Entries 10-13 (Chart 4) detail the use of DMF as the solvent and varying the reaction temperature. With increasing temperature higher conversions were found with an optimum at 120 °C (entry 12). Higher temperatures (> 120 °C) were found to lead to more ortho-substituted product e.g., selectivity (para : ortho) decreases from 10 : 1 to 5 : 1. Entries 14-17 (Chart 4) detail the use of DMSO as the solvent. Although entry 14 was comparable to the optimal DMF result, complications of removing DMSO led to this being discontinued. Entries 18-21 (Chart 4) detail the use of 1,2-DCB as the solvent. Similarly, entry 18 was comparable and gave a slightly better para : ortho ratio than DMF (entry 12), but difficulties removing a high b.p. solvent ruled out further investigation. Furthermore, in both the DMSO and 1,2-DCB examples evidence for the degradation of was found above 160 °C. With the optimal conditions for a one-pot para-selective SEAr identified a screen of variously substituted anilines (probing sterics and electronics), heterocycles and oxygen containing systems were screened (Chart 5). The one-pot method applied to compounds 4e, 4f and 4g (Chart 5) resulted in dramatic improvements in conversion and isolated yield compared to the step wise procedure (Charts 2-3). 4e increased from a linear 11% yield to 44%, 4f increased from a linear 18% yield to 40%, and 4g increased from no reaction to 5% isolated yield. A regioisomer of 4g gave a similar low yield of 7% (4h) demonstrating the deactivating effect of the di-chloro-aryl ring system. However, other electron withdrawing groups are well tolerated. The nitro containing example (4i) proceeded in a modest 64% conversion (60% isolated). N,N-dimethylaniline proceeded smoothly to afford the para-substituted sulfonate in 70% isolated yield (4j). Moving to other heteroatoms, the hydroxyl group of the sterically demanding anaesthetic, propofol, was readily sulfonated in an 88% isolated yield . Thiophene was readily sulfonated in the 2-position (6) in a 65% yield, protected and unprotected pyrroles were sulfonated in 51 and 60% yields respectively. A tetrasubstituted pyrrole was prepared in an excellent 79% yield and N-methylindole was sulfonated at the C3 position with an 80% isolated yield. Furthermore, a fluorine containing building block was readily sulfonated in 45% isolated yield . In turn these sulfonated (hetero)aryl systems can be further manipulated to sulfonyl chlorides, sulfonamides, and sulfinates as building blocks in medchem.