a,b
a Reaction conditions: Carbon rod anode (Ø = 6
mm), carbon rod cathode (Ø = 6 mm), constant current = 10 mA, undivided
cell, 1 (0.5 mmol), 2 (0.8 mmol), S (0.6 mmol), TBAI
(0.5 mmol), MeCN (4 mL), H2O (2 mL), room temperature,
N2, 12 h. b Isolated yield.
As mentioned above, many examples of the synthesis of thiosulfonates and
selenosulfonates are presented in the literature, but the methods to
synthesize sulfonotelluroates remains a challenge. Our proposed
electrocatalytic three-component reaction could be extended to the
synthesis of sulfonotelluroates using elemental tellurium as the
tellurium source (Scheme 6). Under the modified
conditions,[12] sulfonotelluroate 5aa was
obtained in 76% yield by the reaction of indole 1a , sodiump -toluenesulfinate 2a , and elemental tellurium.
Moreover, the electronic characteristics and positional variations of
substituents on the phenyl ring of indoles have no effect on the product
yield. Further, an array of structurally diverse indoles can
successfully participate in this cascade cross-coupling. Further,
various functional groups such as Me, OMe, and NO2 can
be well-suited for this transformation (5ab —5af ).
Interestingly, benzothiophen also gave the corresponding product
(5ag ) in 47% yield, and N-ethyl-indole gave the desired
product (5ah ) in 62% yield. Further, in this method,
cyclopropyl or 4-chlorophenyl-substituted sodium sulfinates could be
used as coupling partners, resulting in the efficient for-mation of
corresponding sulfonotelluroates (5ai and 5aj ).
Scheme 6 Synthesis of sulfonotelluroates