β-Aryl-α-nitro-α,β-enals as heterodienes and dienophiles.

As demonstrated with the β-(2-furyl)-substituted analogue 1b, β-aryl-α-nitro-α,β-enals (1) behave as heterodienes against enamines and enol ethers using their enal unit (e.g., 1b → 12).

Synthesis, structure, and E-Z isomerization of beta-(hetero)aryl-alpha-nitro-alpha,beta-enals.

The first general methodology for the gram-scale preparation of previously overlooked beta-(hetero)aryl-alpha-nitro-alpha,beta-enals (3) is reported. Condensation of (hetero)aromatic aldehydes with 2-nitroethanol gave the E-isomers of uncommon beta-(hetero)aryl-alpha-hydroxymethyl-alpha,beta-unsatured-nitroalkenes (2), as determined by NOE and X-ray studies. alpha-Nitro-alpha,beta-enals 3 were subsequently obtained by hypervalent iodine oxidation of 2 as E-Z-mixtures in solid form.