ChemInform Abstract: Stereoselective Quaternary Center Construction via Atom‐Transfer Radical Cyclization Using Silicon Tethers on Acyclic Precursors.

Abstract

Hydroxycarboxylic acids (ether carboxylic acids) and esters P 0280 Stereoselective Quaternary Center Construction via Atom-Transfer Radical Cyclization Using Silicon Tethers on Acyclic Precursors. -Radical allylation and vinylation proceeds with complete formation of 2,3-syn-alcohols tolerating aliphatic and aromatic substituents and various protecting groups. -(DUPLESSIS, M.; WALTZ, M.-E.; BENCHEQROUN, M.; CARDINAL-DAVID*, B.; GUINDON, Y.; Org. Lett. 11 (2009) 14, 3148-3151; Inst. Rech. Clin. Montreal, Montreal, Que. H2W 1R7, Can.; Eng.) -R. Steudel 52-062

Radical Group Transfer of Vinyl and Alkynyl Silanes Driven by Photoredox Catalysis

“…[19][20] Scheme 5. Proposed mechanism By comparison, subjecting iodide 4a to BEt3 and trace levels of oxygen with 1 H NMR monitoring results in the formation of a cyclized iodide intermediate (17,Scheme 4c). Under these conditions a conventional radical chain reaction is initiated, where cyclized radical intermediate 14 propagates the reaction by abstracting an iodide from 4a.…”

“…[14][15][16] Following the radical cyclization reaction, addition of a fluoride source results in elimination and desilylation. A similar strate-gy has also been applied to activated, tertiary bromides, 17 and in a radical cyclization cascade strategy to set multiple contiguous stereocenters. 18 Scheme 1.…”