Efficient and Atom-Economic Synthesis of α-Substituted β-Chromonyl-α,β-unsaturated Carbonyls through Molecular Rearrangement

A wrong NMR prediction between the ester carbonyls of the keto ester and conjugated ester moieties in 4f led us to a wrong stereochemical assignment (coincidentally rightly captioned, however). Keto esters 4a- g should be read in E-configuration in Table 1 and Schemes 2-4. The corrected Figure 1 (structure B) and the corresponding modified paragraph (on page 404 of the original manuscript) are given below. The authors apologize for these mistakes.

Similar NOE effects were observed in the case of keto ester 4f. While irradiation of C2-H in 4f resulted in signal enhancement of C1′-H, the latter on irradiation led to the signal enhancement for C2-H besides a weak signal enhancement for the methylene(-OCH ₂Me) proton of conjugated ester (established by HMBC and HSQC NMR experiments) (Figure 1, B). Thus, E-configuration was assigned to the keto esters 4a-g.

Figure 1