Five-Membered Metallacyclic Allenoids: Synthesis and Structure of Remarkably Stable Strongly Distorted Cyclic Allene Derivatives

摘要

Incorporation of allenic moieties into small rings leads to unfavorable bending and planarizing distortions. The resulting strain has precluded the direct observation of 1,2-cyclo-pentadiene (1) or 1,2-cyclohexadiene (2) to date. Information about such highly strained cyclic allenes was derived from trapping reactions and quantum chemical calculations. The cycloallenes 1 and 2 are chiral, with calculated enantiomer-ization barriers of less than 1-5 (1) and 14-18 kcalmol~(-1).