Alkynes alkenyne

Catalyzed hydrogenation of alkynes, alkenynes, and alkadienes.1 This catalyst effects highly c/s-selective hydrogenation of triple bonds of alkynes and alkenynes, with easy recovery of the complex by filtration. It also effects only 1,2-addition in hydrogenation of even hindered 1,4-substituted 1,3-butadienes. 

Table 4.13. 13C Chemical Shifts of Alkynes [246, 247], Polyalkynes [248], Alkenynes [249] and Cycloalkynes [250] (<5C in ppm).

CHCI3) to conjugated alkenynes, with the nitrogen on the terminal carbon, to give a variety of alkynic and allenic adducts, often in good yield. A 1,4-azidoselenation of cyclohexadiene was discussed earlier (Section 3.S.S.2). 

The reaction was successfully extended to the hydroformylation of propargyl-type alcohols [154] and propargylamine [155], the silylative cyclocarbonylation of alkynes [156], silylcarbocyclization of alkenynes and diynes [157-160], and other transformations of C=C bonds in the presence of HSiRa and CO (e. g., [161]). A generalized catalytic cycle for the silylformylation of 1-alkynes catalyzed by rhodium-cobalt clusters is illustrated in Scheme 6. 

Ogawa, T., Kusume, K., Tanaka, M., Hayami, K., Suzuki, H. An alternative method for the stereospecific synthesis of conjugated alkenynes via the copper(l) iodide assisted cross-coupling reaction of 1-alkynes with haloalkenes. Synth. Commun. 1989,19, 2199-2207. 

Pirguliyev, N. S., Brel, V. K., Zefirov, N. S., Stang, P. J. Stereoselective synthesis of conjugated alkenynes via palladium-catalyzed coupling of alkenyl iodonium salts with terminal alkynes. Tetrahedron 1999, 55, 12377-12386. 

Hydroamination/bicyclization of aminodialkenes, aminodialkynes, and amino-alkenynes opens a straightforward route to pyrrolizidines and indolizidines in a tandem C-N and C-C bond forming process. An important prerequisite for the success of this reaction sequence is a sufficient lifetime of the rare-earth metal alkyl intermediate formed in the initial insertion process of the alkene/alkyne in the Ln-amide bond in order to permit the carbocyclization step (Scheme 9) [99,174],... 

Alkynes and alkadienes (alkenes with two double bonds) have the general formula C H2n-2- Alkenynes (hydrocarbons with one double bond and one triple bond) and alkatrienes (alkenes with three double bonds) have the general formula Cn 2n-4 and so forth. 

In lUPAC nomenclature, a hydrocarbon containing both double and triple bonds is called an alkenyne. The chain is numbered starting from the end closest to either of the functional groups. When a double bond and a triple bond are at equidistant positions fiom either terminus, the double bond is given the lower number. Alkynes incorporating the hydroxy function are named alkynols. Note the omission of the final e of -ene in -enyne and of -yne in -ynol. The OH group takes precedence over both double and triple bonds in the numbering of a chain. 

The rules for naming alkynes are essentially the same as those formulated for aUcenes. Molecules with both double and triple bonds are called alkenynes, the double bond receiving the lower number if both are at equivalent positions. Hydroxy groups are given precedence in numbering aUcynyl alcohols (alkynols). 

Unsaturated acyclic hydrocarbons with double and/or triple bonds are generally designated as alkenes, alkynes, and alkenynes multiple unsaturation is indicated by the numerical prefixes di, tri, etc. alkatrienes, alkenediynes etc. 

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