Rearrangements complex

Friedel Crafts acetylation of butadiene complex 56 proceeds smoothly to give a mixture of 1-acetyldienes 58 and 59 via the cationic 7r-allyl complex 57 [16]. Intramolecular Friedel-Crafts acylation with the acid chloride of the diene complex 60, promoted by deactivated AICI3 at 0 °C, gave the cyclopentanones. The (Z)-dienone complex 61 was the major product and the ( )-dienone 62 the minor one [17]. Acetylation of the 1,3-cyclohexadiene phosphine complex 63 proceeded easily at —78°C to give the rearranged complex 65 in 85% yield. Without phosphine coordination, poor results were obtained [18,19], In this reaction, the acetyl group at first coordinates to Fe, and attacks at the terminal carbon of the diene from the same... 

High energy, leads to multiple cleavages and rearrangements, complex mass spectra to interpret... 

C(E)R] This method was extended by Wojcicki and co-workers 110,111) to utilize coordinatively unsaturated metal fragments as electrophiles, whereby new synthetic methods for homo- and heterobinuclear and trinuclear metal-/u--allenyl complexes were developed. The difference between this approach and that of Stone and co-workers (89,90) is that the unsaturation is contained entirely within the ligand, which, as a result of this, often rearranges. Complex 28 was obtained in high yields from the reaction of the iron-propargyl precursor and diiron nonacarbonyl (111). 

Splicing <1% Regulatory 23% Small insertions/deletions 7% Gross lesions (large insertions/deletions, repeats, rearrangements, complex)... 

Claisen rearrangement. Complexation of the ethereal oxygen with ATPH prior to rearrangement ensures a high (E) (Z) ratio of 4-alkenals. ATPH is more effective than -nethylaluminum bis(2,6-diphenylphenoxide), but less effective than aluminum ns[(2-a-naphthyl-6-phenyl)phenoxide]. Two chiral analogs of the latter have been... 

The path followed by the hydrogenation reactions catalyzed by the mono-/A-hydrides (2a and 2b) is not so clear, but the kinetic data strongly suggest that the binuclear grouping is retained, at least during the early stages of reaction. A possible first step is the formation of a rearranged complex, such as (A), proposed for the stoichiometric reaction with dienes. 

A probable mechanism for this rearrangement postulates the intermediate formation of a hydroxide-ion addition complex, followed by the migration of a phenyl group as an anion ... 

Nickel(O) forms a n-complex with three butadiene molecules at low temperature. This complex rearranges spontaneously at 0 °C to afford a bisallylic system, from which a large number of interesting olefins can be obtained. The scheme given below and the example of the synthesis of the odorous compound muscone (R. Baker, 1972, 1974 A.P. Kozikowski, 1976) indicate the variability of such rearrangements (P. Heimbach, 1970). Nowadays many rather complicated cycloolefins are synthesized on a large scale by such reactions and should be kept in mind as possible starting materials, e.g. after ozonolysis. 

Within the cubane synthesis the initially produced cyclobutadiene moiety (see p. 329) is only stable as an iron(O) complex (M. Avram, 1964 G.F. Emerson, 1965 M.P. Cava, 1967). When this complex is destroyed by oxidation with cerium(lV) in the presence of a dienophilic quinone derivative, the cycloaddition takes place immediately. Irradiation leads to a further cyclobutane ring closure. The cubane synthesis also exemplifies another general approach to cyclobutane derivatives. This starts with cyclopentanone or cyclohexane-dione derivatives which are brominated and treated with strong base. A Favorskii rearrangement then leads to ring contraction (J.C. Barborak, 1966). 

Thallium(III) acetate reacts with alkenes to give 1,2-diol derivatives (see p. 128) while thallium(III) nitrate leads mostly to rearranged carbonyl compounds via organothallium compounds (E.C. Taylor, 1970, 1976 R.J. Ouelette, 1973 W. Rotermund, 1975 R. Criegee, 1979). Very useful reactions in complex syntheses have been those with olefins and ketones (see p. 136) containing conjugated aromatic substituents, e.g. porphyrins (G. W. Kenner, 1973 K.M. Smith, 1975). 

