Preparation of Fluoroadamantane Acids and Amines:  Impact of Bridgehead Fluorine Substitution on the Solution- and Solid-State Properties of Functionalized Adamantanes

Functionalized adamantanes are utilized as medicinal therapeutics and a practical route to novel bridgehead fluorinated adamantylamines and acids including fully fluorinated 3,5,7-tri-fluoroadamantane-1-carboxylic acid 1 and 3,5,7-trifluoroadamantane-1-amine 2 is described. Potassium permanganate-mediated bridgehead hydroxylation followed by DAST fluorination was utilized to sequentially insert bridgehead fluorine atoms. 13C NMR chemical shifts of mono-, di-, and trifluoroadamantylamines, acids and carbamates reveal long-range fluorine-mediated electronic effects within the adamantane framework, most notably by substrates bearing three bridgehead fluorine atoms. The impact of multiple bridgehead fluorine substitution on structure (X-ray crystallography) and on physicochemical parameters such as acidity (pKa) and lipophilicity (log P) which are important for the design of medicinal therapeutics is assessed.