Allyl complexes synthesis

Nickel-allyl complexes prepared from Ni(CO)4 and allyl bromides are useful for the ole-fination of alkyl bromides and iodides (E.J. Corey, 1967 B A.P. Kozikowski, 1976). The reaction has also been extended to the synthesis of macrocycles (E.J. Corey, 1967 C, 1972A). 

In 1989 we reported on the synthesis and structure of the first l,3-diphospha-2-sila-allylic anion 3a [4], mentioning its value as a precursor for phosphino-silaphosphenes. In analogy to 3a we obtained the anions 3b-f [5] by treatment of 4 equivalents of the lithium phosphide 1 with the adequately substituted RSiC, of which 3b and 3c were investigated by X-ray analyses. The very short P-Si bond lengths (2.11-2.13 A) of 3a-c and the almost planar arrangement of Pl-Sil-P2-Lil indicate the cr-character of the Lithium P-Si-P allyl complex. 

Attempts to synthesize transition metal alkyl compounds have been continuous since 1952 when Herman and Nelson (1) reported the preparation of the compound C H6>Ti(OPri)3 in which the phenyl group was sigma bonded to the metal. This led to the synthesis by Piper and Wilkinson (2) of (jr-Cpd)2 Ti (CH3)2 in 1956 and a large number of compounds of titanium with a wide variety of ligands such as ir-Cpd, CO, pyridine, halogen, etc., all of which were inactive for polymerization. An important development was the synthesis of methyl titanium halides by Beerman and Bestian (3) and Ti(CH3)4 by Berthold and Groh (4). These compounds show weak activity for ethylene polymerization but are unstable at temperatures above — 70°C. At these temperatures polymerizations are difficult and irreproduceable and consequently the polymerization behavior of these compounds has been studied very little. In 1963 Wilke (5) described a new class of transition metal alkyl compounds—x-allyl complexes,... 

The general interligand C—C coupling reaction shown in Eq. (8) for (metalla-/3-diketonato)BF2 compounds also occurs directly with metalla-/3-diketonate anions, thereby precluding the need to prepare the neutral difluoroboron complexes (53). As a one-pot synthesis, metal carbonyl acetyl compounds can be converted to neutral 77-allyl complexes [Eq. (12)]. 

Jordan RF, LaPointe RE, Bradley PK, Baenziger N (1989) Synthesis and chemistry of cationic alkyl, alkenyl, and allyl complexes derived from the soluble, cationic hydride (CH4Me)2Zr(H) (THF)+. Organometallics 8 2892-2903... 

The alkylidyne tricobalt nonacarbonyl complexes (2) are produced from the reaction of the cobalt tetracarbonyl anion with 1,1,1-trihaloalkanes [4], under conditions analogous to those used for the synthesis of the n-allyl complexes. Although the yields for (2) appear to be low (Table 8.3), they are better than, or comparable with, those obtained by the traditional procedures [8] and are obtained under more amenable conditions. 

The earliest alternative to cyclopropene insertion as a viable vinylketene synthesis was published by Hoffmann118 in 1972. Upon reaction of 206.a with diiron nonacarbonyl, the vinylketene complex 207 was isolated in low yield. The analogous bromide and iodide substrates formed the 77-allyl complexes 208, although a trace of 207 was isolated from the reaction of the bromide 206.b. 

Keto esters such as acetoacetate without a substituent at the a-carbon. namely with two acidic protons, first attack the central carbon of the allenylpal-ladium to form the zr-allyl complex 89. Then intramolecular attack of the enolate oxygen of the 0-keto ester at the rr-ully l system takes place to form the nieihv-lenedihydrofuran 90 as a primary product, which is easily isomerized to the turn 91. The /3-diketone 92 reacts similarly to give the furan 93[40], The reaction can be applied to the synthesis of the phenyIthiomethyl-substituted furan 94. which is useful for the synthesis of natural products such as neoliacine. [41]... 

The effects on coupling efficiency and regiochemical control in nonsymmetrical allyl complexes as a function of added ligand in these reactions has been determined155,156 (vide infra) and applied in the synthesis of flexibilene and humulene.157... 

