Cyclotrimerization Subject

As a control experiment, benzonitrile and phenylacetylene were subjected. o the standard cyclotrimerization conditions. Benzoniti e did not react. 

Nitrogen-containing 15-membered trialkyne macrocycles, such as l,6,ll-frw(aiylsulfonyl)-l,6,ll-triazacyclopentadeca-3,8,13-triynes and enediynes as 1,6,11-frw(arylsulfonyl)-1,6,11-triazacyclopentadeca-3-ene-8,13-diynes have been prepared and subjected to a [2+2+2]-cyclotrimerization process catalyzed by transition metal complexes, e.g., RhCl(CO)(PPh3)2 <05JOC2033>. The reaction of pemosylated diethylenetriamine and 2-substituted propan-1,3-... 

Nickel(O) complexes also catalyze a variety of cyclooligomerizations of butadiene. Hiis process, studied intensively by Wilke and Jolly and co-workers, can lead to a myriad of products that depend on the reaction conditions (Scheme 22.22). The cyclotrimerization of butadiene to cyclododecatriene was one of the first organometaUic reactions subjected to careful mechanistic studies, and these studies led to the proposal that tiiis process occurs by the mechanism shown in Scheme 22.23. Again, the bis-ri -allyl complex containing 12 carbon atoms was isolated and characterized. It has been shown to enter the catalytic cycle as shown. 

Chemo- and regioselective ruthenium-catalyzed cyclotrimerization of alkynes was accomplished through a temporary boron tether. Crude aryl boronates were obtained in a one-pot procedure in which they were subjected to a Suzuki-Miyaura coupling with aryl halides (Scheme 9.50) [103]. 

Cyclotrimerization of acetylenes to form benzene derivatives has probably been the most studied of all organometallic reactions of acetylenes. A few reviews of the subject have appeared (Hiibel, 1968 Bowden and Lever, 1968 Otsuka and Nakamura, 1976a Dickson and Fraser, 1974). The same or different acetylenes can be incorporated to produce several possible substitution patterns. Trimerization of symmetrical alkynes produces hexasub-stituted benzenes, while unsymmetrical alkynes may lead to 1,3,5- or 1,2,4-trisubstituted derivatives. 

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