PTC in the polyenolate‐mediated [10+2]‐cycloaddition for the synthesis of α,α‐disubstituted amino acid precursors

The manuscript describes a formal [10+2] higher‐order cycloaddition between 2‐benzylideneindan‐1‐ones and α‐alkilidene azlactones as higherene precursors and higherenofiles respectively. The reaction is realized under Brønsted‐base catalysis utilizing the phase transfer catalysis approach. The key intermediate is an isobenzofulvene‐derived polyenolate which acts as a 10‐electron component in the higher‐order cycloaddition. By using this strategy, a series of structurally diverse compounds containing a polycyclic hydrocarbon scaffold was prepared in 79‐99% yields. In addition, the potential of the obtained [10+2]‐cycloadducts has been confirmed by transformations, including the synthesis of a highly‐valuable alpha,alpha‐disubstituted N‐protected alpha‐aminoester.