1.2.4- Thiadiazines applications

Three classes of compound dominate this section, namely the 6-azapteridines or pyrimido[4,5- ][l,2,4]triazines, the 7-azapteridines or pyrimido[5,4-i ][l,2,4]triazines, and the pyrazinothiadiazines, particularly the pyrazino[2,3-r ][l,2,6]thiadiazine 2,2-dioxides. None of the other systems that have appeared in this chapter show important applications. 

The main successful applications of monocyclic 1,2,4-thiadiazines in earlier years have been the use of bis[4-(3,4,5,6-tetrahydro-l,l-dioxo-2//-l,2,4-thiadiazinyl)]methane (62, Taurolidine, Taurolin, Drainsept) as an antibacterial agent and 3,4,5,6-tetrahydro-2//-l,2,4-thiadiazine 1,1-dioxide (63, Taurultam) as both an antibacterial and antifungal agent (66FRP1458701). Claimed uses of 1,2,4-thiadiazines are listed in Table 11. 

In all the reported agrochemical applications a sulfur heterocycle is used. The 2,2-dioxo-pyrazolo[3,4-c][l,2,5]thiadiazines <90MI 713-01) and the 5,6-dipyridyl[l,2,5]thiadiazolo[3,4-6]pyr-azine (183) <84BRP2122492> are fungicidal. The 2,2-dioxopyrazolo[3,4-c][l,2,6]thiadiazines are herbicides <80USP4182623). 

Application of theoretical methods to study dipole moments of 1,2,6-thiadiazine 1,1-dioxide derivatives has been reported (82JOC536). The calculated values by the CNDO/2 method, using ideal or experimental... 

Table 4 Various applications of syntheses of [l,2,4]triazolo[3,2-a][l,3,4]thiadiazines.

The spectrum of activity is attractive for application in a number of industrial systems, e.g. as a broad spectrum microbidde which prevents fungal blooms in metal working fluid systems. However, there are limitations, including the finding that 3,5-Dimethyl-tetrahydro-l,3,5-2H-thiadiazine-2-thione is very unstable at increased temperatures. Under alkaline conditions it is found that more decomposition products are formed than under pH neutral conditions (e.g. wet-end system). 

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