2- Methyl-3-butyn

Acetylene is also protected as propargyl alcohol (300)[2H], which is depro-tected by hydrolysis with a base, or oxidation with MnOi and alkaline hydrolysis. Sometimes, propargyl alcohols are isomerized to enals. Propargyl alcohol (300) reacts with 3-chloropyridazine (301) and EtiNH to give 3-diethylami-noindolizine (303) in one step via the enal 302[2I2]. Similarly, propargyl alcohol reacts with 2-halopyridines and secondary amines. 2-Methyl-3-butyn-2-ol (304) is another masked acetylene, and is unmasked by treatment with KOH or NaOH in butanol[205,206,213-2l5] or in situ with a phase-transfer cata-lyst[2l6]. 

The carbonylation of 2-methyl-3-butyn-2-oI (50) in benzene gives teraconic anhydride (51). Fulgide (53) (a dimethylenesuccinic anhydride derivative), which is a photochromic compound, can be prepared by the carbonylation of 2,5-dimethyl-3-hexyne-2,5-diol (52)[21], The reaction proceeds under milder conditions when PdlOAc) is used as a catalyst in the presence of iodine [23],... 

Methylbutynol. 2-Methyl-3-butyn-2-ol [115-19-5] prepared by ethynylation of acetone, is the simplest of the tertiary ethynols, and serves as a prototype to illustrate their versatile reactions. There are three reactive sites, ie, hydroxyl group, triple bond, and acetylenic hydrogen. Although the triple bonds and acetylenic hydrogens behave similarly in methylbutynol and in propargyl alcohol, the reactivity of the hydroxyl groups is very different. 

Electrochemical addition of perfluorobutyl iodide to 2-methyl-3-butyn-2-ol followed by basic dehydroiodmation and thermal cleavage gives perfluorobutyl-acetylene in an overall yield of 83% [34] (equation 26)... 

It should be noted that a considerable acceleration of the reaction for low-reactive 4-iodopyrazoles is observed for substrates in which acceptor substituents at the pyrazole nitrogen atom additionally play the role of protecting group. Thus, it has been shown (88M253) that iV-phenacyl- and iV-p-tosyl-4-iodopyrazoles interact with phenylacetylene, 2-methyl-3-butyn-2-ol, and trimethylsilylacetylene at room temperature for 3-24 h in 70-95% yields (Scheme 56). 

In 1988, Linstrumelle and Huynh used an all-palladium route to construct PAM 4 [21]. Reaction of 1,2-dibromobenzene with 2-methyl-3-butyn-2-ol in triethylamine at 60 °C afforded the monosubstituted product in 63 % yield along with 3% of the disubstituted material (Scheme 6). Alcohol 15 was then treated with aqueous sodium hydroxide and tetrakis(triphenylphosphine)palladium-copper(I) iodide catalysts under phase-transfer conditions, generating the terminal phenylacetylene in situ, which cyclotrimerized in 36% yield. Although there was no mention of the formation of higher cyclooligomers, it is likely that this reaction did produce these larger species, as is typically seen in Stephens-Castro coupling reactions [22]. 

Using NaOH as the base, diarylacetylenes have been synthesized from either 2-methyl-3-butyn-2-ol [121] or trimethylsilylacetylene [122], In both cases, NaOH unmasked the protections after the first coupling reaction, revealing the additional terminal alkynyl functionality. Therefore, coupling the adduct 141, derived from 2-iodothiophene and 2-methyl-3-butyn-2-ol, with 2-iodobenzothiophene provided diarylacetylene 142 [121], Analogously, dithienylacetylene (143) was obtained when 2-iodothiophene and trimethylsilylacetylene were subjected to the same conditions [122],... 

See 4-Ethoxy-2-methyl-3-butyn-2-ol See other ACETYLENIC COMPOUNDS... 

A three-necked 500mL round-bottom flask was fitted with a reflux condenser, magnetic stir bar, stopper, and gas lnlet/outlet adapters. Under dry nitrogen the flask was charged with m-bromophenol (10.Og, 57.8 mmol), 2-methyl-3-butyn-2-ol (5.0g, 59.4 mmol) and 250 mL of distilled trlethylamlne resulting in a pale yellow solution. The mixture was heated at reflux for 15 min while... 

Methylethylldene)bis(4,l-phenyleneoxy-4,1-phenylene-sulf onyl-4,1-phenyleneoxy-3,1-phenylene)]bis[2-methyl-3-butyn-2-ol] IV... 

In previously employed end-capping schemes a palladium catalyst was used to directly connect a protected ethynyl group (2-methyl-3-butyn-2-ol) to a bulky intermediate. This procedure results in the entrapment of catalyst metals which must be laboriously removed from the final AT-product. If these metals are not removed, premature curing of the system occurs which narrows... 

The monomer/oligomer mixtures were used In the third step of the reaction sequence, the replacement of bromine with 2-methyl-3-butyn-2-ol by use of the bls(trlphenylphosphlne) palladium chloride catalyst system. This reaction used a trlethylamine/pyridine solvent system to replace the bromines on the ether sulfone with ethynyl groups protected by acetone adducts. The acetone protecting groups were then removed In a toluene/methanol/potasslum hydroxide solvent system. 

Carbonylative coupling of iodobenzene with 2-methyl-3-butyn-2-ol under 65 bar carbon monoxide afforded phenylfuranones (double carbonylation) in reasonable yields (Scheme 6.32) [69]. The reaction is thought to proceed through the formation of a benzoylpalladium intermediate which either reacts with the alkynol or liberates benzoic acid hence the formation of considerable amounts of the latter. 

Several catalytic test reactions have been used for indirect characterization of acid and base properties of solids (78). Among them, decomposition of alcohols such as 2-propanol (79,80), 2-methyl-3-butyn-2-ol (81,82), 2-methyl-2-butanol (83), cyclo-hexanol (84), phenyl ethanol (55), and t-butyl alcohol (86) have been investigated. In... 

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