The first highly enantioselective arylogous Michael reaction (AMR) of 3‐unsubstituted phthalides has been described. This phase‐transfer methodology, which uses catalytic amounts of KOH/18‐crown‐6 catalyst in mesitylene in the presence of N,O‐bis(trimethylsilyl)acetamide (BSA), gives access to a broad range of 3‐monosubstituted phthalides with high levels of syn diastereoselectivity and good yields, starting from 3‐unsubstituted derivatives and diverse α,β‐unsaturated carbonyl compounds. The reaction also applies to unactivated 3‐alkyl phthalides to afford 3,3‐dialkyl derivatives. A plausible mechanism has been suggested. DFT analysis of possible transition states gives a rationale of the high syn diastereoselectivity observed and its correlation with the solvent's dielectric constant.
Invited for the cover of this issue are the groups of Giorgio Della Sala at the Università degli Studi di Salerno and Luigi Cavallo at the King Abdullah University of Science and Technology. The image depicts the transition state involved in the crown ether catalyzed arylogous Michael reaction of phthalides. Read the full text of the article at 10.1002/chem.201900168.
Crowned wedding: A highly diastereoselective arylogous Michael reaction of unactivated phthalides was achieved using catalytic amounts of KOH and 18‐crown‐6. DFT calculations of the transition state revealed the key role of the K+⊂crown complex in the syn‐diastereoselective coupling of phthalide ion and Michael acceptor, which, in the cover picture, are portrayed by Robin Hood and Maid Marian. In the drawing, which takes inspiration from a famous scene captured on the Nottingham Castle wall, King Richard the Lionheart, representing the crown complex at the top of the transition state, joins the hands of the lovers. More information can be found in the Full Paper by L. Cavallo, G. Della Sala, et al. on page 7131.
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