Table 2 Reductive amination of chitosan with benzaldehyde and pic-BH3

From: Facile and efficient synthesis of N-benzyl chitosan via a one-pot reductive amination utilizing 2-picoline borane

Run

Feed molar ratio

Benzylation degree (%)a

Residual imine moiety (%)b

Yield (%)c

-NH2

-CHO

pic-BH3

4

1

1

1

46

0

63

4’d

1

1

1

49

0

54

5

1

2

2

80

0.22

70

6

1

2

3

100e

0.15

87

  1. aBased on the deconvoluted integral ratio between protons 2 (N-benzyl chitosan) and 2’ (chitosan) in 1H NMR spectra
  2. bBased on the integral ratio between the proton (ca. 9.8 ppm) and the sum of the protons 2 (N-benzyl chitosan) and 2’ (chitosan) in the 1H NMR spectra
  3. cThe 100% yield is based on the mass of 100% N-benzyl chitosan
  4. dLow-molecular-weight chitosan (with a degree of deacetylation ≈99%) was utilized. This was prepared from commercial chitosan (degree of deacetylation = 75–85%, viscosity (1 wt.% in 1% acetic acid at 25 °C) = 20–300 cP, Sigma‒Aldrich (low molecular weight grade)). The deacetylation process was conducted in the same manner as that for medium-molecular-weight chitosan.
  5. eDeconvolution was not possible for the signals of 2 (N-benzyl chitosan) and 2’ (chitosan)
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