48824 nately between the pyrrolic rings, l_, gives rise to a family of coplanar porphyrin vinylogs, the platyrins? Like the porphyrins,[m,n,m,n]platyrins (m and n = odd numbers) are conjugated tetraazaannulenes containing 4n + 2 a-electrons. Thus,they might be expected to be "aromatic"(diatropic).2 The synthesis of the first member of this new system 3 was accomplished using the following sequence of reactions. 1 2 3 Acid-catalyzed (HBF4) condensation of 3,4_dimethylpyrrole with 1,3-cyclohexanedione in ethanol gave in 35% yield the deep blue trimethine salt 4_ [mp 245-6'; IR (Nujol): 3350 (NH), 1565 and 1535 cm-l (C=C); Vis XCHC1 max 3 nm: 540 sh, 580; m/e = 226 (parent-HBF4); PMR: Table I]. Partial reduction of 4 with NaBH4 in CH3CN (neat): 3380 cm -' (NH), 1625 and 1580 cm-l o-pyrrolic), 5.67 (m, lH, C=C-Ii), 3.60 (m, C!,), 1.98 (s, 9H, (X3)1. Bis-formylation ride in dichloroethane gave in 80% overall afforded 2 as a pale yellow air-sensitive oil [IR (C-C); PMR (CDC13): 67.4 (2H, Nli), 6.24 (m, 2H, lH, CL2-C=C), 2.4-1.5 (6H, Ct12-W2-Cs,, 2.07 (s,3H, of 5 with dimethylformamide and phosphorus oxychloyield from 4 the dialdehyde 5 [mp 174-6' (dec.);