Although this catalytic reaction appeared to be of synthetic interest, it has since then neither been applied in synthesis nor further developed. This might be attributed in part to problems with reproducibility and catalyst stability under the reaction conditions, although the Hieber complex was used in a stoichiometric manner for the preparation of a variety of 7i-allyl-Fe complexes. These latter compounds served as starting materials for a plethora of subsequent reactions [34]. The results obtained by Nakanishi and coworkers on the stability and reactivity of n-allyl-Fe-nitrosyl complexes proved such intermediates to be reactive towards a variety of nucleophiles however, the Fe complexes formed upon nucleophilic substitution were catalytically inactive. Hence, in order to maintain the catalytic activity, the formation of intermediate 7i-allyl-Fe complexes had to be circumvented. About 3 years ago we started our research in this field and envisioned the use of a monodentate ligand to be a suitable way to stabilize the proposed catalytically active G-allyl complex. The replacement of one CO by a non-volatile basic ligand was thought to prevent the formation of the catalytically inactive 7t-allyl-Fe complex (Scheme 7.21). 

Di(carbene)gold(I) salts, oxidation, 2, 293—294 Dicarbido clusters, with decarutheniums, 6, 1036 Dicarbollide amides, with tantalum, 5, 184 Dicarbollide thorium complexes, synthesis and characterization, 4, 224—225 Dicarbollyl ligands, in nickel complexes, 8, 185 Dicarbonyl complexes arylation with lead triacetates diastereoselectivity, 9, 389 enantioselectivity, 9, 391 mechanisms, 9, 387 reaction examples, 9, 382 indium-mediated allylation, 9, 675 with iridium, 7, 287 reductive cyclization, 10, 529 in Ru and Os half-sandwiches, 6, 508 with Zr—Hf(II), 4, 700... 

Among 7i-allyl complexes of several transition metals, the chemistry of n-allylpalladium has been studied most extensively. From the standpoint of organic synthesis, reactions involving 7i-allylpalladium complexes are by far the most important therefore, their synthetic applications are mainly treated in this chapter. 

As an example of carbometallation, the 1,4-carbosilylation product 218 is obtained by the reaction of dienes, disilanes and acid chlorides of aromatic and a,/i-unsaturatcd acids at 80 °C. The phenylpalladium 216 is formed by the oxidative addition of benzoyl chloride, followed by facile decarbonylation at 80 °C, and reacts with butadiene to generate the benzyl-7i-allylic complex 217. Then, transmetallation with the disilane and reductive elimination afford 4-silyl-2-butenylbenzene 218 [92], Regioselective carbomagnesation of isoprene with allylic magnesium bromide 219 catalysed by Cp2TiCl2 gives 220, which is useful for terpene synthesis [93,94],... 

The (IsQ-coordinated species [Mo(CO)3(py)3] prepared from [Mo(CO)6] and pyridine is useful for the synthesis of various jr-allyl molybdenum compounds (68JOM(13)Pl, 970M5365). The 3-allyl complexes [( 3-allyl)Mo(CO)2Br(py)2] form [( 3-allyl)Mo(CO)2(S,S)(py)] with the anionic S,S-donors, dithiocarbamates and xanthates of sodium and potassium, M (S,S) (81JOM(218)185). [( 3-C3H5)Mo(CO)2(py)2Br] (68JO M(14)375) with thallium hexafluorophosphate in acetonitrile gives... 

The chiral anisole derivative 37 has been used in the synthesis of several asymmetric functionalized cyclohexenes (Table 9) [22]. In a reaction sequence similar to that employed with racemic anisole complexes, 37 adds an electrophile and a nucleophile across C4 and C3, respectively, to form the cyclohexadiene complex 38. The vinyl ether group of 38 can then be reduced by the tandem addition of a proton and hydride to C2 and Cl, respectively, affording the alkene complex 39. Direct oxidation of 39 liberates cydohexenes 40 and 41, in which the initial asymmetric auxiliary is still intact. Alternatively, the auxiliary may be cleaved under acidic conditions to afford /y3 -allyl complexes, which can be regioselectively attacked by another nucleophile at Cl. Oxidative decomplexation liberates the cyclohexenes 42-44. HPLC analysis revealed high ee values for the organic products isolated both with and without the initial asymmetric group. 

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