| dc.contributor.author | Kong, Xianqi. | en_US |
| dc.date.accessioned | 2014-10-21T12:36:22Z | |
| dc.date.available | 1994 | |
| dc.date.issued | 1994 | en_US |
| dc.identifier.other | AAINN93781 | en_US |
| dc.identifier.uri | http://hdl.handle.net/10222/55415 | |
| dc.description | The dibutylstannylene acetals of carbohydrate-derived primary-secondary 1,2-diols 4, 104, 105 and 06 were found to be oxidized regiospecifically to corresponding $\alpha$-hydroxyketone derivatives in much better yields (81% to 95%) by N-bromosuccinimide in chloroform solution at room temperature than had previously been done with bromine. One of the products, 3-deoxy-1,2-O-isopropylidene-$\alpha$- scD-erythro-hexofuranos-5-ulose (10), exists to about 20% in solution as a mixture of dimers. One of the dimers can be obtained as a solid and its structure was determined tentatively by a combination of NMR experiments and MM3 molecular mechanics calculations. | en_US |
| dc.description | The regioselectivity of p-toluenesulfonation of dialkylstannylene acetals obtained from carbohydrate-derived primary-secondary 1,2-diols (4, 66, 104-106, 113-117) was investigated. For a given diol, the regioselectivity depended on solvent, reaction temperature, and the alkyl groups on the tin atom. Selectivity at secondary position increased on changing the solvent from toluene to chloroform, and also increased on lowering reaction temperature (to 5$\sp\circ$C) with prolonged reaction time. Among all factors, the nature of the alkyl groups on tin atom had the greatest influence. When the R groups were changed from butyl to bigger groups such as isopropyl, selectivity for reaction at secondary oxygen atoms was improved. Reversed regioselectivity was achieved through using hexamethylenestannylene acetals. | en_US |
| dc.description | The causes of regioselectivity for dialkylstannylene acetal reactions were explored by means of $\sp{119}$Sn NMR spectral measurements and kinetic considerations. It was postulated that p-toluenesulfonation of dialkylstannylene acetals occurs through equilibrating dimers and the regioselectivity obtained was attributed to competition between dimer populations and rates of reaction at individual oxygen atoms. | en_US |
| dc.description | A general method for the preparation of pure dialkyltin oxides was developed which involved preparation of dialkyldiphenyltin derivatives and selective cleavage of the two phenyl groups with chloroacetic acid. | en_US |
| dc.description | Thesis (Ph.D.)--Dalhousie University (Canada), 1994. | en_US |
| dc.language | eng | en_US |
| dc.publisher | Dalhousie University | en_US |
| dc.publisher | | en_US |
| dc.subject | Chemistry, Organic. | en_US |
| dc.title | The effects of changing alkyl groups on the structures and selectivities of dialkylstannylene acetals. | en_US |
| dc.type | text | en_US |
| dc.contributor.degree | Ph.D. | en_US |
