Di-n-butyltin oxide (DBTO)

Abstract

(A) The starting diol was activated by DBTO and then, without isolation of the tin intermediate, treated with an electrophilic reagent2 (e.g. bromoglycoside,7 BnBr, allylBr, BzCl,8 TsCl, or t-BuMe2SiCl), to afford the monosubstituted product. This monosubstitution is regioselective: in most cases only one derivative is isolated. (B) The original work of David and Thieffry showed that regioselective oxidations of the stannylene by bromine formed an α- or β-hydroxy ketone.8 It was later demonstrated that N-bromosuccin-imide (NBS)9 and 1,3-dibromo-5,5-dimethylhydantoin10 can replace Br2 in this reaction. (C) Bu2SnO was used as a catalytic, neutral and mild agent in the preparation of nitriles from the corresponding thioamide or primary alkyl or aryl amides under microwave irradiation or reflux.11 (D) Di-n-butyltin oxide was used to mediate the cycloaddition of trimethylsilyl azide to 4′-methyl-2-biphenylcarbonitrile to give 5-substituted tetrazole in good yield. This tetrazole subunit is important in certain angiotensin II inhibitors.12 (E) The dehydrative condensation of 1,2-aminoalcohols with carbon dioxide (5 MPa) has been achieved in N-methylpyrrolidone (NMP) with Bu2SnO (10 mol%), and 2-oxazolidinones were obtained in 53-94% yield. These are useful intermediates for the synthesis of many target molecules, including polymers, agricultural chemicals, and biologically active compounds.13 (F) Diisopropyl L-tartrate was converted to its stannylene acetal and the tin intermediate was directly treated with isothiocyanate. The resulting unstable cyclic N-benzoyl iminocarbonate was then immediately treated with a bromide nucleophile (Bu 4NBr). The desired N-benzoyloxazolidin-2-one was obtained in 81% overall yield. This method allows the conversion of syn-diols to syn-amino alcohols.14 (G) Steliou and Hanessian reported a useful approach towards the preparation of lactones and lactams, including several macrocyclic types (macrolides), directly from ω-hydroxy and ω-amino carboxylic acids, by using catalytic amounts of DBTO under neutral conditions and without resorting to high dilution techniques.15.