Intermolecular organic transformation

With regards to oxidative reactivity, it seems that dicopper(II) end-on peroxo complexes are basic, or nucleophilic, in nature, without oxidizing substrates such as PPha or 2,4-di-tert-butylphenol. Instead, O2 is released and PPhs binds, or deprotonation of the phenol occurs leading to a Cu -hydroperoxide. By contrast, the side-on bound dicopper(II) peroxide and its isoelectronic isomer, the dicopper(III) bis(p-oxo) species, both are electrophilic and have been shown to react with a wide array of substrates, in intramolecular (ligand) oxidations, and intermolecular organic transformations. Our group has extended the oxidative capability of CU2O2 complexes to novel (for copper chemistry) substrates such as tetrahydrofuran and dimethylaniline, which are oxidized to 2-hydroxy-tetrahydrofuran, and methylaniline plus formaldehyde, respectively. 

Cascade intermolecular carbopalladations of alkynes followed by intramolecular trapping with electrophiles represent not only a novel type of organic transformation involving vinylpalladium intermediates, but also provide synthetically useful routes toward differently substituted indenols, indanones, indenones, and naphthy-lamines." Although these protocols are restricted to the intramolecular trapping with electrophiles, a wide application of this methodology toward the synthesis of various types of complex carbocychc compounds may be anticipated in the near future. 

Organolanthanide complexes are known to be highly active catalysts for a variety of organic transformations, which can be either intramolecular or intermolecular in character. Successful intramolecular transformations include hydroelementation processes, which is the addition of a H-E (E = N, O, P, Si, S, H) bond across unsaturated C-C bonds, such as hydroamination, hydroalkoxylation, and hydrophosphination. Intermolecular transformations include a series of asymmetric syntheses, the amidation of aldehydes with amines, Tishchenko reaction, addition of amines to nitriles, aUcyne dimerization, and guanylation of terminal aUcynes, amines, and phosphines with carbodiimides. 

The catalytic activity of 4 in intermolecular hydroamination of alkynes by anilines as well as in the intramolecular alkene and alkyne hydroamination has been reported [40]. The results show that in the presence of ]PhNMe2H+][B(CgF5) ], 4 could catalyze these reactions very efficiently (2.5 mol% catalyst, 20 - 80 °C). It was su ested that the Cp moiety was protonolyzed to give Cp H, which was identified by NMR. In most cases, excellent yields were achieved, indicating a possible high potential of Zn-Zn-bonded complexes for catalytic organic transformations. As the presumed mechanism is not discussed further, it is hitherto unclear whether a Zn species is prevalent in the catalytic cycle. 

L.F. Tietze, T. Huebsch, E. Voss, M. Buback, W. Tost, Intra- and rntermolecular hetero-Diels-Alder reactions. 23. Intermolecular hetero-Diels-Alder reactions of enamino ketones at high pressure. The first significant pressure-induced diasteieoselectivity in organic transformations,... 

Due to its marked atom economy, the intramolecular hydroamination of alkenes represents an attractive process for the catalytic synthesis of nitrogen-containing organic compounds. Moreover, the nitrogen heterocycles obtained by hydroamination/cyclisation processes are frequently found in numerous pharmacologically active products. The pioneering work in this area was reported by Marks et al. who have used lanthanocenes to perform hydroamination/cyclisation reactions in 1992. These reactions can be performed in an intermolecular fashion and transition metals are by far the more efficient catalysts for promotion of these transformations via activation of the... 

This chapter deals with [2 + 2]cycloadditions of various chromophors to an olefinic double bond with formation of a four-membered ring, with reactions proceeding as well in an intermolecular as in an intramolecular pattern. Due to the variety of the starting materials available (ketones, enones, olefins, imines, thioketones, etc.. . .), due to the diversity of products obtained, and last but not least, due to the fact that cyclobutanes and oxetanes are not accessible by such a simple one-step transformation in a non-photo-chemical reaction, the [2+2]photocycloaddition has become equivalent to the (thermal) Diels-Alder reaction in importance as for ring construction in organic synthesis. 

Intermolecular oxygen atom transfer from a metal complex to an organic substrate is an archetypical reaction step in oxidation catalysis. As the transformation of O2 into metal 0x0 groups by oxidative addition is a well-precedented process (Sect. 2.2), its combination with transfer of the oxygen atom to an oxidizable substrate ( S ) constitutes a catalytic cycle for aerobic oxidations (Eq. 21). Examples of such cycles exist in organometallic chemistry, by virtue of 0x0 complexes with carbon-based ancillary hgands. 

