Chromium-Templated Benzannulation
of (η<sup>5</sup>-Cyclohexadienyl)Mn(CO)<sub>3</sub>-Methoxy-Cr(CO)<sub>5</sub> Carbenes
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Abstract
Pentacarbonyl{methoxy-[1-(η<sup>5</sup>-4-methoxy-6-phenylcyclohexadienyl)tricarbonylmanganese]carbene}chromium
(<b>5</b>) accessible from (η<sup>5</sup>-1-bromo-4-methoxy-6-phenylcyclohexadienyl)tricarbonylmanganese
(<b>4</b>) and Cr(CO)<sub>6</sub> undergoes a chromium-templated
benzannulation with 3-hexyne to give monometallic Cr complex <b>12</b> in 60% yield. The key feature of this reaction is the participation
of a conjugated double bond of the η<sup>5</sup>-cyclohexadienyl-Mn
moiety in the [3+2+1] benzannulation reaction. The X-ray structure
of complex <b>12</b> reveals a <i>syn</i> position
of the phenyl group with respect to the Cr tripod, supporting the
participation of the Mn moiety in the benzannulation process
