Environmentally benign process for the synthesis of 2,3-disubstituted benzo[b]thiophenes using electrophilic cyclization

Sodium halides as the source of electrophilic halogens in green synthesis of 3-halo- and 3, n -dihalobenzo[ b ]thiophenes

“…in the presence of catalytic Pd (2 mol %) and catalytic copper (4 mol %) using trimethylamine as solvent (Scheme 2). 18,19 Using these conditions, a variety of functionalized 2-akynylthioanisoles 6 – 15 were synthesized with isolated yields between 89 and 98% (Scheme 2).…”

“…We have determined previously that copper(II) sulfate pentahydrate and sodium halide react in the presence of 2-alkynylthioanisoles 1 to afford mono-halogenated benzo[b]thiophene derivatives 2 in isolated yields up to 98% (Scheme 1). 18 In this all-inclusive study, we have expanded upon this foundation through the implementation of new and varied functional groups to test the flexibility of this reaction as well as to demonstrate a scaffold upon which dihalogenated analogues may be achieved. The reaction of bromo-substituted 2-akynylthioanisoles 3 under the same reaction conditions gives dihalogenated benzo[ b ]thiophenes 4 with isolated yields up to 96% (Scheme 1).…”

Synthesis and structure elucidation of some novel thiophene and benzothiophene derivatives as cytotoxic agents

“…The solid product formed upon pouring into an ice/water mixture was collected by fi ltration, washed with water and crystallized from ethanol to give 11 (Table I). (12). -A solution of 8a (3.04 g, 0.01 mol) containing a catalytic amount of piperidine (0.50 mL) and benzaldehyde (1.06 g, 0.01 mol) was heated in an oil bath at 120 °C for about 2 hours and then boiled in ethanol (20 mL) for a few minutes.…”

Visible-light-induced oxidant and metal-free dehydrogenative cascade trifluoromethylation and oxidation of 1,6-enynes with water

“…The cyclization of 1,6-enynes can be a powerful transformation that allows for the construction of C 3 -aryloyl/acylated heterocycles ( Scheme 1 , eqn (2)). 15 – 17 1,6-Enyne substrates under transition metal (TM)-catalyzed reaction conditions are rearranged to benzofuran, 15 benzothiophene 16 and indole 17 heterocycles, and thus restrict the use of TM to access the desired C 3 -aryloylated heterocycles. On the other hand, the use of oxidants such as hypervalent iodine reagents, peroxides, and oxygen, which are required for the generation of the CF 3 radical and as a source of oxygen under TM-free conditions, led to the cleavage of the vinylic carbon–heteroatom (oxygen, sulfur, nitrogen, etc. )…”