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Updated: Jul 16, 2026

Sulfate Separation by Selective Crystallization with a Bis-iminoguanidinium Ligand
Published on: September 8, 2016
Regioselective (biomimetic) synthesis of a pentasulfane from ortho-benzoquinone
David Aebisher1, Edyta M Brzostowska, Adaickapillai Mahendran
1Department of Chemistry, Graduate Center & The City University of New York (CUNY), Brooklyn College, Brooklyn, New York 11210, USA.
Abstract:
A mechanism is proposed for the formation of cyclic 5,6,7,8,9-pentathiabenzocycloheptene-1,2-diol, 4, from the reaction of o-benzoquinone with reduced elemental sulfur, H2Sx. 1,6-conjugate addition to the quinone is favored over 1,4-conjugate addition. Hydrogen bonding to the quinone oxygen enhances the nucleophilicity of H2Sx by facilitating the removal of the S-H proton. We propose that initially formed 3-polysulfidobenzene-diol intermediates are oxidized to their corresponding quinones and closure of the polysulfur ring subsequently takes place at the C3-C4 bond leading to 4. A possible mechanism for the formation of the pentasulfur linkage in 4 is discussed, which is the key moiety found in a number of natural products.
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