1048364-48-2Relevant articles and documents
3,5-Bis(trifluoromethyl)phenyl sulfones for the highly stereoselective Julia-Kocienski synthesis of α,β-unsaturated esters and weinreb amides
Alonso, Diego A.,Fuensanta, Monica,Gomez-Bengoa, Enrique,Najera, Carmen
, p. 2915 - 2922 (2008)
The 3,5-bis(trifluoromethyl)phenyl (BTFP) sulfones tert-butyl α-(BTFPsulfonyl)acetate (4) and Weinreb α-(BTFPsulfonyl)-acetamide (5) have successfully been employed in the Julia-Kocienski olefination of aldehydes with K2CO3 as the base at 120°C in DMF under solid/liquid phase-transfer catalysis conditions to afford α,β- unsaturated esters and Weinreb amides, respectively. The corresponding products were obtained in good yields and with high E stereoselectivities (E/Z up to >99:1), especially in the case of the amides. A detailed computational study of the Julia-Kocienski olefination with BTFP sulfone 4 was carried out and confirmed the existence of an equilibrium in the initial addition of the sulfone enolate to the aldehyde and, in contrast to other proposed mechanisms, a non-concerted final elimination of SO2 and 3,5-bis-(trifluoromethyl) phenoxide. A plausible explanation for the high E diastereoselectivity observed in the reaction has been suggested based on kinetic considerations at spirocyclic TS2 and thermodynamic factors during the elimination after TS2. ESI-MS studies carried out during the olefination reaction of benzaldehyde with BTFP sulfone 4 were used to characterize the sulfone enolate and the intermediate assumed for the reaction mechanism. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
