2‐ and 3‐Fluorocyclobutane Building Blocks for Organic and Medicinal Chemistry

Abstract Multigram synthesis of 3‐fluorinated cyclobutane building blocks has been disclosed. The proposed synthetic schemes were based on nucleophilic fluorination and eventually led to 3‐fluorocyclocutanecarboxylic acid as a key target compound and intermediate. Further functional group transformations provided monofluorinated cyclobutane‐derived alcohols, amines, bromides, thiols, sulfonyl chlorides, etc. Furthermore, the synthesis of diastereopure cis‐ and trans ‐isomeric 2‐ and 3‐fluorocyclobutanecarboxylic acids and amines was also performed. In both cases, diastereomer separation was used to obtain pure stereoisomers. The effect of the fluorine position and relative spatial orientation on the physicochemical properties of the corresponding monoflurinated derivatives was studied by measurements of p K a and log P values.