Hydrochloric Acid → 2-(2-Methyl-4-nitrophenylimino)-3-isobutyl-4,4-dimethyl-1,3-thiazolidine

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N-Isobutyl-1,1-dimethyl-2-hydroxyethanamine was prepared in a manner analogous to Method B4a. HCl was bubbled into a solution of N-isobutyl-1,1-dimethyl-2-hydroxyethanamine (1.45 g, 10 mmol) in toluene (20 mL) until saturation. SOCl2 (10 mmol) was added to the solution dropwise at room temp., stirred at room temp. for 1 h and at 50° C., for 1 h. The resulting mixture was concentrated under reduced pressure and the residue was dissolved in CHCl3 (20 mL). To the resulting solution was added 2-methyl-4-nitro-phenyl isothiocyanate (1.94 g, 10 mmol), then a solution of Et3N (10 mmol) in CHCl3 (10 mL) was added dropwise at room temp. The resulting mixture was heated at the reflux temp. for 3 h, then concentrated under reduced pressure. The residue was dissolved in EtOAc (100 mL) and the resulting solution was sequentially washed with a 10% aq. NaOH solution (50 mL) and a saturated NaCl solution (50 mL), dried (MgSO4) and concentrated under reduced pressure. The residue was purified by chromatography (9% EtOAc/pet. ether) and the resulting solids were recrystallized (pet. ether) to give 2-(2-methyl-4-nitrophenylimino)-3-isobutyl-4,4-dimethyl-1,3-thiazolidine (0.6 g, 63%): mp 97° C. When appropriate, the product was converted into the HCl salt by dissolving the free base (5 mmol) in Et2O (50 mL) and treating this solution with a 2N ethereal HCl solution until no more solid precipitated. The resulting slurry was filtered and the resulting solids were washed with Et2O (25 mL) followed by EtOAc (25 mL).

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