A Highly Efficient Palladium‐Catalyzed One‐Pot Synthesis of Unsymmetrical Aryl Alkyl Thioethers under Mild Conditions in Water

Abstract

A palladium-catalyzed, one-pot synthesis of unsymmetrical aryl alkyl thioethers involving aryl halides (aryl bromides and chlorides), thiourea and alkyl bromides has been realized under mild conditions (room temperature to 50 8C) in water with polyoxyethanyl a-tocopheryl sebacate (PTS) as amphiphile. The PTS/water could be recycled in up to eight runs without an obvious change in its activity.

Improved, Odorless Access to Benzo[1,2-d;4,5-d′]- bis[1,3]dithioles and Tert-butyl Arylsulfides via C-S Cross Coupling

“…Considering the aforementioned transformation of 4-bromoanisole so 7 , Park et al [ 30 ] used a Pd(dba) 2 /dppf catalyst system and obtained a yield of 87% using S- tert -butylthioacetate as sulfur source, however with an increased temperature of 110 °C. Exploiting the in situ formation of thiolates from tert -butyl bromide and thiourea, Wang et al [ 31 ] obtained S- tert -butylthiobenzene (yield 76%) and 4-nitro-S- tert -butylthiobenzene (yield 77%) from the respective aryl bromides using a Pd 2 dba 3 /XPhos catalyst system and yields were significantly higher for primary alkyl substrates.…”

“…Although C-S cross-coupling reactions using appropriate thiol surrogates are known, these usually need to be synthesized from the corresponding thiols, such as alkyl thioacetates [ 30 ]. Another possibility has been described by Wang et al [ 31 ] in form of a one-pot synthesis, in which the necessary thiolate nucleophile was generated in situ using an alkyl bromide and thiourea as the sulfur source. Nonetheless, the yields for tertiary substrates stalled due to a competing elimination pathway.…”

Concise Synthesis of Dithiophene Derivatives by a Palladium‐ Catalyzed Multiple C–S Cross Coupling/Cyclization Sequence

“…Transition metal‐catalyzed C−S bond forming reactions using thiols or thiolates are well known, but were only occasionally utilized in the de novo synthesis of sulfur‐containing heterocycles. In that sense the application of hydrogen sufide surrogates,,,,, for example, thiourea or potassium thioacetate is a highly desirable alternative to thiols since handling and preparation of these malodorous and often air‐sensitive compounds is avoided. Recently, we utilized thiourea and potassium thioacetate, as hydrogen sulfide surrogates for the construction of benzothiophene, thienothiophene and DTT derivatives through single C–S cross‐coupling/cyclization and C–S coupling/C–H activation ,…”

Efficient Cu-catalyzed base-free C–S coupling under conventional and microwave heating. A simple access to S-heterocycles and sulfides

“…Aryl coupling reactions employing different palladium species as catalysts represent the most extensively studied approaches to form new C Ar –S bonds [21–23]. Nevertheless, copper or iron-mediated coupling reactions have become a convenient alternative to the expensive Pd/ligand systems due to the lower cost of the former, its stability, and the ready availability of the ligands.…”