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Azaferrocenes

Azaferrocene is methylated by n-butyllithium with subsequent treatment with methyl iodide resulting in formation of 25-27 [83JOM(251)C41]. The acetyl-ated complex Ti -(3-acetyl-2,4-dimethylpyrrolyl)cyclopentadienyliron was also described [74JOM(77)69]. The stmcture of 2-methylazaferrocene was studied extensively (69AG150 96JOC7230 97JA1492 97JOC444). [Pg.122]

Azaferrocene reacts with aromatic hydrocarbons in the presence of aluminium chloride, giving rise to the cationic complexes of the type (Ti -arene)(Ti -cyclopenta-dienyl)iron(l+) isolated as BF4 salts [87JOM(333)71]. The complex 28 is obtained by reaction of the sulfane compound [Cp(SMc2)3Fe]BF4 with pentamethyl-pyrrole [88AG(E)579 88AG(E)1468 90ICA(170)155]. The metallic site in this center reveals expressed Lewis acidity (89CB1891). [Pg.123]

Carbonylation of azaferrocene includes a rr a rearrangement of the pyrrolyl ligand and is reversible (82IC868). The similar process under the influence of the other TT-acidic ligands [PE3, R2NPE2 (R = Me, Et), MeN(PE2)2, r-BuNC, n-PrNC, Mc2N(CH2)2NC, and PhNC)] occurs. Derivatives based on 29 are isolated. [Pg.123]

Organometallic chemistry of pyrrole is characterized by a delicate balance of the ti N)- and -coordination modes. Azacymantrene is an illustration of the considerable nucleophilicity of the heteroatom. However, azaferrocene can be alkylated at C2 and C3 sites. Ruthenium and osmium, rhodium, and iridium chemistry revealed the bridging function of pyrroles, including zwitterionic and pyrrolyne complex formation. The ti (CC) coordination of osmium(2- -) allows versatile derivatizations of the heteroring. [Pg.178]

Hodous BL, Ruble JC, Fu GC (1999) Enantioselective addition of alcohols to ketenes catalyzed by a planar-chiral azaferrocene catalytic asymmetric synthesis of arylpropionic acids. J Am Chem Soc 121 2637-2638... [Pg.174]

Later, several other copper catalysts bearing dinitogen ligands [bipyridine derivatives (76),232,233 diamines (77),234 bis(azaferrocene) (78),235 bisferrocenyldiamine (79),159 and bis(oxazoyl) binaphthyl (80)236] have been introduced (Scheme 62), but asymmetric induction by them does not exceed that by complex (75). [Pg.245]

Figure 9. Two views of Fu s bis(azaferrocene) CuOTf-styrene complex. [Adapted from (64).]... Figure 9. Two views of Fu s bis(azaferrocene) CuOTf-styrene complex. [Adapted from (64).]...
In the 1990s, short peptides,and other nucleophiles °° ° were used as organocatalysts for a number of enantioselective acyl transfer processes transformations that set the stage for the more recent research in the area of nucleophilic catalysis.One of the most appealing approaches to enantioselective acyl transfer was outlined by Fu using an azaferrocene catalyst (6) [Eq. (11.6)]. While these pyridyl systems are not organic catalysts in the strictest sense, these azaferrocene compounds function as chiral dimethylaminopyridine equivalents for a broad range of acyl transfer processes ... [Pg.318]

Miscellaneous Reactions Berkessel " has identified peptide-like urea-based bifiinctional organocatalysts for the highly efficient dynamic kinetic resolution of azalactones (Scheme 11.14a). Another selective hydrogen-bonding activation mechanism that enables the addition of pyrroles to ketenes using catalytic quantities of azaferrocene 36 has been introduced by Fu and coworkers (Scheme 11.14b). ° ... [Pg.333]

The first class of amine-based nucleophilic catalysts to give acceptable levels of selectivity in the KR of aryl alkyl. yec-alcohols was a series of planar chiral pyrrole derivatives 13 and 14, initially disclosed by Fu in 1996 [25, 26]. Fu and co-workers had set out to develop a class of robust and tuneable catalysts that could be used for the acylative KR of various classes of. yec-alcohols. Planar-chiral azaferrocenes 13 and 14 seemed to meet their criteria. These catalysts feature of a reasonably nucleophilic nitrogen and constitute 18-electron metal complexes which are highly stable [54-58]. Moreover, by modifying the substitution pattern on the heteroaromatic ring, the steric demand and hence potentially the selectivity of these catalysts could be modulated. [Pg.242]

Metal complexes of pyrrole have also been investigated as substrates for lithiation reactions, with both iron and rhenium Tj -pyrrole derivatives having been found to undergo a-lithiation [90H(31 )383]. Azaferrocene was the first derivative of this type to be studied [83JOM(25l)C41], but it was found that lithiation was not selective and occurred equally in both rings. However, notwithstanding this, it has recently been reported that isomer-ically clean products can be obtained in certain circumstances from reaction with certain carbonyl compounds (Scheme 12) (89MI2). [Pg.169]

