The Synthesis of Four Isomeric Tetramethyltetracarbethoxyporphyrins¹

Substituted Deuteroporphyrins. I. Reactions at the Periphery of the Porphyrin Ring1

“…Here, the ßcarbon-/3-carbon bonds are far less isolated, and are expected to be less susceptible to electrophilic attack, than in the case of the hemins or free-base porphyrins for which X-ray data has shown distances of about 1. 35 A, a value only slightly greater than is associated with a bond order of 2, namely 1.335 A.54 Additional factors of possible influence in the selectivity of these electrophilic substitution reactions include (1) the relative ability of adducts such as III and IV to accommodate the positive charge, possibly more readily achieved in the protonated species (simply by proton loss) than in Fe3+ complex; (2) the role(s) of complexes ( and ) as intermediates. 57 The ability of porphyrins to form molecular complexes has long been known.4*•58 Further studies can be expected to clarify the importance of these possibilities.…”

“…Crystals were obtained from chloroform-methanol: 20.3 g (49%); mp 242.5°( lit.4b mp 234-236°); in potassium bromide acetyl carbonyl stretching frequency was found at 1661 cm-1; nmr, acetyl methyl protons were found as two singlets at 3.29 and 3.23 at infinite dilution in CDCls and as one singlet at 3. 35 in CDCls with 2.5% Fe-CCOOH.…”

Simple Formation of an Abiotic Porphyrinogen in Aqueous Solution

“…In aqueous buffer solutions at neutral or alkaline pH, the Soret (B) band is broad with maximum at 410 nm, and the visible (Q) bands are broadened and indistinct. By contrast, in N,N-dimethylformamide (DMF) or DMF/H 2 O (9:1), the B band appears at 427 nm and the Q bands are relatively sharp; the spectrum is nearly identical to that of the similarly substituted synthetic compound 2,7,12,8,13, (Kleinspehn et al 1966). Similar behavior in aqueous versus organic media is exhibited by coproporphyrin and other porphyrins that bear four or fewer alkyl carboxy groups (Mauzerall 1965;Brown et al 1976;Morales-Rojas and Yatsimirsky 1999).…”

“…The molar absorption coefficient employed was 300,000 M −1 cm −1 on the basis of reported data including 284,000 M −1 cm −1 for the type-I porphyrin 2,7,12,17-tetracarboethoxy-3,8,13,18-tetramethylporphyrin in CHCl 3 (Kleinspehn et al 1966). Values for the type II-IV regioisomers were 287,000, 251,000, and 247,000 M −1 cm −1 , respectively (Kleinspehn et al 1966). The yield of porphyrin was assessed by the intensity of the Soret peak after correcting for the baseline (Lindsey et al 1987).…”