Recent developments in asymmetric alkynylations

Chloramphenicol Base: A New Privileged Chiral Scaffold in Asymmetric Catalysis

“…Chloramphenicol base itself is a syn 2‐amino‐1,3‐diol scaffold, which is also found in the structure of many other biologically active products and in chiral inductors for various asymmetric transformations, especially for the enantioselective alkynylation of carbonyl and imine compounds. Good reactivities and stereoselectivities can be obtained using the below ligands (Scheme ).…”

Convergent Synthesis of α‐Branched Amines by Transition‐Metal‐Catalyzed C−H Bond Additions to Imines

“…The direct addition of terminal alkynyl CÀH bonds to imines, while an important contribution, has recently been reviewed and will not be discussed in the context of this review. [4] 2. Direct CÀH Bond Addition to Imines to Provide Racemic Products 2.1 C(sp 2 )ÀH Bond Addition…”

Asymmetric Synthesis of Less Accessible α‐Tertiary Amines from Alkynyl Z‐Ketimines

“…[1] Among these,n onproteinogenic a,a-dialkyl-a-amino acids, for instance,have attracted considerable interest in medicinal chemistry and peptide science due to their unique properties. [4][5][6][7][8][9][10][11][12][13][14][15][16] Accessing chiral a-tertiary amines with multiple alkyl substituents in an optically pure form is not trivial;h owever, some methods utilizing 3,3-sigmatropic rearrangement, [5] 1,2rearrangement, [6] asymmetric alkylation [7,8] or asymmetric 1,2-addition [9] have been developed for the asymmetric synthesis of these compounds. Conventionally, tetrasubstituted carbon centers of a-tertiary amines are constructed through various carbon-carbon bond or carbon-nitrogen bond forming reactions (Scheme 1).…”

“…[9][10][11][12][13][14][15][16] Ah igh level of enantiofacial discrimination at the ketimine by utilizing ac hiral catalyst or achiral auxiliary is crucial for asymmetric synthesis of a-tertiary amines.The geometry of the N-substituent of the ketimine has adramatic effect on the enantioselectivity. [9][10][11][12][13][14][15][16] Ah igh level of enantiofacial discrimination at the ketimine by utilizing ac hiral catalyst or achiral auxiliary is crucial for asymmetric synthesis of a-tertiary amines.The geometry of the N-substituent of the ketimine has adramatic effect on the enantioselectivity.…”

“…[11,12,17] The E/Z ratio of the ketimine is dependent on the difference in size between the ketimine substituents.D ue to rapid E/Z isomerization, as ignificant size difference between the two substituents on the imine carbon is required to render one geometric isomer more favorable. [9][10][11][12][13][14][15][16] On the other hand, ak etimine with two similar alkyl groups exists as an inseparable mixture of nearly equal amounts of E and Z-ketimines and inevitably yields the addition product in low stereoselectivity even when using the reliable chiral auxiliary-based methods (Scheme 2a). [9][10][11][12][13][14][15][16] On the other hand, ak etimine with two similar alkyl groups exists as an inseparable mixture of nearly equal amounts of E and Z-ketimines and inevitably yields the addition product in low stereoselectivity even when using the reliable chiral auxiliary-based methods (Scheme 2a).…”