Dibutyltin oxide catalyst

Two earlier studies (Kenar et al., 2005 Knothe et al., 2000) were conducted on the effects of compounds synthesized with hydrocarbon tail-group structures resembling those of FAME with attached bulky moieties. These studies examined novel fatty diesters made from reaction of diols with acids and diacids with 2-octanol in toluene solvent with p-toluene sulfonic acid catalyst and branched-chain esters of carbonic acid (carbonates) synthesized in nonyl alcohol with n-dibutyltin oxide catalyst. None of the synthesized compounds demonstrated effectiveness in decreasing CP or PP of SME. 

TSE at 165°C optionally with on-line microwave treatment to effect transreaction, or TSE at 165-200°C / morphology development along screw axis vs. processing conditions in three different extruders / rheology / TGA-GC / selective solvent extraction / SEM / mechanical properties / use to fix morphology of EVAc + E-MAc dispersed phase in PP matrix / dibutyltin oxide catalyst (0-4)... 

PC/HDPE/EAA/dibutyltin oxide catalyst Haake mixer/SEM/DSC/rheology/ formation of PC-EAA copolymer Yin et al. 2007... 

PBT (70)/EVAc (10-20)/PE (10-20) Internal mixer at 230 C/SEM/dibutyltin oxide catalyst (0-4 %)/encapsulation of PE dispersed phase by PBT-EVAc copolymer Legros et al. 1997... 

PBT (50-10)/EVAc (9 % or 28 % VAc) (50-90) Internal mixer at 230 °C/selective solvent extraction/NMR/FTIR/SEM/model reactions/dibutyltin oxide catalyst (0-1 %)/blends optionally -1- PE Pesneau et al. 1997... 

PETG (90-80)/EVAc (10-20) Internal mixer at 210 °C/SEM/NMR model study/rheology/DMA/interfacial tension measurements by breaking thread method/dibutyltin oxide catalyst (0-1 %) Lacroix et al. 1996a, b... 

Hu and Lambla (1995) have blended EMAc (90-65 parts) with monohydroxy-terminated PS (10-35 parts) in an internal mixer at 180-220 °C in the presence of dibutyltin dilaurate or dibutyltin oxide catalyst. A compatibilizing copolymer arises from transesterification between pendent ester groups of EMAc and terminal hydroxy groups of PS. The effects oti blend properties of PS molecular weight were reported. The effects of processing conditions and addition of solvent on conversimi kinetics were studied. 

Polyhydric alcohol mercaptoalkanoate esters are prepared by reaction of the appropriate alcohols and thioester using -toluenesulfonic acid catalyst under nitrogen and subsequent heating (16,17). Organotin mercapto esters are similarly produced by reaction of the esters with dibutyltin oxide (18). Pentaerythritol can be oxidized to 2,2-bis(hydroxymethyl)hydracryhc acid [2831-90-5] C H qO, ... 

Chemical Properties. Trimethylpentanediol, with a primary and a secondary hydroxyl group, enters into reactions characteristic of other glycols. It reacts readily with various carboxyUc acids and diacids to form esters, diesters, and polyesters (40). Some organometaUic catalysts have proven satisfactory for these reactions, the most versatile being dibutyltin oxide. Several weak bases such as triethanolamine, potassium acetate, lithium acetate, and borax are effective as stabilizers for the glycol during synthesis (41). 

Organotin compounds such as monobutyltin oxide, the main substance used, accounting for 70% of consumption, dibutyltin oxide, monooctyltin oxide, and dioctyltin oxide are used in certain esterification and transesterification reactions, at concentrations between 0.001% and 0.5% by weight. They are used in the production of substances such as phthalates, polyesters, alkyd resins, fatty acid esters, and adipates and in trans-esterifications. These substances are in turn used as plasticizers, synthetic lubricants, and coatings. Organo-tins are used as catalysts to reduce the formation of unwanted by-products and also provide the required colour properties (ETICA, 2002). 

Carbamates have been prepared by heating ethyl carbamate with a higherboiling alcohol in the presence or absence of catalysts [31-33], Aluminum iso-propoxide has been reported [34] to be an excellent catalyst for the interchange reaction between ethyl carbamate and benzyl alcohol. The interchange reaction is also effective for /V-alkyl carbamates as well as unsubstituted carbamates [35]. This catalyst is effective in preparing mono- and dicarbamates in excellent yields from primary and secondary alcohols and diols. Other effective catalysts are dibutyltin dilaurate [36], dibutyltin oxide [37], sulfuric acid or p-toluenesulfonic acid [31], and sodium metal (reacts with alcohols to give the alkoxide catalyst) [33]. 

In the synthesis of carbamates, R NH.C02R, from A iV -dialkylureas, (R NH)2CO, and dialkyl carbonates, (RO)2CO, dibutyltin oxide, Bu2SnO, acted as an efficient catalyst. The proposed mechanism (Scheme 13) involves addition of the dialkyl carbonate to Bu2SnO to give an adduct (43), which is attacked by the urea to yield a new tin complex (44) and one molecule of carbamate. Attack by dialkyl carbonate upon this complex (44) yields a further molecule of carbamate and regenerates the original tin complex (43), which can continue the catalytic cycle.42... 

To achieve better conversions in less time, several common acid, base and transition metal catalysts were screened for the purpose of lowering the reaction temperature in the glycerin process. The results for each category of catalyst are represented in Figure 6.6. All reactions were performed with crude (neutralized) glycerin. The activity of the catalysts is compared based on a standard reaction time at 180 °C for 4 hours and normalized based on equal equivalents of metal content per moles of acid. The organo-metal catalysts, tetrabutyltitanate (TBT), dibutyltin oxide (DBTO), and tinoxalate (SnOx) were the most efficient catalysts. Overall, while tin compounds are effective catalysts, they can be problematic because of their potential toxicity, unless they can be removed from the product in a cost effective manner. 

