L,2-alkadien-4-ynes

In addition to propargylic carbonates, propargylic chlorides react with terminal alkynes in the presence of triethylamine or diisopropylamine. 5-Butyldodeca-3,4-dien-6-yne (165) was obtained in 91% yield by the reaction of 3-chloro-4-nonyne (164) with 1-heptyne in diisopropylamine (Section 11-45). Coupling of the propargylic acetate 166 with 1-heptyne is possible in the presence of three equivalents of zinc chloride with or without cuprous iodide to give the l,2-alkadien-4-yne 167 [40]. 

Reaction of terminal alkynes formation of l,2-alkadien-4-ynes. . . ... 

Reactions of Terminal Alkynes Formation of l,2-Alkadien-4-ynes... 

Chlorobenzenes activated by coordination of Cr(CO)3 react with terminal alkynes[253). The 1-bromo-1,2-alkadiene 346 reacts with a terminal alkyne to afford the alka-l,2-dien-4-yne 347[254], Enol tritlates are used for the coupling with terminal alkynes. Formation of 348 in the syntheses of ginkgolide[255] and of vitamin D are examples[256] Aryl and alkenyl fluorides are inert. Only bromide or iodide is attacked when the fluoroiodoalkene 349 or fluoroiodoar-ene is subjected to the Pd-catalyzed coupling with alkynes[257-259]. 

Another difference between the two mechanisms is that the former involves 1,2-and the latter 1,3-shifts. The isomerization of 1-butene by rhodium(l) is an example of a reaction that takes place by the metal hydride mechanism, while an example of the 7i-allyl complex mechanism is found in the Fe3(CO)i2-catalyzed isomerization of 3-ethyl-l-pentene. A palladium catalyst was used to convert alkynones RCOCSCCH2CH2R to 2,4-alkadien-l-ones, RCOCH=CHCH=CHCHR. The reaction of an en-yne with HSiCls and a palladium catalyst generated an allene with moderate enantioselectivity (see p 148 for chiral allenes). ... 

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