1.3- Oxazinium ion

As shown in Figure 1, the fully conjugated ring systems that appear in this chapter include the aromatic oxazinium ion 1, which has six ring 7t-electrons, but of which there is no experimental knowledge. The fully conjugated noncharged... 

With methyl p-toluenesulphonate all polymerisations proceed via ionic intermediates (oxazolinium or oxazinium ions), initiation and propagation being formulated as follows e.g. ... 

H NMR spectrum of the solution was identical to that of polymerising solutions initiated by methyliodide and proceeding via the oxazinium ion iodide. 

Enamines (e.g., morpholinocyclohexene) react with an oxazinium ion yielding two products—a butadiene analog (105) and a tetrahydroquino-line (106),4,194 as shown in Eq. (79). 

The heterocyclic systems of 1,3-oxazinium ions are widely used in the organic synthesis . Thus, 5,6-dihydro-4/f-l,3-oxazines 40, being a cyclic derivative of 1,2-aminoalcohols, can serve as Cj-synthones for the preparation of aldehydes, ketones and carboxylic acids . The 47/-l,3-oxazines 47 can undergo oxidative dehydrogenation by treatment with the trityl salts or benzoquinone to form the 3-azapyrylium salts 48, which then give various jV-acylenamine derivatives 49-52 by reaction with water or with active methylene comjKJunds (equation 18) . 

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