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.
A General Method for the Enantioselective Synthesis of Pantolactone Derivatives
作者:David A. Evans、Jimmy Wu、Craig E. Masse、David W. C. MacMillan
DOI:10.1021/ol026489d
日期:2002.10.1
An efficient enantioselective synthesis of beta,beta-dialkyl-gamma-substituted pantolactones has been achieved utilizing the cationic [Sc((S,S)-R-pybox)](Cl)(2)(+), R = Ph (9), t-Bu (10), complex in a catalyzed aldol reaction as the key step. The pantolactone derivatives are isolated in high enantiomeric excesses. [reaction: see text]
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.
Repeated Use of the Catalyst in Ln(OTf)<sub>3</sub>-Catalyzed Aldol and Allylation Reactions
作者:Shu Kobayashi、Iwao Hachiya、Yoshinori Yamanoi
DOI:10.1246/bcsj.67.2342
日期:1994.8
triflate)-catalyzed aldol reactions of silyl enol ethers with aldehydes and allylation reactions of tetraallyltin with aldehydes proceeded smoothly in a water–ethanol–toluene system. The reactions proceeded much faster in the above solvent than in water–tetrahydrofuran. Repeated use of the catalyst in these reactions was realized by a very simple procedure.