Unique template effects of distannoxane catalysts in transesterification of diol esters

Ester interchange reactions catalyzed by tin compounds in reactive processing: NMR contribution via reactions with model compounds

“…Which mechanism may be plausibly proposed? To explain the catalytic efficiency of the dimeric distannoxane in alcoholysis of esters, Otera and Nozaki [6] assumed an exchange at the endo tin site (with Sn-X giving Sn-OR) and then coordination of the ester on the neighboring tin site.…”

“…For a long time, tin compounds proved to be excellent catalysts in interchange reactions involving esters: the catalytic efficiency of alkoxy trialkyl tin compounds in ester/alcohol interchange reaction was discovered in the 1970 by Pereyre et al [1], that of dibutyltin derivatives such as diacetate, dichloride, dioxide, sulfide in ester/alcohol reactions by Poller and Retout [2] and more recently Otera et al [3][4][5][6] showed the quite higher efficiency of R 4 Sn 2 X 2 O dimers. These distannoxanes (DS) are crystalline compounds and are obtained by partial hydrolysis-condensation of Bu 2 SnX 2 .…”

Organocatalysis: Fundamentals and Comparisons to Metal and Enzyme Catalysis

“…Hassner The zinc cluster Zn 4 (OCOCF 3 )O is an amphoteric compound (the metallic centers are Lewis acids and the oxygen centers are Lewis bases). This is also the case with distannoxane catalysts of type 4 ( Figure 6) [38][39][40][41]. Other oxometallic species catalyze nucleophilic acyl substitution reactions with protic nucleophiles.…”

“…Transesterification (Scheme 2), reactions producing esters by catalytical alcoholysis of other esters, also play an important role in the industry, for instance in the manufacture of glycerol esters in fat chemistry (e.g., biodiesel), the transesterification of dimethyl carbonate to diethyl carbonate, or the production of polyethylene terephthalate from dimethyl terephthalate. For these reactions, the usual catalysts are Brønsted mineral acids (H 3 PO 4 , H 2 SO 4 , HCl) [24][25][26], and organic acids such as MeSO 3 H and p-toluenesulfonic acid (TsOH) [27], alkoxides such as NaOR, KOR, ROMgBr [28][29][30][31][32], Lewis bases such as 4-dimethylaminopyridine (DMAP) [33,34], 1,8-diazabicyclo [5.4.0]undec-7-ene (DBU) [35], Lewis acids such as BX 3 [36], or AlCl 3 [37], amphoteric Catalysts 2016, 6, 128 5 of 65 compounds (compounds able to react either as acids or bases) such as Bu 3 SnOR [38][39][40][41], perfluorotin oxides [42], Al(OR) 3 [43,44], titanium oxides chlorides [45][46][47][48] or palladium oxides [49,50]. More recently, diaminocarbenes have been introduced as catalysts as well [51][52][53][54].…”

“…The adamantyl moiety of 38 enters the lyophilic cavity of one cyclodextrin, the leaving group (p-nitrophenolate) enters the other cyclodextrin unit, repelling water molecules [141]. The substrate is thus forced to approach the zinc pyridinecarboxaldoxime anion that adds (Scheme 19) onto its carboxylic moiety, generating an acyl-catalyst intermediate that is then hydrolyzed into p-nitrophenol (40) and the carboxylic product (39). Several applications of cyclodextrins as catalysts have been reported [142].…”