Single-crystal-to-single-crystal synthesis of a pseudostarch <i>via</i> topochemical azide–alkyne cycloaddition polymerization

Ravi, Arthi; Shijad, Amina; Sureshan, Kana M.

doi:10.1039/d1sc03727g

Cited by 17 publications

(13 citation statements)

References 50 publications

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“…It is noteworthy that the proton signals corresponding to 2 are retained in the 1 H NMR during the TAAC reaction of Co-I, implying that only molecules of 1 participated in the TAAC reaction and molecules of 2 remained intact (Figure 5a, peaks marked with red circles). Along the similar lines, while reduction in the azide peak intensity, in the time-dependent FTIR spectra, is usually expected and observed during TAAC reactions, [52][53][54][55] significant persistence of the azide stretching signal at 2104 cm À 1 in the FTIR spectrum of even completely reacted Co-I also indicates that the compound 2 is intact in the crystal even after complete reaction (Figure 5b). Formation of polymers with high molecular weight (based on GPC analysis) also support the progress of TAAC reaction along the supramolecular chain of 1 without the intervention of 2.…”

Section: Methodssupporting

confidence: 75%

Tuning the Regioselectivity of Topochemical Polymerization through Cocrystallization of the Monomer with an Inert Isostere

et al. 2022

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Regiochemistry of topochemical reactions depends on the crystal packing and biasing the regiochemistry necessitates precise crystal engineering. The pristine crystals of monomer 1 upon topochemical azidealkyne cycloaddition (TAAC) reaction give a 1 : 1 blend of 1,4-and 1,5-triazole-linked polymers due to the presence of two self-sorted reactive conformers in the crystal. We designed a binary isomorphous cocrystal of monomer 1 and a structurally similar dummy molecule 2 to limit the number of reactive conformers of 1 to one and thus to get one type of polymer. Equimolar solution of 1 and 2 in chloroform-acetone mixture gave two 1 : 1 cocrystals Co-I and Co-II. The Co-II, a chloroform adduct, on heating undergoes desolvation and polymorphic transition to Co-I. Co-I is isomorphic to 1 and 2 and possess self-sorted arrays of 1 and 2. Heating Co-I results in the TAAC polymerization giving 1,4-triazolyllinked polymer of 1 selectively, showing the power of crystal engineering in regiocontrol. Chemical reactions governed by the molecular arrangementin crystals-topochemical reactions-are attractive in terms of greener, catalyst-free and solvent-free reaction conditions, nonnecessity of chromatographic purification, and their ability to form unique products that are not accessible by the conventional solution-phase methods. [1][2][3][4][5][6] However unlike solution-state reactions that are well-explored, factors that influence topochemical reactions are still poorly understood. [7][8][9][10] The solution-state reactivity of molecules could be easily regulated by altering the reaction conditions such as solvent, reagents, catalyst, etc. However in the case

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Section: Methodssupporting

confidence: 75%

Tuning the Regioselectivity of Topochemical Polymerization through Cocrystallization of the Monomer with an Inert Isostere

et al. 2022

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“…Ravi et al reported the synthesis of a crystalline polysaccharide-mimic by TAAC polymerization. 98 They designed a topochemical reactive crystal of a glucose-mimicking monomer decorated with azide and alkyne units via crystal engineering. Upon heating, these pre-organized monomer crystals underwent regiospecific TAAC polymerization to yield 1,4-triazolyl-linked pseudopolysaccharide (pseudostarch), and the crystalline pseudostarch showed better thermal stability than many natural polysaccharides.…”

Section: Four Branches Of Polymer Crystalsmentioning

confidence: 99%

Recent progress in single-crystal structures of organic polymers

et al. 2022

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“…Cyclitol/pyranoside derivatives having two equatorial hydroxy groups at vicinal positions are known to arrange, in their crystals, in a zigzag fashion forming hydrogen‐bonded 1D‐chains (Figure 1a) [14] . We have exploited this consistent packing of this supramolecular synthon for designing pyranoside and cyclitol‐based monomers for TAAC polymerization [10b, 15] . By strategically positioning the azide and alkyne units in the plane of symmetry of myo ‐inositol, a monomer having two vicinal diol has been made, which crystallized as stacks of hydrogen‐bonded 2D‐layers (Figure 1b), as designed, thereby forming a head‐to‐tail arranged monomers along the stacking direction and underwent TAAC polymerization [10b] .…”

Section: Figurementioning

confidence: 99%

“…We have exploited this consistent packing of this supramolecular synthon for designing pyranoside and cyclitol‐based monomers for TAAC polymerization [10b, 15] . By strategically positioning the azide and alkyne units in the plane of symmetry of myo ‐inositol, a monomer having two vicinal diol has been made, which crystallized as stacks of hydrogen‐bonded 2D‐layers (Figure 1b), as designed, thereby forming a head‐to‐tail arranged monomers along the stacking direction and underwent TAAC polymerization [10b] . In order to check the feasibility of TAAC reaction with internal alkynes, we planned to exploit this reliable supramolecular glue for the design of monomer.…”

Section: Figurementioning

confidence: 99%

Topochemical Cycloaddition Reaction between an Azide and an Internal Alkyne

2022

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Here we report the synthesis of a trisubstituted-1,2,3-triazole-linked polymer using a topochemical azide-alkyne cycloaddition (TAAC) reaction. A cyclitolderived monomer having an azide and an internal alkyne group was designed. The four hydroxy groups present in this monomer dictate its crystal packing such that the monomer molecules are arranged head-to-tail, thereby placing the internal alkyne and the azide units of adjacent molecules proximally. Although the alignment of the reactive groups in the monomer crystal is not favourable for a topochemical reaction, a reactive orientation can be achieved by the rotation of the reactive groups. Upon heating the crystals, the monomer underwent topochemical polymerization to yield the trisubstituted-1,2,3-triazole-linked-polycyclitol. This study demonstrates a new synthetic strategy for cycloaddition reaction between non-polarized internal alkynes and azides to yield trisubstituted triazoles.

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Single-crystal-to-single-crystal synthesis of a pseudostarch via topochemical azide–alkyne cycloaddition polymerization

Abstract: There is high demand for polysaccharide-mimics as enzyme-stable substitutes for polysaccharides for various applications. Circumventing the problems associated with the solution-phase synthesis of such polymers, we report here the synthesis...

Cited by 17 publications

References 50 publications

Tuning the Regioselectivity of Topochemical Polymerization through Cocrystallization of the Monomer with an Inert Isostere

Tuning the Regioselectivity of Topochemical Polymerization through Cocrystallization of the Monomer with an Inert Isostere

Recent progress in single-crystal structures of organic polymers

Topochemical Cycloaddition Reaction between an Azide and an Internal Alkyne

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