Cyclic-distannoxane

Shanzer and Mayer-Shochet have utilized disubstituted stannoxanes as covalent templates for the formation of tetralactones. In this procedure, a dialkyl stannoxane is condensed with a glycol to form a cyclic-distannoxane as illustrated below. In a typical preparation, the distannoxane (i) was dissolved in CCI4 (ca. 0.04 At) at reflux and sebacoyl chloride (2 eq) was added dropwise at reflux. After heating for 20 h, the solution was concentrated to a solid. Chromatography afforded the tetralactone in 30% yield. ... 

The borohydride reduction of BrRe(CO)s in the presence of PPhMe2 and HSnBu3 forms (CO)4Re(PMe2Ph)H. The tin hydride adduct could not be isolated, but upon water work-up a cyclic dirhenium distannoxane 86 was isolated264. 

Acetalization. Distannoxanes of this type are useful catalysts for esterification (15,89) because they can activate both alcohols and carbonyl groups on the same template. Of a number of stannoxanes, 1 is found to be the most efficient catalyst for acetalization of aldehydes and ketones with ethylene glycol. In particular it can promote acetalization of cyclic a,)3-enones, which u,sually proceeds in low yield. 

Thioethers. A mixture of diphenyl sulfoxide and HMPA treated with SmL in THF under N2 at 20 for 1 min, diluted with hexane, and filtered through Florisil - diphenyl sulfide. Y 94%. The method can also be used for the rapid deoxygenation of sulfones (which may be viewed as protected thioethers). E Diphenyl sulfone under the same conditions - diphenyl sulfide. Y 93%. Esters remained intact and, in some cases, sulfoxides were selectively reduced in the presence of ketones. F.e. inch formation of cyclic tert. amines from N-oxides, tert. phosphines from phosphine oxides, and distannanes from distannoxanes, s. Y. Handa et al., J. Chem. Soc. Chem. Commun. 1989, 298-9 review of synthesis and use of polysulfoxides s. V.A. Nikonov, G.V. Leplyanin, Sulfur Reports 9, 1-23 (1989). 

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