Synthesis of multi‐substituted dibenzo[b,d]furan

Abstract

The synthesis of multi-substituted dibenzo [b,d]furan derivatives 7a-b and 11a-b from readily available starting materials is described. These compounds are important intermediates for synthesis of molecules having wide therapeutic applications.

Synthesis of Dibenzofurans by Palladium-Catalysed Tandem Denitrification/C-H Activation

“…Gajera and co-workers have reported a synthesis of dibenzofurans in which the intramolecular Cu-catalysed coupling of diazonium salt was a key step. 11 To the best of our knowledge, there are few reports on palladium catalysed synthesis of dibenzofuran from diazonium salts. 11,12c Herein, we wish to disclose the details of an efficient synthesis of dibenzofurans from diazonium salts of diaryl ethers catalysed by palladium acetate in 80-93% yield.…”

“…In general, there are mainly two ways to construct dibenzofuran derivatives (Scheme 1) and other miscellaneous methods. 5 One involves initial formation of diaryl ether compounds, followed by a ring closure using light, 6 iodine, 7 triflate, 8 palladium, 9 decarboxylation/C-H activation, 10 CuI, 11 or Pschorr-type ring closure (Scheme 1, path a). 12 The second approach involves initial preparation of biaryl derivatives through the Suzuki reaction, and then formation of an intramolecular ether bond using dehydration, 13 Hartwig-Buchwald protocol, 4b C-H activation/C-O cyclisation 14 or an intramolecular SN Ar reaction (Scheme 1, path b).…”

Dibenzofuran Derivatives Inspired from Cercosporamide as Dual Inhibitors of Pim and CLK1 Kinases

“…The first method involves ortho-(aryloxy)aryldiazonium salts as intermediates to form an intramolecular C-C bond via a free-radical cyclization (Figure 2) [42][43][44]. Before obtaining the diazonium salt, the advantage of this approach relates to the nitro function that promotes the access to diaryl ethers 5-8 during the initial SN Ar reaction between 1-iodo-2-nitrobenzene and phenolic derivatives 1-4 (Scheme 1).…”

“…Before obtaining the diazonium salt, the advantage of this approach relates to the nitro function that promotes the access to diaryl ethers 5-8 during the initial SN Ar reaction between 1-iodo-2-nitrobenzene and phenolic derivatives 1-4 (Scheme 1). The first method involves ortho-(aryloxy)aryldiazonium salts as intermediates to form an intramolecular C-C bond via a free-radical cyclization (Figure 2) [42][43][44]. Before obtaining the diazonium salt, the advantage of this approach relates to the nitro function that promotes the access to diaryl ethers 5-8 during the initial SNAr reaction between 1iodo-2-nitrobenzene and phenolic derivatives 1-4 (Scheme 1).…”

“…The combined organic extracts were dried over sodium sulfate and filtered. The solvent was evaporated in vacuo and the residue was purified by silica gel column chromatography using cyclohexane/ethyl acetate (6/4) as the eluent to give compound 17 (43 6-Amino-1,3-dimethoxydibenzo[b,d]furan-4-carboxamide (18) To a solution of 1,3-dimethoxy-6-nitrodibenzo[b,d]furan-4-carboxamide 14 (50 mg, 0.16 mmol) in methanol (10 mL) at room temperature, saturated aqueous ammonium chloride (5 mL) and zinc dust (55 mg, 0.85 mmol) were added sequentially. After stirring for 30 min at room temperature, additional zinc was added (55 mg, 0.85 mmol) and the reaction mixture was refluxed for 2 h. After the addition of water, the aqueous layer was extracted with ethyl acetate (100 mL) and the resulting organic layer was washed with water (2 × 50 mL).…”