Silicones and silicone rubbers are omnipresent in household and industrial products such as lubricants,c oatings, sealants,i nsulators, medicald evices, etc. This plethora of applicationsa rises from their unparalleled properties including hydrophobicity,l ow surfacee nergy,c hemical inertness, extreme temperature stability,e lasticity,a nd biocompatibility.E vent hough silicones have been known for more than five decades, their chemistry is still far from fully understood. Industrially,t he vast majority of processesf or their synthesis, transformation, andu se are based on rather well established, alas outdated technologies, which are frequently empirical and poorly investigated. Thisr eview attempts to summarize the different approaches for the synthesis of silicone rubbers by vulcanizationorc uring of silicone polymers, the catalysts used, and the corresponding reaction mechanisms. Apart from the well-known methods (radical, hydrosilylation, and metal-based condensation), novel approaches such as organo-and bio-catalysis are also addressed.

The acetals of aromatic aldehydes, cinnamic aldehydes and-with lower yields-also of aliphatic aldehydes react withThe reaction does not Ethyl hydrogen malonate reacts with these acetals analogously in the absence of any catal>Tst, -4 reaction mechanism is proposed, inmalonic acid in the presence of pyridine and piperidine in the manner of a Knoevenagel reaction. proceed via the free aldehydes.giving the corresponding ethyl hydrogen arylidene-and cinnamylidene-malonates. voking the formation of a hydrogen-bonded complex between the two components of the reaction mixture.In a study to be published elsewhere, it was found that the acetals of 2-phenyl-1,2,3,6-tetrahydro-and 2-phenyl-hexahydrobenzaldehyde react with malonic acid in the presence of pyridine and piperidine in the manner of a Knoevenagel reaction, giving the corresponding hydrogenated 2-phenylcinnamic acids, with liberation of carbon dioxide. A systematic study of the reaction between dialkyl acetals of aldehydes and malonic acid led to the following conclusions : the diethylacetals of aromatic and of cinnamic aldehydes condense with malonic acid in quantitative yields. The aromatic aldehyde acetals thus give cinnamic acids. This is particularly noteworthy in the case of p-diinethylaminobenzaldehyde diethylacetal ; this aldehyde is refractory in the Perkin reaction' but gives2 by Doebner's method a yield of 85Y0. Bulky o-substituents (not, e.g., o-methoxy) decrease the yield under the same operating conditions (to 50-607,) ; prolongation of the reaction time gives satisfactory yields also in these cases. It appears that these substituents decrease the rate a t which condensation takes place. The acetals of aliphatic and hydroaromatic aldehydes react more slowly than those of aromatic ones, giving a,&unsaturated monocarboxylic acids. The yields were low, but at least in a number of these cases the acetals have been recovered, so that not the yield but rather the conversion rates appear to be affected adversely.The reaction between the acetals of cinnamic aldehydes and malonic acid leads to mixtures of the corresponding malonic and monocarboxylic acids ; i t has been shown that the former are decarboxylated only slowly, even in boiling ~y r i d i n e .~ Thus it must be assumed that the proximity of the aryl groups accelerates the decarboxylation. This assumption is supported by the observation that ethyl hydrogen (p-methylbenzy1idene)-malonate

This Focus Review describes state-of-the-art methods for the preparation of antimicrobials ilicones. Given the diversity of antimicrobiala ctivity and their mechanisms, the performance of these materials is highly dependento nt he characteristics of the polymeric matrix. Therefore, different synthetic routes have been developed, such as 1) physical treatments,2 )chemical transformations, and 3) copolymerization. This classification is not exclusive,s os ome products belong to more than one class. Herein, we attemptt op resent ah andy overview of the development of antimicrobial silicones, their most important application fields, the most relevant antimicrobiala ssays,a nd, as the title suggests, an overview of the most relevant preparation methods.

Silicone rubbers are so widespread in our daily lives that we take their presence for granted. But, how are the fine threads of polydimethylsiloxane (PDMS) woven into sturdy silicone rubbers? Depending on the desired material properties, organosilicon polymers can be cross‐linked through most diverse mechanisms, from the “classic” radical‐based methods to the modern metal‐free or enzymatic approaches, always based on catalysis. These technologies, even the older ones, are still subject of intense research and inspiration for the development of fascinating new catalytic methodologies and materials. More information can be found in the Focus Review by Esteban Mejía et al. on page 1180 in Issue 11, 2017 (DOI: 10.1002/asia.201700304).

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