1- Hydroxy-8- naphthalene 1,3-oxazines

A single-step process for preparing oxazine derivatives via the condensation of an a-hydroxyaldehyde and o -amino-/3-hydroxy naphthalene (3) is illustrated in Eq. 2 ... 

Theoretical calculations of minimum-energy structures and thermodynamic terms using self-consistent field theory with thermodynamic and solvation corrections concluded that the cyclization of l-hydroxy-8-(acetylamino)naphtha-lene 1 to give 2-methylnaphth[l,8-r7,< ][l,3]oxazine 2 with the liberation of water was much less favorable (AG = —2.0kj moP, A/7 = 4-31.0kj mol , and TAS = 4-33.1 kjmoP at 298.2 K) in the gas phase than the corresponding ring closure of l-amino-8-(acetylamino)naphthalene, which was in qualitative agreement with experimental observations for the reactions in solution <1998J(P2)635>. 

Pm-positioned hydrazono (formed in situ) and hydroxy groups on naphthalene react on heating the compound in ethane-1,2-diol similarly, 8-acyl-1-naphthol oxime yields a 1,2-oxazine. Both reactions proceed in high yield. 

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