Regioselective (Biomimetic) Synthesis of a Pentasulfane from <i>ortho</i>-Benzoquinone
作者:David Aebisher、Edyta M. Brzostowska、Adaickapillai Mahendran、Alexander Greer
DOI:10.1021/jo062677w
日期:2007.4.1
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.