(Diethylamino)sulfur Trifluoride (DAST) as a Useful Reagent for the Preparation of 2-Oxazolines from 1,2-Amido Alcohols
1995; Elsevier BV; Volume: 41; Issue: 5 Linguagem: Inglês
10.3987/com-94-6987
ISSN1881-0942
AutoresJean‐Paul Lellouche, Pierre Lafargue, Pierre Guénot,
Tópico(s)Asymmetric Synthesis and Catalysis
ResumoAcyclic 1,2-amido alcohols (6) react efficiently with a slight excess of (diethylamino)sulfur trifluoride (DAST) to afford the corresponding 2-oxazolines (10) in good yields ranging between 57-95 %.Even at the low temperature of -78 "C, a rapid (< 1 h) and stereoselective amide cyclization is observed without formation of acylaziridine by-products.The scope of this cyclization is discussed.The synthetic potential of 2-oxazoline nucleus relies essentially on its specific chemical properties.Particularly attractive is its easy transformation or elaboration into conventional functional groups.I It acts for example as a masked carboxylic group lb-d,2 and as an efficient ortho-metallation directing moiety. 1 4 3 Moreover, this nucleus showed interesting potentials in the field of asymmetric synthesis.I d Thus, Cz-symmetrical his(4.5dihydrooxazolyl)methaneshave been used successfully in the asymmetric version of numerous reactions like Diels-Alder reaction, hydrosilylation of ketones, olefin cyclopropanation and aziridination.7 Further interest arose recently from the discovery of oxazolines incorporated as peptide mimetics into the backbone of biologically active compounds isolated from marine sources.8 Synthetic procedures leading to 2-oxazolines include bimolecular reactions such as the reaction of amino alcohols with imidates, 1.9 unimolecular rearrangements of acylaziridines, 18'0 or cyclizations of hydroxy amides and related compounds.1,8dJ1
Referência(s)