Prefunctionalization

The biological significance of glycoporphyrins, their limited natural occurrence, and their widespread applications have made the availability of such compounds a scientific challenge for several research groups. Synthetic approaches have consisted in the direct glycosylation of prefunctionalized porphyrins or chemical synthesis from suitable glycoconjugates precursors. 

With respect to the polymeric backbone, two approaches exist for the preparation of functional polymers, the polymerization or copolymerization of monomers which carry the desired functionality, and secondly the chemical modification of preformed polymers. The former concept, the polymerization of prefunctionalized monomers, was often tested in the early days of polymer-assisted syntheses, e. g. in the preparation of polymers containing pyridine [12] or quinone [13] residues, and benzaldehyde [14] or phosphine [15] functionalities. Although the latter approach demands that the synthetic organic chemist acquires profound knowledge of polymers and polymerization, this strategy can have advantages because... 

C-H activation. Turnovers up to 50 were achieved [20], The cyclization is highly regioselective, obviating the need for prefunctionalized arenes. 

Hypervalent iodine(lll) was shown to catalyze the direct cyanation of iV-tosylpyrroles and -indoles under mild conditions, without the need for any prefunctionalization <2007JOC109>. Phenyliodine(m) bis(trifluoroacetate)-induced oxidative regioselective coupling of pyrroles in the presence of bromotrimethylsilane gave a series of electron-rich bipyrroles <2007S2913>. 

For direct liquid chromatography the native CDs are primarily immobilized via one or two primary hydroxyl groups, e.g. via a carbamate group onto a prefunctionalized silica... 

Fig. 2 Different paths to obtain hybrid materials from molecular sources. Path A Sol-gel routes (Al conventional route for hybrid nanocomposites, A2 molecularly homogenous hybrids). Path B Assembly of nanobuilding blocks (ANBB), of prefunctionalized or postfunctionalized clusters or nanoparticles. Route C or D involve the use of templates capable of self-assembly, giving rise to organized phases. Path E involves integrative synthesis combining precedent paths from A to D and other processes, such as the use of lithography, casting, organogels or latex beads as templates, controlled phase separations, or external fields. (From Ref. l) (View this art in color at www.dekker.com.)...

Fig. 5 Prefunctionalization (A) and postfunctionalization (B) routes toward hybrid materials organized in the mesoscopic scale. The meso-organized precursors are synthesized by reacting an inorganic precursor in the presence of a supramolecular template (surfactant). By Route A, organic functions can also be embedded within the walls. (View this art in color at www.dekker.com.)...

Scheme 3 Schematic representation of the two-steps electrostatic grafting of a cationic Mni2 derivative on a prefunctionalized gold surface (reprinted from [99])...

Fig. 2 The construction of a polymer-cushioned lipid bilayer membrane. (A) Architecture constructed in a sequential way first, onto the functionalized substrate a polymer layer (cushion) is deposited by adsorption from solution and covalent binding, followed by the (partial) covalent attachment of a lipid monolayer containing some anchor lipids as reactive elements (B) able to couple the whole monolayer to the polymer cushion. (C) Alternatively, a lipopolymer monolayer, organized, e.g., at the water-air interface can be co-spread with regular low-mass amphiphiles and then transferred as a mixed monolayer onto a solid support, prefunctionalized with reactive groups, able to bind covalently to the polymer chains of the lipopolymer molecules, (B). (D) By a fusion step (or a Langmuir Schaefer transfer) the distal lipid monolayer completes the polymer-tethered membrane architecture...

As illustrated in this chapter, oxidative cross-dehydrogenative coupling (CDC) has provided the opportunity to simplify organic synthesis by presenting an alternative to the separate steps of prefunctionalization and defunctionalization that have traditionally been part of synthetic design. In the near future, we anticipate the development of CDC reactions that will be more efficient and effective to provide a positive economical and ecological impact on the next generation of C-C bond formation processes. 

An interesting S-Aj-Aj triad assembly has been organized by coupling a diad S-Aj to a secondary electron acceptor, Aj, on a solid support that orients the components in a triad array capable of vectorial ET. The covalently linked Ru(II)-tris(bipyridine) chromophore and jV,Af -tetramethylene-2,2 -bipyridinium diad (8), Ru -DQ, has been exchanged onto zeolite L that is prefunctionalized with N,N -dibenzyl-4,4 -... 

Reactive compatibilization of the recycled LDPE or HDPE with GRT was carried out by preparing prefunctionalized components to provide chemical... 

The catalytic asymmetric CDC reaction of starting materials without prefunctionalization is evidently one of the most direct and powerful methods in organic synthesis. This chapter summarizes and discusses the outstanding achievements that have been made in the past decade in the field of enan-tioselective CDC reactions. Various catalytic systems, including well-defined... 

Several methods exist to incorporate the functional moiety in an ECP prefunctionalization of the monomer [122,239,242,243], postfunctionalization of the electrosynthesized polymer [244], or simple doping of the ECP [230]. Each one has its own advantages and drawbacks functionalization of the monomer is usually easier than one of the polymer but it usually makes electropolymerization more difficult due to steric hindrance and/or electronic (e.g., inductive) effects. Of course this can be overcome by copolymerization but the functional moiety is more diluted and sometimes less efficient. Conversely, postfunctionalization sometimes leads to an unhomogeneous distribution of the functional moiety in the material due to differences in the reactivity of surface and bulk functional groups. 

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