Additions to Acetylenic Compounds

Addition of HOCl to vinyl chloride yields chloroacetaldehyde (106) addition to acetylenic compounds produces dichloroketones (107) (see... 

Preparation by Addition of Tertiary Phosphines to Acetylenic Compounds Substituted by Electron-Withdrawing Groups... 

Secondary amines, such as dimethylamine, diethylamine, diisopropylamine, dicyclohexylamine, A(-methylaniline, aziridine, and azetidine, are reported to undergo cis addition to acetylenic esters, giving rise to simple 1 1 Michael adducts, in each case. These adducts have been successfully employed in the synthesis of different heterocyclic compounds. 

Many such activated acyl derivatives have been developed, and the field has been reviewed [7-9]. The most commonly used irreversible acyl donors are various types of vinyl esters. During the acylation of the enzyme, vinyl alcohols are liberated, which rapidly tautomerize to non-nucleophilic carbonyl compounds (Scheme 4.5). The acyl-enzyme then reacts with the racemic nucleophile (e.g., an alcohol or amine). Many vinyl esters and isopropenyl acetate are commercially available, and others can be made from vinyl and isopropenyl acetate by Lewis acid- or palladium-catalyzed reactions with acids [10-12] or from transition metal-catalyzed additions to acetylenes [13-15]. If ethoxyacetylene is used in such reactions, R1 in the resulting acyl donor will be OEt (Scheme 4.5), and hence the end product from the acyl donor leaving group will be the innocuous ethyl acetate [16]. Other frequently used acylation agents that act as more or less irreversible acyl donors are the easily prepared 2,2,2-trifluoro- and 2,2,2-trichloro-ethyl esters [17-23]. Less frequently used are oxime esters and cyanomethyl ester [7]. S-ethyl thioesters such as the thiooctanoate has also been used, and here the ethanethiol formed is allowed to evaporate to displace the equilibrium [24, 25]. Some anhydrides can also serve as irreversible acyl donors. 

Acetylenic Compounds are organic compounds contg at least one triple bond -O C-. They may be hydrocarbons, alcohols, acids, aldehydes, etc. The acetylenic hydrocarbons include, in addition to acetylene (qv), the higher members, such as allylene or propyne H,CC s CH, crotonylene or butyne -2 HjCC i C.CHj, valerylene or pentyne - 2 H, C2.C C.CH, etc... 

Grignard-type Addition of Acetylenic Compounds to Imines... 

Addition of NaX or BuJNX to l-alkyn-3-ones.1 In the presence of these two reagents, sodium or ammonium salts undergo conjugate addition to acetylenic carbonyl compounds. This reaction provides mm-P-halovinyl ketones or N,N-diethyl m-P-haloacrylamides. 

Addition of nitriles to acetylenic compounds proceeds with chemoselectivity in contrast with the corresponding base-promoted reactions, where the products derived from acetylides are contaminants. The RuH2(PPh3)4-catalyzed reaction of ethyl 2-cyanopropionate (12) with methyl propiolate (14) at room temperature gave 15 in 90 % yield. 

The selenosulfonates (26) comprise another class of selenenyl pseudohalides. They are stable, crystalline compounds available from the reaction of selenenyl halides with sulftnate salts (Scheme 10) or more conveniently from the oxidation of either sulfonohydrazides (ArS02NHNH2) or sulftnic acids (ArS02H) with benzeneseleninic acid (27) (equations 21 and 22). Selenosulfonates add to alkenes via an electrophilic mechanism catalyzed by boron trifluoride etherate, or via a radical mechanism initiated thermally or photolytically. The two reaction modes produce complementary regioselectivity, but only the electrophilic processes are stereospecific (anti). Similar radical additions to acetylenes and allenes have been reported, with the regio- and stereochemistry as shown in Scheme 11. When these selenosulfonation reactions are used in conjunction with subsequent selenoxide eliminations or [2,3] sigmatropic rearrangements, they provide access to a variety of unsaturated sulfone products. 

The latter compound undergoes carbonyl olehnation, olefin metathesis and addition to acetylenes . 

The cyclotrimerization of alkynes to give benzene derivatives is perhaps the most general reaction of these compounds in the presence of transition metal complexes. Practically any mono- or di-substituted alkyne, in addition to acetylene itself, may be cyclotrimerized. In addition, cocycloadditions involving more than one different alkyne are possible with some degree of selectivity, and intramolecular versions of the reaction have seen sophisticated development. 

Additions to multiple bonds catalyzed by radical initiators produce novel synthetic methods. Carboxylic acids add to acetylenic compounds in the presence of organic peroxides. Acetic acid and acetylene yield adipic acid 1-hexyne and acetic acid give octen-3-oic acid. Radical amination of olefins with hydroxylamine sulfonic acid and hydroxylamine in the presence of FeCla gives the corresponding l-amino-2-chloro compounds. ... 

The sulfur-iodine bond appears to be very weak. RFS02I were unstable at room temperature and decomposed spontaneously to give RFI and S02. These compounds cannot be isolated in a free state but their solutions in CH2C12 at — 30 °C have been prepared and used directly18,64. The sulfonyl iodides were found to react spontaneously with multiple bonds in three ways (i) by addition to electron-rich olefins without elimination of S02, (ii) by addition to acetylenes and electron-poor olefins to give adducts with loss of S02 and (iii) by reaction with CH2=CHCOR (R = H, Me) to give RfS02CH2CH2C0R. 

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