Pyridone sulfonates

Synthesis of pyridone sulfonates as water-tracing compounds. 

These reactions are useful because they run under mild conditions, use inexpensive or easily recoverable starting materials, and have short reaction times. The major problem in purification is the separation of the sodium pyridone sulfonate from excess sodium sulfite, sodium bromide, and sodium bromoalkyl sulfonate. However, these latter compounds usually would not interfere with the use of the pyridone sulfonate as a water tracer. From a practical point of view, the pyridone sulfonates need not be purified, but can be used directly. A modified synthetic procedure involves the treatment of the pyridone sodium salt with a tenfold excess of a,iu-dibromoalkane in acetonitrile, followed by removal of the excess dibromide by vacuum distillation. The resulting product is treated with an excess of sodium sulfite in aqueous ethanol. Evaporation of the solvent yields a useful tracer. Procedures given in the experimental section were... 

Table II Relative Fluorescence and Spectroscopic Data for Pyridone Sulfonates...

Separations of pyridone sulfonates were performed using an Altex Ultrasphere I.P. Cig S-pm, 4.6 x 150 mm column. The 3-carbamoyl-2(lM)pyridone series was separated using a mobile phase of 89%... 

Pyridone IV was converted to its sodium salt by treatment with an equimolar amount of sodium methoxide in methanol (see procedure below under formation of the 3-phenyl-2(lH)pyridone sulfonates). The sodium salt was next treated with the methyl ester of a-bromo-p-toluic acid, obtained by treatment of the acid with BF3 etherate. 

General Procedures for the Synthesis of the Pyridone Sulfonates VIa,b,c and VIIa,b,c (25). A solution of 1.25 mmol of the sodium salt of 3-carbamoyl-2(lH)pyridone(III) or 3-phenyl-2(lH)pyridone and 1.25 mmol of the corresponding bromosulfonate sodium salt in 50 mL of acetonitrile was brought to reflux and stirred for 24 h. The reaction mixture was cooled and filtered through a sintered glass... 

Analytical samples of l-alkyl-3-substituted 2(lH)pyridone sulfonates were obtained by using a Whatman Partisll M-9 10/50 ODS-2 C18 column. The 3-carbamoyl series compounds were obtained using a mobile phase of 90% water and 10% acetonitrile with a flow rate of 3.3 mL per minute. The 3-phenyl series compounds were obtained using a mobile phase of 85% water and 15% acetonitrile with a flow rate of 3.3 mL per minute. Any 3-substituted 2(lH)pyridone was retained at the head of the column. 

Since sulfonate groups have been used in other ground-water tracers, the goal of this work was to synthesize several N-substi-tuted pyridone alkyl sulfonates which might be less susceptible to adsorption as well as more soluble. Alkyl sulfonates of varying chain lengths would be unique in a water system and separately identifiable by HPLC analysis. Two series of compounds were synthesized (Vla-c and Vlla-c). These compounds could be prepared by treating compounds III and IV with the appropriate lu-bromoalkyl sulfonate. 

A series of bromoalkyl sulfonates was therefore needed to form the N-alkyl sulfonated 2-pyridones. Formation of bromoalkyl sulfonates has not been described extensively in the literature (19). 

Aminopyridine and l-methyl-2-pyridone are sulfonated under milder conditions (H2S04-S03, 140°C) in the 5-position. 2,6-Di-r-butylpyridine is converted into the 3-sulfonic acid under mild conditions (S02-S03, 0°C) because reaction of S03 at the nitrogen atom is prevented sterically thus, reaction occurs on the free base, under conditions where this is the majority species. 

Heterocyclic coupling components that have been coupled with diazotized ami-nophenyltrimethylammonium chloride are l-alkyl-6-hydroxy-2-pyridone [93], 1-amino-3-hydroxy-isoquinoline [94], and 2,4-diamino-6-hydroxypyrimidine [95], The trialkylammoniumaryl residue may also be connected to the aromatic diazo component via a sulfone or a sulfonamido function [96], Disazo dyes in this series (e.g., 34) [77901-21-4] may also be generated from monoazo dyes that still contain a primary amino group by dimerization using phosgene [97] or cyanuric chloride [98],... 

Hydroxypyridines undergo a variety of other electrophilic substitution reactions. Sulfonation of 2-pyridone with 10% oleum at 180° gave the 5-sulfonic acid.69 110 A-Methyl-2-pyridone is similarly sulfonated with chlorosulfonic acid. The action of fuming sulfuric acid gave a mixture of the 5-sulfonic acid and the 3,5-disulfonie acid. A nitro group at C-5 is said not to hinder the reaction, sulfonation at the... 

Pyridones, aminopyridines, and diazines with two strongly activating substituents, readily undergo nitration, sulfonation, and halogenation (reactivity approximately that of benzene). 

SgAr reactions (halogenation, nitration, sulfonation) with 2- and 4-pyridones occur in the 3- and/or 5-positions more readily than in pyridine. 

The pyridones can be readily halogenated, nitrated and sulfonated. Substitutions in acidic solutions usually proceed via attack on the free pyridone, but in very strong acid, where there is almost complete protonation, 4-pyridone undergoes a slower nitration, via the 0-protonated salt, but with the same regioselectivity. ... 

Metal-acid solutions have been employed in the reduction of nitropyridines to aminopyridines. Zinc dust and acetic acid have been used in the preparation of 3-amino-l-benzyl-4-pyridone or 3-amino-l-benzyl-S-iodo-4-pyridone from the corresponding 3-nitro derivatives. Tin or iron in acids is more popular. For example, 3-amino-2-(o-bromobenzyloxy)-pyridine is obtained by the reduction of 2-(o-bromobenzyloxy)-3-nitropyridine using iron and hydrochloric acid. Various ferrous salts have also been effective reducing agents. Several derivatives of phenyl 5-amino-2-pyridyl sulfide (K-16) (or the sulfone)are... 

Pyridinol or 2-nitro-3-pyridinol and chlorosulfonic acid in chloroform containing dimethylaniline give the 3-pyridyl bisulfate. 2-Pyridone gives the unstable A-sulfonate and 4-pyridone gives both the A-sulfonate and the... 

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