N-Aryl pyrazoles were prepared from anilines in a three step telescoped approach. An aniline was diazotized to give the diazonium fluoroborate, followed by reduction with tin(II) chloride to give the corresponding hydrazine, which in turn reacted with a ketoenamine to give the N-aryl pyrazole. The deprotection of the methyl ether was accomplished with PhBCl 2 to give the final product. The continuous flow methodology was used to minimize accumulation of the highly energetic and potentially explosive diazonium salt and hydrazine intermediates to enable the safe scale-up of N-aryl pyrazoles. The heterogeneous reaction mixture was successfully handled in both lab scale and production scale. A continuous extraction was employed to remove organic impurities from the diazotization step, which eliminated the need for chromatography in the purification of the final N-aryl pyrazole.

Many years ago anidulafungin 1 was identified as a potentially useful medicine for the treatment of fungal infections. Its chemical and physical properties as a relatively high molecular weight semisynthetic derived from echinocandin B proved to be a significant hurdle to its final presentation as a useful medicine. It has recently been approved as an intravenous treatment for invasive candidaisis, an increasingly common health hazard that is potentially life-threatening. The development and commercialization of this API, which is presented as a molecular mixture of anidulafungin and D-fructose is described. This includes, single crystal X-ray structures of the starting materials, the echinocandin B cyclic-peptide nucleus (ECBN • HCl) and the active ester 1-({[4′′-(pentyloxy)-1,1′:4′,1′′-terphenyl-4-yl]carbonyl}oxy)-1H-1,2,3-benzotriazole (TOBt). Details of the structure and properties of starting materials, scale-up chemistry and unusual crystallization phenomena associated with the API formation are discussed.