4
Tetrahedron Letters
Xn
X1
X6d
Reference
No thiol coating)
After coating
by 1 in ethanol
After coating
by 6d in water
(
2
K Saq
2
K Saq
2
K Saq
Yn
Y1
Y6d
2
Figure 3. Color change of silver plates after aqueous K S (0.6 wt%) soaking
Three pieces of silver-plating metal (30 mm length) were prepared from commercially available long strings (20 mm width, 0.2 mm thickness).
The three pieces were washed with deionized water, and dried at 100–120˚C for 5 sec to afford Xn, X1 and X6d. The pieces X1 and X6d were
dipped into 1 in ethanol (0.1 wt% = 3.50 mmol/L) [19] and 6d in water (0.2 wt% = 3.30 mmol/L) at 55˚C for 30 sec, respectively, and washed
with deionized water, and dried at 100–120˚C. No pre-treatment was carried out for Xn. After being cooled to room temperature, all the three
pieces Xn, X1 and X6d were soaked with K Saq (0.6 wt%) at 22˚C for 1 min. Then, these surfaces were washed with deionized water at 22˚C
2
and dried at 100–120˚C for 5 sec to afford Yn, Y1 and Y6d, respectively.
The color of Yn was dark yellow, which indicated the direct effect from K
2
Saq. In contrast, color change from X1 to Y1, as well as from X6d
to Y6d, was highly suppressed. It is noteworthy that mottled pattern was partially observed in Y1 [20] but smooth surface was observed in all
the area of Y6d.
Conclusion and perspective
In conclusion, synthesis of organothiol–BGL003 was successfully carried out within a few steps in high chemical yields. A thioester of
each synthetic intermediate was stable during the following chemical reactions (carbodiimide condensation and methanolic solvolysis
under acidic condition). In contrast, the thioester in the organothiol–BGL003 was probably cleaved to release original organothiol in
situ at the metal surface. Accordingly, predictable result after coating with organothiol–BGL003 in water is as exactly same as with
organothiol in organic solvent, due to the molecular design of organothiol–BGL003.
In fact, anticorrosive performance of organothiol–BGL003 in water was as high as, or slightly higher than, that of organothiol in
organic solvent. We believe that the result reported in this paper will solve one of the environmental problems. To deploy this result for
the practical use, the synthetic process in a large scale is under optimization.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to
influence the work reported in this paper.
Acknowledgments
HN acknowledges the major financial support from Chemical Denshi Co. Ltd., as well as official support from Tokushima University.
MIA acknowledges the financial support from Chemical Denshi Co. Ltd for his doctor course study in Tokushima University.
References and notes
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9
1
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0. It is authorized that succinic acid is a food additive as a supplement by FDA.