The aromatic hydroxyaldehydes 3a-3g, 5a-5f, 8 , 10 can be prepared by the action of BCl3, BBr3 or trifluoromethanesulfonic acid, on the aryl formates 1a-1f, 4a-e, 7, 9 via Fries rearrangement. BBr3 is more effective than BCl3. The activating ability of BBr3 can be improved by addition of FeCl3. Rearrangements which are induced by trifluoromethanesulfonic acid can give rise to the formations of regioisomers, which might be different from the products formed when the reaction is performed with Lewis acids. The yields of the aldehydes are lowered by subsequent condensation reactions. This view was confirmed by the isolation of a condensation product, which was characterized as a dibenzo[a,j]xanthene derivative 6 by crystal structure analysis. For the Fries rearrangement of formyl groups a new mechanism is proposed. 2-Hydroxy-1-naphthaldehyde 5c can be obtained in good yield from formic acid, BBr3, and 2 -naphthol.
芳香羟基醛类化合物3a-3g、5a-5f、8、10可通过BCl3、BBr3或三氟甲磺酸作用于芳基甲酸酯1a-1f、4a-e、7、9来制备,通过弗里斯重排反应。BBr3比BCl3更有效。BBr3的活化能力可以通过添加FeCl3来改善。由三氟甲磺酸诱导的重排反应可能导致产生位置异构体的形成,这与在Lewis酸存在下进行反应形成的产物可能不同。醛类产物的产率会因随后的缩合反应而降低。通过结晶结构分析,这一观点得到了验证,通过分离得到的缩合产物,被鉴定为二苯并[a,j]苯并二氢吖啶衍生物6。对于甲酰基团的弗里斯重排反应提出了一个新的机制。2-羟基-1-萘醛5c可以通过甲酸、BBr3和2-萘酚以较高的产率获得。