Synthesis and Diels-Alder Reactivity of 5,6,7,8-Tetramethylidene-2-bicyclo[2.2.2]octanol and -octanone. Selective Oxidations of the Corresponding Bis(irontricarbonyl) Complexes

✍ Scribed by Raphy Gabioud; Pierre Vogel

• Publisher: John Wiley and Sons
• Year: 1983
• Tongue: German
• Weight: 914 KB
• Volume: 66
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.19830660417

✦ Synopsis

Hydroboration of the syn, anti-[Fe (CO)3]2 double complex 24 of the readily available 5,6,7,8-tetramethylidene-2-bicyclo [2.2.2]octene (22) gave the corresponding doubly complexed 2-bicyclo [2.2.2]octanol 25. Cr03-oxidation furnished ketone 27. The syn-Fe (CO)3-groups in 25 and 27 were oxidized selectively with trimethylamine oxide and yielded the corresponding anti-Fe (C03)-monocomplexed tetraenes 26 and 28. The anti-Ft;e(C0)3-group in 28 could be removed, and 5,6,7,8-tetramethylidene-2-bicyclo [2.2.2]octanone (11) was obtained. NaBH4-reduction of 11 afforded tetraenol 10. TCE-cycloadditions to 10 and 11 ( k , ) were at least 10 times as fast as those (k2) to the corresponding monoadducts 35/36 and 34, respectively. This Diels-A lder reactivity difference vanishes ( k l z k2) with methyl propynoate. The latter dienophile added to the anti-Fe (C0)~-monocomplexed tetraenone 28 with 'para'-regioselectivity. Introduction. -The 2,3,5,6-tetramethylidenebicyclo [2.2.n]alkanes 1 are very attractive starting materials for the preparation of polycyclic, polyfunctional systems by two successive Dicls-Alder additions with different dienophiles [2]. The 2,3,5,6-1 2 3 I ) *) Interaction between non-conjugated chromophores, Part 20. Part 19, see [l].