Dibutyltin dimethoxide

On the basis of molecular weight measurements and infrared spectroscopy it has been suggested (61, 62) that dibutyltin dimethoxide, di-n-propoxide, and di-n-butoxide are associated into dimers in the pure liquid state, [5a], whilst the di-t-butoxide is monomeric, [5b]. 

The chemical shifts clearly enable one to differentiate between the two species [5a] and [5b] dibutyltin dimethoxide, diethoxide, di-n-propoxide, and di-n-butoxide all show low-frequency shifts (—159 to —165 ppm), whereas the di-t-butoxide and di-s-butoxide, in which the... 

The use of performed dibutyltin dimethoxide is advantageous12-14 reactions of diols are complete in 5-15 min in benzene at reflux. This technique avoids the problems with working in methanol just mentioned, and gives better yields. The preparation of stannylene acetals is also accelerated by microwave irradiation,15 and selective reactions can be performed, albeit in low yields, on some diols and polyols by microwave irradiation in the presence of a catalytic amount of dibutyltin oxide.16,17... 

Dibutyltin oxide, dibutyltin dimethoxide, and hexabutyldistannoxane are commercially available. Di-f-butyltin dichloride is commercially available, but reactions of di-f-butylstannylene acetals are often very slow. In certain cases, there are advantages in using bulkier tin oxides or tin oxides that are sterically restricted, such as cyclic tin oxides.19,20 Non-commercial dialkyltin oxides may be prepared conveniently by the reaction of dialkyldiphenyltin with chloroacetic acid followed by sodium hydroxide.21 This procedure works well for the preparation of stannacycloalkanes as well as bulky dialkyltin oxides. 

Under similar conditions, dibutyltin oxide reacts with dimethyl carbonate to give the distannoxane (MeO)Bu2SnOSnBu2(OMe), but dibutyltin dimethoxide can also be prepared from the reaction of dibutyltin oxide with methanol and dimethyl carbonate under elevated temperature and pressure.6-7... 

For small-scale manipulations, and in those cases where prolonged heating would affect the substrate, the use of the commercially available dibutyltin dimethoxide in place of the less reactive dibutyltin oxide, is advisable [59] (Scheme 3). 

The diol 19 (1 mmol) was taken up in dry benzene (or toluene) (40 mL) and the dibutyltin dimethoxide (1.1 mmol) added in one portion. Benzene (20 mL) was then removed by distillation and the tin acetal solution allowed to cool to r.t.To the solution was added benzyl bromide (1.1 mmol) and tetra-N-butylammonium iodide (1.5 mmol) and the temperature was then raised to 50 °C and maintained until the reaction was complete by TLC. The reaction mixture was quenched by the addition of water (10 mL) and standard worked-up. The crude was purified by flash chromatography on silica gel to give 20 (83%). 

Dibutyltin dimethoxide can also be employed for the selective alkylation and acylation of diols [91b,c]. 

Di-/er/-butyltin dichloride, see Sn-00159 Dibutyltin diethoxide, see Sn-00255 Dibutyltin dihydride, see Sn-00170 Di-/e r/-butyltin dihydroxide, see Sn-00169 Dibutyltin dimethoxide, see Sn-00208 Dibutyltin diphenoxide, see Sn-00353 >Dibutyltin oxide, see Sn-00162 Di-r rr-butyltin selenide, Sn-00165... 

Lepoittevin B, Pantoustier N, Devalckenaere M, Alexandre M, Kubies D, Calberg C, Jerome R, Dubois P (2002) Poly(E-caprolactone)/clay nanocomposites by in-situ intercalative polymerization catalyzed by dibutyltin dimethoxide. Macromolecules 35(22) 8385-8390... 

SAP-N (Me)3 (Cjgj/dibutyltin dimethoxide SAP-N (Me)2(EtOH)(Cjg)/dibutyltin dimethoxide SAP-N (MeXEtOHjjiCjgj/dibutyltin dimethoxide SAP-P+IMejjICjgj/dibutyltin dimethoxide LAP-N+(Me)3(Cjg)/dibutyltin dimethoxide LAP-N+(Me)2(EtOH)(Cig)/dibutyltin dimethoxide LAP-N+(Me)(EtOH)2(Cig)/dibutyltin dimethoxide LAP-P (Me)3(Cjg)/dibutyltin dimethoxide Intercalated... 

