Abstract
The conversion of renewable biomass resources to synthetically valuable chemicals is highly desirable, but remains a formidable challenge in regards to the substrate scope and reaction conditions. Here we present the development of tris(pentafluorophenyl)borane–catalysed conversion of furans via ring-opening and closing cascade processes to afford silicon-functionalized synthetic chemicals under transition metal-free conditions. The furan ring-opening with hydrosilanes is highly efficient (TON up to 2,000) and atom-economical without forming any byproduct to give rise to α-silyloxy-(Z)-alkenyl silanes. Additional equivalents of silane smoothly induce a subsequent B(C6F5)3-catalysed cyclization of initially formed olefinic silane compounds to produce anti-(2-alkyl)cyclopropyl silanes, another versatile synthon being potentially applicable in the synthesis of natural products and pharmacophores.
Highlights
The conversion of renewable biomass resources to synthetically valuable chemicals is highly desirable, but remains a formidable challenge in regards to the substrate scope and reaction conditions
Described is the development of a boron-catalysed cascade silylative transformation of furans (I) involving selective ring-opening and closing processes, allowing for the sequential formation of two types of new silylated products of a-silyloxy-(Z)alkenyl silanes (II) and trans-(2-alkyl)cyclopropyl silanes (IV) (Fig. 1b)
The subsequent ring-closing of initially ring-opened a-silyloxy-(Z)-alkenyl silanes (II) is readily enabled by additional equivalent of hydrosilane leading to silylcyclopropanes (IV) without the need to isolate the ring-opened compounds II
Summary
The conversion of renewable biomass resources to synthetically valuable chemicals is highly desirable, but remains a formidable challenge in regards to the substrate scope and reaction conditions. Despite of such progresses on furan transformation reactions, there have been no developments far for the selective conversion of furans to ring-opened products bearing a sp[3] C À Si bond at ambient conditions.
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