AT-methylmorpholine

Reactions have been carried out adjacent to the epoxide moiety in order to examine the effects, if any, that the epoxide has on subsequent reactions with respect to the regio- and stereochemical outcome. Dihydroxylation using osmium tetraoxide and Sharpless asymmetric dihydroxylation reactions have been extensively studied using substrates 29 and 31. Initial studies centred on the standard dihydroxylation conditions using AT-methylmorpholine-AT-oxide and catalytic osmium tetraoxide. The diastereomeric ratios were at best 3 2 for 29 and 2 1 for 31, indicating that the epoxide unit had very little influence on the stereochemical outcome of the reaction. This observation was not unexpected, since the epoxide moiety poses minimal steric demands (Scheme 21). 

The reaction using 11a as a substrate in the presence of several oxides as additives revealed that addition of tributylphosphine oxide, hexamethylphos-phoric triamide, and dimethyl sulfoxide all accelerate the reaction considerably. Furthermore, when about 10 molar amounts of AT-methylmorpholine AT-oxide (NMO) is added to the alkyne-cobalt complex 12b in THF,the reaction proceeds even at room temperature and cyclopentenone 13 b is obtained in 37% yield accompanied by another rearranged product, the methylenecyclobutanone 35, obtained in 23% yield as a mixture of ( )-and (Z)-isomers (Scheme 14). These facts indicate that dissociation of the carbonyl ligand of the alkyne-cobalt complex 12 is the rate-determining step in this rearrangement. This is also supported by the fact that under a CO atmosphere in refluxing THF the reaction is completely suppressed. 

TPAP (Pr4N"Ru04 ) is an air-stable oxidant for primary and secondary alcohols. It is commercially available and environmentally friendly since it is used in catalytic amounts in the presence of a co-oxidant such as AT-methylmorpholine-iV-oxide (NMO). 

Still due to the strong cohesion of this material, cellulose is insoluble in most organic solvents. Only some highly polar mixtures such as A, A -dimethylacetamide/ lithium chloride, AT-methylmorpholine/water, Cu(OH)2/ammonia, trifiuoroacetic acid/alkyl chloride, calcium thiocyanate/water, and ammonium thiocyanate/liquid ammonia are solvents of cellulose. In spite of the potential applications of such solutions, they are exploited relatively little due to their high cost. 

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