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. 2009 Sep 9;131(35):12576-8.
doi: 10.1021/ja9058926.

Improved dienophilicity of nitrocycloalkenes: prospects for the development of a trans-Diels-Alder paradigm

Woo Han Kim  1 , Jun Hee Lee, Samuel J Danishefsky
Affiliations

Improved dienophilicity of nitrocycloalkenes: prospects for the development of a trans-Diels-Alder paradigm

Woo Han Kim et al. J Am Chem Soc. .

Abstract

The development of an efficient and stereoselective trans-Diels-Alder paradigm is described. A central element of this transformation is the introduction of a temporary dienophilic functionality (A), which serves both to activate the substrate for Diels-Alder cycloaddtion and, through its subsequent removal, to facilitate conversion of the cis-fused cycloadducts to the trans-fused series.

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Figures

Figure 1
Figure 1
Structures of the tertiary bridge head radical.
Scheme 1
Scheme 1
Trans-Diels-Alder Paradigm.
Scheme 2<sup>a</sup>
Scheme 2a
aKey: (a) CF3CH2OH, 80 °C, MW, 12 h, 61%. (b) HF, CH3CN, rt, 30 min. (c) nBu3SnH, AIBN, benzene, reflux, 2 h. (d) CF3CH2OH, 80 °C, MW, 6 h, 72%.
Scheme 3<sup>a</sup>
Scheme 3a
aKey: (a) xylene, reflux, 36 h. (b) 0.05 M HCl, THF, 2 h, 67% for 2 steps. (c) nBu3SnH, AIBN, benzene, reflux, 2 h, 89%. (d) TFAA, benzene, Dean-Stark, 24 h, 60%. (e) toluene, 130 °C, 36 h, 90%. (f) nBu3SnH, AIBN, benzene, reflux, 2 h. (g) HF, CH3CN, rt, 10 min, 53% for 2 steps.
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