Enantioselective catalytic borane reductions of aromatic ketones: Syntheses and application of two chiral β-amino alcohols from (S)-porretine

1,2-Amino Alcohols and Their Heterocyclic Derivatives as Chiral Auxiliaries in Asymmetric Synthesis

“…Examples of the additives are 3,5dimethylphenol, 217,[220][221][222][223] and N-ethylaniline. 218,219 Darvon alcohol (35) was the first amino alcohol, although it is 1,3 in construction, that did not require the use of additional additives to provide useful levels of induction (Scheme 33). 215,216,224,225 Care still has to be exercised with the darvon alcohol-lithium aluminum hydride system, as not only the degree of induction may be affected by the age of the reagent, but its sense as well.…”

“…240,241 The amino alcohol derived from 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid by reaction with phenyl Grignard does provide for moderate asymmetric induction for the borane reduction of aromatic ketones. 35 Amino alcohols have been employed as ligands for early transition metals to provide complexes where the metal is in a highly asymmetric environment. 242 A zirconium catalyst of this type has provided 93% ee for the opening of cyclohexene oxide with isopropyldimethylsilyl azide.…”

“…32 The Grignard reaction with amino acid derivatives to afford R,R-disubstituted β-amino alcohols has proven efficient with many examples (Scheme 4). [33][34][35] The synthesis of β-amino alcohols 7 can be achieved by NaBH 4 reduction of N-protected N-carboxyanhydrides 8 (Scheme 5). 36,37 In addition, N-protected mixed anhydrides can be reduced with this reagent to provide 1,2-amino alcohols.…”

Iridium-catalyzed asymmetric hydrogenation of olefins using TIQ phosphine–oxazoline ligands

“…23 Previous reports have described the application of N,P-derived TIQ oxazoline ligands for asymmetric C-C bond-forming reactions. [24][25][26] Herein we report a new class of iridium phosphineoxazoline catalysts for the asymmetric hydrogenation of olefins.…”

Synthesis and Screening of C1‐Substituted Tetrahydroisoquinoline Derivatives for Asymmetric Transfer Hydrogenation Reactions

“…Previous reports on the use of TIQ derivatives as catalytic ligands have yielded limited success, with poor to moderate enantioselectivities in asymmetric catalysis such as allylic alkylation [9] and borane mediated hydrogenation reactions. [10,11] Recently a related study of different TIQ ligands on the addition reaction of diethylzinc to benzaldehyde was reported with promising results. [12] Given the reports in literature thus far, we aimed to couple the catalytic success of the chiral amino alcohol-containing class of ligands, with the innovation of the TIQ scaffold towards the development of a novel series of efficient C 1 and C 3 -α Phenyl substituted TIQ amino alcohol ligands for ATH reactions.…”