Organotin catalysts

In more recent years, molded flexible foam products are becoming more popular. The bulk of the molded flexible urethane foam is employed in the transportation industry, where it is highly suitable for the manufacture of seat cushions, back cushions, and bucket-seat padding. TDI prepolymers were used in flexible foam mol ding ia conjunction with polyether polyols. The introduction of organotin catalysts and efficient siHcone surfactants faciHtates one-shot foam mol ding, which is the most economical production method. 

Organotins are used as catalysts in room temperature vulcanization via a condensation reaction. Dibutyltin laurate is the most commonly used organotin catalyst for this application. It is typically used at between 0.01% and 0.1% by weight. Between 50 and 100 tonnes of organotin catalysts were used in the production of silicones in the EU in 2000 (ETICA, 2002). 

Typical uses for silicones that employ organotin catalysts include ... 

Organotin catalysts are used in a wide variety of urethane applications, aiding formation of the urethane bond in applications such as ... 

Schreiber and co-workers (436) prepared a library calculated to contain 2.18 million polycyclic compounds through the 1,3-dipolar cycloaddition of a number of nitrones with alkenes supported on TentaGel S NH2 resin (Scheme 1.83). (—)-Shikimic acid was converted into the polymer bound epoxycyclohexenol carboxylic acid 376 (or its enantiomer), coupled to the resin via a photolabile linker developed by Geysen and co-workers (437) to allow release of the products from the resin in the presence of live cells by ultraviolet (UV)-irradiation. A range of iodoaromatic nitrones (377) was then reacted with the ot,p-unsaturation of the polymer-bound amide in the presence of an organotin catalyst, using the tandem esterification/ dipolar cycloaddition methodology developed by Tamura et al. (84,85) Simultaneous cyclization by PyBrop-mediated condensation of the acid with the alcohol... 

Organotin catalysts have been tested as well with good results for the transesterification of oils. Unfortunately, these compounds are very soluble in fatty acid esters, complicating their separation and adding to environmental concerns. ... 

Scheme 14. Kinetic resolution of 1,2-diols using organotin catalyst 59...

The 1,1-binaphthyl ring system is a key component of a number of chiral ligands that have been used as catalysts for asymmetric synthesis <1992S503>. Chemo- and stereoselective (. )-stannepin-catalyzed monobenzoylation of terminal 1,2-diols 312 afforded ( -enantiomer-enriched 2-benzoylated diols 313 in moderate selectivity. Only a trace of 1-benzoylated diols 314 was observed (Equation 55). Thus, the method was successfully applied to kinetic resolution of racemic 1-phenyl-1,2-ethanol using a chiral organotin catalyst <2000JOC996>. 

It can be observed that the non-oxidative stability of all systems increases as a function of age time under both environments. Each system exhibits an initial rapid increase in thermal stability over the first 24 hours of aging followed by a more gradual increase over the remainder of the study. It is reasonable to assume that these initial increases are in part due to the loss of pro-degradants such as 2-ethylhexanoic acid and other reaction by-products such as propanol from the elastomer system (2-ethylhexanoic acid is a hydrolysis product of the active organotin catalyst, tin(II) 2-ethylhexanoate and propanol is formed during the TPOS/silanol condensation reaction). 

Reduction. PMHS and an organotin catalyst, bis(dibutylacetoxytin)oxide (UBATO), in a refluxing protic solvent (usually ethanol) specifically reduce aldehydes and ketones to alcohols in high yield. One equivalent of siloxane hydride is required per mole of substrate with the solvent contributing a proton ... 

Addition polymerisation of nitriles using organotin catalysts like tributyltin methoxide at 333-403 K > ). 

Organotin compounds are effective catalysts for the isocyanate-hydroxyl reaction. Tin catalysts have a slight odour, and low amounts are required to achieve a high reaction rate. Examples of organotin catalysts are stannous octoate, stannous oleate, dibutyltin dilaurate and dibutyltin di-2-ethylhexoate. They are often used in conjunction with small concentrations of antioxidants such as tertiary-butyl catechol resorcinol and tartaric acid. 

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