PHOSPHORUS, SULFUR, AND SILICON AND THE RELATED ELEMENTS
5
complete conversion.However, product 2a was not recovered ethylacetate in hexane). After the completion of reaction, the
but thiocarbamate A was remained intact.
reaction mixture was transferred into centrifuged tubes and
Having the optimal conditions in hand, It is examined the mixture was centrifuged for 10 min by using centrifuga-
that the scope of this procedure for the substrates having tion machine. Black color solid was settled at the bottom of
electron donating and electron withdrawing substituents on centrifuge tubes. The clear solution was concentrated by
the aryl rings. It is confirmed that acetone gave the target using rotary evaporator and the crude mixture was purified
product in quantitative yield. Therefore, the various sub- by silica gel (60-120 mesh) column chromatography using
strates bearing electron donating and electron withdrawing 2% ethylacetate in hexane as eluent to obtain phenyl isothio-
cyanate as an oily liquid.
groups are taken under the below shown reaction conditions
Table 4). The phenyl ring having electron donating groups
(
such as 4-methyl, 4-methoxy gave their respective aromatic
isothiocyanates (Table 4, entries 3-4) in an excellent yield.
Conclusion
The unsubstituted phenyl ring also gave target product in In summary, we have developed methodology for the con-
quantitative yield (Table 4, entry 1). Electron withdrawing struction of aryl/alkyl isothiocyanates from amines using
groups such as 4-fluoro and 4-chloro substituents gave their Iron catalysis under mild reaction conditions. No other by-
final products in 65-85% yields (Table 4, entries 2 and 7), products except target products were observed during the
however, unfortunately, the aryl ring having strong electron reaction process. The reactions were rapid, facile and
withdrawing group,–NO on second position gave no prod- accomplished at room temperature. All the substrates
2
uct. In oder to explore the diversity of substrates, we have yielded their target products in good to excellent yields.
tried the reaction with 4-cyano aniline under optimized
reaction conditions, but, no target product was provided,
Acknowledgements
whereas the reaction gave target product in high yield at
8
Disubstituted and ortho-substituted aryl rings gave their
respective isothiocyanates in good yield (Table 4, entry 9).
Finally aliphatic amines reactivity was studied and very
ꢀ
0 C and using strong base K CO (Table 4, entry 9).
2 3
The authors are thankful to management, J.K.C. College, Guntur for
providing work space and to Icon Pharmaceutical Lab for providing
instrumental support.
interestingly they produced their respective final products in ORCID
high yield (Table 4, entries 10-12).
Madhavi Nannapaneni
Experimental
References
General information
[
1] (a) Zheng, N.; McWilliams, J. C.; Fleitz, F. J.; Armstrong, J. D.;
Volante, R. P. Palladium Catalyzed Synthesis of Aryl Sulfides
Ligand Precursors for Transition Metal Catalyzed Cross-
Coupling Reactions: C ꢁ C, C ꢁ N, and C ꢁ S Bond Formation
Aniline, CS , FeCl , Fe(NO ) .H O, Fe (SO ) .H O, FeCl ,
2
3
3 3
2
2
4 3
2
2
Et N, pyridine, sodium bicarbonate, sodium acetate and
3
sodium hypo phosphate are purchased from Aldrich and
used without further purification. The solvents are pur-
chased and dried according to standard procedure prior to
1
use. H NMR (400 MHz) spectra are recorded with a Varian
b-Keto Ester as a Novel, Efficient, and Versatile Ligand for
Copper (I)-Catalyzed C ꢁ N, C ꢁ O, and C ꢁ S Coupling
jo070443m (d) Sperotto, E.; van Klink, G. P. M.; de Vries, J. G.;
van Koten, G. Ligand-Free Copper-Catalyzed C ꢁ S Coupling of
Punniyamurthy, T. Efficient Copper(I) Catalyzed C–S Cross
Correa, A.; Carril, M.; Bolm, C. Iron-Catalyzed S-Arylation of
Bolm, C. On the Role of Metal Contaminants in Catalyses with
4
00 spectrometer. Infrared (IR) spectra are recorded as a
Perkin Elmer Spectrum on FT-IR spectrometer.
Representative experimental procedure for the synthesis
of isothiocyanates
Aniline (2 mmol, 186 mg)/substituted aniline/aliphatic amine
was added into the acetone (3 mL) slowly while stirring and
followed by subsequently carbon disulfide (20 mmol (10 eq),
1
520 mg) and sodium acetate (2 mmol (1 eq), 164 mg)were
added to that prior solution at room temperature and stir-
ring was continued until get the yellow color solid. The
reaction was monitored by TLC. Soon after forming the
Modhave, R. K.; Patil, A. B.; Yewale, S. Novel Synthesis of
0
intermediate thiocarbamate, to this, FeCl (50 mol%, 81 mg)
Anthelmintic Drug 4-Isothiocyanato-4 -Nitrodiphenyl Ether and
3
and sodium acetate (2 mmol, 1 eq, 164 mg) were added
slowly for 5 min and stirring was further extended for 1 h at
room temperature. During this period, a black color precipi-
tate was observed and settled at bottom of round bottom
flask. The progress of reaction was investigated by TLC (5%
[
2] (a) Mukerjee, A. K.; Ashare, R. Isothiocyanates in the
Bound Isothiocyanates and Their Synthetic Equivalents as