66049-31-8Relevant academic research and scientific papers
DMAP-organocatalyzed O-silyl-O-(or C-)-benzoyl interconversions by means of benzoyl fluoride
Poisson, Thomas,Dalla, Vincent,Papamica?l, Cyril,Dupas, Georges,Marsais, Francis,Levacher, Vincent
, p. 381 - 386 (2007)
A mild and efficient transprotection of alcohols from silyl ethers 1a-f to benzoates 2a-f is reported in fair to good yields (50-98%). This silyl-acyl exchange reaction proceeds readily in acetonitrile at room temperature in the presence of benzoyl fluoride and DMAP as an acyl transfer catalyst. A two-step 'one-pot' DMAP-catalyzed silylcyanation-transprotection sequence which gives the corresponding O-benzoyl cyanohydrines 2g-l in high yields (72-98%) from various benzaldehyde and ketone derivatives is also reported. This original organocatalytic acyl transfer process was also found to be effective in the O-benzoylation of trimethysilyl enolates 1m-o, providing enol esters 2m-o. Lastly, the potential of this strategy is also illustrated by a DMAP-mediated Claisen condensation between ketene silyl acetals 1p-r and benzoyl fluoride. Georg Thieme Verlag Stuttgart.
Asymmetric Oxidation of Enol Derivatives to α-Alkoxy Carbonyls Using Iminium Salt Catalysts: A Synthetic and Computational Study
Page, Philip C. Bulman,Almutairi, Saud M.,Chan, Yohan,Stephenson, G. Richard,Gama, Yannick,Goodyear, Ross L.,Douteau, Alice,Allin, Steven M.,Jones, Garth A.
, p. 544 - 559 (2019/01/11)
We report herein the first examples of asymmetric oxidation of enol ether and ester substrates using iminium salt organocatalysis, affording moderate to excellent enantioselectivities of up to 98% ee for tetralone-derived substrates in the α-hydroxyketone products. A comprehensive density functional theory study was undertaken to interpret the competing diastereoisomeric transition states in this example in order to identify the origins of enantioselectivity. The calculations, performed at the B3LYP/6-31G(D) level of theory, gave good agreement with the experimental results, in terms of the magnitude of the effects under the specified reaction conditions, and in terms of the preferential formation of the (R)-enantiomer. Just one of the 30 characterized transition states dominates the enantioselectivity, which is attributed to the adoption of an orientation relative to stereochemical features of the chiral controlling element that combines a CH interaction between a CH2 group in the substrate and one of the aromatic rings of the biaryl section of the chiral auxiliary with a good alignment of the acetoxy group with the other biaryl ring, and places the smallest substituent on the alkene (a hydrogen atom) in the most sterically hindered position.
Enantioselective synthesis and stereoselective rearrangements of enol ester epoxides
Zhu,Shu,Tu,Shi
, p. 1818 - 1826 (2007/10/03)
Enol esters can be epoxidized with high enantioselectivities using the fructose-derived chiral ketone 1 as catalyst and Oxone as oxidant. A detailed study of enantiomerically enriched enol ester epoxides has revealed that the acid-catalyzed rearrangement can proceed through two distinct pathways, one with retention of configuration and the other with inversion. The competition between the two pathways is highly dependent upon the nature of the acid catalyst. A strong acid favors retention of configuration and a weak acid favors inversion of configuration. Under thermal conditions, these epoxides rearrange highly stereoselectively with inversion of configuration. Either enantiomer of an α-acyloxy ketone can be formed from one enantiomer of an enol ester epoxide by judicious choice of reaction conditions.