The a- (171-) complexes are known for pyrroles and phospholes. For pyrroles, both N-metal derivatives (10) and organometallic compounds (82) and (83) are described. A similar situation is observed in pyrrolylimido complexes Pwu-[MX(NNC4H4)(dppe)2]+ and cis,mer-[WX2(NNC4H4) (PMe2Ph)3], whose reaction ability has been studied comprehensively (95JA12181). A mixed 771 175 coordination is realized in the binuclear Cr(CO)5 complex of azaferrocene (90MI4). [Pg.16]

In addition, azaferrocene catalyst 8 has been utilized by Fu and co-workers to perform enantioselective additions of alcohols to prochiral ketenes [51]. Aryl alkyl ketenes are substituted with MeOH to give a-aryl ester products in good enantioselectivities and very good yields, with higher enantiomeric excesses obtained for products with larger alkyl groups (Scheme 12). Use of 2,6-di-f-butylpyridinium triflate as a proton shuttle substantially enhances the enanti-... [Pg.201]

Solvent toluene Xitr = visible light t = 100-200 K (azaferrocene AF coordinated by nitrogen atom)... [Pg.209]

Pioneering work by Pracejus et al. in the 1960s, using alkaloids as catalysts, afforded quite remarkable 76% ee in the addition of methanol to phenylmethyl-ketene [26-29]. In 1999 Fu et al. reported that of various planar-chiral ferrocene derivatives tried, the azaferrocene 35 performed best in the asymmetric addition of methanol to several prochiral ketenes [30, 31]. In the presence of 10 mol% catalyst 35 (and 12 mol% 2,6-di-tert-butylpyridinium triflate as proton-transfer agent), up to 80% ee was achieved (Scheme 13.16). [Pg.363]

Not only N, but also C atoms can take part as donor centers in azacymantrene 760 (E = N, R = H) and azaferrocene 763 (R = H). In this respect, the formation of a trinuclear osmium-carbonyl adduct 768 is representative, which takes place in the reaction of the indicated azacenes with acetonitrile complex of triosmium decarbonyl [482] ... [Pg.241]

The compounds in this section can be divided into two categories those in which the heterocyclic group is a substituent on the metallocene, such as heterocyclic compounds containing cyclopentadienyl-manganese tricarbonyl, and those in which a heteroatom is in a ring of the metallocene, such as in azaferrocene. [Pg.41]

Azaferrocene (206) has been prepared by the reaction of sodium pyrrole, cyclopentadienylsodium, and ferrous chloride,157 or better by the reaction of potassium pyrrole with cyclopentadienyliron dicarbonyl iodide.158 It has been found159 that dioxane is a better solvent than benzene for this latter reaction. This reaction has also been applied to 2,4- and 2,5-dimethylpyrrole,158 3-acetyl-2-methyl-and 3-acetyl-2,4-dimethylpyrrole,160 and 2-methylpyrrole.159 The 2-methylazaferrocene from this latter pyrrole has been resolved with (—)6,6 -dinitrodiphenic acid.159 A compound (207) believed to be an intermediate in the formation of azaferrocenes has been isolated.161... [Pg.43]

The azametallocenes, such as 206 and 208, are less stable than their cyclopentadienyl analogs.158 The pKa for azaferrocene (206) is similar to that of quinoline, whereas the manganese compound was a much weaker base.158 Azaferrocene yields a picrate and a methiodide, but, as might be expected, it does not undergo electrophilic substitution.158 The mass spectra of azametallocenes have been discussed.1636 The preparation of cyclopentadienyliodobis(imidazole)cobalt(III)iodide has been reported.1630... [Pg.43]

It has also been demonstrated that a planar-chiral azaferrocene derivative of 4-(pyrrolidino)pyridine is an excellent catalyst for the enantioselective Staudinger reaction, providing P-lactams 24 with very good stereoselection and yield <02JACS1578>. [Pg.105]

The first versatile system for the copper-catalyzed asymmetric coupling of alkynes with nitrones to form c/.v-p-lactarns has been developed using a bis(azaferrocene) ligand <02JACS4572>. [Pg.105]

Aromatic heterocycles such as thiophene, pyridine, and pyrrole are also able to form arene complexes, for example (7j5-C4H4N)(7j5-CsHs)Fe (azaferrocene), (7j5-C4H4S)Cr(CO)3, and (tj6-CsH5N)W(CO)3. [Pg.691]


See other pages where Azaferrocenes is mentioned: [Pg.116]    [Pg.121]    [Pg.122]    [Pg.127]    [Pg.70]    [Pg.325]    [Pg.175]    [Pg.32]    [Pg.33]    [Pg.7]    [Pg.137]    [Pg.164]    [Pg.145]    [Pg.60]    [Pg.366]    [Pg.241]    [Pg.76]    [Pg.80]    [Pg.80]    [Pg.146]    [Pg.230]   
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See also in sourсe #XX -- [ Pg.325 ]

See also in sourсe #XX -- [ Pg.13 , Pg.43 ]

See also in sourсe #XX -- [ Pg.9 ]

See also in sourсe #XX -- [ Pg.79 , Pg.121 ]

See also in sourсe #XX -- [ Pg.199 ]




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Azaferrocene

Azaferrocene

Azaferrocene-based ligand

Azaferrocenes chiral derivatives

Catalyst azaferrocene

Chiral azaferrocene derivatives

Ferrocene azaferrocenes

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