Tetramethylthiouronium

Most compounds within this group are partially saturated and are dealt with in that section. Azine approach. In the reaction between ethyl bromo(pyridin-2-yl)acetate (435) and tetramethylthiourea the first formed tetramethylthiouronium salt is cyclized to the thiazole (436). The 3-dimethylamino group is readily hydrolyzed yielding the corresponding lactam... 

S- 1 -Oxido-2-pyridinyl)-1,1,3,3-tetramethylthiouronium Hexafluorophosphate (HOTT), 463 CioH,602... 

N -hydroxy-5-norbornene-2,3-dicarboximide N -hydroxysuccinimide S -(1 -oxido-2-pyridinyl)-1,1,3,3 -tetramethylthiouronium hexafluorophosphate N, N-bismesitylimidazolylidene N -carboxyanhydride... 

S-(l-Oxido-2-pyridinyl)l,l,3,3-tetramethylthiouronium tetrafluoroborate, NH4CI, DIPEA, DMF, 30 min, rt (46-99% yield of primary amide). "... 

Next, alcohol 35 was transformed into 36 by reductive dehydroxylation via the nonisolated intermediate xanthate. Hydrolysis of the ester group in 35 to form 30 was followed by decarboxylation to generate 37 by using an improved Barton s method employed with HOTT (5-(l-oxido-2-pyr-idinyl) 1,1,3,3-tetramethylthiouronium hexafluorophos-phate) [35]. Treatment of 37 with TBAF furnished alcohol, which was converted into the proposed structure of paesslerin A by using scandium-catalyzed acetylation. Unfortunately, comparisons of the H- and C-NMR data of the synthetic compound with those reported for the natural product revealed that the substances are not identical. The 2D-NMR data for synthetic 29 are fiiUy consistent with the structure of the target. The result clearly demonstrates that a revision of the structure of natural paesslerin A is required (Scheme 4.17). 

Barton, D. H. R. and Samadi, M., The invention of radical reactions. 25. A convenient method for the synthesis of the acyl derivatives of N-hydroxypyridine-2-thione, Tetrahedron, 48, 7083,1992. Garner, R, Anderson, J. T. and Dey, S., S-(l-oxido-2-pytidinyl)-l,l,3,3-tetramethylthiouronium hexafluorophosphate a new reagent for preparing hindered barton esters,/. Org. Chem., 63,5732,1998. Prabhakar, S., Lobo, A. M., and Santos, A., A, Convenient method for the synthesis of N-hydroxy thiobenzamides (C-arylthiohydroxamic acids). Synthesis, 829,1984. 

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