Functionalisation Functionality

The required nitrite esters 1 can easily be obtained by reaction of an appropriate alcohol with nitrosyl chloride (NOCl). The 3-nitroso alcohols 2 formed by the Barton reaction are useful intermediates for further synthetic transformations, and might for example be converted into carbonyl compounds or amines. The most important application for the Barton reaction is its use for the transformation of a non-activated C-H group into a functional group. This has for example been applied for the functionalisation of the non-activated methyl groups C-18 and C-19 in the synthesis of certain steroids. ... 

Woolfson and Mahmoud have classified the routes to preparation of decorated self-assembling peptide materials [53] as (1) co-assembly, where the functional part is already attached to a self-assembling component prior to assembly, and (2) postassembly, where a non-functionahsed self-assembled structure is modified by covalent or non-covalent means. This discussion adheres to this classification. A third route, beyond the scope of this review, is the use of structured peptides as templates for inorganic materials. Section 4.1 discusses functionalised self-assemblies formed from co-assembly-type approaches, while post-assembly modifications of self-assembled structures are considered in Sect. 4.2. 

Self-assembly is not restricted to merely a mixture of functionalised and non-functionalised, but otherwise identical, sequences. It is possible to use distinct sequences in mixtures and combine functionality. The formation of modified fibrils... 

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]... 

Norbomene derivatives are very popular monomers for ROMP due to a comparably high ring strain and good functionalisability. The latter is needed to append any desired functional unit to the monomer [98, 99]. 

While the synthesis of fnnctionalised secondary alcohols and amines can be achieved withont catalyst by the addition of organolithium and organomagnesium reagents to C=N and C=0 gronps, these methods lack a significant functional group tolerance. In order to overcome this limitation and access to more functionalised compounds, the catalytic arylation of aldehydes and imines has been extensively studied [2]. 

High compatibility of the additive with the polymer matrix usually extends performance but at the expense of extractability. Lack of extractability is of analytical concern, e.g. in case of functionalised oligomer and polymeric additives, grafted and reactive additive functionalities, and chemisorbed and absorbed additives. More generally, additive recovery levels significantly lower than the target level may arise from various situations ... 

As already shown, it is technically possible to incorporate additive functional groups within the structure of a polymer itself, thus dispensing with easily extractable small-molecular additives. However, the various attempts of incorporation of additive functionalities into the polymer chain, by copolymerisation or free radical initiated grafting, have not yet led to widespread practical use, mainly for economical reasons. Many macromolecular stabiliser-functionalised systems and reactive stabiliser-functionalised monomers have been described (cf. ref. [576]). Examples are bound-in chromophores, e.g. the benzotriazole moiety incorporated into polymers [577,578], but also copolymerisation with special monomers containing an inhibitor structural unit, leading to the incorporation of the antioxidant into the polymer chain. Copolymers of styrene and benzophenone-type UV stabilisers have been described [579]. Chemical combination of an antioxidant with the polymer leads to a high degree of resistance to (oil) extraction. 

The ability to downgauge, decrease part weight, improve barrier properties and reach new levels of product performance are propelling polyolefins into new markets previously dominated by other plastics. The high growth rate in PP production capacity is mainly being driven by the ability of PP to replace other resins on a cost/performance basis. For example, functionalisation of PP by incorporation of acrylic functionality has extended its weatherability performance. Interpolymer competition will have a significant impact on the amount and type of additives used. 

Properly functionalised additives can react with polymer substrates to produce polymer-bound functions which are capable of effecting the desired modification in polymer properties, hence the use of the term reactive modifiers. As an integral part of the polymer backbone, reactive modifiers are useful vehicles for incorporating the desired chemical functions to suit the specialised application. Being molecularly dispersed, the problem of solubility expressed under 2 above is avoided. Implicitly, the bound-nature of the function is not subjected to the normal problems of the loss of additives from the surface which are common with both high and low molecular mass additives. The bound nature of the function must be fully defined for the conditions of service. 

An alternative strategy to obtain silica immobilised catalysts, pioneered by Panster [23], is via the polycondensation or co-condensation of ligand functionalised alkoxysilanes. This co-condensation, later also referred to as the sol-gel process [24], appeared to be a very mild technique to immobilise catalysts and is also used for enzyme immobilisation. Several novel functional polymeric materials have been reported that enable transition metal complexation. 3-Chloropropyltrialkoxysilanes were converted into functionalised propyltrialkoxysilanes such as diphenylphosphine propyltrialkoxysilane. These compounds can be used to prepare surface modified inorganic materials. Two different routes towards these functional polymers can be envisioned (Figure 3.4). One can first prepare the metal complex and then proceed with the co-condensation reaction (route I), or one can prepare the metal complex after the... 

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).

This review focuses on the cross-metathesis reactions of functionalised alkenes catalysed by well-defined metal carbene complexes. The cross- and self-metath-esis reactions of unfunctionalised alkenes are of limited use to the synthetic organic chemist and therefore outside the scope of this review. Similarly, ill-defined multicomponent catalyst systems, which generally have very limited functional group tolerance, will only be included as a brief introduction to the subject area. 

For the cross-metathesis of functionalised alkenes the ill-defined classical catalyst systems currently offer very few advantages (cost and heterogeneous catalysis) over the more functional group tolerant Schrock and Grubbs alkylidene... 

Functionalisation at OH-2 thus led to a series of 1,2-bisfunctionalised platforms prepared from two model lactones, one monosaccharidic (a-gluco) and one disaccharidic (ot-malto). Allylamine and propargylamine were used as model functional appendages due to the wide scope of their possible subsequent chemistry. Their addition on the lactones occurs in high yield and very mild conditions (room temperature, THF, no catalyst,... 

To date, typical SPE materials are based on silica gel or highly cross-linked styrene-divinylbenzene (PS-DVB). The former is functionalised with distinct chemical groups to yield various sorbents with non-polar or polar characteristics. Non-polar materials are modified with alkyl groups of different chain length (C18, C8, C2), while polar sorbents have cyano-, amino-, or diol-bonded groups. Ion-exchange phases have either anionic or cationic functional groups. 

The covalent functionalisation of CNTs is the alternative and extremely promising approach for applications in fields such as that of functional and composite materials and that of biology. According to the location of the functional groups, two main strategies are used to covalently functionalise CNTs with biomolecules (i) defect functionalisation, and (ii) sidewall functionalisation. 

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