Titanated vinylallenes

Titanated vinylallenes generated from the coupling of acetylenes and propargyl carbonates [38] undergo facile, unidirectional electrocyclization to give cyclobutene derivatives under extremely mild reaction conditions as shown in Eq. 9.17 [39]. 

In other examples, also involving propargyl carbonates, the parent derivative 86 was first coupled with 87 - obtained by reaction of 5-octyne with the titanium diiso-propoxide - propene complex at -50 °C, providing the titanated vinylallene 88, which on hydrolysis furnished the vinylallenes 89 in good yield [29]. Carbonate 90 in the presence of a Pd° catalyst readily decarboxylated and yielded the allenylpalladium intermediate 91, which could be coupled with various vinyl derivatives to afford the vinylallenes 92. Since X represents a functional group (ester, acetyl), functionalized vinylallenes are available by this route [30]. 

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See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

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