Alkenynes

The addition of 1,3-dipoles to alka-l,3-diynes has been studied in less detail than that to conjugated alkadienes and alkenynes (80UK1801). Conjugated diynes get involved in [2- -3]cycloaddition at the unsubstituted acetylene bond. 

Hydrocarbons with one triple bond and one double bond (alkenynes) and alkenes... 

Alkadiene and alkatriene => diene and triene alkadiyne and alkenyne => diyne and enyne. 

Unexpectedly, some diazoesters seem to react by way of carbene intermediates even in highly ionic media at room temperature.276 With acetic acid alone 2-furyldiazoacetic ester supplies two products retaining the furan ring. But if the acetic acid is mixed with ether or dichloromethane then a Z-alkenyne (Scheme 53) appears just as if a carbene had been formed. The... 

A final example that is so remarkable to deserve mention is the photoisomerization of alkenyne 61 to its isomer 63 (equation 21)149. In a recent reinvestigation of the reaction, Johnson and coworkers have provided computational evidence for the intermediacy of the 1,2-cyclobutadiene isomer 62 in the phototransposition reaction150. 

A typical intramolecular rearrangement involves 1,4-addition across the conjugated system of alkenynes to give allenes (Eq. 36). 

The 1,4-addition to the conjugated system of 1,3-alkenynes yields allenes in many reactions. When the addition occurs 1,2- or 3,4- acetylenes or dienes... 

The Ojima group has extended their studies of silylformylation to include more complex substrates, such as alkenyne, dialkyne, alkynyl nitrile, and ethynyl pyrrolidinone. Use of rhodium or rhodium-cobalt metal complexes catalyzes the silylformylation of these substrates with high chemoselectivity, as the other functionalities present are inert to the reaction.122b,c d... 

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

Hydrocarbons with more than one triple bond are called alkadiynes, alkatriynes, and so on, according to the number of triple bonds. Hydrocarbons with both double and triple bonds are called alkenynes (not alkynenes). The chain always should be numbered to give the multiple bonds the lowest possible numbers, and when there is a choice, double bonds are given lower numbers than triple bonds. For example,... 

Miyaura, N. Yamada, K. Suginome, H. Suzuki, A. Novel and convenient method for the stereo- and regiospecific synthesis of conjugated alkadienes and alkenynes via the Pd-catalyzed cross-coupling reaction of 1-alkenyl-boranes with bromoalkenes and bromoalk-ynesj. Am. Chem. Soc. 1985, 107, 972-980. 

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. 

Hydrocarbons with both double and triple bonds are known as alkenynes. 

Schwebel, D. and Margaretha, P. (2000) Photocydoaddition of 2H-l-benzopyran-3-carbonitriles and 2H-l-benzothiopyran-3-carbonitriles to alkenes and alkenynes. Helvetica Chimica Acta, 83, 1168-1174. 

If a hydrocarbon contains both triple and double bonds, it is named as an alkenyne. The carbon atoms with the double bond bear the smaller number. 

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],... 

Hydrocarbons with both double and triple bonds are known as alkenynes. The locant number for the double bond precedes the name, and the locant for the triple bond follows the infix -en- and precedes the suffix -yne. 

Higher homologs can also be prepared by dehalogenation, the requisite dihaloalkenes being obtained either from the appropriately substituted allyl alcohols146 or from the conjugated alkenynes and concentrated hydrobromic acid.147... 

The photochemical addition of 9,10-phenanthraquinone, tetrachloro-1,2-benzoquinone (and benzil) to alkenynes (285) has been reported.167 The addition of the quinones takes place to the ethylenic bond of the alkenyne to yield alkynyl dioxins (286) and (287). The reaction is not stereospecific and a biradical intermediate is proposed to account for the loss of the stereochemical integrity of the olefin. Ishibe et a/.168 have published the results of an investigation of the photoaddition of p-benzoquinone, 1,4-naphthoquinone, 2-methyl-1,4-benzoquinone,... 

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