Remarkable Levels of Enantioswitching in Catalytic Asymmetric Hydroboration
作者:Sean M. Smith、James M. Takacs
DOI:10.1021/ol101932q
日期:2010.10.15
phosphites and phosphoramidites are effective ligands for rhodium-catalyzed asymmetric hydroborations of β,γ-unsaturated amides, achieving up to 99% ee. However, the sense of stereoinduction, R or S, is surprisingly dependent on rather subtle features of the ligand. For example, catalysts employing a TADDOL phenylphosphite and those using the closely related N-methylaniline-derived phosphoramidite of the same
A flavor or fragrance composition containing 3-hydroxy-4-methylalkanoic acids, 4-methylalk-3-enoic acids and/or their esters of formula (I)
wherein R
1
, R
2
and R
3
have the same meaning as given in the description is disclosed.
[EN] A flavor or fragrance composition containing 3-hydroxy-4-methylalkanoic acids, 4-methylalk-3-enoic acids and/or their esters of formula (I), wherein R1, R2 and R3 have the same meaning as given in the description is disclosed. [FR] La présente invention porte sur une composition d'arôme ou de parfum qui contient des acides 3-hydroxy-4-méthylalcanoïques, des acides 4-méthylalk-3-énoïques et/ou leurs esters de formule (I), où R1, R2 et R3 ont la même signification que celle définie dans la description.
Amide-Directed Catalytic Asymmetric Hydroboration of Trisubstituted Alkenes
作者:Sean M. Smith、James M. Takacs
DOI:10.1021/ja908257x
日期:2010.2.17
rhodium-catalyzed reaction is stereospecific. In addition, simple TADDOL-derived phenyl monophosphite ligands in combination with Rh(nbd)(2)BF(4) afford highly enantioselective catalysts (seven examples, 91-98% ee). These catalysts provide an alternative methodology to prepare Felkin or anti-Felkin acetate-aldol products and related derivatives that are obtainable from the intermediate chiral organoboranes