Mass Spectra of New Functionally Substituted Heterocycles: V. First Example of McLafferty Rearrangement in the Series of 5-(1-Ethoxyethoxy)-2,3-dihydropyridines and 3-(1-Ethoxyethoxy)pyridines Derived from α-Lithiated 1-(1-Ethoxyethoxy)allene and Methoxymethyl Isothiocyanate