General Synthetic Strategies

Numerous synthetic approaches have been used to embed boron within PAH structures. We present a few representative examples of modern strategies to build these architectures below, along with a brief example of chemistry based on B-W functionalized boraarenes to construct complex it-conjugated materials. 

Two methods have been developed for the synthesis of AB diblock copolymers (a) sequential addition of monomers and (b) coupling of two appropriately end-functionalized chains. The first method is the most widely used 

Other more complex linear block co-, ter- and quarterpolymers, such as ABC, ABCD, ABABA can be prepared using the previously mentioned methods. An important tool in the synthesis of block copolymers involves the use of post-polymerization chemical modification reactions. These reactions must be performed under mild conditions to avoid chain scission, crosslinking, or degradation, but facile enough to give quantitative conversions. Hydrogenation, hydrolysis, hydrosilylation and quaternization reactions are among the most important post-polymerization reactions used for the preparation of block copolymers. 

Nanotubes of dichalcogenides such as M0S2, MoSc2 and WS2 are also obtained by employing processes far from equilibrium, such as arc discharge and laser ablation [229]. By far the most successful routes employ appropriate chemical reactions. Thus, M0S2 and WS2 nanotubes are conveniently prepared by starting with 

W) as a means of preparing the nanotubes [231]. Other methods employed for the synthesis of dichalcogenide nanotubes include hydrothermal methods where the organic amine is taken as one of the components in the reaction mixture. 

In a typical experiment they used trimethylgallium and ammonia as precursors with argon or nitrogen as carrier gas and maintained the deposition temperature at 

600-700 °C. The ZnO nanowire templates were subsequently removed by thermal reduction and evaporation, resulting in ordered arrays of GaN nanotubes on the substrates. 

Some of the important inorganic nanotubes synthesized and characterized in the 

The engineering of materials at the nanoscale level with novel properties, through controlled synthesis and assembly, is an important issue. In recent years, nanotechnology has reached a stage whereby it is possible to produce, characterize and specifically tailor, the functional properties of nanoparticles. Nanoparticle synthesis has been pursued intensively not only for fundamental scientific interest but also for many technological applications [16, 30, 55-58], and the synthesis of uniformly sized (or monodisperse) nanoparticles has become a very important research area [59-63]. The two fundamentally different approaches used to synthesize nanomaterials are known as top-down and bottom-up  

The choice of approach is very important with regards to any further processing of the nanomaterials for possible applications. During the past few years, bottom-up techniques based on the self-assembly of building blocks have attracted considerable attention for the synthesis of anisotropic nanoparticles. The use of some popular bottom-up techniques, for the rational design of spherical and highly 

Particle size distribution (uniformity) Monodispersity of the nanoparticles 

Shape control High yield with the desired shape 

Scale-up Optimization of the synthetic strategy at large scale 

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The name corrphycene for [18]porphyrin(2.1.0.1) is derived from the fact that these compounds combine structural elements from corrins/ corroles, porphyrins and acenes. Two general synthetic strategies have been developed for the final cyclization step of a linear tctrapyrrole leading to the macrotetracycle. 

The synthesis of cyclic compounds is a battle for the yield. The general synthetic strategies of CPOs are illustrated in Fig. 2. The first one involves one-pot synthesis using a porphyrin unit (method A), and the second one is the ringclosing reaction of the chain-shaped PO (method B) [11]. 

The first approach to lithium boratabenzenes (Scheme 3) was an elegant adaption of a more general synthetic strategy (81). Hydrostanna-tion of 1,4-pentadiyne (82) with Bu2SnH2 gives the stanna-2,5-cyclohexadiene 24 (83,84), which on treatment with PhBBr2 produces... 

RG. 66. Commercially available dendrimer scaffolds commonly used for glycodendrimer syntheses, and general synthetic strategies for synthesis of glycodendrimers. 

Launay, N., Caminade, A.M., Lahana, R., and Majoral, J.P. (1994) A general synthetic strategy for neutral phosphorus-containing dendrimers. Int. Ed. Engl. 33, 1589-1592. 

A typical synthesis. The preparation of (213 m, n = 1) serves to illustrate the general synthetic strategy used to obtain this class of polyether cage. Starting from diaza-18-crown-6 and the required diacid chloride, condensation followed by reduction yields the corresponding cryptand, 2.2.2 (Dietrich, Lehn Sauvage, 1970 Dietrich, Lehn, Sauvage Blanzat, 1973)-see [4.8],... 

In the case of giant wheel (molybdenum blue) compounds, the general synthetic strategy involves the acidification (pH 1) and reduction of an aqueous molybdate(VI) solution [possible reducing agents iron powder, tin(II) chloride, molybdenum(V) chloride, ascorbic acid, cysteine, hydroxylamine, hypophos-phorous acid, sodium dithionite, or hydrazine sulfate].On the other hand, an icosahedral ball-shaped cluster can be formed in an aqueous Mo(VI)... 

This review covered recent developments in the synthesis of branched (star, comb, graft, and hyperbranched) polymers by cationic polymerization. It should be noted that although current examples in some areas may be limited, the general synthetic strategies presented could be extended to other monomers, initiating systems etc. Particularly promising areas to obtain materials formerly unavailable by conventional techniques are heteroarm star-block copolymers and hyperbranched polymers. Even without further examples the number and variety of well-defined branched polymers obtained by cationic polymerization should convince the reader that cationic polymerization has become one of the most important methods in branched polymer synthesis in terms of scope, versatility, and utility. 

SCHEME 16.1 Structures of multivalent architectures and their general synthetic strategies, (a) Convergent approach, (b) Divergent approach. 

Adding a perspective of genealogy to a general synthetic strategy has most certainly added a heightened sense of satisfaction and a keen anticipation of new possibilities. 

In view of the fact that benzylic cations are responsible for the initiation, graft copolymerization is feasible when the polymer supported pyridinium salts are employed. Endo and co-workers [41] prepared vinyl monomers having pyridinium salt structure. In this case, p-chloromethyl styrene was used as the benzyl halide and the general synthetic strategy was followed. The polymerizable salt was then homo and copolymerized with styrene (Scheme 7). 

General Synthetic Strategies for Strain Compounds of Ae Cydophane... 

General Synthetic Strategies for Strained Compounds of the Cyclophane Type... 

Scheme 10-18. General synthetic strategy for five to-THF acetogenins developed by...

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