The hexadehydro-Diels–Alder (HDDA) reaction is a method to form and trap highly functionalized benzynes in one reaction under relatively mild conditions. We report here reactions of various conjugated cyclic enals with asymmetric benzynes generated by the HDDA cycloisomerization to produce several benzopyrans with a spirocyclic sp<sup>3</sup> carbon. Reactions were carried out in 1,2-dichloroethane at 90 °C overnight. Endocyclic enals tested failed to react, while all exocyclic enals tested successfully trapped the benzyne. These enals included ones containing medium-sized and bicyclic rings, fused conjugated systems containing a heteroatom and a vinylogous lactam with a stereocenter.

Synthesis of spirocyclic pyranoarenes via enal trapping of HDDA-generated benzynes

253rd National Meeting (2017)

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