Chotana GA, Kallepalli VA, Maleczka RE, Smith MR. Iridium-catalyzed borylation of thiophenes: versatile, synthetic elaboration founded on selective C-H functionalization.
Tetrahedron 2008;
64. [PMID:
24385669 DOI:
10.1016/j.tet.2008.02.111]
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Abstract
Iridium-catalyzed borylation has been applied to various substituted thiophenes to synthesize poly-functionalized thiophenes in good to excellent yields. Apart from common functionalities compatible with iridium-catalyzed borylations, additional functional group tolerance to acyl (COMe), and trimethylsilyl (TMS) groups was also observed. High regioselectivities were observed in borylation of 3-and 2,5-di-substituted thiophenes. Electrophilic aromatic C-H/C-Si bromination on thiophene boronate esters is shown to take place without breaking the C-B bond, and one-pot C-H borylation/Suzuki-Miyaura cross-coupling has been accomplished on 2- and 3-borylated thiophenes.
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