Helix-sense-selective Polymerization of an Achiral Phenylacetylene
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چکیده
منابع مشابه
Helix-sense selective polymerization of carbodiimides: building permanently optically active polymers from achiral monomers.
The helix-sense selective polymerization of achiral monomers by homochiral catalysts was investigated. Polymerization of chiral carbodiimides (N-(R)-2,6-(dimethylheptyl)-N'-phenylcarbodiimide) by achiral catalysts yields polymers that undergo mutorotation at elevated temperatures, thus illustrating that these chains are formed under kinetic rather than thermodynamic control. Building on this ob...
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Poly(isocyanidcs), ( R N = C < ) n, can be prepared from isocyanidcs, R N += C " , by the catalytic action of nickel(II) compounds. The main chain of these polymers is a rigid helix. This helical conformation results from a restricted rotation around the single bonds that connect the main-chain carbon atoms. Polymerization of achiral isocyanides generally gives a racemic mixture of leftand righ...
متن کاملMacromolecular helicity inversion of an optically active helical poly(phenylacetylene) by chemical modification of the side groups.
An optically active helical poly(phenylacetylene) was synthesized by the copolymerization of phenylacetylenes bearing optically active hydroxy or ester groups obtained by the kinetic resolution of a racemic phenylacetylene with lipase; the helix-sense was inverted from one helix to another by the further chemical modification of the hydroxy groups with achiral bulky isocyanates or an acid chlor...
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We studied hydrogen-bonding assemblies in a series of dumbbell-shaped hydrazine derivatives, namely oxalyl N',N'-bis(3,4-dialkoxybenzoyl)-hydrazide (BFH-n, n = 4, 6, 8, 10) and oxalyl N',N'-dibenzoyl-hydrazide (FH-0). It has been demonstrated that NH-1 protons of BFH-n precipitated from tetrahydrofuran (THF) or dimethylformamide (DMF) were involved in intramolecular H-bonding to form 6-membered...
متن کاملUnexpected helicity control and helix inversion: homochiral helical nanotubes consisting of an achiral ligand.
The ligand tppda has been designed and synthesized as molecular leverage for helicity control when reacted with Cd(2+) ions. The guests MeOH or DMF preferentially stabilize the P-helical isomer, while the guest H2O causes a helix inversion to give the M-helical isomer as the major isomer without any chiral auxiliary.
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ژورنال
عنوان ژورنال: Kobunshi
سال: 2004
ISSN: 0454-1138,2185-9825
DOI: 10.1295/kobunshi.53.946