Decarboxylation of 5-substituted 2-pyridinecarboxylic acids

Abstract

The rates of decarboxylation of 5-nitro-2-pyridinecarboxylic, 2,5-pyridinedicarboxylic, 5-iodo-2-pyridinecarboxylic, and 5-methoxy-2-pyridinecarboxylic acids in 3-nitrotoluene have been measured. The AG*, AH*, and AS* were then calculated. An examination of the linear free-energy plot of relative rates vs. the ap constants suggests that electron withdrawal from the 5 position results in lower AG* values. The observation that 2-pyridinecarboxylic acid does not fall on the same straight line as these acids, suggests that I can either lead to the cyclic transition state (IV) or to the zwitterion intermediate (II) which then decarboxylates. The pathway that a particularly substituted 2-pyridinecarboxylic acid follows depends upon the electron density on the ring nitrogen. A mechanism is given which is consistent with the available data. An assumption of this interpretation is that some monomer exists in solution at high temperature.

Carbon-13 and oxygen-18 isotope effects in the decarboxylation of nicotinic acid of natural isotopic composition

“…(3)]. 15 In the decarboxylation of NA the zwitterion 1 NA is probably preceded by the different intermolecular hydrogen bonded dimers being in equilibrium.…”

Dinuclear Coordination Compounds Based on a 5-Nitropicolinic Carboxylate Ligand with Single-Molecule Magnet Behavior

“…Still, there is a great interest in the design and use of novel ligand conferring interesting properties. In this case, we chose 5-nitropicolinic acid (1, H5Npic, Scheme 1) 4 as the supporting ligand due to its similarity to 5-aminopicolinic acid, with which we have previously synthesized novel lanthanide-containing prodrugs with antitumor properties and single-ion magnet (SIM) behavior. 5 Ligand 1 exhibits three different coordination modes (Scheme 1a−c), where the carboxylate moiety is key enabling the intermetallic connections.…”

Arylation of 2-substituted pyridinesvia Pd-catalyzed decarboxylative cross-coupling reactions of 2-picolinic acid

“…The decarboxylative cross-coupling reaction of 2-picolinic acid was considered not favorable compared to the decarboxylative cross-coupling of similar benzene acids based on the literature. [13][14][15] However, the occurrence possibility of this reaction exists and it was worth to be investigated. Salvador Conejero and co-workers reported a simple, general route to 2-pyridylidene transition metal complexes.…”

“…Firstly, the decarboxylative cross-coupling reaction of 2-picolinic acid (1a) and 4-bromobenzonitrile (2a) was investigated as the model reaction as shown in Table 1. We investigated various Pd sources (5 mol% loading) and ligands initially (Table 1, entries 1- 14). When BINAP was used as the ligand, 75% yield of the desired decarboxylative cross-coupling product was obtained (Table 1, entry 10).…”