The dehydration of glucose and other hexose carbohydrates to 5‐(hydroxymethyl)furfural (HMF) was investigated in imidazolium‐based ionicliquids with boricacid as a promoter. A yield of up to 42 % from glucose and as much as 66 % from sucrose was obtained. The yield of HMF decreased as the concentration of boricacid exceeded one equivalent, most likely as a consequence of stronger fructose–borate