Chiral interaction between aromatic aldehydes and a polymer bearing large chiral rings obtained by cyclopolymerization of bisacrylamide

Abstract

This paper describes the investigation of an interaction between chiral induction behavior and a chiral polymer obtained by cyclopolymerization of a bisacrylamide (1) prepared from a-pinene and acrylonitrile. Poly(1) can interact with aromatic aldehydes, as confirmed by infrared (IR), circular dichroism (CD), diffusion-ordered nuclear magnetic resonance spectroscopy (DOSY) and 1-D nuclear Overhauser effect difference (1-D NOE) measurements. The observed induced CD demonstrates that the chiral framework of poly(1) forced aldehydes to remain in chiral environments. IR, DOSY and 1-D NOE measurements on mixtures of poly (1) Keywords: chiral interaction; cyclopolymerization; radical polymerization INTRODUCTION Chiral polymers have been used as stationary phases for chiral separation 1-10 and as templates for asymmetric reactions. 11-15 To achieve high performance with a chiral polymer, the polymer needs appropriate functional groups and a rigid structure. As a candidate, we designed a chiral polyacrylamide prepared through cyclopolymerization of a chiral bisacrylamide (1) (Scheme 1). 16 The monomer can easily be prepared by a one-step reaction of a-pinene and acrylonitrile. 17 The cyclopolymerization proceeds through the formation of 10-or 11-membered chiral rings. Although the structure of the rings has not been clarified completely by spectroscopic analyses, computational calculation suggested that the 11-membered ring formations are significantly predominant over 10-membered ring formations because of steric hindrance and the stability of propagating radicals. The details will be described elsewhere. In spite of the typically unfavorable large ring formation, this cyclopolymerization can yield soluble polymers bearing the desired cyclic units in quantitative yields. The selectivity of the cyclopolymerization without branching was confirmed by matrix-assisted laser desorption-ionization time of flight mass spectroscopy analysis of poly(1) obtained by reversible additionfragmentation chain transfer (RAFT) polymerization, indicating that poly(1) has only one initiating and terminating group originating from the chain transfer agent. The circular dichroism (CD) spectra of the resulting polymers show Cotton effects originating from the amide moieties in chiral environments and suggest the potential application of poly(1) as a chiral polymer. The chiral rings in poly(1) contain

Complex polymer architectures through free-radical polymerization of multivinyl monomers

“…Contemporary experimental strategies to engineer MVMs for cyclopolymerization. Cyclopolymerization can be achieved by either using small DVMs (A) 87,[91][92][93]95,96,179 or by orienting the vinyl moieties close to one another through the use of a bulky template (Ba), [100][101][102][103][104][105][180][181][182][183] a metal template (Bc), [106][107][108] by exploiting hydrogen bonding (Bb) [110][111][112] or by constraining the reacting monomers in nanochannels (C) 115 . Figure 6.…”

Cyclopolymerization of a bisacrylate through selective formation of a 19-membered ring

“…However, the low concentration often limits the yields of polymers. 4,9 Effective strategies for improvement of the cyclization tendency involve conformational orientation of two polymerization groups with cyclic structures [10][11][12][13][14][15][16][17][18][19][20][21] or templates such as metal cations 22,23 and selective alternating copolymerization. 24,25 In the most common method, namely, the design of oriented monomers, additional constraints by steric hindrance 12,13,19 and hydrogen bonding 17 are effective in improving the cyclization tendency.…”

“…15,17,20 A bismethacrylate monomer, BMCH (trans-1,2-bismethacryloyloxyethylcarbamoyloxycyclohexane), can be prepared via the reaction of 2-methacryloyloxyethylisocyanate and trans-1,2-cyclohexanediol. The radical polymerization of BMCH proceeded through the selective cyclopolymerization because of the orientation of the methacrylate moieties by the cyclohexane ring and the hydrogen bonding of the urethane groups and gave a polymer consisting of repeating 19-membered ring units.…”