Abstract
Athel Beckwith chose to embark on a career in free radical chemistry at a time when it was largely ignored by all but a small coterie within the broader Organic Chemistry community. Of his many contributions in this area, the mechanistic clarification and exploitation of the cyclization of hex-5-enyl radical-containing systems is undoubtedly the most significant, leading to what is now, in a multitude of variants, a universally-used, powerful, sophisticated, selective, general synthetic methodology. This account revisits and highlights the early studies carried out by the Beckwith group at The University of Adelaide from the late-1960s to 1980, a period when the main breakthroughs in kinetic and mechanistic understanding were made, and the implications for wider synthetic utility in more complex hex-5enyl systems became apparent.