Pd‐Catalyzed Annulation of β‐Iodovinyl Sulfones with 2‐Halophenols: A General Route for the Synthesis of 3‐Sulfonyl Benzofuran Derivatives

Abstract

The palladium‐catalyzed annulation between β‐iodovinyl sulfones and 2‐halophenols or 1‐bromo‐2‐naphthol or 2‐bromo‐3‐pyridinol is presented. The annulation process involving oxa‐Michael addition‐elimination and intramolecular Heck reaction leading to form 2,3‐disubstituted benzofurans (aryl benzofuryl sulfones) in good to high yields. The regioselective tandem construction of C−O and C−C bonds has been achieved with a variety of substitution patterns. Moreover, the tandem process is reliable at gram‐scale reactions and a plausible mechanism is also proposed.

K3PO4‐Promoted Cycloannulation of (E)‐β‐Iodovinyl Sulfones with ortho‐Hydroxy‐Chalcones/Cinnamates for the Synthesis of 2,3,4‐Trisubstituted 4H‐Benzopyran Derivatives

“…This observation ruled out that the alkynyl sulfone precursor 6 may not involve in the process, 6 usually observed from 1 a under basic conditions [13b] . The isotopic experiments were subsequently employed using deuterated β‐iodovinyl sulfone 1 a‐ D (98%‐ d ) [12a–c] and the standard reaction progressed slightly slower rate (Scheme 6b). Next, the same reaction was further performed at room temperature and isolated a mixture of 3 a‐ D and 3 a (1:9 ratio) in 88% yield (Scheme 6c).…”

“…As expected, the phenoxide ion A may generate from ortho ‐hydroxy chalcone 2 a in the presence of K 3 PO 4 . Subsequently, oxa‐Michael addition [12c,d] of A onto ( E )‐β‐iodovinyl sulfone ( 1 a ) could form β‐aryloxy sulfone anion B . In path‐A, the loss of iodine may allow for the formation of vinyl sulfone ( E , Z )‐ 3 a .…”

Accessing Medicinally Relevant O‐Benzofused Heterocycles through C−X Activation: Recent Trends

“…In this context, Reddy et al reported the regioselective synthesis of 3-arylsulfonylbenzofurans, naphthofurans and furanopyridine derivatives via palladium-catalyzed annulation of halophenols with β-iodovinyl sulfones (Scheme 5). [25] The reaction comprises a tandem sequence of an oxa-Michael addition/ Heck-Mizoroki reaction and demonstrated important functional group tolerance by delivering a broad scope of the aryl disubstituted benzofuran derivatives in high yields. This standard reaction procedure enabled the construction of a wide variety of disubstituted benzofuran structures in good yields.…”

Unified Radical Sulfonylative-Annulation of 1,6-Enynols with Sodium Sulfinates: A Modular Synthesis of 2,3-Disubstituted Benzoheteroles

“…Benzofurans, benzothiophenes, and indoles are widely distributed in bioactive natural products, pharmaceuticals, and functional organic materials (Figure a). , In sharp contrast, sulfones are an indispensable functional group in organic synthesis as well as a blueprint in medicinal and agrochemical chemistry (Figure b). In continuation of our efforts on organosulfur chemistry and cycloannulation strategies, herein, we report a novel and highly efficient AgNO 3 -catalyzed cascade sulfonylative-cyclization of propargylic alcohol-bearing 1,6-enynes with sodium sulfinates to access 2,3-disubstituted benzoheterole derivatives. More interestingly, a three-component reaction is also realized using 1,6-enynols, aryldiazonium salts, and Na 2 S 2 O 5 (as an SO 2 surrogate) to generate similar analogues, which would be an attractive alternative to existing methods.…”