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Title: Synthesis and chemistry of benzo-1,2,4-thiadiazines
Author: Clark, E. R.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2008
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Forty-five 3-aryl benzo-1,2,4-thiadiazine derivatives have been prepared and twenty-two derivatives characterised by X-ray diffraction. Their solid-state molecular structures reveal low energy pathways for deformation through (i) rotation of the aryl group; (ii) folding of the heterocycle about the transannular S….N vector. This largely qualitative assessment has been supported by ab initio DFT (B3LYP/6-31G) calculations. Improvements to the published syntheses the related 3-aryl benzo-1,2,4-thiadiazine 1-chlorides have increased yields and selectivity. A new route to these salts has been developed utilising SOC12 as the source of SIV which exhibits lower degrees of chlorination of the benzo-fused ring. A total of six benzo-substituted 3-aryl benzo-1,2,4-thiadiazine 1-chlorides have been prepared of which five were characterised by X-ray diffraction. Conformational polymorphism was identified in 1,6,7-trichloro-5-chloromethyl-8-methyl-3-phenyl-benzo-1,2,4-thiadiazine and the energy barrier to interconversion between polymorphs probed by ab initio DFT calculations. Electrochemical studies on the 1-chloride salts reveal a good correlation between the E1/2 for their 1e- reduction and their LUMO energies from ab initio DFT (B3LYP/6-31G) calculations. Solution state EPR studies have been performed on the radicals formed by oxidation of 3-aryl-benzo-1,2,4-thiadiazines or reduction of 3-aryl-benzo-1,2,4-thiadiazine 1-chlorides respectively. Correlation between the experimental heterocyclic spin density estimated from the McConnell relationship and the calculated spin density from semi-empirical (AM1, PM3, PM5) were found to be poor. 3-pyrid-2-yl benzo-1,2,4-thiadiazine (LH) has been shown to react with CuCl2.2H2O and anhydrous CoCl2 to form the chelate complexes CuCl2(LH), CuCl2(LH)2 and CoCl2(LH)2 which have been characterised by X-ray diffraction.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available