《Tab.1 Effects of catalyst, additive, and solvent on yielda》

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《"串联反应合成2-氨基-3,5-二氰基-4H-吡喃衍生物（英文）"》

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aReactions were carried out using cyanochalcone（1a）（0.5mmol） ，malononitrile（2）（0.5 mmol） ，and base（0.05 mmol）in dichloromethane（5 m L）at 10℃for 20 h；bThe amount of additives:10 mol%（base）；silica gel is 200～300 mesh.

Initially，we screened a variety of bases for catalysts as shown in Tab.1（Entries 1～13）.Among the screened catalysts，inorganic bases showed superior catalytic activities when compared with organic bases.With the weak base sodium bicarbonate as the catalyst，the yield of the desired pyran product was 83.3%（Entry 1）.The moderate base catalysts sodium carbonate and potassium carbonate afforded the products in 82%and 88%yields，respectively（Entries 2and 4）.Although potassium hydroxide afforded product 3a in 97%yield（Entry 3），sodium hydroxide provided only a moderate yield of 72%（Entry 5）.Turning to sodium acetate，the product 3a was obtained in89%yield（Entry 6）.Finally，the weak base zinc acetate was proved to be the most efficient，affording the pyran product 3a in 98%yield（Entry 7）.In comparison，organic bases showed overall lower catalytic abilities as DMAP and DABCO gave 68%（Entry 8）and61%（Entry 9）yields，respectively.Using zinc acetate as the catalyst，the effect of additives was also examined.Among the additives we tested（Entries 10～13），none of them was shown to further improve reaction efficiency according to the corresponding yields.For this reason，additives were not employed in the reaction optimization process.