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)

Abstract

Results and Discussion. -The readily prepared pentaene 2 gives the bis(tricarbony1iron) complex 3 in good yield on heating with Fe,(CO), in hexane/MeOH [5]. The two Fe(CO), groups in trans positions remove one of the two mirror planes in the free ligand. In terms of the reaction chemistry, they play the role of protecting groups ') , )It has been called a 'doubly-doubly convergent' synthesis, see [3]. This has already been achieved with the 2,5-bis[(Z)-(2-nitrobenzenesulfenyl)methylene]-3,6-bis(methy~ene)-7-oxabicyclo[2.2.l]heptane, see [4].

Synthesis and 1H‐, 13C‐, and 57Fe‐NMR spectra of mono‐ and bis[tricarbonyl(η4‐diene)iron], and (η3‐allyl)tetracarbonyliron trifluoroborate complexes

“…In particular, C (8) and H-C(3) are twisted out of the n-plane to a considerable extent (Table 13). This effect has also been observed in other substituted [Fe(CO),(diene)] complexes investigated by X-ray crystallography [3d] [36] [37], irrespective of the nature of the substituent. We, therefore, conclude that the conformational distortion in 34 is mainly caused by steric interaction between H-C(3) and the 3yn'-oriented , and by a similar interaction of this Me group and H-C(3), respectively, with the Fe-atom.…”

Stereoselective Double Friedel‐Crafts Acylation of trans‐μ‐(2,3,6,7‐Tetramethylidenebicyclo[3.2.1]octane)bis(tricarbonyliron). Crystal Structure of trans‐μ‐{(1RS,2RS,3SR,5RS,6SR,7SR)‐C,2,3,C‐η:C,6,7,C‐η‐[(Z,Z)‐1,1′‐(3,7‐Dimethylidenebicyclo[3.2.1]octane‐2,6‐diylidene)di(2‐propanone)]}bis(tricarbonyliron)

“…Out of 4 possible modes of attacks by the acylating agent, only one leads to a substitution product for the monoacylation 445. The preference for the diene moiety coordinated to the endo-Fe(CO), group was expected by analogy with the monoacylations of 8 and 18 that we had also found to be stereoselective and to give the monoacylated products 19 [5] and 20, respectively [6]. The preference for the 'endo '-Fe(CO), coordinated diene was attributed to an electronic factor [7]: the hypothetical intermediate 21 of the Friedel-Crafts acylation is expected to be more stable then the isomeric species 22 because of the destabilizing effect of the Fe(CO), dipole on remote allylic cations.…”

Synthesis and Reactivity of η4-Diene-Fe(CO)3 Complexes from exo-2-Oxazolidinone Dienes. A Facile Generation of Stable Conjugated Enol-Enamido Species

“…Although the tricarbonyliron group has been useful as a stabilizing group for dienes and related unsaturated systems, , the Fe(CO) 3 group can assist the functionalization of the diene in the η 4 -coordination complex through a variety of reactions with a high regio- and stereoselectivity. − , Therefore, we decided to explore the reactivity and selectivity of complexes 6 − 8 in such reactions. Thus, following the acylation protocol described by Franck−Newmann for the synthesis of optically active alcohols, diene 7a was submitted to similar Friedel−Crafts conditions (AcCl, AlCl 3 , CH 2 Cl 2 , 0−20 °C) . However, the reaction gave rise to the full recovery of the starting material, even if the acylation agent (Ac 2 O) and the catalyst (BF 3 ·Et 2 O) were changed.…”