VANADIUM(II) CHLORIDE 1
Vanadium(II) Chloride (90 95% yield),4 and aryl azides to the corresponding amines
and N2 (70 95% yield) (eq 3).5
VCl2
N3 NH2
VCl2
[10580-52-6] Cl2V (MW 121.84)
(3)
THF, H2O
InChI = 1/2ClH.V/h2*1H;/q;;+2/p-2/f2Cl.V/h2*1h;/q2*-1;m
R R
InChIKey = ITAKKORXEUJTBC-OUXHBNONCC
R = H, 2-Me, 4-Cl, 4-F, 2-CF3
(nitro group to carbonyl conversion; hydrodehalogenation of
Ä…-halo ketones; reductions; reductive cleavage of oximes;
reductive hydrolysis of 2,4-DNP derivatives)
Reductive Cleavage of Oximes. Aqueous solutions of VCl2
have been employed in the mildly exothermic deoximation of
Alternate Names: vanadium dichloride; vanadium chloride.
oximes to the corresponding carbonyl compounds in 75 90%
ć%
Physical Data: mp 910 C (subl); d 3.23 g cm-3.
yield (eq 4).6
Solubility: sol with decomposition in hot and cold water; sol
alcohols, DMF, THF, ethers.
OH OVCl2
Form Supplied in: commercially available as a green deliquescent
N N NH
solid. VCl2
H+
THF, H2OH2O
 VOCl2
O
Vanadium(II) Chloride. Many reagents based on chro-
mium(II), titanium(II), and titanium(III) ions have found utility
(4)
in organic synthesis because of their redox potentials (Table 1).
Vanadium(II) chloride has found application in modern organic
87%
synthesis in part because its redox potential (+0.255 V) is
greater than the SnII SnIII couple (-0.15 V) although lower than
CrII CrIII (+0.41 V) or TiII TiIII (+0.37 V).1 A variety of syn-
thetic transformations have been documented.
Reductive Hydrolysis of 2,4-Dinitrophenylhydrazones.
The regeneration of carbonyl compounds from 2,4-dinitrophenyl-
Conversion of the Nitro Group to the Carbonyl Group.
hydrazones is often problematic owing to the acid stability of the
When an aqueous solution of vanadium chloride is added to a pri-
parent molecules. Vanadium chloride promotes the hydrolysis to
mary or secondary aliphatic nitro compound dissolved in a mix-
the respective carbonyl moiety in 67 95% yield via initial reduc-
ture of water, hydrochloric acid, and DMF, a moderate to good
tion of the nitro group.7
yield (50 70% typically) of the corresponding ketone is isolated
(eq 1).2 The pH-dependent procedure involves initial reduction
Other Vanadium(II) Reagents. Aryl and alkyl halides are re-
and subsequent hydrolysis of the resulting carbonyl imine.
duced by a number of low-valent transition metals.8 The complex9
Several alternative methods are known3 which will effect the
VCl2(py)4 reduces activated (e.g. Bn Cl) but not unactivated
same transformation.
halo compounds (e.g. vinyl halides). This reagent is selective
NO2 VCl2 O
towards the formation of coupled R R products to the exclu-
DMF, H2O
sion of R H-type products. In contrast, CrII reduces10 Bn Cl
(1)
53%
to various ratios of bibenzyl and toluene (dependent on the re-
action conditions). Bis(cyclopentadienyl)vanadium11 (Cp2V) is
also effective in these reactions. In an extension of earlier work,12
2,2,2-trichloroacetanilide has been selectively reduced to 2,2-
Ä…
Hydrodehalogenation ofÄ… Ketones. When an aqueous
Ä…-Halo
dichloroacetanilide using VCl2(py)4. Other complexes13 of di-
solution of vanadium chloride is added to Ä…-halo ketones1 in THF,
valent vanadium having the general formula V(amine)4X2 are
a mildly exothermic reaction ensues which yields the halogen-free
also known. The amine can be either aromatic (e.g. picoline) or
product after extractive workup (eq 2). Yields are generally quite
aliphatic (e.g. ethylenediamine). The V(amine)4X2 chemistry
high, ranging between 80 and 98%.
remains largely unexplored.
O O
Recently, a bimetallic VII species, [V2Cl3(THF)6]2[Zn2Cl6],
Br
VCl2
prepared in situ from VIII, has been introduced14 to achieve the
THF, H2O
stereoselective cross coupling of two different alkanals under mild
(2)
98%
conditions. The intermolecular pinacol cross-coupling reaction
has been modified15 to include chiral aldehydes which yield syn-
Br Br
diols in a 91:9 diastereoisomeric ratio (up to 84% ee). Reduc-
tive cyclization of ´,µ-enals has also been demonstrated16 to pro-
Reductions. This reagent also reduces benzils to ben- ceed with excellent stereoselectivity (eq 5), in contrast to what is
zoins (THF H2O, 80 90% yield),4 quinones to hydroquinones obtained with other reagents such as SmII.
Avoid Skin Contact with All Reagents
2 VANADIUM(II) CHLORIDE
[V2Cl3(THF)6]2[Zn2Cl6]
7. Olah, G. A.; Chao, Y.-L.; Arvanaghi, M.; Surya Prakash, G. K., Synthesis
CH2Cl2
1981, 476.
CO2Me
CHO 68%
8. Kustin, K., Prog. Inorg. Chem. 1969, 13, 107.
9. Cooper, T. A., J. Am. Chem. Soc. 1973, 95, 4158.
CO2Me CO2Me
+ (5) 10. de Liefde Meijer, H. J.; Janssen, M. J.; van der Kerk, G. J. M., Recl. Trav.
Chim. Pays-Bas 1961, 80, 831.
OH OH
11. Eisch, J. J.; King, R. B., Org. Synth. 1965, 1, 65.
24:1
12. Cooper, T. A.; Sonneberg, F. M., J. Org. Chem. 1975, 40, 55.
13. Kamar, M. M.; Larkworthy, L. F.; Patel, K. C.; Philips, D. J.; Beech, G.,
Aust. J. Chem. 1974, 27, 41.
1. Ho, T.-L.; Olah, G. A., Synthesis 1976, 807.
14. Raw, A. S.; Pedersen, S. F., J. Org. Chem. 1991, 56, 830.
2. Kirchoff, R., Tetrahedron Lett. 1976, 2533.
15. Annunziata, R.; Cinquini, M.; Cozzi, F.; Giaroni, P.; Benaglia, M.,
Tetrahedron 1991, 47, 5737.
3. (a) McMurry, J.; Melton, J., J. Am. Chem. Soc. 1971, 93, 5309.
(b) McMurry, J.; Melton, J.; Padgett, H., J. Org. Chem. 1974, 39, 259.
16. Inokuchi, T.; Kawafuchi, H.; Torii, S., J. Org. Chem. 1991, 56, 4983.
4. Ho, T.-L.; Olah, G. A., Synthesis 1976, 815.
5. Ho, T.-L.; Henninger, M.; Olah, G. A., Synthesis 1976, 815. Benoit Vanasse & Michael K. O Brien
6. Olah, G. A.; Arvanaghi, M.; Surya, G. K., Synthesis 1980, 220. Rhône-Poulenc Rorer Pharmaceuticals, Collegeville, PA, USA
A list of General Abbreviations appears on the front Endpapers