19 F chemical shifts, coupling constants and conformational preferences in monosubstituted perfluoroparacyclophanes

In the process of studying the chemistry of perfluoro[2.2]paracyclophanes (PFPCs), a novel class of compounds, it became necessary to identify some disubstituted products. To achieve this goal, we characterize in this work some monosubstituted PFPCs, identifying their 19 F 19 F coupling patterns, and establishing a methodology for the assignment of their 19 F chemical shifts. The pattern of coupling constants indicates a skewed geometry in which the upper deck moves towards or away from the substituent, depending on the substituent electron‐donor character and size. Quantum chemical calculations, performed at the HF/6‐311 + G(d,p)//B3LYP/EPR‐III level of theory, confirmed the conformations inferred from coupling constants and reproduced well the values of the couplings. Transmission mechanisms for the FC term of four‐ and five‐bond 19 F 19 F couplings are discussed in detail. Understanding the conformational preferences of PFPCs and how they are reflected by the coupling constants facilitates the assignment of 19 F chemical shifts in monosubstituted PFPCs and the identification of the disubstituted products. Copyright © 2011 John Wiley & Sons, Ltd.