Reaction of o-benzyne with tropothione involving biradical processes.
A benzyne-tropothione reaction was studied experimentally and computationally. Three isomeric products were detected by a careful experiment using two benzyne sources. The three equimolar products were identified. The expected symmetry-allowed [4+2] or [8+2] cycloadduct was not detected. In order to explain the unexpected products, density functional calculations and complete active space self-consistent field (CASSCF) calculations were carried out. The benzyne is, first, added to the tropothione via one-center C-S bond formation. Then a singlet biradical intermediate is formed. In the biradical, an alpha hydrogen atom of the tropothione moiety is moved to the benzyne moiety. A closed-shell intermediate is generated. This allene-type intermediate is isomerized to the second intermediate. The intramolecular proton shift in the latter leads to the three products. The biradical character of the benzyne has a key role in the present reaction and was discussed in reference to other benzyne reactions.
Yamabe
Shinichi
S
Department of Chemistry, Nara University of Education, Takabatake-cho, Nara 630-8528, Japan. yamabes@nara-edu.ac.jp
Minato
Tsutomu
T
Ishiwata
Akihiro
A
Irinamihira
Osamu
O
Machiguchi
Takahisa
T