Stoichiometric Applications of Acyclic π-Organoiron Complexes to Organic Synthesis

Abstract

Abstract:The application of acyclic (diene)iron complexes and (pentadienyl)iron cations in organic synthesis has steadily increased over the past 20 years. This is due to their ease of preparation, their stability toward a wide variety of reaction conditions, the manifold method for removal of the Fe(CO) 3 group, and the low cost of iron carbonyls. The (tricarbonyl)iron adjunct may serve in three capacities: i) as a protecting group for conjugated dienes, ii) to direct the formation of chiral centers adjacent to the complexed dient, and iii) to stabilize the formation of positive charge adjacent ot the complexed diene (i.e. pentadienyl cations). Specific examples of these attributes will be presented in this review. One of the advantages of stoichiometric organometallic reagents is the ability to repeatedly utilize the same metal center to control a number of different bond forming reactions. Six examples will be presented which demonstrate this potential for acyclic (diene)iron complexes and (pentadienyl) iron cations.

Unusual diastereoselective reduction of 2-propionyl-3,3′,4,4′-tetramethyl-1,1′-diphosphaferrocene to the corresponding alcohol by BH3·Me2S. X-Ray diffraction and DFT study

“…Extraction with dichloromethane, drying (Na 2 SO 4 ), evaporation to dryness, column chromatography (eluent dichloromethane) and crystallization (dichloromethane-pentane) afforded 1 as red crystals. Yield 312 mg (93%): 1 H NMR (CDCl 3 ) d 4.00 (d, 2 J PH = 37.5 Hz, 1H, CHP), 3.67 (d, 2 J PH = 36.0 Hz, 2H, CHP), 2.61 (m, 2H, CH 2 ), 2.39 (s, 3H, Me), 2.10 (s, 3H, Me), 2.04 (s, 3H, Me), 1.98 (s, 3H, Me), 1.06 (t. 3 1-(3,3 0 ,4,4 0 -Tetramethyl-1,1 0 -diphosphaferrocene-2-yl)propan-1-ol (2). A solution of 1 (290 mg. 0.86 mmol) and BH 3 ÁSMe 2 (1 ml of 2 M solution in THF, 2 mmol) in THF (10 ml) was refluxed for 2 h. After cooling to room temperature MeOH (5 ml) was added and the solvents were evaporated.…”

“…as ligands for asymmetric catalysis. Its stereochemistry has been thoroughly studied in the case of aldehydes bearing (Z 6 -arene)Cr(CO) 3 , 1 (Z 5 -cyclohexadienyl)Mn(CO) 3 , 2 (Z 4 -diene)-Fe(CO) 3 , 3 ferrocenyl, 4 phosphaferrocenyl, 5 and 1,1 0 -diphosphaferrocenyl 6 moieties. In this reaction, when the nucleophile Nu À a H À , a stereogenic center at the formyl carbon atom is created.…”

A reversible decoration of multi-walled carbon nanotubes (MWCNTs) by acyclic η4-(1E,3E)-dienyl-Fe(CO)3 complexes

“…Preparation of acyclic cationic and non-cationic iron complexes in both CO and PPh 3 series. Neutral h 4 -(1E,3E)-dienyl-and cationic U-shaped isolated h 5 -pentadienyl-Fe(CO) 2 L (L ¼ CO or PPh 3 , a or b series, Scheme 1) iron complexes tested in this study have been readily prepared using well-known procedures: Fe 2 CO 9 -mediated complexations of (1E,3E)-dienes, [23][24][25] Me 3 NOmediated C^O to PPh 3 ligand exchanges, 28 complex-stereodirected nucleophilic additions of organolithium reagents onto adjacent carbonyl functions, [23][24][25] and complex-assisted Lewis acid-mediated ionizations. [23][24][25]29 More specifically, all the related detailed synthetic procedures and characterization data of neutral and cationic iron complexes tested in adsorption experiments onto MWCNT sidewalls have been gathered in ref.…”

“…Here, we demonstrate that selected acyclic disubstituted h 4 -(1E,3E)-dienyl-Fe(CO) 3 iron complexes [23][24][25] (Scheme 1) show a non-destructive and reversible affinity for sidewalls of MWCNTs.…”

Synthetic applications of cationic iron and cobalt carbonyl complexes

“…Such complexes are stable enough to be isolated, analyzed, and stored for long periods of time if protected from light and moisture, but are nevertheless highly reactive towards a wide variety of nucleophiles in the presence of a base. 2 Both acyclic 3 and cyclic 4 cationic complexes have been prepared, the latter class encompassing cyclohexa-, cyclohepta-and even cyclooctadienyl complexes. 2 Of these, the cyclohexadienyl-derived complexes have been the most studied, and further discussion will be limited to this class of compounds.…”