A new era for homolytic aromatic substitution: replacing Bu3SnH with efficient light-induced chain reactions. Issue 16 (8th April 2016)

• Record Type: Journal Article
• Authors: Gurry, Michael; Aldabbagh, Fawaz
• Is Part Of: Organic & biomolecular chemistry. Volume 14:Issue 16(2016)
• Page Start: 3849
• Page End: 3862
• Publication Date: 2016-04-08
• Subjects: Chemistry, Organic -- Periodicals; Bioorganic chemistry -- Periodicals; Chemistry, Physical organic -- Periodicals; 547
• DOI: 10.1039/c6ob00370b
• Languages: English
• ISSNs: 1477-0520

Abstract

Abstract : Recent advances such as visible-light photoredox catalysis have largely superseded radical initiator-mediated substitutions onto arenes and aromatic heterocycles. Abstract : Herein is a pertinent review of recent photochemical homolytic aromatic substitution (HAS) literature. Issues with using the reductant Bu3 SnH in an oxidative process where the net loss of a hydrogen atom occurs is discussed. Nowadays more efficient light-induced chain reactions are used resulting in HAS becoming a synthetic mechanism of choice rivaling organometallic, transition-metal and electrophilic aromatic substitution protocols. The review includes aromatic substitution as part of a tandem or cascade reaction, Pschorr reaction, as well as HAS facilitated by ipso -substitution, and Smiles rearrangement. Recently visible-light photoredox catalysis, which is carried out at room temperature has become one of the most important means of aromatic substitution. The main photoredox catalysts used are polypyridine complexes of Ru(ii ) and Ir(iii ), although eosin Y is an alternative allowing metal-free HAS. Other radical initiator-free aromatic substitutions have used 9-mesityl-10-methylacridinium ion and N, N -bis(2, 6-diisopropylphenyl)perylene-3, 4, 9, 10-bis(dicarboximide) as the photoredox catalyst, UV-light, photoinduced electron-transfer, zwitterionic semiquinone radical anions, and Barton ester intermediates.