Aggregation studies of lithium dialkylamides. The role of aggregates in the carbonylation reaction
摘要:
C-13 NMR spectroscopy and isotopic exchange in carbonylation intermediates have been successfully employed to characterize aggregation of lithium dialkylamides in THF solution. It is shown that lithium (3-oxapentamethylene)amide forms a 1:1 mixed aggregate with morpholine. The aggregate remains even in diluted THF solution. Lithium pentamethyleneamide also forms aggregates with piperidine while the less acidic amines do not form mixed aggregates with the corresponding lithium dialkylamide either in the solid state or in THF solution. The product composition in the carbonylation reaction of lithium dialkylamides is highly dependent on their aggregation states, and this phenomenon can be successfully used for synthetic purposes.
New Insights into the Chemistry of Lithium Carbamoyls: Characterization of an Adduct (R<sub>2</sub>NC(O)CLi(OLi)NR<sub>2</sub>)
作者:Norma S. Nudelman、Guadalupe E. García Liñares
DOI:10.1021/jo9908445
日期:2000.3.1
the reaction mixtures showed the presence of similar intermediates in all cases: adducts of this type have not been reported before. These dilithiated intermediates were trapped with methyl iodide giving the corresponding doubly methylated derivatives. Isolation of substituted glyoxylamides and quantitative determination of the products yields constitute further evidence of the whole reaction scheme
Development of an organo- and enzyme-catalysed one-pot, sequential three-component reaction
作者:Angela Kinnell、Thomas Harman、Matilda Bingham、Alan Berry、Adam Nelson
DOI:10.1016/j.tet.2012.02.010
日期:2012.9
A one-pot, three-component process is described which involves both organo- and enzyme-catalysed carbon-carbon bond-forming steps. In the first step, an organocatalyst catalyses the aldol reaction between acetaldehyde and a glyoxylamide. After dilution with additional aqueous buffer, and addition of pyruvate and an aldolase enzyme variant, a second aldol reaction occurs to yield a final product. Crucially, it was possible to develop a reaction in which both the organo- and enzyme-catalysed reactions could be performed in the same aqueous buffer system. The reaction described is the first example of a one-pot, three-component reaction in which the two carbon-carbon bond-forming processes are catalysed using the combination of an organocatalyst and an enzyme. (C) 2012 Elsevier Ltd. All rights reserved.