from l‐ and d‐xylose, and l‐ and d‐arabinose, respectively. These monosaccharide‐based chiral macrocycles were tested as phase transfer catalysts in a few asymmetric reactions. The xylal‐based crown compounds proved to be efficient catalysts in a few liquid‐liquid phase reactions. The epoxidation of trans‐chalcone and the Darzens condensation of α‐chloroacetophenone with benzaldehyde took place with
The chiral monoaza-15-crown-5 lariat ethers annellated to methyl-4,6-O-benzylidene-α-d-glucopyranoside-1 or mannopyranoside 2 have been applied as phase-transfercatalysts in the epoxidation of substituted chalcones and chalcone analogues with tert-butylhydroperoxide resulting in significant asymmetricinduction. It was found that the position of the substituents in the aromatic ring of the chalcone
Abstract New recyclable monoaza-15-crown ethers have been synthesized starting from ( R , R )-(+)- and ( S , S )-(−)-hydrobenzoin. These macrocycles proved to be efficient and reusable phase transfer catalysts in a few asymmetric reactions under mild conditions. The asymmetric epoxidation of trans -chalcone took place with up to 81% ee, while using other chalcone derivatives, the products were formed
摘要 以 ( R , R )-(+)- 和 ( S , S )-(-)- 氢安息香为原料合成了新的可回收单氮杂-15-冠醚。在温和条件下的一些不对称反应中,这些大环被证明是有效且可重复使用的相转移催化剂。反式查耳酮的不对称环氧化反应的 ee 高达 81%,而使用其他查耳酮衍生物时,生成的产物 ee 高达 68-88%。还使用溴丙二酸二乙酯在一些缺电子烯烃的环丙烷化中测试了基于氢安息香的套索醚,以提供具有良好对映选择性(54-75% ee)的产物。催化剂通过成盐回收,然后萃取,并在不损失活性和对映选择性影响的情况下重复使用。
Asymmetric epoxidation of α,β-unsaturated ketones under phase-transfer catalyzed conditions
作者:Shigeru Arai、Hiroki Tsuge、Takayuki Shioiri
DOI:10.1016/s0040-4039(98)01646-3
日期:1998.10
Asymmetricepoxidation of a,b-unsaturated ketones with H2O2 was developed using a chiral quaternary ammonium salt as the phase-transfer catalyst. A catalytic amount of N-[4-(iodo)benzyl]cinchoninium bromide, easily prepared from cinchonine, was effective in the asymmetricepoxidation for producing the corresponding desired products with up to 92% ee under mild reaction conditions.
使用手性季铵盐作为相转移催化剂,开发了H 2 O 2对a,b-不饱和酮的不对称环氧化。容易由辛可宁制备的催化量的N- [4-(碘)苄基]辛基溴化铵在不对称环氧化中有效,可在温和的反应条件下生产相应的所需产物,其ee最高为92%。
Photochemistry of aromatic .alpha.,.beta.-epoxy ketones. Substituent effects on oxirane ring-opening and related ylide behavior