Heteroatom Bond Formation

Cobalt-catalyzed C—C and C-heteroatom bond formation in transformations of heterocycles 97SL876. 

Transition-Metal-Based Carbon-Carbon and Carbon-Heteroatom Bond Formation for the Synthesis and Decoration of Heterocycles... 

Examples of "very tnixed"-metal cluster-assisted C-heteroatom bond formation are still rare, with both literature extant examples involving coupling of bridging phosphido ligand with a C-ligand. Phosphido, hydrido, and alky tie were assembled stereospecilically to afford PPh2(( /.v-CR=CHR) (Fig. 29),-" while an unusual... 

C-C and C-E (E = heteroatom) bond formations are valuable reactions in organic synthesis, thus these reactions have been achieved to date by considerable efforts of a large number of chemists using a precious-metal catalysts (e.g., Ru, Rh, and Pd). Recently, the apphcation range of iron catalysts as an alternative for rare and expensive transition-metal catalysts has been rapidly expanded (for recent selected examples, see [12-20, 90-103]). In these reactions, a Fe-H species might act as a reactive key intermediate but also represent a deactivated species, which is prepared by p-H elimination. 

Maes BUW (2006) Transition-Metal-Based Carbon-Carbon and Carbon-Heteroatom Bond Formation for the Synthesis and Decoration of Heterocycles. 1 155-211 Maiti M, Kumar GS (2007) Protoberberine Alkaloids Physicochemical and Nucleic Acid Binding Properties. lO. 155-210... 

Transition Metal-Catalyzed Carbon-Heteroatom Bond Formations... 

Relatively soon after the discovery that aqueous solutions containing PtCl - and PtClg- can functionalize methane to form chloromethane and methanol, a mechanistic scheme for this conversion was proposed (16,17). As shown in Scheme 4, a methylplatinum(II) intermediate is formed (step I), and this intermediate is oxidized to a methylplatinum(IV) complex (step II). Either reductive elimination involving the Pt(IV) methyl group and coordinated water or chloride or, alternatively, nucleophilic attack at the carbon by an external nucleophile (H20 or Cl-) was proposed to generate the functionalized product and reduce the Pt center back to Pt(II) (step III) (17). This general mechanism has received convincing support over the last two decades (comprehensive reviews can be found in Refs. (2,14,15)). Carbon-heteroatom bond formation from Pt(IV) (step III) has been shown to occur via nucleophilic attack at a Pt-bonded methyl, as discussed in detail below (Section V. A). 

Cathodic substitution stands for C,C bond or C, heteroatom bond formation with cathodically generated anions. The question of regioselectivity is encountered in the reaction of such anions with allyl halides (path a) or in the reaction of allyl anions generated in an ECE process from allyl halides (path b). Cathodic reductive silylation of an allyl halide proceeds regioselectively at the less substituted position (Fig. 15) [91]. From the reduction potentials of the halides it is proposed that the reaction follows path b. 

This article discusses the anodic synthesis of heterocyclic compounds that have appeared during the last decade. The mechanistic aspects involving intramolecular, intermolecular cyclizations and the homogeneous vs heterogeneous anodic oxidations were considered. This review deals with the recent advances in anodic oxidations in which heterocyclic compounds were synthesized through carbon-heteroatom and heteroatom-heteroatom bond formation. 

Very few transition-metal catalyzed electroreductive carbon-heteroatom bond formations have been described. The electrochemical silylation of allylic acetates was carried out in the presence of Pd-PPha [131]. The electrosynthesis of arylthioethers from thiophenol and aryl halides [132] and the coupling of bromobenzene with dichlorophenylphosphine [133] were performed with Ni-bpy as catalyst. 

An example of C—Si bond formation concludes this overview of carbon heteroatom bond formation. Reflux of bromide 62 in benzene and in the presence of small amounts of (TMS)3SiH and AIBN afforded the silabicycle 63 in 88 % yield (Reaction 7.64) [76]. The key step for this transformation is the intramolecular homolytic substitution at the central silicon atom, which occurred with a rate constant of 2.4 x 10 s at 80 °C (see also Section 6.4). The reaction has also been extended to the analogous vinyl bromide (Reaction 7.65) [49]. 

This chapter mainly concerns common rearrangements of organolithium compounds which are synthetically valuable in terms of a C—C bond or C—heteroatom bond formation. 

Carbon-heteroatom bond formation by free-radical chain additions to... 

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