3-Oxatricyclo(3.1.0.02,6)hexan-4-one

3-oxabicyclo[3.2.0]hept-6-ene-2,4-dione

3,4-diazatricyclo[3.1.0.02,6]hex-3-ene

1-cycloprop-2-en-1-yl-2-diazonioethenolate

Cyclopropenylketen