Transition metal mediated Exo selective Diels-Alder reactions: Preparation of 2-cobalt-substituted 1,3-dienes containing C-2 symmetric 2,3-dibenzobicyclo[2.2.2]octanedione dioxime equatorial ligands and their use in thermal and Lewis acid catalyzed 4+2 cycloadditions

被引:53
作者
Wright, MW [1 ]
Welker, ME [1 ]
机构
[1] WAKE FOREST UNIV, DEPT CHEM, WINSTON SALEM, NC 27109 USA
关键词
D O I
10.1021/jo951505o
中图分类号
O62 [有机化学];
学科分类号
070303 ; 081704 ;
摘要
The preparation of C-2 symmetric 2,3-dibenzobicyclo[2.2.2]octanedione dioxime is reported. This ligand is then used in the preparation of a (pyridine)(glyoxime)(2)cobalt(III) chloride complex. The chloride is reduced to a cobaloxime anion which reacted with allenic electrophiles to produce (pyridine)(glyoxime)(2)cobalt-1,3-dienyl complexes. Thermal and Lewis acid catalyzed Diels-Alder reactions of these dienyl complexes as well as the complexes with glyoxime = diphenylglyoxime and dimethylglyoxime are reported. In most cases these Diels-Alder reactions are anti (exo) selective, and in many cases diastereoselectivities are >20:1. Cycloadduct demetalation reactions are also reported which preserve cycloaddition stereochemistry and provide cobalt complexes which can be recycled into the starting dienyl complex.
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页码:133 / 141
页数:9
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