Corner Opening of Cyclopropanes by Mercury(II) and Thallium(III) and Transmetalation of the Intermediate Organomercurials. A Novel, Stereoselective Approach to Cyclobutanes and Cyclopropanes

Article abstract of DOI:10.1021/ja00080a021

The reactivity of the two isoelectronic cations (Hg²⁺ and Tl³⁺) toward the cyclopropane rings is compared, and further evidence for the exclusive corner selectivity for Hg²⁺ is provided by isotope labeling.Cleavage of cyclopropyl derivative 1 with Hg(NO3)2, followed by KBr quenching, afforded the stable, rearranged organomercurial 3, whose transmetalation has been studied.Whereas reaction of 3 with Pd(II) afforded lactol 4, treatment with Me2CuLi resulted in the formation of cyclobutanol derivative (3 -> 29); analogous conjugate addition has also been accomplished (32 -> 35).Similarly, the organomercurial 22, obtained from 21 as the major product on the Hg(II)-mediated ring-opening, reacted with Me2CuLi or AlCl3 to give the ring-closure product 21.These reactions represent a novel method for the stereoselective construction of four- and three-membered rings.The stereochemistry of the key steps of these transformations has been established by using stereospecifically deuterated substrates 1b, 3b, 21b, and 22b.