References and Notes
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2 For a review on base-catalyzed hydroaminations,
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3a
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Beller M.
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6 Gaylord Chemical Company, L.L.C. http://www.gaylordchemical.com/bulletins/Bulletin102B/Bulletin102B.pdf
(accessed Jan 28, 2011).
7
General Procedure
Exemplified by the Reaction of Styrene (1) with
p
-Toluidine (2)
An
oven-dried Schlenk tube equipped with a Teflon stopcock and a magnetic
stirring bar was transferred to a nitrogen-filled glove box and
charged with p-toluidine (343 mg, 3.2
mmol), styrene (208 mg, 2.0 mmol), dry DMSO (1.0 mL), and KOH (99.99% from
Sigma-Aldrich, 6 mg, 0.1 mmol, 5 mol%). The tube was sealed,
and the resulting mixture was heated to 70 ˚C
for 4 h. After the tube had been cooled to r.t. the reaction mixture
was poured into an aq NaOH solution (1 M, 10 mL) and extracted with
CH2Cl2 (3 × 10
mL). The combined organic layers were dried (MgSO4) and
concentrated under vacuum in the presence of Celite®.
Finally, the crude product was purified by flash chromatography
(light PE-EtOAc, 20:1) to give amine 3a (359
mg, 1.7 mmol, 85%) as a pale yellow oil. ¹H
NMR (500 MHz, CDCl3): δ = 2.22
(s, 3 H), 2.86 (t, J
H,H = 7.1
Hz, 2 H), 3.33 (t, J
H,H = 7.1
Hz, 2 H), 3.46 (s, 1 H, NH), 6.51 (d, J
H,H = 8.2
Hz, 2 H), 6.97 (d, J
H,H = 8.0
Hz, 2 H), 7.16-7.23 (m, 3 H), 7.26-7.31 (m, 2
H) ppm. ¹³C NMR (126 MHz, DEPT, CDCl3): δ = 20.3
(CH3), 35.4 (CH2), 45.3 (CH2), 113.1
(CH), 126.3 (CH), 126.5 (C), 128.5 (CH), 128.7 (CH), 129.7 (CH),
139.3 (C), 145.7 (C) ppm. IR (neat): ν = 3404, 3025,
2918, 2861, 1615, 1519, 1318, 1259, 1182, 1080, 1031, 808, 699 cm-¹.
HRMS (70 eV): m/z calcd for
C15H17N: 211.1361; found: 211.1365.
8 Under comparable conditions, much lower
yields were obtained with toluene (<5%), 1,4-dioxane
(<5%), THF (9%), and DME (9%).
9 A base-catalyzed addition of the
DMSO anion to styrene has been reported: Walling C.
Bollyky L.
J. Org. Chem.
1964,
29:
2699
10 Azeotropic data of H2O-hexane:
TAz = 61.6 ˚C, PAz = 101.33
kPa; ywater = 0.2110. See: Lide DR.
Handbook
of Chemistry and Physics
87th ed.:
CRC
Press;
Boca Raton:
2006.
p.6-161