Chiral α-substituted allylboronic acids were synthesized by asymmetric homologation of alkenylboronic acids using CF 3 /TMS-diazomethanes in the presence of BINOL catalyst and ethanol. The chiral α-substituted allylboronic acids were reacted with aldehydes or oxidized to alcohols in situ with a high degree of chirality transfer. The oxygen-sensitive allylboronic acids can be purified via their isolated diaminonaphthalene (DanH)-protected derivatives. The highly reactive purified allylboronic acids reacted in a self-catalyzed reaction at room temperature with ketones, imines, and indoles to give congested trifluoromethylated homoallylic alcohols/amines with up to three contiguous stereocenters.

The catalytic asymmetric allylboration of cyclic imines with γ,γ‐disubstituted allylboronic acids provides products with adjacent stereocenters in high yield and stereoselectivity. Various electrophiles, including 3,4‐dihydroisoquinolines and indoles, were prenylated in a fully stereodivergent fashion by switching the E/Z geometry of the allylboronate and/or the enantiomer of the BINOL catalyst. 3‐Methylindole provided products with three adjacent stereocenters with high stereoselectivity in one synthetic operation.

Synthesis and application of allenylboronic acids is presented. The successful synthetic applications are based on the possibility of the versatile transformations of the unprotected B(OH)2 group in situ under the propargylboration conditions.

Abstract:The catalytic asymmetric allylboration of cyclic imines with g,g-disubstituted allylboronic acids provides products with adjacent stereocenters in high yield and stereoselectivity.V arious electrophiles,i ncluding 3,4-dihydroisoquinolines and indoles,were prenylated in afully stereodivergent fashion by switching the E/Z geometry of the allylboronate and/or the enantiomer of the BINOL catalyst. 3-Methylindole provided products with three adjacent stereocenters with high stereoselectivity in one synthetic operation.The allylboration reaction has become an indispensable method for the stereoselective synthesis of homoallylic alcohols and amines.[1] Recently,o ur group described the first catalytic asymmetric synthesis of homoallylic alcohols from g,g-disubstituted allylboronic acids and ketones,furnishing products bearing adjacent quaternary stereocenters. [2] Extending this reaction to imines for the synthesis of chiral amines with adjacent stereocenters is important as these motifs are common in drug-like molecules and natural products.[3] In addition, ac omparison of the asymmetric allylboration of ketones and imines using similar catalysts is highly interesting in terms of the stereoinduction.Although great progress has been made towards the allylboration of imines, [4] asymmetric examples have remained sparse.[5] Hoveyda [5f] and co-workers recently reported on the catalytic asymmetric allylboration of phosphinoyl imines,w hich provides access to enantioenriched products containing adjacent stereocenters.While this work is impressive,t he substrate scope is currently limited to monosubstitution at the g-position of the allylboronate,a nd only the anti products could be formed. Ac omplementary approach has been reported by the Aggarwal group [5g] for the enantiospecific allylboration of imines,k etimines,a nd indoles with enantioenriched g,g-disubstituted allylboronates. This method is impressive in its ability to provide amines with adjacent quaternary stereocenters in as tereodivergent manner,y et it proceeds through chirality transfer and requires enantioenriched precursors.M erging the merits of these two methods into am anifold wherein achiral g,gdisubstituted allylboronates undergo allylboration with imines in ac atalytic asymmetric fashion would be highly desirable.I no ur quest to fill this niche,w et hought that the allylboration of indole would be af ertile proving ground. Allylborations at the C2 position of indole have been reported by the groups of Aggarwal,[5g] Batey, [6] Bubnov, [7] and our group.[4c] Af ormidable challenge is to realize these reactions by asymmetric catalysis.In our previous studies, [4c] we found that ah ighly diastereoselective allylboration of indole could be achieved under mild conditions using a g,g-disubstituted geranylboronic acid, thus forming an indoline bearing an exocyclic quaternary stereocenter.C hong [5b] and Wu have reported on the asymmetric allylboration of cyclic imines using BINOL modified allylboronates whereas the Schaus group [8] described t...

Metal-free asymmetric catalysis for the synthesis of sterically encumbered amino-acids was developed using allyl- and allenylboronic acid reagents.