An entry to non-racemic β-tertiary-β-amino alcohols, building blocks for the synthesis of aziridine, piperazine, and morpholine scaffolds
作者:Aleksandra Narczyk、Sebastian Stecko
DOI:10.1039/d0ob01315c
日期:——
corresponding β,β′-dialkyl-substituted non-racemic allyl alcohols. In addition, an asymmetric synthesis of such highly substituted allylicalcohols via either enantioselective 1,2-reduction of enones, enzymatic kinetic resolution, or a functionalization of chiral propargyl alcohols, with discussion of scope and limitations of each method is reported.
Stereospecific, Nickel-Catalyzed Suzuki–Miyaura Cross-Coupling of Allylic Pivalates To Deliver Quaternary Stereocenters
作者:Kelsey M. Cobb、Javon M. Rabb-Lynch、Megan E. Hoerrner、Alex Manders、Qi Zhou、Mary P. Watson
DOI:10.1021/acs.orglett.7b02063
日期:2017.8.18
Recognizing the importance of all-carbon, quaternary stereocenters in complex molecule synthesis, a stereospecific, nickel-catalyzed cross-coupling of allylic pivalates with arylboroxines to deliver products equipped with quaternary stereocenters and internal alkenes was developed. The enantioenriched allylic pivalate starting materials are readily prepared, and a variety of functional groups can be incorporated on both the allylic pivalate and the arylboroxine. Additional advantages include the use of a commercially available and air-stable Ni(II) salt and BISBI ligand, mild reaction conditions, and high yields and ee's. The observed stereoinversion of this reaction is consistent with an open transition state in the oxidative addition step.
Highly enantioselective asymmetric hydrogenation of (E)-β,β-disubstituted α,β-unsaturated Weinreb amides catalyzed by Ir(i) complexes of SpinPhox ligands
The Ir(I) complexes of chiral spiro phosphinoâoxazoline ligands (SpinPhox) have demonstrated good to excellent enantioselectivity in the asymmetric hydrogenation (AH) of a variety of (E)-β,β-disubstituted α,β-unsaturated N-methoxy-N-methylamides, affording the corresponding optically active Weinreb amides with up to 97% ee.
followed by in situ aldolization, which results in highly functionalized chiral and achiral cyclohexenones. The achiral version of this Robinson annulation features a hitherto unprecedented Michael reaction of β-keto acids with sterically hindered β,β′-substituted enones and provides access to all carbon quaternary stereocenter-containing cyclohexenones (11 examples, 43–83% yield). In addition, an asymmetric