Theoretical DFT study of the NMR parameters, shielding and spin-spin coupling constant, of the products of a pinacol alkenylboronates? DielsAlder reaction.

M. NATALIA C. ZARYCZ; MARGARITA M. VALLEJOS; SILVINA C. PELLEGRINET; PATRICIO F. PROVASI

Montevideo

Congreso; QUITEL 2016, 42nd International Congress of Theoretical Chemists of Latin Expression; 2016

Universidad de la Republica. Uruguay.

We have studied theoretically some magnetic properties for selected products of the Diels-Alder reactions for pinacol alkenylboronates with cyclopentadiene, which recently were synthesized and their structures were determined by a combination of spectroscopic methods such as Infrared (IR), 1D and 2D Nuclear Magnetic Resonance (NMR) and High Resolution Mass Spectrometry (HRMS). We calculated the NMR parameters, shielding (σ) and spin-spin coupling constant (J), for five reported boronate cycloadducts at B3LYP/cc-pVTZ-J level of theory, in order to help the elucidation of the NMR experimental spectra, i.e., to verify the assigned signals and to clarify the origin of ambiguous ones. We also seek to predict some signals that could not be experimentally determined and therefore gives further support to the NMR structure characterization of this kind of compound.We found that most of the experimental assignments are in good agreement with our calculations. The computational data exhibit to be a good tool to clarify the nuclei which gives the signals that could not be conclusively assigned experimentally. We also propose some possible σ and J values which could not be measured experimentally. Moreover we analyze carefully the shieldings and coupling constants within the bicyclo [2.2.1]heptane backbone and separately in the boron-substituent.