Science of Synthesis

Kündig, E. P.; Pache, S. H., Science of Synthesis, (2003) 2, 164.

The reaction of chromium carbene complexes with alkynes to give naphthol derivatives (Dötz annulation) has been extensively studied (‌Scheme 6‌).[‌88‌–‌91‌] A dissociative mechanism has been proposed, involving the loss of one carbonyl ligand followed by alkyne coordination, carbene insertion, carbonyl insertion, electrocyclization, and finally tautomerization to the naphthol skeleton. The carbene carbon preferentially couples to the alkyne carbon bearing the smaller substituent. On heating, the initially formed naphthol complex ‌23‌ undergoes haptotropic rearrangement to the isomer ‌24‌, containing the tricarbon­ylchromium fragment coordinated to the unsubstituted naphthalene ring. If an aminocarbene is used, carbonyl insertion does not take place and ‌25‌ is the sole product. In some cases an oxycarbene can also lead to the five-membered ring, and product selectivity can be controlled to some extent by variations on carbene structure, solvent, temperature, and concentration. Vinylcarbene complexes react analogously, producing phenol derivatives such as ‌26‌. Although the primary products of these annulation reactions are η6-arene complexes, these are often not isolated but directly treated with iodine or exposed to air and sunlight to remove the metal. In order to isolate the chromium complex with good yields, it is usually necessary to protect the phenol or naphthol function formed in the reaction.[‌92‌]

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References

Meeeeee Meeeeeeeeee

• 8.Meeeee-Meee, (8888) M 88-8, 888.