酸,S-脯氨酸,S-樟脑酸和S-扁桃酸作为手性助剂。与ChiMO材料的行为相反,在含有麻黄碱的纯硅质介孔MCM-41二氧化硅(孔径为3.2 nm)中,二苯并戊烯烯的吸附失败,这可以解释为是由于内部硅烷醇含量高和亲水性高而引起的。硅质MCM-41样品。