The total synthesis of cystothiazole A is described. Key steps of the synthesis include an Evans asymmetric catalytic aldol reaction, which established the required C-4-C-5 stereochemistry. The [2,4']-bis(thiazole) was obtained applying our methodology of electrophilic activation of amide. Semistabilized Wittig reaction between the phosphonium salt 3 and the aldehyde 2 afforded 1 in nine linear steps and 38% overall yield.
Lewis acid catalysis in a supercritical carbon dioxide (scCO2)-poly(ethylene glycol) derivatives (PEGs) system: remarkable effect of PEGS as additives on reactivity of Ln(OTf)3-catalyzed Mannich and aldol reactions in scCO2
作者:Ichiro Komoto、Shū Kobayashi
DOI:10.1039/b106437c
日期:——
Use of poly(ethylene glycol) derivatives (PEGs) as additives
in supercritical carbon dioxide (scCO2) was found to be
effective for Mannich and aldol reactions of silyl enolates with aldehydes
and imines, and formation of emulsions was observed in these systems.
N-Allylideneamines 1a, b were prepared from acrolein and diphenylethyl or trityl amine in the presence of Ti(OEt)4. Double nucleophilicaddition of various ketene silyl (thio)acetals and trimethylsilyl cyanide to these imines proceeded efficiently to give, after workup with TFA, homoglutamic acid derivatives 3 and valerolactam 5.
Synthesis of β-Amino Esters by Bismuth Triflate Catalyzed Three-Component Mannich-Type Reaction
作者:Thierry Ollevier、Etienne Nadeau
DOI:10.1055/s-2005-923594
日期:——
Bismuth triflate catalyzes the Mannich-typereaction of a variety of in situ generated aldimines using aldehydes, anilines, and silyl enol ethers in a three-componentreaction. The reaction proceeds rapidly and affords the corresponding protected beta-amino ketones in high yields (up to 94%).
In the presence of silica gel or titanium tetrachloride, ketenesilylacetals or ketenesilyl thioacetals underwent 1,4-addition with α,β unsaturated aldimines which possess a large triphenylmethyl group at the imino nitrogens followed by reduction with sodium cyanoborohydride to give aminopropylated products, δ-amino esters, in good yields.