Epoxides, amino functionalization using

Numerous carbacyclic, or sulfur-containing, analogues of mono- and difluoronucleo-sides have been synthesized as potential antivirals. In the carbacyclic series, the starting compound is hydroxymethylcyclopentene oxide. Rearrangement of this oxirane creates a new unsaturation that can be oxidized further into another epoxide. An amino function can then be introduced on the 4 position and can be used to build the base (Figure 6.13). 

The principle of miniemulsion polymerization to polyadditions of epoxyresins was successfully transferred to mixtures of different epoxides with varying diamines, dithiols, or diols which were heated to 60°C to form the respective polymers [125]. The requirement for the formulation of miniemulsions is that both components of the polyaddition reaction show a relatively low water solubility, at least one of them even below 10 5 g l1. The diepoxide bisphenol-A-diglycidylether was successfully used as epoxy component. In order to vary the obtained polymeric structure, tri- and tetra-functionalized epoxides were also used. As amino components a NH2 terminated poly(propylene oxide) with Mw=2032 g mol1, 4,4 -diaminobibenzyl, 1,12-diaminododecane, and 4,4 -di-aminodicyclohexylmethane were applied. As other addition components beside amine, 1,6-hexanedithiol and Bisphenol A were used. The hydrophobic compo-... 

Oxidation and Bromination of Other Functional Groups. Selective oxidation of alcohols may be achieved using a 1 1 complex of NBS and tetrabutylammonium iodide, whereas 1,2-diols are converted into 1,2-diketones using iV-bromosuccini-mide. An efficient and mild procedure has been reported for the preparation of benzoic acids via oxidation of aromatic carbonyl compounds by employing NBS and mercuric acetate. Selective and efficient oxidation of sulfides to sulfoxides has been achieved with NBS in the presence of /3-cyclodextrin in water. Epoxides and aziridines are conveniently oxidized to the corresponding a-hydroxy or Q -amino ketones using cerium(IV) ammonium nitrate and NBS. ... 

When a better leaving group than LiNSC R (e.g., OMe) is present at the a-position, retention of the potentially useful sulfonamide moiety occurs (e. g., in the conversion of aziridine 271 into the highly functionalized amino ether 272 Scheme 5.69) [98]. It should be noted that the analogous chemistry with epoxides of allylic diethers failed this could again (see above) be possibly due to the higher pKa of the epoxide proton relative to the aziridine proton. 

Terashima et al. 231) reported an asymmetric halolactonization reaction. This highly stereoselective reaction permits the synthesis of intermediates for the preparation of chiral a,a-disubstituted a-hydroxycarboxylic acids (227)231c), a-hydroxyketones (228) 231c), functionalized epoxides (229) 231d,e) and natural products 231h,j). Only amino acids have so far been used as a source of the chiral information in the asymmetric halolactonization reaction. Again, the best results have been obtained by using cyclic imino acid enantiomers, namely proline. 

There are many electrophiles which not only terminate living polymer chains but also produce end-group substitution. For example, macromolecules with hydroxyl, carboxyl, thiol, or chlorine termini can be prepared by reacting living polymers with such compounds as epoxides, aldehydes, ketones, carbon dioxide, anhydrides, cyclic sulfides, disulfides, or chlorine (15-23). However, primary and secondary amino-substituted polymers are not available by terminations with 1° or 2° amines because living polymers react with such functionalities (1.). Yet, tert-amines can be introduced to chain ends by use of -N-N-di-methylamino-benzaldehyde as the terminating agent (24). 

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