A Convergent and Flexible Approach to Hydroxylamines, Hydrazines and Related Structures

Abstract

Intermolecular xanthate transfer radical addition to protected allyl hydroxylamine or hydrazine provides a new, flexible, and convergent route to adducts which can be readily elaborated into complex aromatic or heterocyclic hydroxylamine or hydrazine derivatives.

Key words

hydrazines - hydroxylamines - xanthates - radical reactions

References

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10

Typical Procedure for 19: Lauroyl peroxide (10-15 mol%) was added portion-wise (in 3-4 portions over several hours) to a degassed, refluxing solution of 800 mg (2 mmol) of xanthate 16 and 1.1 g (4.0 mmol) of olefin 2b in 2 mL of
1,2-dichloroethane under argon. The reaction was regularly monitored for the disappearance of the starting material by thin layer chromatography. Upon completion, the solvent was removed under reduced pressure and the residue purified by chromatography on silica gel (heptane/EtOAc 98/2-95/5) to give compound 17 (1.58 g, 98%) as a colourless oil; it consisted of a 3:2 mixture of diastereo-isomers, which were used without further purification in the next step. ¹H NMR (CDCl₃, 250 MHz, ppm): δ = 6.72 (bs, 1 H, NH), 4.62 (q, 2 H, OCH₂, J = 6.5 Hz), 4.52 (d, 1 H, CH, J = 7.2 Hz), 4.01-3.79 (m, 3 H, CH₂N, CHS), 3.71 (s, 3 H, COOCH₃), 3.35 (s, 3 H, OCH₃), 3.31 (s, 3 H, OCH₃), 3.08-3.02 (m, 0.6 H, CHCOO), 2.99-2.91 (m, 0.4 H, CHCOO), 2.14-1.79 (m, 2 H, CH₂), 1.60 (s, 18 H, 6CH₃), 1.59 (t, 3 H, CH₃, J = 6.5 Hz); ¹³C NMR (CDCl₃, 62.5 MHz, ppm): δ = 211.6 (CS), 172.4 (COO), 154.5-154.4 (2 COO), 104.1/104.0 (CH), 81.2-80.9 (2 Cq, Boc), 69.9 (OCH₂), 54.4-54.2 (2 CH₃), 53.0/52.9 (NCH₂), 51.8 (CH₃), 47.7/46.7 (CHS), 45.2 (CHCOO), 46.1 (CH₂), 27.9 (CH₃), 13.5 (CH₃); IR (CCl₄): 3326 (m), 1736(vs), 1479 (m), 1443 (m), 1394 (m), 1368 (m), 1220 (s), 1155 (s), 1051 (s)cm^-1.
A solution of xanthate 17 (800 mg, 1.5 mmol), Bu₃SnH (0.75 mL), and AIBN (22 mg) in benzene (15 mL) was heated to reflux for 2 h under an inert atmosphere. The solvent was then removed under reduced pressure and the residue was purified by chromatography on silica gel (pentaneÆheptane-EtOAc, 7:3) to give 18 (602 mg, 97%) as a colourless oil. This material was used in the next step without further purification. ¹H NMR (CDCl₃, 300 MHz, ppm): δ = 6.58 (s, 1 H, NH), 4.50 (d, 1 H, CH), 3.69 (s, 3 H, COOCH₃), 3.53-3.34 (m, 2 H, CH₂N), 3.35 (s, 3 H, OCH₃), 3.34 (s, 3 H, OCH₃), 2.76-2.72 (m, 1 H, CH), 1.68-1.37 (22 H, 2 CH₂ and 6 CH₃); ¹³C NMR (CDCl₃, 75 MHz, ppm): δ = 173.3 (COO), 155.3-155.2 (2 COO), 104.6 (CHO) 80.8-80.7 (2 Cq), 54.5-54.4 (2 CH₃), 52.6 (CH), 51.5 (NCH₂), 48.7 (OCH₃), 28.1 (CH₃), 25.2-25.0 (2 CH₂); IR (CCl₄): 3329 (broad), 1735(vs), 1454 (m), 1398 (m), 1369 (m), 1253 (m), 1161 (s), 1067 (m)cm^-1.
A solution of 18 (280 mg, 0.7 mmol) in 1,2-dichloroethane (2 mL) and trifluoroactic acid (2 mL) was stirred for 1 h at r.t. under argon. The mixture was then evaporated under reduced pressure and the residue dissolved in a mixture of 1,2-dichloroethane (2 mL) and triethylamine (2 mL) and kept at r.t. for 48 h. The solvent was removed and the crude residue was extracted with dichoromethane and distilled water. The organic layer was dried over sodium sulfate. Evaporation under reduced pressure and purification by chromatography on silica gel (heptane-EtOAc, 1:1) afforded 19 as a colourless oil (50 mg, 48%). ¹H NMR (CDCl₃, 250 MHz, ppm): δ = 6.25 (d, 1 H, CH=, J = 7.3 Hz), 3.68 (s, 3 H, OOCH₃), 3.04 (m, 1 H, CH), 2.52-2.34 (m, 1 H, NH), 2.34-2.25 (m, 2 H, CH₂N), 2.24-2.12 (m, 2 H, CH₂), 1.94-1.89 (m, 2 H, CH₂); ¹³C NMR (CDCl₃, 62.5 MHz, ppm): δ = 173.1 (COO), 153.1 (CH=), 53.9 (CH₂N), 51.8 (OOCH₃), 46.8 (CH), 27.6 (CH₂), 23.8 (CH₂); IR (CCl₄): 3432, 2947, 1735, 1670, 1322, 1266, 735 cm^-1. Calcd for C₇H₁₂N₂O₂: C, 53.83; H, 7.74%. Found: C, 53.69; H, 7.51%.