Enolboration and ring expansion with the chiral B-X-10-R-9-borabicyclo[3.3.2]decane

The enolboration of ethyl ketones with three new chiral borane species (B-OTf-10-Ph-9-BBD, B-I-10-Ph-9-BBD and B-Cl-10-Ph-9-BBD) is presented. The effect of the leaving group and the base on the geometry of the enolate is studied. The enantio- and diastereoselectivity of the aldol addition of the enolborinates to simple aldehydes are studied and compared to other existing chiral boron reagents. The comparison of the PhBBD with the TMSBBD system was also addressed.; A novel chiral borane reagent, B-R-3,4-bis-(trimethylsilyl)-2-bora-bicyclo[3.3.3]undecane, has been prepared via a novel ring expansion process. The addition of Grignard reagents to the B-(α-chloromethyl)trimethylsilyl-10-TMS-9-BBD affords the new [3.3.3] ring system. No precedent for this process has been previously observed. Moreover, differences in reactivities and product distributions were observed when the corresponding organolithium reagents were used. The formation of a new symmetric B-R-2,4-bis-(trimethylsilyl)-3-bora-bicyclo[3.3.3]undecane was observed when using certain organolithiums.; The novel B-OMe-3,4-bis-(trimethylsilyl)-2-borabicyclo[3.3.3]undecane is presented as a new chiral borane intermediate which can be obtained in a straightforward manner via the protonolysis of its B-propynyl derivative. Consequently, this new boron ligation can be transformed in a broad variety of useful borane reagents.