Regioselective (biomimetic) synthesis of a pentasulfane from ortho-benzoquinone.
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.
Aebisher
David
D
Department of Chemistry, Graduate Center & The City University of New York (CUNY), Brooklyn College, Brooklyn, New York 11210, USA.
Brzostowska
Edyta M
EM
Mahendran
Adaickapillai
A
Greer
Alexander
A
D016227:Benzoquinones / Q000737:chemistry*; D032701:Biomimetics; D006860:Hydrogen Bonding; D007700:Kinetics; D008958:Models, Molecular; D010084:Oxidation-Reduction; D013438:Sulfhydryl Compounds / Q000138:chemical synthesis* / Q000737:chemistry
D016227:Benzoquinones; D013438:Sulfhydryl Compounds; C025225:2-benzoquinone