74676-21-4Relevant articles and documents
A new selective allyl transfer reagent: Facile entry to β-hydroxy enol silyl ethers bearing two contiguous stereogenic centers
Szymoniak,Lefranc,Besancon,Moise
, p. 815 - 819 (1995)
η3-Allyltitanium(III) complexes functionalized on the C-2 with a silyloxy group can be prepared by the reaction of titanocene dichloride with isopropylmagnesium chloride in the presence of the corresponding 2-silyloxybutadienes. These complexes undergo a highly regio- and diastereoselective addition with aldehydes to produce, depending on the treatment applied, anti diastereomeric β-hydroxy silyl enol ethers or β-hydroxy ketones. Two defined contiguous stereocenters make the enol silyl ethers containing them versatile synthons for further stereocontrolled transformations. The reaction constitutes a new method for directing electrophiles to the α-position of the α,β-enone system.
A catalytic aldol reaction and condensation through in situ boron "ate" complex enolate generation in water
Aelvoet, Karel,Batsanov, Andrei S.,Blatch, Alexandrea J.,Grosjean, Christophe,Patrick, Leonard G. F.,Smethurst, Christian A.,Whiting, Andrew
, p. 768 - 770 (2008/12/20)
(Chemical Equation Presented) Cooperation is key: N-Butyl-1-benzimidazole- 2-phenylboronic acid hydroxide complex catalyzes the aldol condensation and aldol addition between hydroxyacetone or acetone, and different aldehydes in water. The catalytic activity results from cooperative interactions between the boronate complex and the imidazole function. Aldol condensation gives the unsaturated methyl ketones of acetone, whereas aldol addition predominates with hydroxyacetone.
Highly diastereo- and enantioselective direct aldol reactions of aldehydes and ketones catalyzed by siloxyproline in the presence of water
Aratake, Seiji,Itoh, Takahiko,Okano, Tsubasa,Nagae, Norio,Sumiya, Tatsunobu,Shoji, Mitsuru,Hayashi, Yujiro
, p. 10246 - 10256 (2008/09/18)
Proline-based organocatalysts have been developed for a highly enantioselective, direct aldol reaction of aldehydes and ketones in the presence of water. While several surfactant-proline combined catalysts have proved effective, proline derivatives with a hydrophobic moiety such as rraw-siloxy-L-proline and cis-siloxy-D-proline, both of which are easily prepared from the same commercially available 4-hydroxy-L-proline. have been found to be the most effective organocatalysts examined in this study, affording the aldol product with excellent diastereo- and enantioselectivities, these two catalysts generating opposite enantiomers. Water affects the selectivity, and poor results are obtained under neat reaction conditions or in dry organic solvents. More than three equivalents of water are required for the best diastereo- and enantioselectivities. while three equivalents is the recommended amount from a synthetic point of view. The reaction proceeds in the organic phase, and also proceeds in the presence of a large amount of water. The large-scale preparation of aldols with the minimal use of an organic solvent, including in the purification step. is described.
