1- Butyne addition reactions

Other examples of addition reactions that form carbon-nitrogen bonds are the reactions of hexafluoro-2-butyne with various heterocydes [77], aromatic... 

Fluonnation likewise significandy destabilizes the multiple bonds in allenes and acetylenes [105] Fluoro- and difluoroacetylene are dangerously explosive, and hexafluoro-2-butyne is very susceptible to both concerted and biradical addition reactions [106,107] (see pp 757 and 767)... 

Hatakeyama et al. [115] have also carried out detailed product studies in the HO-initiated oxidation of the alkynes both in the presence and in the absence of NOx. The major products consisted of a-dicarbonyl compounds, i.e., HC(0)CHO from acetylene, CH3C(0)CH0 from propyne and CH3Q0)C(0)CH3 from 2-butyne, as well as HC(0)OH from acetylene and propyne and CH3C(0)OH from 2-butyne. The formation of these products was attributed to 02-reactions of the hydroxyvinyl radicals resulting from the addition reaction of HO with the alkynes, e.g.,... 

Indium-promoted reaction of l,4-dibromo-2-butyne with carbonyl compounds gives 1,3-butadiene derivatives via the allenic indium intermediates (Scheme 56).220 Similar indium-mediated l,3-butadien-2-ylation reactions of optically pure azetidine-2,3-diones have been investigated in aqueous media, offering a convenient asymmetric entry to the 3-substituted 3-hydroxy-/ -lactam moiety (Equation (40)). The diastereoselectivity of the addition reaction is controlled by the bulky chiral auxiliary at Q4 221 222... 

Complex 3c, a catalytic precursor for addition reactions to alkynes (65), reacts at room temperature with a variety of terminal alkynes in alcohols to produce stable alkoxyl alkyl carbene ruthenium(II) derivatives 109 in good yields (Scheme 7). Reaction of 3c (L = PMe3), with trimethylsilyacetylene in methanol gives the carbene ruthenium complex 110, by protonolysis of the C—Si bond, whereas with 4-hydroxy-l-butyne in methanol the cyclic carbene complex 111 is obtained (65,66). 

Cycloadditions [40] Perfluoro-2-butyne is a highly reactive dienophUe and many [4 + 2] cycloaddition and 1,3-dipolar addition reactions involving this alkyne have been reported (Table 7.20). Moreover, [2 + 2] additions with hydrocarbon alkenes are possible (Table 7.20). 

Free-radical additions Free-radical addition reactions involving perfluoro-2-butyne are also possible, as indicated in Figure 7.95 [327, 328]. 

Alkynes are electron rich, as shown in the electrostatic potential map of acetylene in Figure 11.4. The two K bonds form a cylinder of electron density between the two sp hybridized carbon atoms, and this exposed electron density makes a triple bond nucleophilic. As a result, alkynes react with electrophiles. Four addition reactions are discussed in Chapter 11 and illustrated in Figure 11.5 with 1-butyne as the starting material. 

Pudovik. A.N., and Khusainova, N.G.. Oxidative condensation and addition reactions of 1-diaIkoxy-phosphinyl-l-acetyl-3-butynes, Zh. Obshch. Khim., 40, 1419, 1970 J. Gen. Chem. USSR (Engl. Transl.), 40. 1403, 1970. 

Support for the intermediate s being a pi-complex comes from the observation that many (but not all) alkyne addition reactions are stereoselective. For example, the addition of HCl to 2-butyne forms only (Z)-2-chloro-2-butene, which means that only anti addition of H and Cl occurs. Clearly, the nature of the intermediate in alkyne addition reactions is not completely understood. 

From what you know about the stereochemistry of alkene addition reactions, predict the configurations of the products that would be obtained from the reaction of 2-butyne with the following ... 

Boron is the prime metal in the area of stoichiometric interactions between metals and unsaturated bonds. Especially, boron hydride additions have been investigated, in particular by H. C. Brown and his students. Nowadays, these addition reactions are well-established text book subjects. A number of reviews on hydroboration have appeared . The development of a clear mechanistic picture lagged far behind the applications in synthesis. It was also the group of Brown that contributed to mechanistic understanding by performing careful kinetic measurements using 9-borabicyclo[3.3.1]nonane, abbreviated as 9-BBN-H, as reagent. Reactive alkynes such as 1-hexyne and 3-methyl-1-butyne exhibited first-order kinetics in 9-BBN-H with a rate constant equal to that of reactive... 

Addition of chlorine to alkynes is slow in the absence of light. For example, 1-butyne is at least a factor of 10 less reactive than 1-butene. The addition reaction is readily initiated by light. The major product when butyne is in large excess is trans-1,2-dichlorobutene ... 

Continuing to work backward one hypothetical reaction at a time, we realize that a synthetic precursor of 1 -butene is 1 -butyne. Addition of 1 mol of hydrogen to 1 -butyne would lead to 1-butene. With 1-butyne as our new target, and bearing in mind that we are told that we have to construct the carbon skeleton from compounds with two carbons or fewer, we realize that 1 -butyne can be formed in one step from ethyl bromide and acetylene by an alkynide anion alkylation. 

Photo-induced addition reaction of aromatic carbonyl compounds with alkynes gives unstable oxetanes. For example, the reaction of benzaldehyde with 2-butyne 138 gives a,(3-unsaturated carbonyl compound 139 by cleavage of intermediate oxetane [80]. 

A solution of 0.60 mol of ethyllithium (note 1) in about 400 ml of diethyl ether (see Chapter II, Exp. 1) was added in 30 min to a mixture of 0.25 mol of 1,4-diethoxy-2-butyne (see Chapter VIII-6, Exp. 8) and 100 ml of dry diethyl ether. The temperature of the reaction mixture was kept between -40 and -45°C. Fifteen minutes after the addition had been completed, 0.5 mol of methyl iodide was added at -40 C, then 100 ml of dry HMPT (for the purification see ref. 1) were added dropwise in 15 min while keeping the temperature at about -40°C. Thirty minutes after this addition the cooling bath was removed, the temperature was allowed to rise and stirring was continued for 3 h. The mixture was... 

A mixture of 0.10 mol of freshly distilled 3-methyl-3-chloro-l-butyne (see Chapter VIII-3, Exp. 5) and 170 ml of dry diethyl ether was cooled to -100°C and 0.10 mol of butyllithium in about 70 ml of hexane was added at this temperature in 10 min. Five minutes later 0.10 mol of dimethyl disulfide was introduced within 1 min with cooling betv/een -100 and -90°C. The cooling bath vjas subsequently removed and the temperature was allowed to rise. Above -25°C the clear light--brown solution became turbid and later a white precipitate was formed. When the temperature had reached lO C, the reaction mixture was hydrolyzed by addition of 200 ml of water. The organic layer and one ethereal extract were dried over potassium carbonate and subsequently concentrated in a water-pump vacuum (bath... 

Ethynylation. Base-catalyzed addition of acetylene to carbonyl compounds to form -yn-ols and -yn-glycols (see Acetylene-DERIVED chemicals) is a general and versatile reaction for the production of many commercially useful products. Finely divided KOH can be used in organic solvents or Hquid ammonia. The latter system is widely used for the production of pharmaceuticals and perfumes. The primary commercial appHcation of ethynylation is in the production of 2-butyne-l,4-diol from acetylene and formaldehyde using supported copper acetyHde as catalyst in an aqueous Hquid-fiHed system. 

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