Pyrolytic cyclisation reactions of 3-azolylpropenyl alcohols; unexpectedly facile thermal decomposition of 5H-pyrrolo[2,1-a]isoindole

Abstract

Flash vacuum pyrolysis (FVP) of 3-azolylpropenyl alcohols 5–7, 12 or 15 at 650–700 °C (10^–2–10^–3 Torr) causes loss of water and cyclisation to give 3H-pyrrolizine 8 and its analogues 9, 10, 13 and 16; at higher temperatures (e.g. 900 °C) 5H-pyrrolo[2,1-a]isoindole 13 decomposes by loss of HCN to give naphthalene 18 and benzofulvene 19 and the mechanism of this transformation is studied by deuterium labelling.