Well-Defined Boron-Containing Polymeric Lewis Acids

Abstract

A general new route to well-defined polymeric Lewis acids via borylation of silylated polymers is reported. Trimethylsilylated polystyrene (PS-Si) of controlled molecular weight and low polydispersity (PDI < 1.15) was obtained via atom transfer radical polymerization (ATRP) of 4-(trimethylsilyl)styrene. The functional polymer PS-Si was quantitatively borylated using BBr3 to give poly(4-dibromoborylstyrene) (PS-B), a novel soluble boron-containing polymeric Lewis acid. PS-B readily reacted with nucleophiles serving as a precursor to a family of new polymers with boron centers of variable Lewis acidity. Reaction of PS-B with Cu(C6F5) gave the highly Lewis acidic polymer poly[4-bis(pentafluorophenyl)borylstyrene], the first polymeric analogue of tris(pentafluorophenyl)borane.

π-Conjugated Organoboron Polymers via the Vacant p-Orbital of the Boron Atom

“…34 They have extended this strategy to the preparation of polythiophenes including boron atom in their main chain by highly selective Sn-B exchange 35 (Scheme 11). The polycondensation between distannylated bithiophene and bifunctional arylboron halide was achieved under mild conditions.…”

Structure and reactivity of a planar chiral naphthylferrocenylcopper heteroaggregate

“…In fact, the reagent (C 6 F 5 Cu) 4 has been successfully employed in areas ranging from molecular Lewis acid chemistry [9,10] to polymeric Lewis acids [11], conjugated materials [12], and even amphiphilic borate block copolymers [13]. With the ultimate goal of developing new chiral naphthylferrocenylborane Lewis acids, we decided to explore the reactivity of the heteroaggregate 2 with boron halides.…”

“…However, pentafluorophenyl copper also serves as a mild reagent in organometallic synthesis, specifically in (a) metal exchange reactions with formation of other arylcopper species and (b) metathesis reactions that involve transfer of the C 6 F 5 groups to other metals and metalloids (Scheme 1) [7,8]. Of particular interest is the aryl group transfer to boron with generation of perfluoroarylboranes [9][10][11][12][13]. This class of compounds has attracted tremendous interest in areas ranging from Lewis acid catalysis to activators in olefin polymerization, and as components of so-called ''frustrated Lewis pairs'', which are able to promote metal-free activation of small molecules, most notably H 2 [14].…”

Recent Advances in the Synthesis and Applications of Organoborane Polymers

“…Our approach involved the "masking" of polystyrene with silyl groups, which were then quantitatively replaced with the desired borane functional groups (Scheme 2) [25,26]. In the first step, the preparation of the TMS-functionalized polymer 4 was accomplished by ATRP [27], a controlled free radical polymerization technique that allows us to adjust the molecular weight by simply varying the ratio of initiator to monomer.…”