Electrophiles, solid-state reaction

Transition metal-catalyzed reactions of ct-diazocarbonyl compounds proceed via electrophilic Fischer-type carbene complexes. Consequently, when cr-diazoketone 341 was treated, at room temperature, with catalytic amounts of [ RhiOAcbh, it gave the formation of a single NH insertion product, which was assigned to the enol stmcture 342. At room temperature, in both solid state and in solution, 342 tautomerizes to give the expected 1-oxoperhydropyr-rolo[l,2-c]oxazole derivative 343 (Scheme 50) <1997TA2001>. 

Another approach to tuning the optical properties and improving the emission of PT derivatives in the solid state was proposed by Holdcroft and coworkers [506] (Scheme 2.68). They used postfunctionalization of P3HT 395 by electrophilic substitution reaction to afford polymers 425 followed by Pd-catalyzed coupling (Suzuki, Stille, or Heck methodologies) of... 

The first chemical transformations carried out with Cjq were reductions. After the pronounced electrophilicity of the fullerenes was recognized, electron transfer reactions with electropositive metals, organometallic compounds, strong organic donor molecules as well as electrochemical and photochemical reductions have been used to prepare fulleride salts respectively fulleride anions. Functionalized fulleride anions and salts have been mostly prepared by reactions with carbanions or by removing the proton from hydrofullerenes. Some of these systems, either functionalized or derived from pristine Cjq, exhibit extraordinary solid-state properties such as superconductivity and molecular ferromagnetism. Fullerides are promising candidates for nonlinear optical materials and may be used for enhanced photoluminescence material. 

Silica gel is also the support of choice for the activation of V-halosuccinimides. The silica functions both as a proton donor which increases the electrophilic nature of the reagent, and as a support with geometrical constraints which contributes to the stereoselectivity. Alkyl and aryl sulfoxides are readily halogenated at the a position with yields of48-80%91. The reactions are carried in the solid state on the surface of TLC plates. The conversion of the optically active alkyl 4-methylphenyl sulfoxide into 1-haloalkyl 4-methylphenyl sulfoxide is accompanied by inversion of configuration at the S-atom. The stereoselectivity in these reactions is much higher than that observed in liquid-phase halogenation. 

Treatment of the yttrium(III) adduct 60 with potassium naphthalenide in dme-diethyl ether mixture results in deprotonation of the C4 carbon and migration to afford the abnormal carbene complex 63 (Fig. 13).72 The C2 binding carbon migrates from the yttrium(III) centre to the incorporated potassium(I) cation. The C4 carbanion forms a short bond with the yttrium(III) centre in the solid state (2.447(2) A) and exhibits a large jYc coupling constant of 62 Hz in solution. Complex 63 may be quenched with a variety of electrophiles. For example, reaction with Me3SiCl silylates the NHC backbone to afford 64. 

The addition of para-tolylamine to 133 afforded the 1,2-addition complex 142 which was characterised in the solid state confirming the cis orientation of the amide to the newly formed methanide centre. Likewise, reaction of 132 with adamantyl alcohol and 133 with methyl iodide, respectively, afforded the 1,2 addition products 143 and 144. The regioselective nature of these 1,2-additions confirmed the nucleophilic nature of the methandiide centres and this contrasts to electrophilic Fischer carbene centres which are usually attacked by incoming nucleophiles. In contrast, complexes 142-144 are formed by attack of electrophilic centres at the methandiide centres. 

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