Allylic derivatives complexes

The addition of carbene to a 3-(halopropyl)-5//-dibenz[7>./]azepine 5 (X = Cl, Br) in a Simmons—Smith reaction is more complex and results in a mixture of the tetracycle 6 (6%), its cyclopropano derivative 7 (48 %), the 5-allyl derivative 8 and the (cyclopropyl)methyl compound 9, the latter two products in a combined yield of 12%.31... 

The breakthrough was achieved with the creation of dialkoxy(tj5-cyclopentadienyl)titanium(IV) chlorides derived from sterically hindered chiral alcohols11 35,35a 36. Allyl derivatives 8 and 10, prepared in situ from complexes 7 and 9, have sufficient stability and reactivity. 

The (pentamethylcyclopentadienyl)zirconium amidinate unit also served as a platform for the synthesis and characterization of remarkable cationic and zwitterionic allyl zirconium complexes derived from trimethylenemethane (TMM). A direct synthetic route to the neutral precursors was found in the... 

Alkali Metal Derivatives of Metal Carbonyls, 2, 1S7 Alkyl and Aryl Derivatives of Transition Metals, 7, 1S7 Alkyl cobalt and Acylcobalt Tetracarbonyls, 4, 243 Allyl Metal Complexes, 2, 32S... 

In 2003, Sigman et al. reported the use of a chiral carbene ligand in conjunction with the chiral base (-)-sparteine in the palladium(II) catalyzed oxidative kinetic resolution of secondary alcohols [26]. The dimeric palladium complexes 51a-b used in this reaction were obtained in two steps from N,N -diaryl chiral imidazolinium salts derived from (S, S) or (R,R) diphenylethane diamine (Scheme 28). The carbenes were generated by deprotonation of the salts with t-BuOK in THF and reacted in situ with dimeric palladium al-lyl chloride. The intermediate NHC - Pd(allyl)Cl complexes 52 are air-stable and were isolated in 92-95% yield after silica gel chromatography. Two diaster corners in a ratio of approximately 2 1 are present in solution (CDCI3). 

The isomerization mechanism is clearly established by labeling experiments. The rearrangement of a to c via a 7i-allyl hydride complex b in the coordination sphere of the metal is a key step in this cayalytic cycle (Scheme 54) [174, 175]. hi case of polyunsaturated derivatives, formation of a stable q" complexes (Scheme 55) is preferred over the rearrangement (a c). 

Nucleophilic Substitution of xi-Allyl Palladium Complexes. TT-Allyl palladium species are subject to a number of useful reactions that result in allylation of nucleophiles.114 The reaction can be applied to carbon-carbon bond formation using relatively stable carbanions, such as those derived from malonate esters and (3-sulfonyl esters.115 The TT-allyl complexes are usually generated in situ by reaction of an allylic acetate with a catalytic amount of fefrafcz s-(triphenylphosphine)palladium... 

The chiral center would be installed from either Unear carbamate 15 or branched carbamate 16 via the asymmetric addition of malonate anion to the 7i-allyl Mo complex reported by Trost et al. [11] to afford the branched chiral malonate derivative 17. Decarboxylation of 17 should provide the mono-carboxylic acid 18. Masa-mune homologation with 18 affords our common precursor 14. Linear carbamate 15 was obtained from the corresponding cinnamic acid, and branched 16 was prepared in one pot from the corresponding aldehyde. 

Monoanions derived from nitroalkanes are more prone to alkylate on oxygen rather than on carbon in reactions with alkyl halides, as discussed in Section 5.1. Methods to circumvent O-alkylation of nitro compounds are presented in Sections 5.1 and 5.4, in which alkylation of the a.a-dianions of primary nitro compounds and radial reactions are described. Palladium-catalyzed alkylation of nitro compounds offers another useful method for C-alkylation of nitro compounds. Tsuj i and Trost have developed the carbon-carbon bond forming reactions using 7t-allyl Pd complexes. Various nucleophiles such as the anions derived from diethyl malonate or ethyl acetoacetate are employed for this transformation, as shown in Scheme 5.7. This process is now one of the most important tools for synthesis of complex compounds.6811-1 Nitro compounds can participate in palladium-catalyzed alkylation, both as alkylating agents (see Section 7.1.2) and nucleophiles. This section summarizes the C-alkylation of nitro compounds using transition metals. 

