N- to C-sulfonyl photoisomerisation of dihydropyridinones: a synthetic and mechanistic study

Pei-Pei Yeh; James E Taylor; Daniel G Stark; David S B Daniels; Charlene Fallan; John C Walton; Andrew D Smith

doi:10.1039/c7ob01699a

N- to C-sulfonyl photoisomerisation of dihydropyridinones: a synthetic and mechanistic study

Org Biomol Chem. 2017 Oct 31;15(42):8914-8922. doi: 10.1039/c7ob01699a.

Authors

Pei-Pei Yeh¹, James E Taylor, Daniel G Stark, David S B Daniels, Charlene Fallan, John C Walton, Andrew D Smith

Affiliation

¹ EaStCHEM, School of Chemistry, University of St Andrews, St Andrews, Fife KY16 9ST, UK. ads10@st-andrews.ac.uk.

PMID: 29035415
DOI: 10.1039/c7ob01699a

Abstract

The scope and limitations of a photoinitiated N- to C-sulfonyl migration process within a range of dihydropyridinones is assessed. This sulfonyl transfer proceeds without erosion of either diastereo- or enantiocontrol, and is general across a range of N-sulfonyl substituents (SO₂R; R = Ph, 4-MeC₆H₄, 4-MeOC₆H₄, 4-NO₂C₆H₄, Me, Et) as well as C(3)-(aryl, heteroaryl, alkyl and alkenyl) and C(4)-(aryl and ester) substitution. Crossover reactions indicate an intermolecular step is operative within the formal migration process, although no crossover from C-sulfonyl products was observed. EPR studies indicate the intermediacy of a sulfonyl radical and a mechanism is proposed based upon these observations.