Reaction of diketene with benzaldehyde (1) in the presence of sulfuric acid gives α-benzylideneacetoacetic acid (5). Similarly, reaction of diketene with cinnamaldehyde (2) and β-phenylcinnamaldehyde (3) gives 2-acetyl-5-phenyl-2, 4-pentadienoic acid (6) and 2-acetyl-5, 5-diphenyl-2, 4-pentadienoic acid (7), respectively.
二乙酰乙烯(diketene)与
苯甲醛(1)在
硫酸存在下反应生成α-苄叉
乙酰乙酸(5)。类似地,
二乙酰乙烯与
桂皮醛(2)和β-苯基
桂皮醛(3)的反应分别生成2-乙酰-5-苯基-2, 4-五烯酸(6)和2-乙酰-5, 5
-二苯基-2, 4-五烯酸(7)。