Hydrochloric Acid → 3-tert-Butyl-5-isopropyl-2-thiohydantoin

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Reaction Steps

Sparteine (0.94 g, 0.0040 mol) was dissolved in 2 mL of THF in a flask equipped with a magnetic stirrer, septum, and nitrogen pressure. The flask was immersed in a −40° bath, and a 1.6 M ethereal solution of methyllithium (2.5 mL, 0.0040 mol) was added by syringe. Then a solution of 3-t-butyl-5-ethylidenethiohydantoin (0.20 g, 0.0010 mol) in 2 mL of THF was added dropwise by syringe over 20 min. After 1 hr, HPLC analysis showed no starting material. The reaction mixture was diluted with 5 mL of saturated aqueous NH4Cl, then 4 mL of 1 M HCl, and then 10 mL of EtOAc. The layers were separated, and the organic layer was washed with 2×30 mL of 1 M HCl. The solvent was removed at aspirator pressure, and the residue was reconcentrated×3 from small amounts of dichloromethane. An HPLC trace at 270 nm revealed a purity of only 71% for the major product, although there was no major impurity. NMR (CDCl3) δ 8.5 (bs, 1H), 3.8 (m, 1H), 0.9-2.8 (m, 16H). It is notable that the methyls of the isopropyl group are magnetically nonequivalent.

Provenance & Evidence