4
Tetrahedron
Table 3. Functional group tolerance towards optimized conditionsa
Entry
Substrate
Product
NRc
Yield (%)b
1
2
2a
--
--
NRc
Scheme 2. Predicted reaction pathway for decarboxylative
chlorination.
3
Benzoic acid
20
Based on current experiments and previous literature,6 a probable
reaction pathway is predicted in Scheme 2. vinyl carboxylic acid
1 reacts with hypochlorite to form chloronium ion a which can
either undergo direct concerted decarboxylation to the
corresponding vinyl chloride 2 (Path 1) or it can form a 4
membered chloropropiolactone. b and the later can undergo
decarboxylation to the product 2 (Path 2).
4
5
Benzaldehyde
NRc
50
--
6
NRc
--
aReaction conditions: 10 mmol of Substrate, 50 mmol of NaOCl, stirred in 15
Acknowledgments
c
mL of acetonitrile at rt for 8 h. bIsolated yield. NR: No Reaction (starting
material, substrate recovered quantitatively).
VNT thanks to University Grant Commission, New Delhi,
India for providing financial support under UGC-Major
research scheme. NTH and SMG thank to University Grant
Commission, New Delhi, India for providing fellowship under
basic science research (UGC-BSR).
To prepare more reactive vinyl halides, we tried few one-pot
shuttling experiments using molecular iodine and bromine (Table
4). It should be noted that, halide shuttling occurred while
reaction progresses and not after it’s done. For example, addition
of I2 or Br2 initially along with NaOCl resulted in the formation
of vinyl iodide or bromide respectively (entries 1 and 4), while
the same was not observed when these molecular halides were
added after completion of the reaction, which means halogen
exchange could not be achieved in this reaction system (entries 2
and 5). However, it is also difficult to say how vinyl halides were
formed in these reactions, because separate reaction of vinyl
carboxylic acid with molecular I2 resulted in 20% yield of the
desired product 3a (entry 3) but use of Br2 did not give any vinyl
bromide 4a (entry 6). This rather suggests that direct
decarboxylative iodination can be done using I2 in the absence of
sodium hypochlorite, however decarboxylative bromination
could not be done only by using Br2.
References and notes
1. (a) Ding J.; You, Y.; Weng Z. Tetrahedron Lett. 2016, 57, 1724. (b)
Tang J.; Gooßen L. J. Org Lett. 2014, 16, 2664. (c) Li,M.; Gutierrez,
O.; Berritt,S.; Pascual-Escudero, A.; Yeşilçimen, A.; Yang, X.;
Adrio, J.; Huang, G.; Nakamaru-Ogiso, E.; Kozlowski, C.; Walsh
P.J. Nat Chem. 2017, 9, 997. (d) Ratovelomanana,V.; Linstrumelle.
G. Tetrahedron Lett. 1981, 22, 315.
2. (a) Johnson, R.; Ingham, R. T. Chem. Rev. 1956, 66, 219. (b) Wilson,
C. V. Org. Reactions, 1957, 9, 332.
3. (a) Cristol, S. J.; Firth Jr., W. C. J. Org. Chem. 1961, 26, 280. (b)
Cristol, S. J.; Gaston, L. K.; Tiedeman, T. J. Org. Chem. 1964, 29,
1279. (c) Davis, J. A.; Herynk, J.; Carroll, S.; Johnson, D. Bunds. J;
J. Org. Chem. 1965, 80, 415.
Table 4. Halide shuttling experimentsa
4. Graven, A.; Jorgensen, K.A.; Dahl, S.; Stanczak, A. J. Org. Chem.
1994, 59, 3543.
5. (a) Chowdhury, S.; Roy S. J. Org Chem. 1997, 62, 199. (b) Naskar,
D.; Chowdhury, S.; Roy, S. Tetrahedron Lett. 1998, 39, 699. (c)
Kuang, C.; Senboku, H.; Tokuda, M. Synlett. 2000, 10, 1439.
6. Solas, D.; Wolinsky, J. Synth. Commun. 1981, 11, 609.
7. Telvekar, V. N.; Arote, N. D.; Herlekar, O. P. Synlett. 2005, 2495.
8. For decarboxylative bromination, see; Telvekar V. N.; Takale, B. S.
Tetrahedron Lett. 2011, 52, 2394.
Entry X2
Yieldb of 2a Yieldb of 3a (X = I) Yieldb of 4a (X = Br)
(%)
31
55
0
(%)
24
0
(%)
--
1
I2
I2
I2
2c
3d
4
5c
6d
--
20
--
--
9. For decarboxylative azidation, see; Telvekar V. N.; Takale, B. S.;
Bachhav H. M. Tetrahedron Lett. 2009, 50, 5056.
Br2 47
Br2 49
18
0
10. For decarboxylative cyanation, see; Telvekar V. N.; Rane R.A.
Tetrahedron Lett. 2007, 48, 6051.
--
Br2
0
--
0
11. For aromatic chlorination using hypochlorite, see; Smith, J. C. J.
Chem. Soc. 1934, 213.
aReaction conditions: 10 mmol of 1a, 50 mmol of NaOCl, 10 mmol of I2/Br2
b
c
stirred in 15 mL of acetonitrile at rt for 8 h. Isolated Yield. Either I2 or Br2
d
12. For benzylic oxidation, see; Jin, C.; Zhang L.; Su,W. Synlett.
2011, 1435.
was added after 8 h. Separate reaction in the absence of NaOCl but in the
presence of I2 (entry 3) or Br2 (entry 6).
13. For oxidation of double bond using NaOCl, see; (a) Jacobsen, E.
N.; Zhang, W.; Muci, A. R.; Ecker, J. R.; Deng, L. J. Am. Chem. Soc.
1991, 113, 7063. (b) Mehltretter, G. M.; Bhor, S.; Klawonn,
M.;Döbler, C.; Sundermeier, U.; Eckert, M.; Militzer, H.-C.; Beller,
M. Synthesis, 2003, 295.