571206-63-8Relevant academic research and scientific papers
Sulphide as a leaving group: Highly stereoselective bromination of alkyl phenyl sulphides
Canestrari, Daniele,Cioffi, Caterina,Biancofiore, Ilaria,Lancianesi, Stefano,Ghisu, Lorenza,Ruether, Manuel,O'Brien, John,Adamo, Mauro F.A.,Ibrahim, Hasim
, p. 9042 - 9050 (2019/10/22)
A conceptionally novel nucleophilic substitution approach to synthetically important alkyl bromides is presented. Using molecular bromine (Br2), readily available secondary benzyl and tertiary alkyl phenyl sulphides are converted into the corresponding bromides under exceptionally mild, acid- and base-free reaction conditions. This simple transformation allows the isolation of elimination sensitive benzylic β-bromo carbonyl and nitrile compounds in mostly high yields and purities. Remarkably, protic functionalities such as acids and alcohols are tolerated. Enantioenriched benzylic β-sulphido esters, readily prepared by asymmetric sulpha-Michael addition, produce the corresponding inverted bromides with high stereoselectivities, approaching complete enantiospecificity at -40 °C. Significantly, the reported benzylic β-bromo esters can be stored without racemisation for prolonged periods at -20 °C. Their synthetic potential was demonstrated by the one-pot preparation of γ-azido alcohol (S)-5 in 90% ee. NMR studies revealed an initial formation of a sulphide bromine adduct, which in turn is in equilibrium with a postulated dibromosulphurane intermediate that undergoes C-Br bond formation.
Asymmetric Schmidt reaction of hydroxyalkyl azides with ketones
Sahasrabudhe, Kiran,Gracias, Vijaya,Furness, Kelly,Smith, Brenton T.,Katz, Christopher E.,Reddy, D. Srinivasa,Aube, Jeffrey
, p. 7914 - 7922 (2007/10/03)
An asymmetric equivalent of the Schmidt reaction permits stereocontrol in ring expansions of symmetrical cyclohexanones. The procedure involves the reaction of chiral 1,2- and 1,3-hydroxyalkyl azides with ketones under acid catalysis; the initial reaction affords an iminium ether that can be subsequently opened with base. A systematic study of this reaction is reported, in which ketone substrates, chiral hydroxyalkyl azides, and reaction conditions are varied. Selectivities as high as ca. 98:2 are possible for the synthesis of substituted caprolactams, with up to 1,7-stereoselection involved in the overall process. The fact that either possible migrating carbon is electronically identical provides an unusual opportunity to study a ring-expansion reaction controlled entirely by stereoelectronic factors. The mechanism of the reaction and the source of its stereoselectivity are also discussed.
