Mass Spectra of New Functionally Substituted Heterecycles:V.* First Example of McLafferty Rearrangement in the Series of 5-(1-Ethoxyethoxy)-2,3-dihydropyridines and 3-(1-Ethoxy-ethoxy)pyridines Derived from alpha-Lithiated 1-(1-Ethoxyethoxy)-allene a

摘要

Previously unknown 5-(1-ethoxyethoxy)-2-methoxy-6-methylsulfanyl-2,3-dihydropyridine,3-(1-ethoxyethoxy)-2-methylsulfanylpyridine,and 2-methylsulfanylpyridin-3-ol were synthesized from alpha-lithiated 1-(1-ethoxyethoxy)allene,methoxymethyl isothiocyanate,and methyl iodide,and their fragmentation under electron impact was studied.At ionizing electron energies of 12 and 60 eV in the temperature range from 50 to 250 deg C,the molecular ions derived from 5-(1-ethoxyethoxy)-2-methoxy-6-methylsulfanyl-2,3-di-hydropyridine and 3-(1-ethoxyethoxy)-2-methylsulfanylpyridine decompose along two main pathways:rupture of the C-O bond in the acetal moiety to give oxonium ions with m/z 73(in the two cases)and 168(pyridine derivative)and unexpectedly facile McLafferty rearrangement with elimination of ethoxyethene molecule to produce fragment ions with mlz 173 and 141,respectively.The latter pathway was not observed previously for dihydropyridines and acetals,and it predominates in the fragmentation of 3-(1-ethoxyethoxy)-2-methylsul-fanylpyridine.Expulsion of methanol molecule from the molecular ion of 5-(1-ethoxyethoxy)-2-methoxy-6-methylsulfanyl-2,3-dihydropyridine occurred only above 170 deg C.