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An efficient melting method for the synthesis of β-indole derivatives via Yonemitsu reaction was developed successfully using aldehyde, indole and Meldrum's acid as the starting materials and 50 μL water as green promoter without other solvent. A series of 5-[(indole-3-yl)-arylmethyl]-2,2-dimethyl-1,3-dioxane-4,6-dione derivatives were synthesized in 55%～ 94% yields. The remarkable advantages of this reaction were mild reaction condition, easy operation, tolerant the substrates with diverse functional groups and environment-friendly. Keywords melting method; multicomponent reaction; water; β-indole derivatives; green chemistry 吲哚骨架是广泛存在于天然产物和药物分子中的 重要结构单元 [1,2] , 特别是 β-取代吲哚衍生物, 已用于构 筑许多重要天然产物和具有生物活性的化合物骨架, 因 此, 其合成方法的研究格外引人注目 [3]. 由醛、 吲哚和麦 氏酸(Meldrum's acid)发生的三组分 Yonemitsu 缩合反应 是有效地合成 β-取代吲哚衍生物的方法之一 [4～11]. 近年 来, 报道了许多反应体系可以促进 Yonemitsu 缩合反应, 例如: 无催化剂条件下乙醇溶液中的反应 [12] 、无催化剂 无溶剂的固相研磨反应 [13] 、在生物质葡萄糖酸水溶液中 反应 [14] 和在新型反应介质低共熔溶剂中的反应 [15] 等.

In order to refine microstructure and improve mechanical properties, size of lamellar colonies and reinforced phase, distribution of elements, and microhardness with different solidification rates were studied by rapid solidification. Results show that microstructure morphology changes from equiaxed grain to granulated dendrites after rapid solidification. When speed of revolution increases, size of lamellar colonies decreases from 53.5 to 16.9 μm and length of TiB particles decreases from 60.1 to 20.4 μm. The B2 phase exists in lamellar colonies and at the boundary of lamellar colonies before rapid solidification and forms in lamellar colonies after rapid solidification. An increase in solidification rate increases degree of supercooling to increase number of nucleation particles which form before solidification front. The β phase incompletely transforms to the α phase and is retained in α phase after rapid solidification. The microstructure does not have enough time to transform completely and high‐temperature microstructure is retained at a higher cooling rate. Test results show that microhardness increases from 453 to 562 HV when speed of revolution increases from 0 to 800 rpm. Improvement of microhardness results from solution strengthening of Nb, Cr, and V, grain refinement strengthening and reduction of the reinforced phase of TiB.