Access to Corrole-Appended Persubstituted Benzofurans by a Multicomponent Reaction: The Dual Role of p-Chloranil

Abstract

A multicomponent reaction among dipyrranes, aryl-propargyl aldehydes, and p -chloranil leading to 10-(benzofuran-2-yl)corroles is described. p -Chloranil was identified as a crucial reagent playing a twofold role: an oxidant taking part in the formation of the corrole macrocycle and a component undergoing heteroannulation to the incipient 10-arylethynylcorrole. A series of corroles bearing persubstituted benzofuran-2-yl moieties have been synthesized, and their fundamental electronic properties have been studied via UV–vis absorption and fluorescence spectroscopies.

Synthesis of N-, O-, and S-heterocycles from aryl/alkyl alkynyl aldehydes

“…70 Aryl alkynyl aldehyde 1a can react with dipyrranes 42a, and p-chloranil 42b to form the corrole macrocycle bearing substituted benzofuran-2-yl 42c (Scheme 58). 71 The presence of p-chloranil was essential in this threesegment reaction. Evaluating other oxidants, such as 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), p-benzoquinone, and bis(acetoxy)iodobenzene (BAIB) resulted in no product.…”

Surprising Route to a Monoazaporphyrin and Full Characterization of Its Complexes with Five Different 3d Metals

“…These tremendous efforts were led by prominent scientists including R. Willstatter, H. Fisher, and R. B. Woodward, whose contributions were recently outlined by Senge et al in an excellent review . Research activity on non-natural porphyrins and related macrocycles continues to flourish because of their relevance to fundamental science, including the study of aromaticity and redox noninnocence, as well as for diverse practical applications. − A partial list includes drug discovery/development, biomimetic catalysis, and clean energy processes. − This also holds true for derivatives in which the metal-coordinating core is modified, being composed of less or more than four N atoms and/or by non-nitrogen elements, ,, as well as for those bearing a different macrocyclic skeleton. ,,, Regarding the latter class, the largest advances are arguably in corroles, N 4 macrocycles with one direct bond between two pyrrole subunits like in the prosthetic group of Vitamin B12 but fully conjugated and aromatic like in classic porphyrins. , One major reason for the interest in corroles is that the seemingly small differences relative to porphyrins, at about 10% reduction in the size of the coordination core and the presence of three rather than two protic nitrogen atoms therein, induce very significant changes in the reactivity/stability of the corresponding metal complexes. ,, The advantageous outcomes of these features have been outlined in quite a few contemporary reviews, which also include recent synthetic breakthroughs, such as access to minimally substituted corroles. ,,, …”

“… 5 , 14 , 16 , 19 Regarding the latter class, the largest advances are arguably in corroles, N 4 macrocycles with one direct bond between two pyrrole subunits like in the prosthetic group of Vitamin B12 but fully conjugated and aromatic like in classic porphyrins. 19 , 20 One major reason for the interest in corroles is that the seemingly small differences relative to porphyrins, at about 10% reduction in the size of the coordination core and the presence of three rather than two protic nitrogen atoms therein, induce very significant changes in the reactivity/stability of the corresponding metal complexes. 3 , 5 , 8 The advantageous outcomes of these features have been outlined in quite a few contemporary reviews, which also include recent synthetic breakthroughs, such as access to minimally substituted corroles.…”