Ti^IV‐Catalyzed Asymmetric Sulfenylation of 1,3‐Dicarbonyl Compounds

Abstract

The electrophilic enantioselective sulfenylation of 1,3-dicarbonyl compounds with phenylsulfenyl chloride is effectively catalyzed by [Ti(TADDOLato)] complexes. The corresponding products are obtained in moderate to high yields. The highest ee values (up to 97 %) are obtained in toluene at room temperature and with a typical catalyst loading of 5 mol %. Bulky ester groups and sterically undemanding substituents at the alpha-position were found to be crucial structural features of the starting materials in order to assure high enantioselectivity. The absolute configuration of one of the chiral products has been determined. The stereochemical course of the reaction is similar to that of analogous [Ti(TADDOLato)]-catalyzed atom-transfer reactions. A common side-reaction the sulfenylated products undergo is a deacylation leading to racemic alpha-sulfenylated esters.

Aromatic Rings in Chemical and Biological Recognition: Energetics and Structures

“…A selectivity of up to 91:9 was obtained in D 2 O. A beneficial effect of the perfluoroarene–arene interactions on the enantioselectivity of a Ti(TADDOLato)‐catalyzed sulfenylation of β‐ketoesters with PhSeCl was found by Jereb and Togni 128. The reaction of a perfluoroarene substrate took place with 72 % ee , which is in slight contrast to the 62 % ee obtained with nonfluorinated arenes.…”

Aromatische Ringe in chemischer und biologischer Erkennung: Energien und Strukturen

“…[124] [128] Die Reaktion eines Perfluoraren-Substrats erfolgte mit 72 % ee im Unterschied zu 62 % ee für ein nichtfluoriertes Aren. Eine asymmetrische Photocyclisierung eines achiralen Diarylethens wurde in fester Phase über Perfluoraren-ArenWechselwirkungen erreicht.…”

“…Ein günstiger Effekt von Perfluoraren-Aren-Wechselwirkungen auf die Enantioselektivität einer Ti(TADDOLato)-katalysierten Sulfonylierung von b-Ketoestern mit PhSeCl wurde von Jereb und Togni gefunden. [128] Die Reaktion eines Perfluoraren-Substrats erfolgte mit 72 % ee im Unterschied zu 62 % ee für ein nichtfluoriertes Aren. Eine asymmetrische Photocyclisierung eines achiralen Diarylethens wurde in fester Phase über Perfluoraren-Aren-Wechselwirkungen erreicht.…”

Regioselective Mono‐ and Bis‐Sulfenylation of Active Methylene Compounds

“…However, mono derivatives are successfully prepared, and this is a limitation of other methods. [29] …”

“…[27] The asymmetric sulfenylation of -keto esters [28] would be expected to provide versatile building templates and synthons for biologically active molecules, [29] which is also in the purview of mono-sulfenylation. Tan et al reported carbon-tetrabromidemediated sulfenylation of active methylenes, via sulfenyl bromides as intermediates.…”