selective aldol reaction mediated by boron compounds and a mild organic base (DBU) was developed. Inclusion of electron-withdrawing groups in the amino acid derivative ligands reacted with BH3·SMe2 forms a boron promoter with increased Lewis acidity at the boron atom and facilitated the carboxylic acid selective enolate formation, even in the presence of other carbonyl groups such as amides, esters, ketones
Diastereoselective Aza‐Mislow–Evans Rearrangement of
<i>N</i>
‐Acyl
<i>tert</i>
‐Butanesulfinamides into α‐Sulfenyloxy Carboxamides
作者:Fan Tang、Yun Yao、Yan‐Jun Xu、Chong‐Dao Lu
DOI:10.1002/anie.201809551
日期:2018.11.19
diastereoselective [2,3] rearrangement of O‐silyl N‐sulfinyl N,O‐ketene acetals derived from chiral N‐acyl tert‐butanesulfinamides was developed, giving α‐sulfenyloxy carboxamides with excellent enantioselectivity. Enolization and subsequent silylation of N‐acyl tert‐butanesulfinamides initiate this aza variant of the Mislow–Evans rearrangement, in which the chirality at the sulfur atom in the rearrangement precursors
Siloxy Esters as Traceless Activators of Carboxylic Acids: Boron‐Catalyzed Chemoselective Asymmetric Aldol Reaction**
作者:Taiki Fujita、Mina Yamane、W. M. C. Sameera、Harunobu Mitsunuma、Motomu Kanai
DOI:10.1002/anie.202109788
日期:2021.11.8
We developed a chiral boron-catalyzed, carboxylic acid-selective asymmetric aldol reaction applicable to multifunctional substrates at late stages for the first time. Computational studies rationalized the reaction mechanism and stereoselectivity through Si/B enediolates acting as the active species.
A catalytic carboxylic acid-selective aldol reaction with trifluoromethyl ketones was developed. Reversible and selective covalent bond formation between a boron catalyst and a carboxylic acid is key to realizing the unprecedented catalytic aldol reaction of simple carboxylic acids. The reaction proceeded chemoselectively at the α-position of carboxylic acid even in the presence of ketone, ester, or