Current Organic Chemistry - Volume 9, Issue 8, 2005

The scope of organometallic reactions on solid phase has lately expanded to include many new reactions. In this review, we summarise the recent developments in this area, covering reactions such as metathesis, carbene insertion, radical-mediated transformations, the use of organomagnesium, organozinc and organocopper reagents, applications of titanium alkylidenes for alkene synthesis, as well as the Pauson-Khand reaction, hydroformylation and other methods using metal carbonyl reagents. Palladium-catalysed reactions are not included as this area has been recently reviewed (vide infra).

Micro-reaction technology is entering more and more into chemical process engineering and chemistry, complementing existing technologies. The benefits of microstructured reactors such as enhanced mass and heat transfer, defined residence time setting, and known, highly regular flow profiles give process intensification following standard chemical protocols. These unique features, however, can achieve more, namely to enable process chemistry with novel features. This includes handling of instable intermediates, safe processing in the explosive regime, setting reaction temperature at unusually high level, and more. In this way, the engineering benefits change the chemistry; thus, it has been termed novel chemistry here. While this has been done in a heuristic manner in the past, first deductive approaches were recently developed based on diffusion-reaction calculations and potential energy profiles which provide a mechanistic understanding what the new tool can do. In this context, many examples for organic reactions in microstructured reactors are described to underline the possible means of novel chemistry by using microstructured reactors.

Chemical functionalization of fullerenes is the first step to investigate their intriguing properties and applications. The versatile functionalization methods have enabled fullerenes to be extensively studied in many fields, and they are found to have uses in medicines, electronics and optoelectronics. The mono-functionalization of C60 is straightforward, however its multiple functionalization is a challenging job for organic chemists. The stepwise multiple additions to C60 yield a mixture of geometric isomers with low yield and low selectivity for respective isomers, and tedious chromatographic separations are required. A general solution to the multiple addition problem is to find a generic linker which can direct the second addition to expected positions on C60 surface, then the third, and so on. Many research groups have developed tether-directed synthetic methodologies to selectively synthesize C60 multiple adducts. The design and synthesis of C60 isomeric multiple adducts using tether-directed approach will be reviewed in this article.

Photodynamic therapy (PDT) has become an increasingly important method for the chemotherapeutic treatment of some cancers. It involves the systemic, topical, or intraperitoneal administration of a nontoxic drug called a photosensitizer, which, to some extent, preferentially localizes in the tumor [1,2]. When the tumor is illuminated with the wavelength of light that is absorbed by the dye, in the presence of oxygen, toxic oxygen reactive species are producedand they can cause tissue necrosis or apoptosis by a combination of mechanisms [3]. The Phthalocyanine complexhas recently become very popular in different areas of science and technology. Due to many useful physical and chemical properties, these complexes have found use in opticaland semi conducting devices [4], electrochemistry [5], catalysis [6], analytical chemistry [7] and photodynamic therapy [8]; and have been extensively reviewed in the last decade [9,10]. The main disadvantage of using phthalocyanines is their enhanced tendency to participate in aggregation processes dependent on the central metal ion, which leads to low solubility in biological aqueous medium. Photosensitizers could be natural or synthetic [11]. In general,the three main families of photosensitizers are porphyrin-based compounds, chlorophyll-based compounds or phthalocyanine derivatives [12]. A number of novel compounds consisting of multifunctional ligands, such as phthalocyanine-nucleobase conjugates, phthalocyanine-dendrimers and crown ethers or macro-aza group moieties have been reported recently. The objective of this review is to describe recent progress in photosensitizer concepts along with an indication of some prominent synergic photosensitizers.