The McMurry Reaction in Porphyrinoid Chemistry

Abstract

The McMurry reaction, first reported in 1974, is an organometallic coupling reaction of aldehydes and ketones, to give alkenes, that relies upon the use of low-valent titanium; the reactive titanium species is obtained from titanium (III) or titanium(IV) chloride and an in situ reducing agent. The first application of the McMurry reaction to polypyrrole chemistry took place in 1986 with the first synthesis of the (2,0,2,0)-porphyrin isomer, porphycene. Since then, numerous macrocyclization reactions of polypyrrole (and other heteroaromatic) compounds have been described, and many new molecules have been reported. Peripheral carbonyl substituents on metallo-porphyrins and -chlorins have been coupled to yield a plethora of bis-porphyrins, bis-chlorins, and their homo-and hetero-bimetallic complexes. Some porphyrin-chlorin systems have also been reported. Thus, this contemporary organometallic coupling reaction has been successfully applied to polypyrrole syntheses and substituent manipulations, and a large number of interesting new compounds have been obtained.

Meso-Formyl, Vinyl, and Ethynyl Porphyrins—Multipotent Synthons for Obtaining a Diverse Array of Functional Derivatives

“…Insertion of the formyl group into porphyrins is a primary functionalization of the tetrapyrrole ring, opening opportunities for further transformations including, but not limited to, Wittig [12][13][14], Grignard [14][15][16], McMurry [17], cycloaddition [18], Knoevenagel [19] reactions, and Schiff bases preparation [20]. Ponomarev made a considerable contribution to the chemistry of formylporphyrins and published a corresponding review about 30 years ago, summarizing works reported up to that date [5].…”

“…Transformation of the formylporphyrins into dimers bonded with an ethene bridge can be performed using low-valent titanium, which is called the McMurry reaction [17] Cu(II) and Ni(II) complexes of OEP-CHO were dimerized under the action of TiCl3 and Zn/Cu to form the corresponding complexes of dimers linked with the ethylene bridge in the form of a mixture of cis and trans isomers (Scheme 26) [69]. Transformation of the formylporphyrins into dimers bonded with an ethene bridge can be performed using low-valent titanium, which is called the McMurry reaction [17]. Cu(II) and Ni(II) complexes of OEP-CHO were dimerized under the action of TiCl 3 and Zn/Cu to form the corresponding complexes of dimers linked with the ethylene bridge in the form of a mixture of cis and trans isomers (Scheme 26) [69].…”

“…Cu(II) and Ni(II) complexes of OEP-CHO were dimerized under the action of TiCl 3 and Zn/Cu to form the corresponding complexes of dimers linked with the ethylene bridge in the form of a mixture of cis and trans isomers (Scheme 26) [69]. Transformation of the formylporphyrins into dimers bonded with an ethene bridge can be performed using low-valent titanium, which is called the McMurry reaction [17] Cu(II) and Ni(II) complexes of OEP-CHO were dimerized under the action of TiCl3 and Zn/Cu to form the corresponding complexes of dimers linked with the ethylene bridge in the form of a mixture of cis and trans isomers (Scheme 26) [69]. Transformation of the formylporphyrins into dimers bonded with an ethene bridge can be performed using low-valent titanium, which is called the McMurry reaction [17].…”

Porphycenes and Related Isomers: Synthetic Aspects

“…Preparation of the parent porphycene 2a is straightforward (four steps from pyrrole); , however, the synthesis of substituted derivatives requires more elaborate synthetic schemes . In general, these syntheses rely on the use of three key reactions: Ullmann reaction to provide the 2,2′-bipyrrole moiety and Vilsmeier–Haack formylation and McMurry coupling to cause the cyclization that leads to a macrocycle, which is oxidized, often in situ, to furnish the corresponding aromatic porphycene (Scheme ).…”

“…Once the required bipyrrolic aldehydes are in hand, the next step is formation of the macrocyclic framework by reductive coupling via the McMurry reaction (Scheme ). This reaction is arguably the most complex step in the synthesis of porphycenes in terms of having a practical procedure.…”