A Facile Method for the Synthesis of 4- Acetylaminobenzo[15]crown-5

The 4-acetylaminobenzo[15]crown-5 is an important intermediate in the synthesis of crown ether cyanine dyes1, in addition, the acetylamino can easily be hydrolyzed to be amine2, to our knowledge which also is an usful intermediate3,4, The classical procedure for the synthesis of 4-acetylaminobenzo[15]crown-5 involves several steps2,5: typically nitration of the benzo[15]crown-5, followed by reduction of the introduced nitro group to form amine, and finally, acylation of the amine to give the am…

A Facile Method for the Synthesis of 4- Acetylaminobenzo[15]crown-5

The 4-acetylaminobenzo[15]crown-5 is an important intermediate in the synthesis of crown ether cyanine dyes1, in addition, the acetylamino can easily be hydrolyzed to be amine2, to our knowledge which also is an usful intermediate3,4, The classical procedure for the synthesis of 4-acetylaminobenzo[15]crown-5 involves several steps2,5: typically nitration of the benzo[15]crown-5, followed by reduction of the introduced nitro group to form amine, and finally,acylation of the amine to give the amide. In the classical procedure, the reduction of the nitro group is usually proceeded under N2 atmosphere and catalysts such as palladium, Raney Ni are usually employed, which constitute a particular inconvenience.We now report a facile one-pot reaction which can be conducted under mild conditions and avoid the time-consuming nitration step and the inconvenient reduction step.The reaction starts with para-selective C-acylation of the benzo[15]crown-5, which is followed by oxime formation and Beckmann rearrangement in situ. The reaction is proceeded by stirring at moderate temperature, a mixture of polyphosphonic acid, benzo[15]crown-5, glacial acetic acid and hydroxylamine hydrochloride (Scheme I), herein polyphosphonic acid act as catalyst.In conclusion, we have found a facile and convenient method for the synthesis of 4-acetylaminobenzo[15]crown-5, with the advantage of mild conditions, simple operation, short reaction time and less pollution compared with the classical procedure. It is a novel procedure for the synthesis of 4- acetylaminobenzo[15]crown-5.