Chain functionalisation

Transformation of a phosphonio-substituted phospholide derivative under conservation of the r-electron system has been demonstrated in a number of cases which include substitution of a ring-hydrogen atom, replacement of a PRs -moiety by a hydride, or reductive de-arylation of a PhsP " - to a phosphinyl substituent PPh2. Subsequent re-quaternisation of the latter allows the formal substitution of a PhsP " - by a modified Ph2(R)P -moiety in a two-step reaction. The application of this scheme is not only perfectly suitable for the synthesis of bis-phosphonio-benzophospholides with different phosphonio-moieties but, since the last reaction stage tolerates a variety of functional groups in the electrophile, offers as well a convenient pathway for the synthesis of side-chain functionalised phosphonio-phospholide derivatives from more simple substituted precursors. 

The carbon chain functionalised with the chromone nucleus characterises the patented saccharin derivatives 412 as agents for treating disorders of the central nervous system. As an example, the synthesis of (R)-(-)-[2-[4- (benzyl [7-(benzyloxy)-6-methoxy-3,4-dihydro-2ff-chromen-2-yl]methyl-amino)-2-butynyl]-l,2-benzisothiazol-3(2ff)-one S,S-dioxide (412 = H,... 

Tomlison R, Heller J, Duncan R, Brocchini S Pendent chain functionalised polyacetals that display pH-dependent degradation A platform for the development of novel polymer therapeutics, Macromolecules 2002, 35, 473 80. 

Israelachvili and his colleagues have used the SEA to study the interactions between surface layers of surfactant and of other molecules representing functionalised polymer chains, adhesion promoters or additives. Typically a monolayer of the molecule concerned is deposited onto cleaved mica sheets. The values of surface energies obtained from the JKR equation (Eq. 18) throw some interesting light on the nature and roughness of surface layers in contact. 

The retention of potent enzyme inhibition and in vitro antiviral activity in the presence of functionalisation with relatively long hydrophobic chains at C-7 of zanamivir has been exploited in the development of di- and poly-valent structmes carrying zanamivir (reviewed in Sun 2007). Multivalent presentation of drug may... 

Regarding bis-NHC chelating ligands, several structures that differ in the motifs used for the enlargement of the tether have been proposed as catalysts for the Mizoroki-Heck reaction. They range from non-functionalised aliphatic chains [23-25] to phenyl [26], biphenyl [27], binaphthyls [28] and to chains containing additional coordination positions like ethers [29], amines [30], and pyridines in an evolution towards pincer complexes [31-35], In most cases, the activity of aryl bromides in Mizoroki-Heck transformations was demonstrated to be from moderate to high, while the activation of chlorides was non-existent or poor (Scheme 6.7). 

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. 

Addition reaction of peroxide-generated macroalkyl radicals with the reactive unsaturation in MA is shown in reaction scheme 4. The functionalised maleic-polymer adduct (II, scheme 4) is the product of hydrogen abstraction reaction of the adduct radical (I, scheme 4) with another PP chain. Concomitantly, a new macroalkyl radical is regenerated which feeds back into the cycle. The frequency of this feedback determines the efficiency of the cyclical mechanism, hence the degree of binding. Cross-linking reaction of I occurs by route c ( scheme 4). 

Table 5 Typical end-functionalisation reactions in anionic chain polymerisation...

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. 

Protected sugar derived acids, having no a-hydroxy substituent, have also been used in die mixed Kolbe reaction [106]. The Kolbe reaction is used to graft short functionalised alkyl chains onto poly(acryIic acid) [107],... 

Hydroformylation of Functionalised Olefins - Introduction of polar substituents such as -C02Me into the alkyl chain of a-olefins considerably extends the scope of Rh/tppts-catalysed hydroformylation in aqueous/organic two phase systems.89,417... 

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