Terminal alkynes Hydroxyl groups which

Alkenyl complexes. These complexes are prepared by reaction of an alkenyllithium with Cr(CO)6 followed by methylation. These a,(l-unsaturated complexes react with terminal alkynes to give, after oxidative work-up, phenols or quinones in which the acetylene group is ortho to the phenolic hydroxyl group derived from carbon monoxide. 

Insight into the mechanism involved was obtained in two labeling studies, as shown in Eqs. 5.24 and 5.25. The former indicates that the carbon bearing the hydroxyl group preferentially forms the new C-C bond to the terminal alkyne carbon. The latter indicates that the alkene geometry is largely retained. These studies support the intervention of a jt-allyl species in which rotation around the ruthenium-allyl axis is slow relative to the rate of reductive elimination and the absence of a n-allyl intermediate. 

Generally, arene(alkoxy)carbene chromium complexes react with aryl-, alkyl-, terminal or internal alkynes in ethers or acetonitrile to yield 4-alkoxy-l-naphthols, with the more hindered substituent ortho to the hydroxyl group . Upon treatment with alkynes, aryl(dialkylamino)carbene chromium complexes do not yield aminonaphthols, but they form indene derivatives . Vinyl(dialkylamino)carbene complexes, however, react with alkynes to yield aminophenols as the main products The solvent is one of the many factors that affects this type of reaction, for which the most important is the polarity and/or coordinating ability of the solvent. The Dotz benzannulation reaction yields either arene chromium tricarbonyl complexes or the decomplexed phenols, depending on the work-up conditions. Oxidative work-up yields either decomplexed phenols or the corresponding quinones. 

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