Axially chiral allenylboranes: catalytic asymmetric synthesis by palladium-catalysed hydroboration of but-1-en-3-ynes and their reaction with an aldehyde

Katalytische Carbonyladdition durch Transferhydrierung: weg von vorab gebildeten Organometallreagentien

“…Hayashi (1993) [33m] fanden (Schema 16). Schließlich beschrieben Keck (1994) [33n] und Denmark (2001) [33] asymmetrische Aldehydpropargylierungen mit Allenylmetallreagentien in Gegenwart von katalytischen Mengen chiraler Lewis-Säuren oder Lewis-Basen.…”

Hydroboration, Diboration, Silylboration, and Stannylboration

“…On the other hand, a monocoordination of an acetylenic triple bond to a rhodium(I)/bisphosphine complex leads to 24. Thus, asymmetric hydroboration of 1-buten-3-yne giving (R)-allenylboronate with 61% ee is carried out by using a chiral monophosphine (S)-(-)-MeO-MOP (MeO-MOP=2-diphenylphosphino-2′-methoxy-1,1′-binaphthyl) [52]. The dehydrogenative coupling of borane is a very attractive method since the reaction directly yields (E)-1-alkenylboronates from alkenes (Table 1-5).…”

Enantioselective Synthesis of Multisubstituted Allenes by Cooperative Cu/Pd‐Catalyzed 1,4‐Arylboration of 1,3‐Enynes

“…[3] Until recently,i ncreasing attention has focused on developing catalytic asymmetric approaches for the synthesis of chiral allenes. [1f,h] Since the pioneering work of the group of Hayashi, [4] 1,3enynes have been gradually considered ideal achiral precursors for the construction of highly valuable chiral allenes,and several metal-or organocatalyzed approaches were established in the past few years. [5][6][7] Among these,enantioselective Cu-catalyzed 1,4-hydrofunctionalization of 1,3-enynes was proven to be an elegant strategy to access nonracemic allenes.…”