156849-69-3Relevant academic research and scientific papers
Chemistry of enoxysilacyclobutanes: Highly selective uncatalyzed aldol additions
Denmark, Scott E.,Griedel, Brian D.,Coe, Diane M.,Schnute, Mark E.
, p. 7026 - 7043 (2007/10/02)
O-(Silacyclobutyl) ketene acetals derived from esters, thiol esters, and amides underwent facile aldol addition with a variety of aldehydes at room temperature without the need for catalysts. The uncatalyzed aldol addition reaction of O-(silacyclobutyl) ketene acetals displayed the following characteristics: (1) the rate of reaction was highly dependent on the spectator substituent on silicon and the geometry of the ketene acetal, (2) the O,O-ketene acetal of E configuration afforded the syn aldol products with high diastereoselectivity (93/7 to 99/1), (3) conjugated aldehydes reacted more rapidly than aliphatic aldehydes, and (4) the reaction was mildly sensitive to solvent. In addition, the aldol reaction was found to be efficiently catalyzed by metal alkoxides. Labeling experiments revealed that the thermal aldol reaction proceeds by direct intramolecular silicon group transfer, while the alkoxide-catalyzed version probably proceeds via in situ generated metal enolates. Computational modeling of the transition states suggests that the boat transition structures are preferred, supporting the observed syn selectivity of the thermal aldol reaction. Both thermal and alkoxide-catalyzed Michael additions were investigated, revealing a competition between 1,2- and 1,4-addition favoring the former.
Stereoselective reduction of 2-methyl-3-oxo esters (or amides) with sodium borohydride catalyzed by manganese (II) chloride or tetrabutylammonium borohydride. A practical preparation of erythro and threo-3-hydroxy-2-methyl esters (or amides)
Taniguchi, Masahiko,Fujii, Hideaki,Oshima, Koichiro,Utimoto, Kiitiro
, p. 11169 - 11182 (2007/10/02)
erythro-3-Hydroxy-2-methylpropionates or erythro-3-hydroxy-2-methylpropionamides were prepared with high stereoselectivity by NaBH4 reduction of the corresponding 2-methyl-3-oxo esters or 2-methyl-3-oxo amides in the presence of a catalytic amount of manganese(II) chloride. On the other hand, reduction of these substrates with n-Bu4NBH4 provided threo-isomers selectively. erythro-Selective reduction of 2-methyl-3-oxo amides with NaBH3CN in 1N HCl-MeOH is also described.
