1-methylborepin, its aromaticity and thermal decomposition

Abstract

1-Methylborepin (I) is judged to be aromatic on the basis of a) the value of its Hückel MO resonance energy, b) the ring-current effect on its 1H NMR spectrum, and c) its degree of aromaticity based on Julg's criterion. The thermal stabilities of hetero-conjugated monocyclic ring systems containing 5, 7, 9, and 11 ring atoms and B or N as the hetero atom are assessed to the basis of orbital symmetry considerations. Hetero-conjugated ring systems containing 2 n + 1 ring atoms (2 n being the number of ring carbon atoms) are predicted to be thermally stable when n is even, and thermally unstable when n is odd.