[摘要]：The first general methodol. for the gram-scale prepn. of previously overlooked b-(hetero)aryl-a-nitro-a,b-enals (3) is reported. Condensation of (hetero)arom. aldehydes with 2-nitroethanol gave the E-isomers of uncommon b-(hetero)aryl-a-hydroxymethyl-a,b-unsatd.-nitroalkenes (2), as detd. by NOE and X-ray studies. a-Nitro-a,b-enals 3 were subsequently obtained by hypervalent iodine oxidn. of 2 as E-Z-mixts. in solid form. They showed varied stability and solvent-dependent thermal-promoted and photopromoted E-Z interconversion. Starting with furfural, exptl. conditions were developed to prep. the corresponding nitroenal 3a enriched in either the E or the Z isomer: E-3a/Z-3a u 90/10 and 20/80, resp. In contrast with other structurally related compds., nitroenals 3 have their (hetero)aryl-vinyl unit and their formyl and nitro groups all in a planar arrangement, both in solid form and in soln.; accordingly, they are colored compds. with predicted high dipole moments. As deduced from soln.-NMR and X-ray data, the C=C and the C=O double bonds in 3 are exclusively s-cis-oriented; this disposition corresponds in fact to the DFT-computed most stable conformer.
