Abstract
Hetero-Michael additions of nitrogen, oxygen and sulfur nucleophiles
to α,β-unsaturated ketones were efficiently catalyzed by
Nafion® SAC-13 perfluorinated resinsulfonic
acid.
Key words
hetero-Michael additions - heterogeneous catalysis - enones - polymer-support - Nafion®
References
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Experimental procedure: Enone (0.25
mmol) and nucleophile (0.375 mmol, 1.5 equiv.) were dissolved in CH3 CN
(0.5 mL) and stirred over Nafion® SAC-13 (15
mg, 60 g˙mol-1 ) at room temperature.
The reaction was monitored by TLC and the product was isolated by preparative
TLC after filtering off the catalyst.
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The ion exchange capacity of Nafion® SAC-13
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Only sluggish conversion was observed
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h) with Pd(CH3 CN)4 (BF4 )2 ;
84% yield (72 h) with Tf2 NH (see ref.
[7
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Catalyst regeneration: Spent Nafion® SAC-13
was stirred over 6 N HCl (0.5 mL) overnight. After filtration, the catalyst
was dried in vacuo for 20 h and reused.
<A NAME="RD08603ST-16">16 </A> Analytical data for 5-(benzyloxycarbonylamino)hexan-3-one: 1 H
NMR (400 MHz, CDCl3 ): δ = 1.00 (t, J = 7.3 Hz, 3 H), 1.19 (d, J = 6.7 Hz, 3 H), 2.38 (q, J = 7.3 Hz, 2 H), 2.53 (dd, J = 5.9 Hz, 15.7 Hz, 1 H), 1.65
(dd, J = 4.8 Hz, 15.7 Hz, 1
H), 4.00-4.10 (m, 1 H), 5.05 (s, 2 H), 5.33 (br, 1 H),
7.22-7.38 (m, 5 H). 13 C NMR
(100 MHz, CDCl3 ): δ = 7.9, 20.9 (CH3 ),
36.9 (CH2 ), 44.3 (CH), 48.2, 66.9 (CH2 ), 128.4, 128.7,
129.9 (Ar-C), 137.0 (ipso -Ar-C), 156.0,
210.5 (C=O). IR (neat, film): cm-1 3323,
3061, 2975, 1706, 1680, 1534, 1254. HRMS [+ESI]:
calc. 272.1263, found: 272.1250 ([C14 H19 NO3 Na]+ ).
Mp: 55-57 °C
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