Synthesis of Novel Pyrrolic Compounds from Nitroarenes and Isocyanoacetates Using a Phosphazene Superbase

Abstract

Utilization of a phosphazene base allows hitherto unreactive nitroaromatic compounds to condense with ethyl isocyanoacetate to give c-annelated pyrroles. On the other hand, 3-nitropyridine reacted under these conditions to give a novel tricyclic heterocycle 13 in modest yield.

Oxidative Metalation of Azuliporphyrins with Copper(II) Salts: Formation of a Porphyrin Analogue System with a Unique Fully Conjugated Nonaromatic Azulene Subunit

“…Mass spectrometric analysis of reactions carried out in the presence of 18 O labeled water showed that no 18 O was incorporated into the copper(ii) complex. In addition, acetate was ruled out as the source of the oxygen because the same complex was formed using CuCl 2 instead of Cu(OAc) 2 , albeit in lower yields. [19] However, our results demonstrate that the azuliporphyrin system holds new and surprising chemical properties and further work in this area is underway.…”

“…[1,2] These systems often exhibit unusual spectroscopic and physical properties [3] and may show varying degrees of aromatic character. [4,5] A particularly promising aspect of carbaporphyrinoid chemistry has been the generation of organometallic derivatives using late-transition-block metals such as nickel, palladium, platinum, [6] and silver.…”

Metalation of Carbaporphyrinoid Systems

“…These porphyrin analogues range from highly aromatic systems to borderline aromatic or nonaromatic macrocycles, and the proton NMR data for these porphyrinoids provide significant insights into the nature of porphyrinoid aromaticity. [17][18][19] Many of these structures form stable organometallic derivatives under mild conditions. Benziporphyrins, azuliporphyrins, oxacarbaporphyrins and N-phenyl pyrazole-containing porphyrin analogues act as dianionic ligands, while benzocarbaporphyrins and tropiporphyrins are trianionic ligands that can stabilize metals in relatively high oxidation states (e.g.…”

“…[28,30] When a carbocyclic dialdehyde is used, carbaporphyrinoid products of type A or type B can be formed (Scheme 1). [17][18][19] In type A, a porphyrin-like conjugation pathway is retained and this allows for highly diatropic structures to be generated. However, in other cases the carbocyclic unit is crossconjugated and the macrocycle becomes less aromatic or nonaromatic.…”

“…[15,16] Shortly after the accidental discover of NCPs, a series of related carbaporphyrinoid systems were reported. [5,[17][18][19] These systems share the CNNN core found in NCPs but have far greater potential for structural diversity. These variables allow for greater differences in both reactivity and spectroscopic properties, and the element of symmetry present in many of these structures also allows for a simplification in the characterization of these systems as well as facilitating greater regiochemical selectivity.…”