PNNL

Abstract

Indanedioneketene, a compound resulting from the thermal degradation of the phenyliodonium ylide of lawsone, dimerises quantitatively to a spiro-oxetanone derivative, a key compound for further transformations. A theoretical DFT study of this unusual for a-oxoketenes [2+2] cyclization reaction both in the gas phase and in dichloromethane solution, provides support for a) a single-step, transitionstate (involving a four-membered cyclic ring) charge controlled, concerted mechanism, and b) a [4+2] cyclization reaction, not observed but studied theoretically in this study. A parallel study of an open chain a,a'-dioxoketene dimerization explains the difference in the stability and reactivity observed experimentally between the cyclic and open chain products.