848
J. Zakrzewski et al.
acetate 95:5, filtered, and placed in a separatory funnel. The precipitate was alkalized as above yielding
0.175 g of an oil (23% of 3 – estimated as above).
2,2,6,6-Tetramethyl-4-isothiocyanatopiperidine-1-oxyl (6a)
Procedure A with NaOH=H2O=CH2Cl2
Thiophosgene (1) (0.302g, 2.62mmol, 200 mm3) was added dropwise with a syringe to 0.438 g of 5a
(2.56 mmol) dissolved in 10 cm3 of a 5% NaOH solution at 5–7.5ꢂC for 10 min. An exotermic process
was observed and the resulting mixture was stirred for 10 min. The precipitate1 (0.613g) was removed
by filtration and dried under vacuum to give 0.362 g of the raw product. It was subjected to column
chromatography to yield 0.293 g of 6a (54%), mp 125.5–127.5ꢂC (Refs. [9, 10a] 127–128ꢂC, Ref. [44]
131–132ꢂC); IR (film): ꢀꢀ ¼ 2187; 2126 cmꢃ1; MS: m=z (%) ¼ 214 (4), 213 (14, M), 199 (4), 198 (3),
183 (5), 154 (12), 140 (10), 128 (12), 127 (9), 126 (12), 124 (11), 112 (17), 109 (7), 100 (11), 98 (6), 92
(6), 85 (4), 81 (6), 78 (8), 74 (7), 72 (7), 69 (100), 56 (11), 55 (12), 53 (7), 41 (45).
2,2,5,5-Tetramethyl-3-isothiocyanatopyrrolidine-1-oxyl (6b; C9H15N2OS)
Procedure C with NEt3=C6H6
Thiophosgene 1 (0.279 g, 2.43 mmol, 185 mm3) in 1 cm3 of benzene (dried azeotropically) was added
dropwise with a syringe to the solution of 0.363 g of 5b (2.31 mmol) and 0.68cm3 of triethylamine in
5 cm3 of benzene at 10–17ꢂC with vigorous stirring. The mixture was stirred at 20ꢂC for 5 min and the
precipitate of triethylamine hydrochloride was filtered off and thoroughly washed with benzene. The
benzene filtrate was washed with sat. NaHCO3 solution, the aq. phase was extracted with 2ꢄ 3 cm3 of
benzene, and the organic layers were dried with anh. MgSO4, filtered, and the solvent was evaporated.
The residue was subjected to column chromatography to give 0.356 g of 6b (77%); IR (film):
ꢀꢀ ¼ 2098 cmꢃ1; MS: m=z (%) ¼ 200 (1), 199 (11, M), 185 (2), 169 (2), 167 (3), 154 (4), 149 (5),
140 (2), 139 (3), 126 (15), 113 (60), 112 (19), 111 (14), 110 (7), 100 (24), 99 (9), 98 (15), 95 (12), 92
(6), 90 (4), 84 (13), 83 (8), 80 (18), 78 (5), 74 (14), 69 (48), 67 (16), 58 (20), 57 (14), 56 (86), 55 (100),
53 (22), 43 (32).
2,2,5,5-Tetramethyl-3-(isothiocyanatomethyl)pyrrolidine-1-oxyl (6c)
Procedure B with NaHCO3=H2O=CH2Cl2
Amine 5c (0.375 g, 2.19 mmol) dissolved in 0.5 cm3 of CH2Cl2 was added dropwise with vigorous
stirring to the mixture of 0.493 g of NaHCO3, 1.25 cm3 of H2O, 1 cm3 of CH2Cl2, and 0.297 g of 1
(2.58 mmol, 197 mm3) at 10–15ꢂC. The mixture was stirred at r.t. for 5 min, CH2Cl2 (5cm3) and 5 cm3
of H2O were added, and the aq. layer was extracted with 3 ꢄ 2 cm3 of CH2Cl2. The organic layer was
dried with anh. MgSO4, filtered, and the solvent was evaporated. The dark-yellow oil (0.463g) was
subjected to column chromatography to give 0.353g of 6c (76%), mp 33–6ꢂC (Ref. [44] 36–7ꢂC);
IR (film): ꢀꢀ ¼ 2080 cmꢃ1; MS: m=z (%) ¼ 214 (2), 213 (14, M), 199 (1), 183 (5), 140 (4), 109 (3), 100
(3), 81 (5), 74 (13), 69 (100), 56 (9), 55 (10), 41 (37).
Acknowledgement
The authors are indebted to Mrs. A. Kielczewska (MSc) and to Mrs. S. Garbaczewska (MSc) for
GLC=MS and GLC analyses.
1
In the case of 6b and 6c, synthesis according to procedure A gave no precipitate. Thus, the reaction
mixture was extracted with CH2Cl2