Regioselective Allylic Amination of the Baylis-Hillman Adducts: An Easy and Practical Access to the Baylis-Hillman Adducts of N-Tosylimines

Abstract

The reaction of the in situ generated DABCO salt of Baylis-Hillman acetate and tosylamide in aqueous THF gave the Baylis-Hillman adduct of N-tosylimine in good yield. The method seems very simple and practical for the preparation of Baylis-Hillman adduct of N-tosylimine.

Baylis-Hillman adducts - N-tosylimine - DABCO - allylic amination - deracemization

References

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7

Other nucleophiles can be used in the reaction such as phenols and primary nitroalkanes, which have the similar pK_a values as that of tosylamide.

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9

Typical Procedure for the Formation of 3a: To a stirred solution of the Baylis-Hillman acetate 1a (496 mg, 2.0 mmol) in aq THF (10 mL, H₂O-THF, 1:1) was added DABCO (270 mg, 2.4 mmol) and stirred at r.t. for 10 min. To the reaction mixture p-toluenesulfonamide (345 mg, 2.0 mmol) was added and the whole mixture was stirred at 60-70 °C for 48 h. After the usual workup process and column chromatography (SiO₂, hexane/ether, 1:1), 3a was obtained as a white solid, 540 mg (75%); mp 100-101 °C (ref. [2a] 90-92 °C); IR (CH₂Cl₂): 3289, 1716, 1327, 1161 cm^-1; ¹H NMR (CDCl₃): δ = 1.14 (t, J = 7.2 Hz, 3 H), 2.41 (s, 3 H), 4.04 (q, J = 7.2 Hz, 2 H), 5.30 (d, J = 9.0 Hz, 1 H), 5.65 (d, J = 9.0 Hz, 1 H), 5.81 (s, 1 H), 6.21 (s, 1 H), 7.13-7.69 (m, 9 H); ¹³C NMR (CDCl₃): δ = 13.89, 21.46, 59.12, 60.97, 126.44, 127.21, 127.51, 127.66, 128.49, 129.44, 137.75, 138.75, 138.84, 143.29, 165.27; CIMS: m/z (%) = 189(92), 204(100), 205(15), 360(1) [MH⁺]. Anal. Calcd for C₁₉H₂₁NO₄S: C, 63.49; H, 5.89; N, 3.90. Found: C, 63.32; H, 5.91; N, 3.94.