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

Abstract

SummaryHydroboration 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-

Stereoselective Double Functionalization of Iron‐Carbonyl Complexes of 5,6,7,8‐Tetramethylidenebicyclo[2.2.2]oct‐2‐ene. Crystal Structure and Absolute Configuration of (–)‐trans‐μ‐[(2S,5R,7S)‐C,5,6,C‐η:C,7,8,C‐η‐(6,7,8‐trimethylidene‐5‐((Z)‐2‐oxopropylidene)‐2‐bicyclo[2.2.2]octyl acetate)]‐bis(tricarbonyliron)

“…toward hydroboration of the diene moieties but leave one face of the endocyclic double bond at C(2),C(3) available for reaction. Thus, hydroboration followed by oxidative workup yields the corresponding alcohol (k)-4 [6] from which the 'exo'-Fe(CO), group can be selectively removed on oxidation with Me,NO [7]. Esterification of alcohol (&)-4 with Ac,O in pyridine gave complex (*)-5 (98%, see Exper.…”

Photogeneration of Octacene and Nonacene

“…The known 5,6,7,8-tetramethylenebicyclo[2.2.2]oct-2-ene [19] (7) is used as a building block for constructing the oligoacene framework of 8 and 9 by successive Diels-Alder reactions followed by aromatization (Scheme 1). Without separation, the two possible stereoisomers of 8 and 9 were transformed into the tetraketones 5 and 6 by dihydroxylation and oxidation.…”

Photochemische Erzeugung von Octacen und Nonacen

“…Das bekannte 5,6,7,8-Tetramethylenbicyclo[2.2.2]oct-2-en (7) [19] diente als zentraler Baustein für den Aufbau des Oligoacengerüsts durch eine Folge von Diels-Alder-Reaktionen mit anschließender Aromatisierung (Schema 1). Die beiden Stereoisomere von 8 und 9 wurden jeweils als Gemisch durch Dihydroxylierung und Oxidation in die Tetraketone 5 bzw.…”