Synthesis of 1,3-oxazines based on piperazine

The oxazines bearing piperazinyl moieties namely 2-(tert-butyl)-6-((4-(2-(8-(tert-butyl)-6-methyl-2H-benzo[e][1,3]oxazin-3(4H)-yl)ethyl)piperazin-1-yl)methyl)-4-methylphenol (1) and its corresponding 2,4-di-tert-butyl-6-((4-(2-(6,8-di-tert-butyl-2H-benzo[e]-[1,3]oxazin-3(4H)-yl)ethyl)piperazin-1-yl)methyl)phenol (2), which was previously isolated were described. The transformation of the piperazinyl tri-tert-butyl-phenol derivatives 6,6′-(((2-(4-(3-(tert-butyl)-2-hydroxy-5-methylbenzyl)piperazin-1-yl)ethyl)-azanediyl)bis-(methylene))bis-(2-(tert-butyl)-4-methylphenol) 3 and 6,6′-(((2-(4-(3,5-di-tert-butyl-2-hydroxybenzyl)piperazin-1-yl)ethyl)-azanediyl)-bis(methylene))bis(2,4-di-tert-butyl-phenol) 4 into 1 and 2, respectively was achieved in high yield by heating and stirring a methanolic solution containing Et₃N and Ga(NO₃)₃·6H₂O in the stochiometric ratio 1:3:1 for 30 min. The novel oxazine-piperazine 1 together with its triphenol-piperazine 3 (H₃L⁴) were structurally characterized by spectroscopic and single crystal X-ray crystallography.