Homolytic Substitution:  A Molecular Ménage à Trois

Abstract

where he is currently Professor of Reactive Chemistry. His research has focused on synthetic, mechanistic, and EPR spectroscopic aspects of free-radical chemistry, and he was awarded the RSC prize for Organic Reaction Mechanisms in 1994. His current research interests include synthetic methods, cascade reactions, and organic conducting and magnetic polymers.

Formation of Cyclic Sulfinates and Sulfinamides through Homolytic Substitution at the Sulfur Atom

“…[1] This ability is largely a consequence of the broad array of transformations that these reactions can accommodate. Yet, among all the available radical processes, intramolecular homolytic substitutions [2,3] have remained much less exploited than cyclization reactions, despite their strong synthetic potential. One solution to access these reactions is to use heteroatoms such as oxygen, [4] selenium, [5][6][7] phosphorus, [8,9] or silicon.…”

Methylcorrinoids Methylate Radicals—Their Second Biological Mode of Action?

“…[16] ) We explain the formation of 3 from 1 and 2 by the substitution of the cobalt ± corrin moiety of 1 by the alkyl radical 6. Such Scheme 3. an intermolecular, homolytic substitution reaction by a (shortlived, organic) radical at a saturated carbon atom directly bound to a metal center is without precedence, [17] but corresponding reactions of (persistent) metal radicaloids (such as Co II -complexes, etc.) are known.…”

“…[18] Homolytic substitution reactions at carbon centers, when examined more closely, were found to take place with stereochemical inversion of configuration. [17,18] As a result of its characteristical low homolytic (Co-C)-BDE [12] 1 has the reactivity of a ªlatentº (persistent) methyl radical towards radicals [19,21] and, similar to coenzyme B 12 (8, a ªreversibly functioning source of an alkyl radicalº), [23] should be considered a partner in biological radical reactions. The enzymatic transfer of a methyl group from 1 to a carboncentered radical should proceed with inversion of the configuration of the methyl group (and should therefore occur with net retention of configuration from methionine).…”

A Radical Roundabout for an Unprecedented Tandem Reaction Including a Homolytic Substitution with a Titanium‐Oxygen Bond

“…In the case of trans-3 a highly strained and thus probably unstable bicyclo [3.3.0] system would be formed. Furthermore, it is of general interest to understand if the carbonϪoxygen bond is formed via a homolytic substitution reaction (S H 2) [41,42] or by a process reminiscent of 5-exo cyclization [43] onto a titaniumϪoxygen double bond as depicted in Scheme 2. Nugent and RajanBabu have suggested that in the opening of epoxides a species with a formal titaniumϪoxygen double bond is formed.…”