Organic solids have received much attention in the last 10 to 15 years especially because of possible technological applications. Typically important aspects of these solids are superconductivity (of quasi one-dimensional materials), photoconducting properties in relation to commercial photocopying processes and photochemical transformations in the solid state. In organic solids formed by nonpolar molecules, cohesion in the solid state is mainly due to van der Waals forces. Because of the relatively weak nature of the cohesive forces, organic crystals as a class are soft and low melting. Nonpolar aliphatic hydrocarbons tend to crystallize in approximately close-packed structures because of the nondirectional character of van der Waals forces. Methane above 22 K, for example, crystallizes in a cubic close-packed structure where the molecules exhibit considerable rotation. The intermolecular C—C distance is 4.1 A, similar to the van der Waals bonds present in krypton (3.82 A) and xenon (4.0 A). Such close-packed structures are not found in molecular crystals of polar molecules. 

Alkene hydroamination has been known for many years, but has been little used as a method in organic synthesis. Tobin Marks of Northwestern recently published a series of three papers that will make this transformation much mote readily accessible. In the first (J. Am. Chem. Soc. 125 12584,2003) he describes the use of a family of lanthanide-derived catalysts for intermolecular hydroamination of alkynes (to make imines, not illustrated) and alkenes. With aliphatic amines, the branched (Markownikov) product is observed, 1 — 2. With styrenes, the linear product is formed. When two alkenes are present, the reaction can proceed (3 —> 4) to form a ring, with impressive regioselectivity. 

Intermolecular and intramolecular nucleophilic substitution of an alcoholic hydroxy group by the triphenylphosphine/dialkyl azodicarboxylate redox system is widely used in the synthesis and transformation of natural products and is known in organic chemistry as the Mitsunobu reaction.1951 This reaction starts with formation of the zwitterionic phosphonium adduct 19 (Scheme 9) from triphenylphosphine and diethyl (or diisopropyl) azodicarbox-... 

Intermolecular cyclopropanation of diazoketones is an effective method in organic synthesis. Wenkert and coworkers have applied this methodology to the synthesis of a substantial number of cyclopropane adducts 2868, 2969 and 307° which are synthetic intermediates in the preparation of natural products (equations 41—43). Copper catalysts were chosen for these transformations. Another interesting application of intermolecular cyclopropanation is to be found in Daniewski s total synthesis of an aromatic steroid. Palladium(II) acetate catalysed decomposition of 4-bromo-l-diazo-2-butanone in the presence of m-methoxystyrene was used to give the cyclopropyl ketone 31 which was a key intermediate in the total synthesis (equation 44)71. 

The mobility of excited states, imposed by intermolecular interactions (see Sec. 2.4), can lead to their collision with each other and/or with other types of excited states as well as trapped or free carriers generated in an organic solid. Such collision processes, realizing various excitonic interactions, may result in annihilation of the excitons and/or their transformation into another set of particles and quasi-particles. As different types of excitonic interactions show up in different optical and electrical phenomena, we divide them into two categories corresponding to the interaction between quasiparticles (exciton-exciton interactions) and to the interaction between quasi-particles and particles (exciton-charge carrier interactions). 

As many organic compounds may transform simultaneously through mono molecular (intramolecular) and bimolecular (intermolecular) processes, it is easy to understand that the shape and size of the space available near the active sites often determine the selectivity of their transformation. Indeed the transition state of a bimolecular reaction is always bulkier than that of a monomolecular reaction, hence the first type of reaction will be much more sensitive to steric constraints than the second one. This explains the key role played by the pore structure of zeolites on the selectivity of many reactions. A typical example is the selective isomerization of xylenes over HMFI the intermediates leading to disproportionation, the main secondary reaction over non-spatioselective catalysts, cannot be accommodated at its channel intersections (32). Furthermore, if a reaction can occur through mono and bimolecular mechanisms, the significance of the bimolecular path will decrease with the size of the space available near the active sites (41). 

Pyrrole syntheses have been organized systematically into intramolecular and intermolecular approaches as well as by the location of the new bonds that describe the pyrrole ring forming step (two examples are illustrated below). Multi-component reactions appear at the end of the section on intermolecular approaches. The final section includes pyrrole syntheses that arise from transformations of other heterocycles. 

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