ChemInform Abstract: Studies on the Intramolecular Competitive Addition of Carbon Radicals to Aldehydo and Alkenyl Groups.

Abstract

Cyclizations of ω-formylalkyl radicals can provide an efficient route to the corresponding cycloalkanols. However, if an ω-vinyl group is present an alternative mode of cyclization exists, and there is competition between cycloalkanol and methyl cycloalkane formation (i.e. (C=O) n versus (C=C) m ). Cyclohexanol formation, (C=O) 6 , usually overwhelms any alternative process, but cyclopentanol and methylcyclopentane processes ((C=O) 5 and (C=C) 5 ) can be competitive. The latter process involves the well-studied 5-hexenyl radical ring closure, and hence by choice of a suitable substrate, where both modes of cyclization are optimal, we have obtained rate data for cyclopentanol (C=O) 5 formation in a direct-competition experiment. The value k c=O ≥9.6×10 5 s −1 is consistent with that obtained by Beckwith and Hay. The study has also helped to define some of the requirements for optimizing the formation of cycloalkanols