Design and Synthesis of Chiral N-Chloroimidodicarbonates: Application to Asymmetric Chlorination of Silyl Enol Ethers
摘要:
New chiral N-chloroimidodicarbonates, which function as efficient chiral chlorinating agents, were designed and synthesized. Among these, C-2-symmetric (1R,2S,5R)-(-)-menthyl-N-chloroimidodicarbonate 2a provided moderate to good enantioselectivity (up to 40%) for the chlorination of silyl enol ethers to afford alpha-chloroketones only in the presence of a suitable Lewis acid such as Sm(OTf)(3).
Depending on the steric hindrance of the reaction centers, hemiacetal vinylogs 1 in the presence of BF3.OEt2 can, with enol ethers, lead to a Michael-typeaddition (4) or an aldolisation-type reaction (3). Hemiacetal vinylog 1b always yields the second reaction leading to β-methoxy-γ,δ-ethylenic carbonyl compounds 4 precursors of polyenic carbonyl compounds 5. Crotonaldehyde and methanol can be used
Synthesis of Optically Active α-Hydroxy Carbonyl Compounds by the Catalytic, Enantioselective Oxidation of Silyl Enol Ethers and Ketene Acetals with (Salen)manganese(III) Complexes
作者:Waldemar Adam、Rainer T. Fell、Veit R. Stegmann、Chantu R. Saha-Möller
DOI:10.1021/ja9726668
日期:1998.2.1
A set of silyl enol ethers and ketene acetals 1a−h with α- and/or β-phenyl as well as alkyl substituents of different steric bulk has been submitted to the enantioselective catalytic oxidation by chiral (salen)MnIII complexes 3. Highest conversions and best enantioselectivities have been obtained with bleach rather than iodosobenzene as oxygen source for the active oxo−metal species. With regard to
Organocatalytic α-trifluoromethylthiolation of silylenol ethers: Batch vs continuous flow reactions
作者:Said Said Abubakar、Maurizio Benaglia、Sergio Rossi、Rita Annunziata
DOI:10.1016/j.cattod.2017.09.013
日期:2018.6
performed under a traditional batch methodology and under continuousflow conditions. In general, yields obtained using the traditional batch process were higher than those observed when the reaction was performed under flow conditions. However, short reaction times, higher productivity and higher space time yields were observed when a flow system process was employed. Preliminary DFT calculations