Treatment of crude meso-tetraphenylporphyrin with 2.3-dichloro-5.6-dicyanobenzoquinone affords a high recovery of ' chlorin-free ' meso-tetraphenylporphyrin (1 ), the excess of quinone and its transformation products being easily removed by adsorption on alumina. This new procedure is also applied to the purification of mesotetraphenylporphyrin metal complexes.1mSO-TETRAPHENYLPORPHYRIN (TPP) (1) has been extensively employed for investigation of the physical and spectroscopic properties of the porphyrin macrocycle and its diverse metal complexes.2 This fact can be related directly to the ease with which TPP can be pre-

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Found: C, 66.2; H, 6.5; N, 7-8. Calc. for C,oH,,-N,O,: C, 66.1; H, 6-4; N, 7.7%), T (CF,*C02H) -0.2 (2H, s) and 0.13 (lH, s) (meso-H), 5-6-59 (8H, m) and 6.6-7-0 (8H, m) (CH,*CH,*CO), 6.0 (3H, s) and 6.2 (9H, s) a-Hydroxy-2,4,6,8-tetrakis-(2-methoxycarbonyZethyl)-23 K.

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. Can. J. Chem. 60, 383 (1982). The preparation of the acetals of a number of pyrrole mono-and dicarboxaldehydes is described. It is shown that, provided the reactivity of the unsubstituted ring positions on the pyrrole nucleus is not too low, a carboxyaldehyde or a carbonitrile group may be substituted onto the pyrrole ring using the Vilsmeier reaction or chlorosulfonyl isocyanate respectively. Vilsmeier formylation of the diacetal, 2,4-di(5,5-dimethyl-1,3-dioxan-2-yl)-pyrrole, followed by hydrolysis gave pyrroie-2,3,5-tricarboxaldehyde.CHARLES E. LOADER, GRAHAM H. BARNETT et HUGH J. ANDERSON. Can. J. Chem. 60,383 (1982). On decrit la preparation des acttals d'un certain nombre de pyrroles mono et de dicarboxaldehydes. On montre, en admettant que la reactivite des positions non substituees du noyau pyrrole n'est pas trop faible, que I'on peut substituer un groupe carboxaldehyde ou carbonitrile du cycle pyrrole en utilisant soit la reaction de Vilsmeier ou I'isocyanate de chlorosulfonyle. La formylation de Vilsmeier du diacetal, di (dimethyl-5,5 dioxanne-1,3 yl-2)-2,4 pyrrole, suivie d'une hydrolyse donne le pyrroletricarboxaldehyde-2.3.5.[Traduit par le journal] Introduction prepare the diacetal, 2-(5,5-dimethyl-l,3-dioxan-2-We recently reported the synthesis of 2-(5,5-di-yl) -4-(2,5,5-trimethyl-1,3 -dioxan-2-yl) -pyrrole,

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