1,2,6-Thiadiazine 1,1-diones synthesis

A review on the synthesis of 1,3,4-thiadiazines and 1,3,4-oxadiazines shows the formation of the diones 105 and 106 (Equation 57) <1998H(49)557>. TPHA3 was preparedby treatment of 107 with DBU in air (Scheme 10) <1998JA2989,... 

Two quite specific methods have been employed for the synthesis of imidazo[2,l- ]-[l,3,5]thiadiazines. In the condensation of l,2-diphenylimidazoline-4,5-dione (726) with a thiocarbonyl isocyanate such as (727), the isocyanate added to (726) in the manner of a Diels-Alder diene to produce (728) (67CB2064). 

Thirupaiah and Vedula devised a one-pot synthesis of substituted 2,3-dihydro-2-(6-(4-hydroxy-6-methyl-2-oxo-2f/-pyran-3-yl)-7f/- [ 1,2,4] tr iazolo [3,4-i ] [ 1,3 >4] -thiadiazin-3-yl)phthalazine-l, 4-diones 13 (Scheme 9) (14SC513). Treatment of 3-(2-bromoacetyl)-4-hydroxy-6-methyl-2f/-pyran-2-one (14) with 4-amino-5-hydrazino-4f/-[l,2,4]triazole-... 

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