Trispirododecane-4,8,12-trione and Other Oligomers of Carbonylcyclopropane. The Organozinc Route

Article abstract of DOI:10.1021/jo00287a022

1-Bromocyclopropanecarboxylic acid (8) and its chloride (9) were prepared from γ-butyrolactone on a 20-100-g scale.Dehalogenation of 9 with zinc-copper couple in acetonitrile gave not only the known dispiro<2.1.2.1> octane-4,8-dione (3) but also the aesthetically pleasing title compound 10 and 6-cyclopropylidene-5-oxaspiro<2.3>hexan-4-one (11) as well as tetracyclic α-alkylidene-γ-butyrolactone 12, i.e., 3-(oxodispiro<2.1.2.1>octan-4-ylidene)tetrahydro-2-furanone. "Zinc carbon enolate" 13a is considered to be an important intermediate en route to 10 in solventacetonitrile.The X-ray crystal structure of 10 shows the molecule to be nearly planar with very short distal cyclopropane carbon-carbon bonds <1.437 (4)-1.452 (4) Angstroem>.