Tandem 6π-Electrocyclization and Cycloaddition of Nitrodienes to Yield Multicyclic Nitroso Acetals

Upon heating, nitrodienes rearrange through 6 pi-electrocyclization to form nitronate intermediates, which can be captured through tandem [3 + 2] dipolar cycloadditions to form highly functionalized nitroso acetals. The one-pot, two-step domino process is highly efficient, proceeding with good facial selectivity and exoselectivity. Dipolarophiles featuring electron-rich, -neutral, and -deficient carbon-carbon double bonds are viable substrates for [3 + 2] cycloadditions with the in situ generated nitronates. In addition, the highly functionalized nitroso acetal products can be hydrogenolyzed selectively to form densely functionalized spirocyclic hydroxy amides or hydroxy gamma-amino acids.