The direct connection of rings A and D at C l cannot be achieved by enamine or sul> fide couplings. This reaction has been carried out in almost quantitative yield by electrocyclic reactions of A/D Secocorrinoid metal complexes and constitutes a magnificent application of the Woodward-Hoffmann rules. First an antarafacial hydrogen shift from C-19 to C-1 is induced by light (sigmatropic 18-electron rearrangement), and second, a conrotatory thermally allowed cyclization of the mesoionic 16 rc-electron intermediate occurs. Only the A -trans-isomer is formed (A. Eschenmoser, 1974 A. Pfaltz, 1977). 

Furthermore, the catalytic allylation of malonate with optically active (S)-( )-3-acetoxy-l-phenyl-1-butene (4) yields the (S)-( )-malonates 7 and 8 in a ratio of 92 8. Thus overall retention is observed in the catalytic reaction[23]. The intermediate complex 6 is formed by inversion. Then in the catalytic reaction of (5 )-(Z)-3-acetoxy-l-phenyl-l-butene (9) with malonate, the oxidative addition generates the complex 10, which has the sterically disfavored anti form. Then the n-a ir rearrangement (rotation) of the complex 10 moves the Pd from front to the rear side to give the favored syn complex 6, which has the same configuration as that from the (5 )-( )-acetate 4. Finally the (S)-( )-mal-onates 7 and 8 are obtained in a ratio of 90 10. Thus the reaction of (Z)-acetate 9 proceeds by inversion, n-a-ir rearrangement and inversion of configuration accompanied by Z to isomerization[24]. 

The ligand effect seems to depend on the substrates. Treatment of the prostaglandin precursor 73 with Pd(Ph3P)4 produces only the 0-allylated product 74. The use of dppe effects a [1,3] rearrangement to produce the cyclopen ta-none 75(55]. Usually a five-membered ring, rather than seven-membered, is predominantly formed. The exceptionally exclusive formation of seven-membered ring compound 77 from 76 is explained by the inductive effect of an oxygen adjacent to the allyl system in the intermediate complex[56]. 

Allylic nitro compounds form rr-allylpalladium complexes by displacement of the nitro group and react with nucleophiles, and allylation with the tertiary nitro compound 202 takes place at the more substituted side without rearrangement to give 203[8,9,128]. 

The reaction of the vinylcyclopropanedicarboxylate 301 with amines affords an allylic amine via the 7r-allylpalladium complex 302[50]. Similarly, three-membered ring A -tosyl-2-(l,3-butadienyl)aziridine (303) and the four-mem-bered ring azetidine 304 can be rearranged to the five- and six-membered ring unsaturated cyclic amines[183]. 

Allylic ester rearrangement is catalyzed by both Pd(II) and Pd(0) compounds, but their catalyses are different mechanistically. Allylic rearrangement of allylic acetates takes place by the use of Pd(OAc>2-Ph3P [Pd(0)-phosphine] as a catalyst[492,493]. An equilibrium mixture of 796 and 797 in a ratio of 1.9 1.0 was obtained[494]. The Pd(0)-Ph3P-catalyzed rearrangement is explained by rr-allylpalladium complex formation[495]. 

Conversion of 5-allylthioimidates into /V-allylthioamides is catalyzed by Pd(Il). 2-Allylthiopyridine (820) is converted into the less stable l-allyl-2-thio-pyridone 821 owing to Pd complex formation[509], Claisen rearrangement of 2-(allylthio)pyrimidin-4-(3//)-one (822) affords the A-l-allylation product 823 as the main product rather than the A -3-allylation product 824[510] The smooth rearrangement of the allylic thionobenzoate 825 to the allyl thiolo-benzoate 826 is catalyzed by both PdCl2(PhCN)2 and Pd(Ph3P)4 by different mechanisms[511],... 

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