Vogdanis and Heitz used a variety of catalysts for the polymerization of EC, ranging from dibutyltin dimethoxide to butyllithium and found that the retention of CO2 decreased as the alkalinity of the catalyst increased. When a more basic catalyst was used, the resultant polymers contained 10-20 mol.% of EC units (reaction temperature was about 150 °C and reaction time was 72-98... 

The polymerization of e-CL was conducted in bulk at 100 °C by using dibutyltin dimethoxide as catalyst and in the presence of 25 to 50 wt% of (organo)clay. In order to collect PCL composites with high inorganic content, polymerizations were terminated at rather low monomer conversion. In agreement with observations made for PCL layered silicate nanocomposites prepared by the same technique and containing a small amount of clay (1-10 wt%), intercalated nanocomposites are recovered when the nanofiller is Cloisite Na or Cloisite 25A. In contrast, partially exfoliated/partially intercalated structures are formed in the presence of Cloisite 30B this situation results from the grafting of PCL chains on the clay surface as already discussed. Then, the desired PCL-based... 

Organotin ethers continue to be employed in selective alkylations. In a study of the Bu2SnO-mediated alkylation of lactosides 1 and 2 aimed at obtaining the 3 -0-ethers, the penta-benzyl ether 2 afforded better yields than the corresponding benzoate 1, and siniilar conditions have been employed for the regioselective benzylation of octyl P-D-galactopyianoside at 0-3 Dibutyltin dimethoxide has been used in place of dibutyltin oxide for selective alkylation of carbohydrate diols. ... 

Use of dibutyltin dimethoxide in place of dibutyltin oxide has been recommended for procedural simplicity and improved reproducibility in legioselective acylations, fcM example at 03 of diol 13. Moderate selectivity has been observed in the benzylation of thioglucoside derivative 14 and related compounds with benzyl bromide under phase transfer conditions. Opening of the known 2,3-carbonate 15 with ethanol or dodecanol gave the two expected 2- and 3-monoesters in nearly equal proportions.A new method for the selective diprotection of a-D-mannopyranosides involved opening of diorthoesters 16 which were formed in situ, as shown in Scheme 1. As only the 2,3-orthoesters opened regioselectively, the 2,4- and 2,6-dibenzoates 17 and 18, respectively. 

Kricheldorf H R and Langanke D (1999) Macrocycles 7. Cyclization of ohgo- and poly(ethyleneglycol)s with dibutyltin dimethoxide — a new approach to (super)macro-cycles, Macromol Chem Phys 200 1174-1182. 

Scheme of the reactor used for the ring-opening polymerisation of eCL initiated by dibutyltin dimethoxide in supercritical CO2. 

Kinetic profile of extraction of tin residues after ring-opening polymerisation in supercritical carbon dioxide initiated by dibutyltin dimethoxide... 

Supercritical carbon dioxide turns out to be a very efficient solvent for the exfoliation of lamellar nanoelays, particularly in the case of in situ polymerisation (Jerome et al, 2001). JCTome et al initiated the eCL polymerisation in supereritieal earbon dioxide by dibutyltin dimethoxide in the presence of montmoriUonite organomodified by the exchange of the Na counterions by... 

The polymerization appeared to be controlled by using catalyst/initiators such as dibutyltin dimethoxide and titanium butoxide. 

Similar results with respect to the initiation step were obtained with dibutyl magnesium [13], aluminum trialcoholates [14], dibutyltin dimethoxide [14], diethyl zinc [14], tin octoate and rare-earth metal compounds as initiators [15-22]. With these initiators, a coordination-insertion mechanism is active which, for some of the initiators, has been studied in detail [30, 31]. A special initiator with an aluminum alcoholate group is that of tetraphenylporphyrin aluminum this has an alkoxy group as the third ligand (RO—Al—TPP) at the aluminum, and is known as the Inoue catalyst [32]. This initiator is active for various monomers, and is therefore used for the preparation of block copolymers with one or two polycarbonate blocks. Initiation occurs by the nucleophiUc addition of RO—Al—TPP to the carbonyl group of the carbonate. 

---