Inter- and Intramolecular Pathways for the Formation of Tetrahydrofurans from β-(Phosphatoxy)alkyl Radicals. Evidence for a Dissociative Mechanism
journal contributionposted on 1999-12-29, 00:00 authored by David Crich, Xianhai Huang, Martin Newcomb
β-(Phosphatoxy)alkyl radicals generated by photolysis of Barton PTOC esters in the presence of allyl alcohol and tert-butyl mercaptan undergo nucleophilic substitution followed by 5-exo-trig radical ring closure leading to tetrahydrofurans in good yield and with high trans selectivity. β-(Phosphatoxy)alkyl radicals obtained by intramolecular hydrogen 1,5-abstraction with an alkoxyl radical undergo nucleophilic displacement providing tetrahydrofurans. The ensemble of results, including the effects of leaving groups and substituents, strongly support a dissociative mechanism for these radical nucleophilic displacement reactions.