F. L. Setliff, Maximillia M. Muguluma, J. Z. Caldwell
1991
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Journal
Journal of the Arkansas Academy of Science
Abstract
Substituted phenyl esters of 5-bromo-2-chloronicotinic acid and 5 bromo 6-chloronicotinic acid were prepared. The acids were first converted to their respective acid chlorides using thionyl chloride, and the acid chlorides were immediately transformed to the esters by treatment with the appropriately substituted phenol in sodium hydroxide solution. Aunique chloride displacement of bromide was observed on attempting to convert 5,6-dibromonicotinic acid to its acid chloride. INTRODUCTION The following procedure was used toprepare the phenyl esters IIIand IV.The dihalonicotinic acidIorII(0.500g; 0.002 mol) and thionyl chloA recent paper (Setliff,et al.) related our continuing interest in the ride (3 mL) were stirred under gentle reflux for 30 min. During this time preparation of dihalonicotinic acid derivatives with potential herbicidal, the acid completely dissolved. The reaction mixture was cooled to room fungicidal, or ascaricidal activity. As an extension of this work, we now temperature, and the excess thionyl chloride was removed under reduced describe the preparation of a series of substituted phenyl esters of 5pressure on a rotary evaporator (oil bath SO'C). The residual viscous oil bromo-2-chloronicotinic acid (I)and S-bromo-6-chloronicotinic acid (II) (the acid chloride) was used to prepare the ester without further purifica(Setliff, 1970). These compounds comprise the first series ofesters with tion. The appropriate substituted phenol (0.01 5 mol) was dissolved in 5 suspected activity synthesized by our group. mL of0.1 Msodium hydroxide, and the resulting solution was added to the acid chloride. The mixture was stirred vigorously at room temperature Br V^',!'' 2 2H for one hour « and then a mixture of *ce (5 g) and water (20 mL) was added while stirring was continued. Inmost cases the ester precipitated. LNs JJ v.. rix"^Is m some cases precipitation was induced by the addition of 10-15mL of N W' cold ethanol to the ice water mixture. The crude ester was collected by t t t vacuum filtration and washed with cold water, followed by ice cold ethanol, and then recrystallized from a small volume ofethanol. Melting points and yields (overall from the acids) are listed inTables 1and 2. MATERIALSANDMETHODS The phenyl 5-bromo-2-chloronicotinates (HI) and the phenyl 5Table 1. Experimental, Infrared, and Elemental Analysis Data for the bromo-6-chloronicotinates (IV)were generated by treating the acid chloSubstituted Phenyl 5-Bromo-2-chloronicotinates (IE) rides of Iand IIwith the appropriately substituted phenol in basic ¦ solution. The acid chlorides were prepared in the normal manner from the n *ym. mp °c ir,v, cm ' Eiimanui Analysis Caicd % (Found %) acids by use of thionyl chloride. The preparative sequence is summarized Ca0 c^./^ c h n in Scheme Ibelow. Scheme I —~ (J a. H 81 91 1748 12S7 48.08(48.38) 2.24(2.26) 4.48(4.41) 1) SOC1 2 v R b 'CI 103 17M 127* 41.49(41.49) 1.72(1.68) 4.03(3.88) r—^ I \~—* / C. Br 51 12