Ytterbium‐Catalyzed Tandem Diels–Alder/Claisen Rearrangement/Decarboxylation of Hetero‐Allenes for the Synthesis of Diarylmethanes

Comprehensive Summary A tandem Diels–Alder reaction/Claisen rearrangement/decarboxylation strategy of N ‐allenamides (or aryloxyallenes) with 3‐alkoxycarbonyl‐2‐pyrones has been developed for the efficient synthesis of diarylmethanes with moderate to good yields. The reaction exhibits good functional group tolerance and can be applied to late‐stage modifications of known drug molecules. Mechanistic studies indicate that the ester group at the 3‐position of 2‐pyrones is essential, and the initial Diels–Alder reaction between the 2‐pyrones and the proximal C=C bond of the N ‐allenamides (or aryloxyallenes) is crucial for the success of the reaction.