Potassium methoxide-dimethyl sulfoxide

Similarly sodium methoxide (NaOCHj) is a suitable base and is used m methyl alco hoi Potassium hydroxide m ethyl alcohol is another base-solvent combination often employed m the dehydrohalogenation of alkyl halides Potassium tert butoxide [K0C(CH3)3] is the preferred base when the alkyl halide is primary it is used m either tert butyl alcohol or dimethyl sulfoxide as solvent... 

Rates of isotopic H/D exchange and racemization of optically active 2-methyl-3-propionitrile in the presence of potassium methoxide can be increased by a factor of 5 10 on going from pure methanol (sr = 32.7) to dimethyl sulfoxide (sr = 46.5) [31, 231, 304]. 

Wrrno reaction, bases n-Butyllithium (see Potassium t-butoxide). Lithium ethoxide. Potassium t-butoxide. Sodium bistrimethylsilylamide. Sodium ethoxide (see Potassium t-butoxide). Sodium bydride-Dimethyl sulfoxide [see DMSO-derived reagent (a)]. Sodium methoxide. 

As noted in Section 5.2.2.1.2.3., the reaction of 1,1-dichlorocyclopropanes with alkoxides does not give the ordinary alkenyl(alkylidene)cyclopropane products when the side chains of the substrate cannot accommodate the double bonds in these positions. Instead, the usual course of the reaction in these cases is double elimination followed by addition of alkoxide to the cyclopropene double bond. Thus, c -l,l-dichloro-2,3-dimethylcyclopropane (1), when treated with potassium isopropoxide in dimethyl sulfoxide at 30 °C, gave a mixture of two isomeric ethers, l-isopropoxy-l-methyl-2-methylenecyclopropane (2) and tra 5-l-isopropoxy-2-methyl-3-methylenecyclopropane (3), in 31% and 35% yield, respectively. When 1 was reacted with potassium rcrt-butoxide in the presence of sodium methoxide the corresponding methyl ethers 4 and 5 were obtained in yields of 35% and 17%. ... 

When isomerization of the double bond of the intermediate cyclopropene into the exo methylene position is energetically unfavored, double elimination followed by double addition of base can occur. Thus, reaction of (cu/tra i )-l,l-dichloro-2-methyl-3-vinylcyclopropane (9) with potassium terf-butoxide plus methoxide in dimethyl sulfoxide gave a mixture of cis- and trans-, -dimethoxy-2-methyl-3-vinylcyclopropane (10). Both double bonds formed via elimination appear to be conjugated with the vinyl group and do not migrate to the exo position. The similar reaction of l,l-dichloro-2-[( )-propenyl]cyclopropane (11) gave a small amount of 1-/ert-butoxy-2-(prop-2-enylidene)cyclopropane (13) in addition to products of double addition. Without added methoxide, 13 was the only product isolated. ... 

The cation of the metal /m.-butoxide strongly influences the rates but not the products of alkene isomerizations. For isomerization of 1-butene in dimethyl sulfoxide solutions at 55°C, the relative catalytic effectiveness of alkali / r/,-butoxides increase in the order NaOBu 1.0 KOBu 116 CsOBu 284, RbOBu, 447. This is probably attributable to the fact that large cations are more weakly bonded to the alkoxide ion than smaller cations . The anion of the alkoxide also strongly influences its catalytic effectiveness. Potassium tert.-buioxide is 126 times as effective a catalyst for 1-butene isomerization as potassium methoxide in dimethyl sulfoxide at 55°C . The rate of potassium / r/.-butoxide-catalyzed 1-butene isomerization in DMSO is strongly retarded by addition of / r/.-butyl alcohol to the solvent, probably due to hydrogen bonding between the alkoxide and the alcohoP . 

DlKETONES Iodine-Dimethyl sulfoxide. Iron carbonyl. Phenyl ben-zenethiosulfonate. Potassium ferri-cyanide. Sodium methoxide. Thionyl chloride. 

A high concentration of a strong base in a relatively nonpolar solvent is used to carry out the dehydrohalogenation reaction. Such combinations as sodium methoxide in methanol, sodium ethoxide in ethanol, potassium isopropoxide in isopropanol, and potassium ferf-butoxide in fcrf-butanol or dimethyl sulfoxide (DMSO) are often used. 

Conventional sodium-, potassium-, or cesium-based initiators in an ether solvent, such as tetrahydrofuran (THF), or in polar media, such as dimethyl sulfoxide (DMSO) or hexamethylphosphortriamide (HMPTA), afford a controlled polymerization allowing the synthesis of end-functional PEO. The chemical mechanism of EO polymerization is relatively simple in view of the well-known stability of alkoxide growing chains toward termination and transfer reactions. The standard method for producing low-MW PEO (PEG) is based on controlled addition of EO to water or alcohols in the presence of alkaline catalysts. The kinetics of EO polymerization, initiated by sodium methoxide in the presence of a small excess of methanol in dioxane involves a contact ion pair of the initiator. The reaction rate in the case of alkaU/alkoxide initiation alone is slow, but increases with the concentration of excess alkanol. Within the variation of excess alkanol concentration, the MW distribution (MWD) of the polymers produced remains narrow. Formation of an alkanol-alkoxide complex as an effective initiator is envisaged. The complex formation loosens the bonding of the tight alkoxide ion pair. 

---