Selective Spiroketalization of Iron Diene Complexes

Significance

Paley and co-workers previously reported the synthesis of enantiomerically pure 1,4-dienes bearing a sulfoxide chiral auxiliary and their diastereoselective complexation with iron (R. S. Paley et al. J. Org. Chem. 1997, 62, 6326). Since this report, the authors have been engaged in investigating stereoselective reactions of the ­organic fragment of the complexes. For example, diastereoselective allylations (R. S. Paley et al. Organometallics 1998, 17, 1841) and stereo­selective pinacol couplings (R. S. Paley et al. J. Org. Chem. 2009, 74, 1611) have been reported. Here, the authors demonstrate a Brønsted acid catalyzed diastereoselective spiroketalization reaction, proceeding in good yields and selectivity.