1 Decarbonylative Halogenation by a Vanadium Complex
2 Sujoy Rana, Rameezul Haque, Ganji Santosh, and Debabrata Maiti*
3 Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
4 * S Supporting Information
5 ABSTRACT: Metal-catalyzed halogenation of the C-H bond and
6 decarbonylation of aldehyde are conventionally done in nature. However,
7 metal-mediated decarbonylative halogenation is unknown. We have
8 developed the first metal-mediated decarbonylative halogenation reaction starting from the divanadium oxoperoxo complex
9 K
3
V
5+
2
(O
2
2-
)
4
(O
2-
)
2
(μ-OH) (1). Aconcerted decarbonylative halogenation reaction was proposed based on experimental
10 observations.
11
■
INTRODUCTION
12 Halogenation occurs during biosynthesis of more than 4000
13 natural products that display biological activity of pharmaco-
14 logical interest including anticancer, antibacterial, antiviral,
15 antifungal, and antiinflammatory activities. Chlorination is the
16 predominant modification in nature, followed by bromination
17 and iodination. Vanadium-dependent haloperoxidases (V-
18 HPOs) are responsible for the majority of halogenation events
19 in marine natural products.
1
A common feature of the
20 haloperoxidases is generation of an η
2
-peroxo intermediate,
21 followed by the formation of vanadium-bound hypohalite,
22 which is responsible for electrophilic halogenation reactions
s1 23 (Scheme 1).
2
24 Like halogenation, aldehyde decarbonylation is another
25 significant event in nature. The heme-peroxo intermediate of
26 Cytochrome P450 catalyzes a number of C-C bond cleavage
27 reactions via aldehyde decarbonylation.
3
Decarbonylation also
28 occurs during biosynthesis of alka(e)ne by cyanobacteria (AD)
29 in which a dinuclear nonheme-iron peroxo complex is the
s2 30 putative active species (Scheme 2).
3d,4
On a related note, an
31 unknown deformylase is also suggested for the DNA
32 demethylase activity.
5
33 Although decarbonylation of aldehyde and halogenation of
34 the C-H bond are common in nature, metal-mediated
35 decarbonylative halogenation is unknown. Therefore, we set
36 out to develop a synthetic system that would deliver a
37 decarbonylative halogenation reaction. We postulated that a
38 s3 divanadium oxoperoxo complex (Scheme 3, M = V) could be a
39 suitable species based on the following: (1) bioinspired
40 vanadium oxoperoxo complexes are known for halogenation
41 s4 reaction (Scheme 4);
2,6
(2) dimetallic peroxo species are
42 suggested to carry out a decarbonylation reaction in
43 cyanobacterial aldehyde decarbonylase (AD; Scheme 2).
4b,c
44 Notably, Nam and co-workers reported decarbonylation of
45 aldehyde by a nonheme-iron(III) peroxo complex.
7
Valentine
46 also illustrated that a synthetic peroxoporphyrin complex,
47 [Fe
III
(TMP)(O
2
2-
)]
-
, can promote direct nucleophilic attack
48 on an aldehyde.
8
49
■
RESULTS AND DISCUSSION
50 A bright-yellow divanadium oxoperoxo complex,
51 K
3
(V
5+
)
2
(O
2
2-
)
4
(O
2-
)
2
(μ-OH) [K
3
V
2
O
12
H
3
, 1], was synthe-
52 sized from V
2
O
5
/KOH at room temperature in 80% yield.
9
The
Received: October 18, 2012
Scheme 1. Vanadium Oxoperoxo Catalyzed Halogenation in
Nature
Scheme 2. Suggested Bimetallic Peroxo Species for
Cyanobacterial AD
Scheme 3. Proposed Decarbonylative Halogenation
Reactions
Scheme 4. Decarbonylative Halogenations by a Vanadium
Catalyst
Article
pubs.acs.org/IC
© XXXX American Chemical Society A dx.doi.org/10.1021/ic302611a | Inorg. Chem. XXXX, XXX, XXX-XXX
bsh00 | ACSJCA | JCA10.0.1465/W Unicode | research.3f (R3.5.i1:3915 | 2.0 alpha 39) 2012/12/04 10:21:00 | PROD-JCA1 | rq_1109586 | 2/26/2013 14:06:49 | 6