Synthesis and investigation of solvent effects on the ultraviolet absorption spectra of 5-substituted-4-methyl-3-cyano-6-hydroxy-2-pyridones

Abstract

A number of 5-substituted-4-methyl-3-cyano-6-hydroxy-2-pyridones from cyanoacetamide and the corresponding alkyl ethyl acetoacetates were synthesized according to modified literature procedures. The alkyl ethyl acetoacetates were obtained by the reaction of C-alkylation of ethyl acetoacetate. An investigation of the reaction conditions for the synthesis of 4-methyl-3-cyano-6-hydroxy-2-pyridone from cyanoacetamide and ethyl acetoacetate in eight different solvents was also performed. The ultraviolet absorption spectra of synthesized pyridones were measured in nine different solvents in the range 200-400 nm. The effects of solvent polarity and hydrogen bonding on the absorption spectra are interpreted by means of linear solvation energy relationships using a general equation of the form ν = νo + sπ*+aα+ bβ, where π* is a measure of the solvent polarity, α is the scale of the solvent hydrogen bond donor acidities and β is the scale of the solvent hydrogen bond acceptor basicities. .

U okviru rada je izvršena sinteza 5-supstituisanih 4-metil-3-cijano-6-hidroksi-2-piridona iz cijanoacetamida i alkiletilacetacetata u prisustvu kalijum-hidroksida u metanolu kao rastvaraču. Alkiletilacetacetati su dobijeni reakcijom C-alkilovanja etilacetacetata odgovarajućim alkilhaloghenidima. Takođe je izvršeno ispitivanje reakcionih uslova za sintezu 4-metil-3-cijano-6-hidroksi-2-piridona iz cijanoacetamida i etilacetacetata u prisustvu KOH, NaOH i K2CO3 u različitim rastvaračima. IR, 1H-NMR i UV podaci su dati za sintetizovane piridone, a IR i 1H-NMR podaci su dati za sintetizovane alkiletilacetacetate. Apsorpcioni spektri 5-supstituisanih 4-metil-3-cijano-6-hidroksi-2-piridona su određeni u devet rastvarača različitih polarnosti u opsegu 200-400 nm. Uticaj polarnosti rastvarača kao i efekat vodonične veze proučavani su metodom linearne korelacije solvatacionih efekata odnosno jednačinom oblika ν = νo + sπ* + aα + bβ, u kojoj je ν apsorpciona frekvenca, π* mera efekata solvatacije vezana za polarnost rastvarača, α mera uspostavljanja vodonične veze sa proton-donorskim rastvaračima, a β mera vodonične veze ostvarene sa proton-akceptorskim rastvaračima. .