Triple bond addition reaction

C C— Carbon-carbon triple bond Addition reactions with halogens, hydrogen habdes hydrogenation to yield alkenes and alkanes... 

Nucleophilic addition to acetylenic sulfoxides provides a,/ -ethylenic sulfoxides. Treatment of 181 with monoalkyl-copper afforded nearly quantitatively /J-alkylated a, / -ethylenic sulfoxides 182 through cis-addition to the triple bond. The reaction with lithium dimethylcuprate also afforded a similar adduct however, the reaction with lithium di-n-butylcuprate was found to give a small amount of ethyl n-butyl sulfoxide 183 besides the... 

The readily available organotin compounds include tin hydrides (stannanes) and the corresponding chlorides, with the tri-n-butyl compounds being the most common. Trialkylstannanes can be added to carbon-carbon double and triple bonds. The reaction is usually carried out by a radical chain process,137 and the addition is facilitated by the presence of radical-stabilizing substituents. 

Hydroboration-oxidation of alkynes preparation of aldehydes and ketones Hydroboration-oxidation of terminal alkynes gives syn addition of water across the triple bond. The reaction is regioselective and follows anti-Markovnikov addition. Terminal alkynes are converted to aldehydes, and all other alkynes are converted to ketones. A sterically hindered dialkylborane must be used to prevent the addition of two borane molecules. A vinyl borane is produced with anU-Markovnikov orientation, which is oxidized by basic hydrogen peroxide to an enol. This enol tautomerizes readily to the more stable keto form. 

The addition of ammonia or primary and secondary amines to acetylenes is greatly enhanced if electron-attracting groups are attached to or conjugated with the triple bond. This reaction may be formulated as in Eq. (31). 

The most common addition reaction of azides in general is the 1,3-dipolar cycloaddition to double and triple bonds. These reactions have been reviewed in this series of books as well as elsewhere, primarily by Huisgen and lately by L abbe, and their mechanism has been discussedThe 1,3-dipolar cycloaddition of azides is generally understood as a concerted process in which the terminal nitrogen of the azido group binds to the atom that is more negative in the olefin, if the olefin happens to be electronically unsymmetric. As a consequence of its concerted nature, it is a stereospecific cis addition. 

The monohydroboration of alkynes is stereoselective, involving a cw-addition of the B-H bond to the triple bond. The reaction of 1-alkynes with dialkylboranes is not only stereoselective, but also regioselective, placing the boron at the terminal carbon of the triple bond. 

Addition reactions Another type of organic reaction appears to be an elimination reaction in reverse. An addition reaction results when other atoms bond to each of two atoms bonded by double or triple covalent bonds. Addition reactions typically involve double-bonded carbon atoms in alkenes or triple-bonded carbon atoms in alkynes. Addition reactions occur because double and triple bonds have a rich concentration of electrons. Therefore, molecules and ions that attract electrons tend to form bonds that use some of the electrons from the multiple bonds. The most... 

The alk)mes contain two pi bonds, both of which are sources of electrons, and they are more reactive than the alkenes. The most common reaction of the alkynes is addition across the triple bond. The reactions with hydrogen and with bromine are typical. 

Of particular interest, however, are those addition polymerizations which proceed as a chain reaction and which mostly involve molecules possessing aliphatic double or triple bonds. The reaction consists of a number of separate phases which follow each other consecutively and rapidly until the polymer attains its final molecular weight, which does not change there-after. ... 

It will be recalled that when addition takes place to unsaturated compounds which are represented as containing a double or triple bond, the reaction takes place in such a way that atoms or groups are added to the adjacent atoms between which the state of unsaturation exists. This is represented by the formulas which are already familiar —... 

The reactivity of dichlorocarbene towards carbon-carbon triple bonds was systematically investigated by Dehmlov in the sixties, and this work has been reviewed". Dehmlov generated the carbene e.g. by decomposition of sodium trichloroacetate in 1,2-dime thoxy ethane. In additions to ene-yne substrates, sometimes the triple bond, whereas in other cases the double bond accepted the carbene. He observed, for instance, that reaction of the carbene with (E)-l,4-diphenylbutene-l-yne-3 gave the triple-bond addition product 20 exclusively. In reaction with 2-methylpentene-l-yne-3, however, the carbene preferred the double bond, leading to 21. Dichlorocarbene generated from potassium f-butylate and chloroform does not add to electron-poor alkynes, indicating electrophilic behavour of the carbene. 

Hydrogen Abstraction Reaction with N, S and -OH = Addition to Triple Bonds = Addition to Olefinic Bonds = Addition to Aromatic Rings = Addition to Fused Rings =... 

In contrast to the reaction with diisobutylaluminium hydride, hydroalumination of disubstituted alkynes with lithium hydridodiisobutylmethylaluminate, obtained from diisobutylaluminium hydride and methyllithium, results in anti addition across the triple bond. Subsequent reaction with aldehydes gives allylic alcohols, with CO2 gives a,p-unsaturated acids and with iodine gives alkenyl iodides, isomeric with the products obtained in the reaction sequences using diisobutylalvmiinium hydride. ... 

Addition of thiols in basic solution to the C=C—C=0 bond system in a,/3 imsaturated ketones, such as 4-benqrlidene-l-buQrl-pyrrolidine-2,3-dione, has been observed, forming with benzenethiol in piperidine, l-butyl-3-hydroxy-4(a-phenylthiobenzyl)-3-pyrrolin-2-one . Addition of thiols primarily to the C=C bond in C=C—C=0 systems in quinones and lactones has been observed . The reactions were studied in neutral or alkaline solution and probably involve attack by the thiolate anion. In compounds containing both carbonyl or carboxyl groups and acetylenic triple bonds, addition occurs primarily across the acetylene bond. Cyclization of the initial product so formed is also observed . ... 

Allynes can be hydrated in the presence of acid and HgS04 by electrophilic addition of a molecule of water to the triple bond. The reaction proceeds by way of a carbocation intermediate. Hydration of acetylene (ethyne) produces acetaldehyde (ethanal). Outline the steps that occur in this transformation. 

PhMe2Si)2CuLi reacts with alkynes via syn addition of the silyl group and copper to the carbon-carbon triple bond In reactions with terminal alkynes, the silyl group becomes attached predominantly to the terminal carbon. The acidic hydrogen of... 

Reaction of terminal alkynes 71 with boron tribromide or B-bromo-9-BBN 74 leads to the addition of B-Br across the triple bond. This reaction furnishes P-bromoalkenylboronates 72-73 stereoselec-tively as the major diastereomer (Scheme 28.19).33... 

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