is removed in vacuo ca 12 mbar 90 c the residue is dissolved in a minimal amount of methanol and the product is precipitated by addition of 5 vol acetone the product is isolated by centrifugation washed with some acetone and then dried in vacuo yields vary depending on product structure and amount of dmso and methanol present during precipitation by concentrating the mother liquor and repeating the precipitation a second crop may be obtained resulting in acceptable yield of the rgtw a solution of the diol 3 0 g 6 5 mmol 1 equiv and 1 3 propanesultone 2 17 g 17 8 mmol 2 7 equiv in thf 6 ml was warmed to 60 u00b0 c and added a solution of kotbu 2 01 g 17 9 mmol 2 7 equiv in thf 14 ml over 15 min additional thf 10 ml was added to help stirring the resulting suspension was cooled to rt and stirred over night thf was removed under vacuum after 20 h at rt the resulting solid was dissolved in minimal amounts of meoh 150 ml under reflux the solution was poured into acetone 450 ml to result in a cloudy mass not possible to isolate by filtration the.