Bi(OTf)3-catalysed prenylation of electron-rich aryl ethers and phenols with isoprene: a direct route to prenylated derivatives

Abstract

Electron-rich aryl ethers and phenols react with isoprene (2-methylbuta-1,3-diene) in the presence of catalytic Bi(OTf)(3) at 40 °C to afford the corresponding prenylated or 2,2-dimethylchroman products, respectively, in moderate to good yields. This transformation offers a convenient and expedient entry to prenylated derivatives of electron-rich aromatics that often display enhanced biological activities. The methodology has been employed in the efficient synthesis of a biologically active natural product and related compounds.

Cyclisations Catalysed by Bismuth(III) Triflate

“…The proposed mechanism would first involve C ‐alkylation at the ortho position of the arene by reaction with the carbocation generated after the activation of isoprene by bismuth(III) triflate. Subsequent cyclisation of the o ‐prenylated phenol, also catalysed by Bi III , would form the substituted chromanes (Scheme ) …”

Acid-catalyzed chemoselective C- and O- prenylation of cyclic 1,3-diketones

“…It should be noted that prenylated resorcinols are also important scaffolds that can be found in diverse natural products [47][48][49][50][51][52]. However, conventional catalytic prenylation of resorcinols often displays poor selectivity and does not yield the O-prenylated product [34][35][36][37][38][39]. Thus, our approach provides an expedient alternative to construct C-and O-prenylated resorcinols with high selectivity.…”

“…Using prenol 4a as the coupling partner in the presence of AlCl3 catalyst resulted in the chemoselectivity of the reaction switching exclusively to O-prenylation [26][27][28][29][30][31][32][33]. Notably, both products 3 and 5 could be aromatized to the corresponding prenylated resorcinols that are otherwise difficult to synthesize [34][35][36][37][38][39].…”

New trends in bismuth-catalyzed synthetic transformations

“…Electron-rich aryl ethers and phenols react with isoprene in the presence of catalytic Bi(OTf ) 3 to afford the corresponding prenylated or 2,2-dimethylchroman products in moderate to good yields (Scheme 42). 48 Prenylated aryl derivatives could also be obtained by Bi(OTf ) 3 -catalyzed [1,3]-rearrangement of aryl 3-methyl-2-butenyl ethers. 49…”