Thiophene Oxidation and Reduction Chemistry

Dearomative Intramolecular (4+3) Cycloadditions of Thiophenes

“…Forging TBO scaffolds also offers further synthetic applications. A potential strategy to access hydrobenzo [7]annulene frameworks as found in β-himachalene and related natural products could involve desulfurization of a TBO scaffold derived from the dearomatization of thiophenes (Scheme 4 A). Attempts to cleave the CÀ S bonds of our TBO structures via reductive desulfurization using Raney nickel or Pd/C [42][43][44] were unfruitful and only alkene hydrogenation was observed in moderate yields (see Supporting Information, Table S2).…”

“…[4] In contrast to the typical electrophilic substitution reactions, [5,6] dearomatization reactions can convert thiophenes into more reactive and complex compounds, expanding their synthetic applications to advance the field of thiophene chemistry. [7] Thiophenes have been used as four-carbon components in dearomative cycloadditions, [8][9][10][11][12][13][14][15][16][17][18][19] eg. in Diels-Alder (4+2) cycloadditions, which allow the construction of polycycles bearing sulfur bridges with high atom economy, albeit typically under conditions involving high-temperature, pressure, or irradiation.…”

“…Due to the similarly high aromaticities of thiophene and benzene, the chemical reactivity of thiophene is akin to electron‐rich benzene derivatives [4] . In contrast to the typical electrophilic substitution reactions, [5,6] dearomatization reactions can convert thiophenes into more reactive and complex compounds, expanding their synthetic applications to advance the field of thiophene chemistry [7] …”

Dimerization reactions with oxidized brominated thiophenes

“…The oxidation of thiophene is well documented in the literature 1 but can be complicated to realize due to the instability of the resulting thiophene S -oxide or S , S -dioxide or due to the availability of oxidation reagents. The methods commonly used are accessible to all concerned reagents such as m-CPBA or H 2 O 2 in acid medium or in the presence of anhydride.…”