Efficient trans-selectivity in the cyclocondensation of (S)-2-[2-(p-tolylsulfinyl)phenyl]acetaldehyde with activated dienes catalyzed by Yb(OTf)3.
Reactions of (S)-2-[2-(p-tolylsulfinyl)phenyl]acetaldehyde 1 with Danishefsky's and related dienes took place in the presence of Yb(OTf)3 in a completely stereoselective manner, mediated by a remote sulfinyl group (1,5-asymmetric induction), to afford the corresponding 2,3-dihydro-4H-pyran-4-ones. These reactions followed a stepwise mechanism, as was corroborated by isolation of the corresponding intermediates, with a high level of trans-selectivity for 4-methyl-substituted dienes. Treatment of the adducts with Raney Ni provided concomitant cleavage of the C-S bond and reduction of the conjugated carbonyl grouping.
García Ruano
José L
JL
Departamento de Química Organica, Universidad Autónoma de Madrid, Cantoblanco, 28049-Madrid, Spain. joseluis.garcia.ruano@uam.es
Fernández-Ibáñez
M Angeles
MA
Maestro
M Carmen
MC