2,3-Dihydro-4<i>H</i>-pyran-4-ones and 2,3-Dihydro-4-pyridinones by Cyclizations of α,β-Unsaturated 1,3-Diketones
作者:Franklyn K. MacDonald、D. Jean Burnell
DOI:10.1021/jo901355e
日期:2009.9.18
β-unsaturated 1,3-diketonescyclize to 2,3-dihydro-4H-pyran-4-ones in an acidic aqueous medium, with exceptions being α,β-unsaturated 1,3-diketones in which the β carbon is substituted by a phenyl group. Addition of 1-butanamine to the reaction medium results in the formation of 2,3-dihydro-4-pyridinones, which appear to arise via an initial 1,4-addition of the amine to the α,β-unsaturated 1,3-diketones.
在酸性水性介质中,多种α,β-不饱和1,3-二酮环化为2,3-二氢-4 H -pyran-4-one,但α,β-不饱和1,3-二酮除外β碳被苯基取代。将1-丁胺添加到反应介质中会导致形成2,3-二氢-4-吡啶酮,这似乎是由于将胺最初添加到α,β-不饱和的1,3-中而发生的,即最初的1,4-添加。二酮。
Highly efficient indium(<scp>iii</scp>)-mediated cyclisation of 5-hydroxy-1,3-diketones to 2,3-dihydro-4H-pyran-4-ones; mechanistic insights from in situFourier transform infrared spectroscopy
作者:Philip C. Andrews、William J. Gee、Peter C. Junk、Harald Krautscheid
DOI:10.1039/b919402a
日期:——
5-Hydroxy-1,3-diketones have been synthesised in a facile one-pot reaction from the treatment of acid chlorides with non-substituted ketones and LiHMDS. Subsequent cyclisation to 2,3-dihydro-4H-pyran-4-ones occurs rapidly and in high yield (89–99%) when mediated by anhydrous indium(III) chloride. A spectroscopic study of the reaction using in situ Fourier transform infrared (FTIR) spectroscopy has shown the reaction to be highly dependent on temperature, metal complex formation and InCl3 concentration. Since the reaction is deactivated by the precipitation of [InCl3·(H2O)3], the concurrent use of a stronger drying agent, such as molecular sieves 4 Å or anhydrous MgSO4, allows the reaction to be successfully carried out at relatively low loadings of InCl3 (1–10%). In their absence, the optimum reaction conditions were found to be a diketone : InCl3 ratio of 3 : 1 in toluene, and a reaction temperature of 80 °C.