In general reaction of an alcohol with the appropriate anhydride or acid chloride in pyridine at 0-20 JC is sufficient. In the case of tertiary alcohols, acylation is very slow in which case a catalytic amount of 4-dimethylaminopyridine (DMAP) can be added to speed up the reaction by a factor of 10,000. Reaction of polyols with acyl chlorides (1.2 equiv) in the presence of hindered bases (2.0equiv) such as 2,4,6-collidine, diisopropylethylamine or 1,2,2,6,6-penta-methylpiperidine in dichloromethane at -78 °C leads to selective acylation of a primary alcohol. Primary alcohols can also be acylated selectively with isopro-penyl acetate or acetic anhydride in the presence of a catalytic amount of 1,3-dichlorotetrabutyldistannoxane 325.1 [Scheme 4.325].602 The catalyst 325.1 is available commercially or can be easily prepared by simply mixing dibutyltin oxide and dibutyldichlorostannane. No aqueous workup is necessary since the catalyst can be removed by simple chromatography. 

The most important hydrogen bond donating group in directed epoxidations is the hydroxy group. For allylic or homoallylic alcohols, peracids or tert-butyl hydroperoxide/vanadylbis[2,4-pentanedionate] (see Houben-Weyl, Vol. IV/la, p 231) are generally the most efficient reagent systems less common catalysts are tri-te/ f-butoxyaluminum, dibutyltin oxide, and molybdenum- and titanium-based systems (see Houben-Weyl, Vol. IV/la, p 227, Vol. E13/2, p 1176). The two classes of reactions show distinct differences in their stereoselectivity patterns. 

It has also been found that p-toluenesulfonation reactions can be conducted with catalytic dibutyltin oxide if a stoichiometric amount of base, normally triethylamine, is present. These conditions can also be used for acylation of l-phenyl-l,2-ethanediol with dibutyltin dialkoxides as catalysts and is also effective in the acylation of glycerophosphoryl choline, but only when 2-propanol is the solvent (Scheme 5.1.3). ... 

Microwave-assisted preparation of aryltetrazoleboronate esters 178 and 2,4-disubstituted-3-(5-tetrazolyl)pyridines 180 were obtained, respectively, from benzonitriles 177 <04OL3265> and nicotinonitriles 179 <04TL2571> with trimethylsilyl azide and dibutyltin oxide. Tetrabutylammonium fluoride was an efficient catalyst for the [3 + 2] cycloaddition reaction of nitriles with trimethylsilyl azide under solvent-free conditions <04JOC2896>. 1-Substituted tetrazoles 182 were synthesized by a [3+2] cycloaddition between isocyanides 181 and trimethylsilyl azide in the presence of hydrochloric acid in methanol <04TL9435>. 

Immiscible polyacrylates have been compatibilized through transesterification between pendent ester groups on one polyacrylate with pendent ester groups on another polyacrylate. Selected examples are listed in Table 5.38. Dibutyltin oxide was used as transesterification catalyst. 

More recently, Caddick et al. [43] studied the selective benzoylation of primary hydroxyl groups using dibutyltin oxide as a catalyst and triethylamine as the base. These experiments again show that the stoichiometry and the mode of heating have a significant effect on the selectivity of the reaction. 

The tetrazole functional group is of particular interest in medicinal chemistry, because of its potential role as a bioisostere of the carboxyl group. In this context, Schulz et al. have demonstrated the synthetic utility of the cyano group of arylni-trile boronates as a source of tetrazole derivatives under microwave conditions. The reaction is conducted with azidotrimethylsilane and dibutyltin oxide as catalyst to provide aryltetrazole boronates in yields ranging from 60 to 93% [56]. In the same manner, microwaves may assist successful conversion of sterically hindered nitriles into tetrazoles [57]. 

Organotin compounds a series of toxic alkyl tin compounds, such as butyl tin chloride and dibutyltin oxide used as plastic stabilizers and catalysts. 

It is also possible to regioselectively mono-O-tosylate various nonprotected hydroxyl functionalities, as illustrated in Scheme 1. This method employs a preliminary activation of a glycopy-ranoside with Dibutyltin Oxide and usually requires the use of a basic catalyst such as 4-Dimethylaminopyridine (DMAP) in conjunction with tosyl chloride. Regioselectivity differs markedly from acylation reactions and is thought to be a function of changes... 

The regioselective 2 -0-tosylation of adenosine with tosyl chloride has been accomplished using 10-20 mol% of dibutyltin dichloride as a catalyst (eq 45). Dibutylchlorotin hydroxide, dibutyltin oxide, bis(dibutylchlorotin) oxide, and tributyltin chloride are also effective catalysts for this reaction and the method has also been used for the ditosylation of several methyl glycosides. 

Ammonia Dibutyltin maleate Dibutyltin oxide Fluorosulfonic acid Phosphine Sodium ethylate Sodium hydride Tetrabutyl titanate Tetraisopropyl titanate p-Toluene sulfonic acid Zirconium butoxide catalyst, condensation reactions Dibutyltin diacetate Piperidine catalyst, conductive polymers Iron (III) toluenesulfonate catalyst, conversion of acetylene to acetaldehyde Mercury sulfate (ic) catalyst, copolymerization Di butyl ether catalyst, cracking Zeolite synthetic... 

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