The study of solvated alkali metal allyl species remains a complex topic due to a variety of reorganization processes. Structural data on alkali metal allyl derivatives include [G3H5Li(TMEDA)] 133,139 where solvated lithium ions act as... 

Calculations of alkali metal allyl derivatives involving all alkali metals (Li-Cs) indicate a preferred geometry with the metal symmetrically bound in a predominantly electrostatic manner to all three carbon atoms.143 Solution studies of allyllithium in ether indicate the compounds to be highly aggregated in THF complex dynamic behavior is observed. 

Allyl methylcarbonate reacts with norbornene following a ruthenium-catalyzed carbonylative cyclization under carbon monoxide pressure to give cyclopentenone derivatives 12 (Scheme 4).32 Catalyst loading, amine and CO pressure have been optimized to give the cyclopentenone compound in 80% yield and a total control of the stereoselectivity (exo 100%). Aromatic or bidentate amines inhibit the reaction certainly by a too strong interaction with ruthenium. A plausible mechanism is proposed. Stereoselective CM-carboruthenation of norbornene with allyl-ruthenium complex 13 followed by carbon monoxide insertion generates an acylruthenium intermediate 15. Intramolecular carboruthenation and /3-hydride elimination of 16 afford the -olefin 17. Isomerization of the double bond under experimental conditions allows formation of the cyclopentenone derivative 12. 

C-NMR spectrum, only the Ru(3) carbonyl groups are not affected by proton decoupling 102). An intermediate isomeric form of the complex HRu3(CO)9(C6H9) has also been isolated, and the X-ray structure (Fig. 13) establishes the coordination of a ir-allene group 103). This isomer converts to the 7r-allyl derivative on warming. 7r-Allyl derivatives may... 

The reaction of methylenesulphones with allyl halides in the presence of quaternary ammonium salts produces the 1-allyl derivatives [52], unlike the corresponding reaction in the absence of the catalyst in which the SN- product is formed (Scheme 6.5). In contrast, alkylation of resonance stabilized anions derived from allyl sulphones produces complex mixtures [51] (Scheme 6.6). Encumbered allyl sulphones (e.g. 2-methylprop-2-enyl sulphones) tend to give the normal monoalkyl-ated products. Methylene groups, which are activated by two benzenesulphonyl substituents, are readily monoalkylated hydride reduction leads to the dithioacetal and subsequent hydrolysis affords the aldehyde [61]. 

In a similar manner, Jt-allyl complexes of manganese, iron, and molybdenum carbonyls have been obtained from the corresponding metal carbonyl halides [5], In the case of the reaction of dicarbonyl(r 5-cyclopentadienyl)molybdenum bromide with allyl bromide, the c-allyl derivative is obtained in 75% yield in dichloromethane, but the Jt-allyl complex is the sole product (95%), when the reaction is conducted in a watenbenzene two-phase system. Similar solvent effects are observed in the corresponding reaction of the iron compound. As with the cobalt tetracarbonyl anion, it is... 

In another report of Singh and Han [61], Ir-catalyzed decarboxylative amidations of benzyl allyl imidodicarboxylates derived from enantiomerically enriched branched allylic alcohols are described. This reaction proceeded with complete stereospecificity-that is, with complete conservation of enantiomeric purity and retention of configuration. This result underlines once again (cf. Section 9.2.2) that the isomerization of intermediary (allyl) Ir complexes is a slow process in comparison with nucleophilic substitution. 

Complexes M(CH2C CC=CMe)(CO)nCp [325 M = Mo, n = 3 M = Fe, = 2 (Scheme 74)] were obtained from the carbonyl anions and l-chlorohexa-2,4-diyne. Subsequent chemistry involves protonation (HBF4) to cationic allene or diene complexes, or addition of MeOH to give allylic derivatives, which are formed with concomitant insertion of CO. The latter can also be obtained from the cationic species and NaOMe. The allene-iron cation reacts with NHEt2 to form an ynenyl complex. The luminescent complex Re(CO)3(5,5 -Bu 2-bpy) 2 (At-C=CC6H4C CC=CC6H4C=C) has been reported. ... 

