Reactions of an Osmium(IV) Complex with Allenedienes: Coordination and Intramolecular Cycloadditions

This is the authors' abstract. We don't add key points for this paper.

The reactions of OsH 2 Cl 2 (P i Pr 3 ) 2 ( 1 ) with dimethyl ( E )-2-(buta-2,3-dien-1-yl)-2-(penta-2,4-dien-1-yl)malonate ( I ), dimethyl 2-((2 E,4 E )-hexa-2,4-dien-1-yl)-2-(buta-2,3-dien-1-yl)malonate ( II ), and dimethyl ( E )-2-(penta-2,3-dien-1-yl)-2-(penta-2,4-dien-1-yl)malonate ( III ) have been studied. The reaction with I affords an OsCl 2 (P i Pr 3 ) 2 (allenediene) complex with the organic ligand coordinated by the terminal double bond of the allene moiety. In toluene at 353 K, this compound evolves into an (η 6 -arene)OsCl 2 (P i Pr 3 ) 2 species. The arene ligand results from an intramolecular (4 + 2) cycloaddition of the coordinated allenediene molecule and subsequent aromatization, with hydrogen loss, of the resulting tetrahydroindene. The reaction of 1 with II gives an allenediene complex similar to that of I . However, in this case, the allenediene species evolves into a hydride carbyne derivative. Complex 1 promotes both (2 + 2) and (4 + 2) cycloadditions of III to give respectively a bicyclo[3.2.0]heptane skeleton featuring a cyclobutane ring and an Os arene derivative similar to that formed with I .