Azides have proven to be useful precursors to amines in organic syntheses. This report describes an improvement of the diazotransfer reaction and the first example of a regioselective azide reduction of compounds containing multiple azides. The use of a specific ratio of solvents and zinc chloride as a catalyst resulted in a more efficient diazotransfer reaction capable of delivering >90% conversion per amine with shorter reaction times than those previously reported. Azides can be reduced with good regioselectivity in moderate yields by a modification of the Staudinger reaction using trimethylphosphine at low temperatures. Electronic factors determine the selectivity for azide reduction, and the reaction is predictable by NMR analysis of the starting material. Several examples for the diazotransfer and regioselective azide reduction reactions are given, and a mechanistic hypothesis for both is proposed.

The replacement of hydrogen atoms with fluorine substituents in organic substrates is of great interest in synthetic chemistry because of the strong electronegativity of fluorine and relatively small steric footprint of fluorine atoms. Many sources of nucleophilic fluorine are available for the derivatization of organic molecules under acidic, basic, and neutral conditions. However, electrophilic fluorination has historically required molecular fluorine, whose notorious toxicity and explosive tendencies limit its application in research. The necessity for an electrophilic fluorination reagent that is safe, stable, highly reactive, and amenable to industrial production as an alternative to very hazardous molecular fluorine was the inspiration for the discovery of selectfluor. This reagent is not only one of the most reactive electrophilic fluorinating reagents available, but it is also safe, nontoxic, and easy to handle. In this Review we document the many applications of selectfluor and discuss possible mechanistic pathways for its reaction.

For Abstract see ChemInform Abstract in Full Text.

Der Ersatz von Wasserstoff durch Fluor in organischen Substraten ist wegen der hohen Elektronegativität des Fluors bei fast gleich bleibendem Raumanspruch von großem Interesse in der Synthesechemie. Viele Quellen für nucleophiles Fluor zur Derivatisierung unter sauren, basischen und neutralen Bedingungen stehen zur Verfügung. Hingegen erforderte eine elektrophile Fluorierung früher den Einsatz von molekularem Fluor, was aufgrund dessen Toxizität und Explosionsneigung zu einer nur begrenzten Anwendung dieser Methode geführt hat. Der Bedarf an einem elektrophilen Fluorierungsreagens, das sicher zu handhaben, stabil und hoch reaktiv ist und in der industriellen Produktion als Alternative zum hoch giftigen gasförmigen Fluor eingesetzt werden kann, führte letztlich zur Entwicklung von Selectfluor (1). Dieses Reagens ist eines der reaktivsten elektrophilen Fluorierungsmittel und dazu noch ungefährlich, nicht toxisch und leicht zu handhaben. In diesem Aufsatz beschreiben wir die zahlreichen Einsatzmöglichkeiten von Selectfluor und diskutieren mögliche Reaktionsmechanismen.

For Abstract see ChemInform Abstract in Full Text.