Trapping of Hexadehydro-Diels–Alder Benzynes with Exocyclic, Conjugated Enals as a Route to Fused Spirocyclic Benzopyran MotifsFinancial support for these studies was provided by the National Institute of General Medical Sciences (R01 GM108762) of the National Institutes of Health. NMR data were recorded, in part, using an instrument purchased through a NIH Shared Instrumentation Grant (S10OD011952).
Received: 13 June 2017
Accepted after revision: 11 July 2017
22 August 2017 (eFirst)
Dedicated with very best wishes to Professor Victor Snieckus on the occasion of his 80th birthday
Exocyclic, conjugated enals react with benzynes generated by heating various triyne-containing substrates to produce spirocyclic benzopyran derivatives. These products are consistent with a mechanistic sequence that involves initial net [2+2] cycloaddition of the benzyne and aldehyde followed by 4π-electrocyclic ring opening and 6π ring closing.