The insertion of allenes in the palladium-carbon a bond of cyclopalladated pyridine derivative 295 (cf. 00CRV3067) affords stable, isolable (ry -allyl) palladium complexes (e.g., 296) (03JOM(687)313). The ideally located imine unit when depalladated reacts selectively with the allyl functionality to yield methylene morphanthridizinium salts 297a-c. 

Allyl bromide, irradiation of, 5 156 Allyl complexes, osmium, 37 244 ligand-centered reactions, 37 343 7t-Allyl derivatives, proton chemical shifts of, 4 182... 

A metal exchange was used to prepare a 4-cupro-l,3-dioxane from the corresponding lithium derivative. This copper species reacted with an allyl cation complex to give addition products with excellent stereoselectivity but with poor regioselectivity when an unsymmetrically substituted allyl cation was employed (Equation 39) <2000SL463, 20040BC1719>. 

Triple-branching functionalization of complex 7 yielded nona-allyl derivative 8 which was demetallated by visible light photolysis in the presence of triphenyl-... 

The typical reluctance of the cod derivatives to react with dioxygen has been overcome, in some cases, by different approaches. Using catalytic amounts of acid [72], the otherwise inert complex [Rh(/c -bpa)(cod)](PF6) reacts with oxygen to give the l-hydroxy-2-rhoda (5,6,7)-allyl derivative [Rh(/c -bpaKCsHiiOHlKPFe) (Scheme 10) with a consumption of one mole of O2 per mol of [Rh(/c -bpa)(cod)](PF6), i.e., it is a 50% atom-economy process. 

The greater effectiveness of hydrogen peroxide is also shown in the reactions of the pentacoordinated complexes [M(A -L )(cod)] supported by N-donor hgands (L = dpa-R [72,79], Cn [79], PysSs [81]) (Fig. 5). While these complexes are unreactive with molecular oxygen, they react with H2O2 to systematically give the l-hydroxy-2-metalla (5,6,7)-allyl derivatives (Scheme 12) as the thermodynamic products. 

Transition metal-catalyzed allylic alkylation is generally considered to involve mechanistically four fundamental steps as shown in Scheme 1 coordination, oxidative addition, ligand exchange, and reductive elimination. A key step of the catalytic cycle is an initial formation of a (7r-allyl)metal complex and its reactivity. The soft carbon-centered nucleophiles, defined as those derived from conjugate acids whose pAj, < 25, usually attack the allyl ligand from the opposite side... 

Novel palladium-catalyzed transformations of allylic alcohol and its derivatives are developed by Yamamoto and his co-workers. Bis(7r-allyl)palladium complexes are considered to be the key intermediates for the allylation of benzyl-idenemalonitrile and benzyl chloride (Scheme 29) (for examples see Refs 176,176a-176d). Asymmetric version of these reactions is being awaited. 

Reaction of the bis(allyl) titanium complexes 16 and 18 with aldehydes occurs in a step-wise fashion with intermediate formation of the corresponding mono (allyl) titanium complex containing the alcoholate derived from 4 and 5 as a ligand at the Ti atom. Then the mono(allyl)titanium complexes combine with a second molecule of the aldehyde. Both the bis (allyl) titanium complexes and the mixed mono(allyl)titanium complexes react with the aldehydes at low temperatures with high regio- and diastereoselectivities. Interestingly, control experiments revealed that for the reaction of the bis (allyl) titanium complexes with the aldehyde to occur the presence of Ti(OiPr)4 is required, and for that of the intermediate mono(allyl)titanium complexes the addition of ClTi(OiPr)3 is mandatory (vide infra). 

The reaction of the acyclic bis(allyl)titanium complexes 16 with the imino esters 23a-c in the presence of Ti(OiPr)4 and ClTijOiPrjs at low temperatures proceeded with >98% regioselectivity and >98% diastereoselectivity and gave the corresponding T-syn-configured unsaturated a-amino acid derivatives E-24 in good yields (Scheme 1.3.11) [21, 22]. 

It is noteworthy that stereoselectivities were high, even with sterically demanding substituents at the double bond. Similarly, the treatment of the cyclic bis (allyl) titanium complexes 18 with the imino esters 23a-c afforded the corresponding B-syn-configured cyclic unsaturated amino acid derivatives -25 and the Z-syn-configured isomers Z-25 with >98% regioselectivity and >98% diaste-reoselectivity in good yields. 

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