Wulff–Dötz reaction

The Dötz reaction is a name reaction in organic chemistry and named after its discoverer Karl Heinz Dötz. The reaction is used to benzoanellation. The reactants Chromcarbene, alkynes, and carbon monoxide are needed.

Mechanism

The reaction begins with the elimination of a carbonyl ligand from the chromium complex to form the carbene 2 This step is rate-limiting for the overall reaction, as observed in studies under CO atmosphere. In the next step, an alkyne in a [2 2 ] cycloaddition added to the complex to form a Chromacyclobutens 3 By opening the cyclobutene ring, the vinyl carbene 4 is then formed. By CO insertion ketene 5, to which the chromium complex is coordinated via the two resulting double bond is produced. In the next step of the ring closure takes place, the ketone 6 is formed. By keto -enol tautomerism, the compound is flavored. The remaining on the aromatic chromium complex can now be removed, for example by reaction with carbon monoxide to carbon chromium hexacarbonyl (Cr (CO ) 6). To this end, a CO pressure of about 50 bar is required. Ultimately, as the naphthol derivative 7 is obtained.

Application

The Dötz reaction has applications in natural product synthesis. Thus, for example, vitamin E (tocopherol ), and K can be synthesized with the Dötz reaction as the key step. The application of Dötz reaction is also favored by the simple synthesis of required Fischer carbenes.