Aerobic oxidative desymmetrization of meso-diols with bifunctional amidoiridium catalysts bearing chiral N-sulfonyldiamine ligands
摘要:
Asymmetric aerobic oxidation of a range of meso- and prochiral diols with chiral bifunctional Ir catalysts is described. A high level of chiral discrimination ability of Cp*Ir complexes derived from (S,S)-1,2-diphenylethylenediamine was successfully demonstrated by desymmetrization of secondary benzylic diols such as cis-indan-1,3-diol and cis-1,4-diphenylbutane-1,4-diol, providing the corresponding (R)-hydroxyl ketones with excellent chemo- and enantioselectivities. Enantiotopic group discrimination in oxidation of symmetrical primary 1,4- and 1,5-diols gave rise to chiral lactones with moderate ees under similar aerobic conditions. (C) 2014 Elsevier Ltd. All rights reserved.
Aerobic oxidative desymmetrization of meso-diols with bifunctional amidoiridium catalysts bearing chiral N-sulfonyldiamine ligands
摘要:
Asymmetric aerobic oxidation of a range of meso- and prochiral diols with chiral bifunctional Ir catalysts is described. A high level of chiral discrimination ability of Cp*Ir complexes derived from (S,S)-1,2-diphenylethylenediamine was successfully demonstrated by desymmetrization of secondary benzylic diols such as cis-indan-1,3-diol and cis-1,4-diphenylbutane-1,4-diol, providing the corresponding (R)-hydroxyl ketones with excellent chemo- and enantioselectivities. Enantiotopic group discrimination in oxidation of symmetrical primary 1,4- and 1,5-diols gave rise to chiral lactones with moderate ees under similar aerobic conditions. (C) 2014 Elsevier Ltd. All rights reserved.
quantitative reduction of aromatic aldehydes, ketones, diketones and oxo aldehydes to alcohols by use of TiCl3/NH3 in aqueous methanol solution is reported. The reducing system distinguishes between different classes of aldehydes and/or ketones, and many functionalities that usually do not survive under reducing conditions are tolerated well. The concept of reversal of chemoselectivity has also been developed
Stereoselective Synthesis ofanti-1,4-Diols by a BH3⋅THF-Mediated Rearrangement of 1,2-Disubstituted Cyclobutenes
作者:Kolja M. Knapp、Bernd Goldfuss、Paul Knochel
DOI:10.1002/chem.200304902
日期:2003.11.7
A new stereoselective rearrangement of cyclobutylboranes, obtained by the hydroboration of 1,2-disubstituted cyclobutenes, provides anti-1,4-diols with good-to-excellent diastereoselectivity. The mechanism of the rearrangement is discussed based on theoretical calculations.
An efficient method for the preparation of C2-symmetric, chiral alk-2-ene-1,4-diols (4) has been achieved, based on the borane-mediated reduction of symmetric alk-2-ene-1,4-diones (2) in the presence of oxazaborolidine (R)-1. In general, the presence of the double bond in 2 has been beneficial (compared with the related saturated 1,4-diketones 3) not only as far as the stereoselectivity in the reduction
Development of Chiral Bis-hydrazone Ligands for the Enantioselective Cross-Coupling Reactions of Aryldimethylsilanolates
作者:Scott E. Denmark、Wen-Tau T. Chang、K. N. Houk、Peng Liu
DOI:10.1021/jo502388r
日期:2015.1.2
aryldimethylsilanolates and arylbromides result in biaryl products with the same configuration and similar enantioselectivities implying that reductive elimination is the stereodetermining step. The origin of stereoselectivity is rationalized through computational modeling of diarylpalldium(II) complex which occurs through a conrotatory motion for the two aryl groups undergoing C–C bondformation.
A regio- and stereoselectivemigration takes place under mild conditions for tertiary organoboranes obtained by hydroboration of tetrasubstituted cyclic alkenes. A subsequent amination proceeds with perfect control of the stereochemistry. The scheme shows an example of this for the reaction of bicyclo[4.3.0]non-1(6)-ene (1) to 2 via intermediates 3 and 4. Compound 2 is formed as the single diastereomer