A-functionalisation

Fig. 16 (a) Sequences of peptides pi6 and B2x-pi6. (b) Biotin-derivatised colibrils binding to a functionalised streptavidin with a functional group. Reproduced by permission of The Royal Society of Qiemistry from Kodama et al. [56]... 

H). On the other hand, the synthesis of unsymmetricaUy iV,iV -substituted congeners is less straightforward as a functionalised imidazole has to be isolated prior to alkylation or arylation. Two main methods are available for imidazole functionaU-sation deprotonation with metalUc Na or K leading to an imidazoUde (I) followed by reaction with RX or reaction of glyoxal with a primary amine, an ammonium salt and formaldehyde (J). Al-functionalised imidazole can then be alkylated or... 

A range of a-functionalised aldehydes have been used to generate acylazolium species via the corresponding enol intermediate. For example, addition of an NHC to an a-halo aldehyde 84 presumably generates the Breslow species 86, with elimination of HX to afford the enol 87. Subsequent in situ tautomerisation generates... 

This ligand has also been used by the same authors to promote the addition of ZnMe2 to a functionalised a,(3-unsaturated ketone in the asymmetric key step of the first enantioselective synthesis of (-)-frontalin. This synthesis started with the naphthalene-catalysed lithiation of a chlorinated ketal (Scheme 4.15) that, after several transmetalation processes, was trapped by reaction... 

Fig. 34. Model of a functionalised (internally or externally) SWNT, which may be closed, open and/or corked reversibly or permanently after filling. Potentially the inner cavity may be filled with a (radio)-imaging agent (for PET/SPECT and/or MRI) or a (radio)therapeutic agent. Such functionalized SWNTs may conceivably act as probe prototype for multimodal imaging/therapy and targeted drug delivery (155).

Ring-opening was not restricted just to norbornenes bicyclo[3.3.0]octenes, cyclooctene and a functionalised cyclobutene were all reactive substrates for these reactions. 

Scheme 2.69 Extended synthesis of a functionalised piperidine library.

The scope of the Negishi-coupling is not limited to aryl and vinyl halides and sometimes acyl chlorides might also be converted to ketones by this protocol. The 2,3-dihalopyrrole derivative shown in 6.22. was converted into its 2-lithio derivative by selective lithium-halogen exchange at -78 °C. Addition of zinc chloride effected the formation of the appropriate pyrrolylzinc chloride, which was coupled with a functionalised butyroyl chloride in the presence of tetrakis(triphenylphosphino)palladium and furnished the expected 2-acylpyrrole in 61% yield.27... 

Allylic esters of fluoroacetic acid were used in the Ireland silyl ketene acetal rearrangement procedures by the Welch group at Albany [164]. For example, Eq. (53) shows a highly diastereoselective rearrangement which formed an early stage in syntheses of 2,3-dideoxy-2-fluoro-3-C-methyl pentose nucleosides [165, 166]. If a stereoselective synthesis of a functionalised monofluorocompound is... 

R. M. Adlington, J. E. Baldwin, A. Basak, and R. P. Kozyrod, Application of radical addition reactions to the synthesis of a C-glycoside and a functionalised amino-acid, J. Chem. Soc. Chem. Commun. p. 944 (1983). 

Scheme 7.18 General strategy of triazines on planar surfaces, (a) functionalisation/linker attachment (b) introduction ofthe first building block (c) attachment of cyanuric chloride (d) stepwise chlorine-substitution (e) cleavage.

It is also possible to make rather more dramatic changes in the structure of the preformed capping group, and 7.11, the cobalt(n) complex of a functionalised triaza macrocyclic ligand, reacts with formaldehyde and nitromethane to give 7.12. 

The graft-to method of attaching dendrons numbers among the polymer-analogous synthetic strategies which start from a functionalised polymer backbone to which convergently preconstructed dendritic units of the desired generation can be fixed in a dense sequence (Fig. 2.16). 

Scheme 15.2 Synthesis of functionalised gold nanoparticles via the in situ reduction of Au(III) in the presence of a functionalised thiol.33...

Metaproterenol 64 is an adrenaline analogue used as a bronchodilator.11 The amine might be inserted by reductive amination on the aldehyde 65 and this might be made by a-functionalisation of the available ketone 66. 

Compound 57 looks like a Diels-Alder adduct but the ketone must be changed 60 and it is much simpler if one alkoxy group is removed 61. Diels-Alder disconnection then gives the known dienophile 62 and a functionalised diene 63. 

Scheme 10.3 Free radical retrosynthetic disassembly of bond d in 7. Advantages it does not necessitate the construction of a functionalised medium-sized ring. It forms the bicyclooctane ring system by a favourable 5-exo-trig pathway. Conformational and steric bias will allow the stereochemistry of the methyl a to the ketone to be controlled.

The simple reductive lithiation and quench of dithioacetals means that a-functionalised - and in particular, a-silylated sulfides are very easy to prepare. Cohen has exploited this in a number of ways for example, a ketenedithioacetal 70 can be used to generate an a-lithiovinylsilane 71 if a silyl halide is used as the electrophile in the first step.85... 

FIG. 11.22 Example of a functionalised side chain liquid crystalline copolymer. After Klaase (2002) See also Jacobson and Landi et al. (1994). 

Figure 2.11 Surface modification using a functionalised ionic liquid...

Oxazolin-2-ylidenes can also be used directly for coordination to metal atoms [109], but then they are not functionalised and therefore not covered by this book. However, it may be interesting to note that their generation is possible as a template synthesis in the coordination sphere of transition metal complexes using a functionalised hydroxyisocyanide [110,111] or the reaction of an epoxide with a hydrogen isocyanide complex [112]. 

Having introduced the golden rule of phosphine chemistry to its carbene analogues we will proceed to break it several times in the following brief sununary of routes to synthesise phosphino functionalised carbenes. The best way to synthesise an imidazolium salt is to react an N-substituted imidazole with an alkyl or aryl halide [235], Thus, it is a good idea to utilise a functionalised alkyl halide. The functional group can then be used to introduce the phosphino group. 

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