Abstract
Danishefsky diene (1-methoxy-3-trialkylsiloxy-1,3-butadiene) is known as a reactive and useful substrate for Diels-Alder reaction to give highly functionalized cyclohexenes. However, the diene is so unstable under acidic conditions that applicable Lewis acid to activate dienophile is quite limited. We developed Yb(OTf)3/BINAMIDE or BINUREA/DBU catalyst, which realized the first example of catalytic asymmetric Diels-Alder reaction of Danishefsky diene and electron-deficient olefins. The Diels-Alder reaction of several types of dienophiles with Danishefsky diene was efficiently facilitated by the catalyst to give exclusively exo adducts. The Diels-Alder adduct can be transferred to various synthetic intermediates. Apparent (+)-non-linear effects between asymmetric induction and the enantiomeric composition of BINAMIDE may suggest the possible formation of a reservoir of non-reactive aggregates. A structure of ytterbium salt was discussed.
