Potassium carbonate, functional group

Alcoholic potassium hydroxide or sodium hydroxide are normally used to convert the halohydrins to oxiranes. Other bases have also been employed to effect ring closure in the presence of labile functional groups such as a-ketols, e.g., potassium acetate in ethanol, potassium acetate in acetone or potassium carbonate in methanol.However, weaker bases can lead to solvolytic side reactions. Ring closure under neutral conditions employing potassiunT fluoride in dimethyl sulfoxide, dimethylformamide or A-methyl-pyrrolidone has been reported in the patent literature. 

Many types of functional groups are tolerated in a Suzuki reaction, and the yields are often good to very good. The presence of a base, e.g. sodium hydroxide or sodium/potassium carbonate, is essential for this reaction. The base is likely to be involved in more than one step of the catalytic cycle, at least in the transmetal-lation step. Proper choice of the base is important in order to obtain good results." In contrast to the Heck reaction and the Stille reaction, the Suzuki reaction does not work under neutral conditions. 

Cyclization of substituted phenylacetylene sequences afforded functionalized macrocycles that were amenable to subsequent manipulation. For example, transesterification of 42 with octanol in the presence of 18-crown-6 ether and potassium carbonate gave the corresponding ester in 85% yield (Scheme 13). The ester functionalities could be reduced by DIBALH to give the hydroxymethyl-substituted macrocycle (43) in 61 % yield. The low yield of this particular transformation is attributed to mechanical losses during purification, due to the highly polar nature of the product. Macrocycle 43 could then be treated with alkyl bromides to give a group of benzyl ether derivatized PAMs. 

The NH groups of sulfonamide functions are also readily alkylated. The 1,2,6-thiadiazine dioxide (74) gives the 2-methyl derivative on treatment with iodomethane in acetone in the presence of potassium carbonate <65CI(L)182). The 1,3,2,4,6-dithiatriazine (75) forms a silver salt (64MI22800), and reaction of the salt with iodomethane gives the expected TV-methyl compound. 

In the course of investigations on allylic and acetylene-allene rearrangements of 3-substituted quinuclidines, it was found that by oxidation and ozonolysis of compounds with functional groups at positions allylic to the double bond, not only the double bonds but also the adjacent carbon-carbon bonds are broken. For example, in the oxidation of 3-hydroxy-3-vinylquinuclidine (119), with potassium permanganate under mild conditions, and in its ozonolysis, qui-nuclidin-3-one (2) is formed along with 3-hydroxy quinuclidine-3-carboxylic acid.161 The positions of double bonds in such systems can be firmly established by NMR spectroscopy, but not by oxidative methods.101... 

Partial sulfation of sucrose can be also achieved. Thus, reaction of sucrose with SOCl2 afforded a mixture of diastereoisomeric cyclic sulfites, which are readily oxidized to sulfates. Treatment of these latter compounds with fatty acids and potassium carbonate provided the ester with the sulfate group placed on 0-4. The sulfate function can be also introduced at other positions as demonstrated by reaction of 6-<9-acyl sucrose and l -O-acylsucrose with S03-pyridine (Scheme ll).150... 

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