New chiral terpene-derived vanadatranes

Article abstract of DOI:10.1016/S0020-1693(02)00847-2

The synthesis of three new chiral vanadatranes by reaction of oxovanadium(V) alcoholates with triethanolamine derivatives obtained from the terpenes (-)-β-pinene, (-)-limonene, and (-)-menthone is reported. Their structure is elucidated by NMR spectroscop

Full text of DOI:10.1016/S0020-1693(02)00847-2

Inorganica Chimica Acta 336 (2002) 147ꢁ150
/
www.elsevier.com/locate/ica
Note
New chiral terpene-derived vanadatranes
a,
Gabriele Wagner *, Rudolf Herrmann , Armando J.L. Pombeiro
b
c
a
Department of Chemistry, University of Surrey, Guildford GU2 7XH, UK
b
Instituto de Tecnologia Qu ´ı mica e Biol o´ gica, Av. da Rep u´ blica (EAN), Apartado 127, 2781-901 Oeiras, Portugal
c
Instituto Superior T e´ cnico, Centro de Qu ´ı mica Estrutural, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
Received 21 November 2001; accepted 13 February 2002
Abstract
The synthesis of three new chiral vanadatranes by reaction of oxovanadium(V) alcoholates with triethanolamine derivatives
obtained from the terpenes (ꢀ)-b-pinene, (ꢀ)-limonene, and (ꢀ)-menthone is reported. Their structure is elucidated by NMR
spectroscopy ( H, C, N, O, V). # 2002 Elsevier Science B.V. All rights reserved.
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15
17
51
1
13
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Keywords: Chiral vanadatranes; Terpene derivatives; NMR spectroscopy ( H, C, N, O, V)
1
. Introduction
temperature to give the corresponding vanadatranes 3a,
b and 3c as air-stable colourless to pale yellow solids
(Fig. 1).
The vanadatranes were fully characterized by the
3
Derivatives and analogues of triethanolamine often
form cage compounds with both main group and
transition metals. Such compounds have been called
atranes (in the case of vanadium, vanadatranes). The
parent compound vanadatrane was first obtained from
triethanolamine and oxovanadium(V) alcoholates by
Voronkov et al. [1] and shows interesting structural
properties: it is a stable monomeric vanadium(V) alk-
oxide and not prone to oligomerization reactions as
most oxovanadium alkoxides are when concentrated or
crystallized.
Only very few chiral vanadatranes have been reported
up to now; in these cases, one of the hydrogen atoms in
all three CH2ꢀ
replaced by an alkyl or phenyl substituent. However,
most of these compounds have been obtained solely in
racemic form [2], and thus only four homochiral
usual techniques (microanalysis, mass spectrometry, IR
and NMR spectroscopy). The presence of the oxovana-
dium(V) unit is clearly reflected in the typical IR signals
ꢀ
1
at 955ꢁ
existence of the Vꢀ
/
965 (Vꢁ
/
O) and 630ꢁ
/
635 (Vꢀ
/
O) cm
[2]. The
N bond is shown by the close
/
5
1
17
15
analogy of the V, O, and N NMR data when
compared with other vanadatranes whose crystal struc-
ture [2,3] is known. Thus, simple oxovanadium(V)
alcoholates show a highly shielded vanadium atom in
i
598 [5]; OV(OPr ) : d
organic solvents (OV(OEt) : d ꢀ
/
3
3
ꢀ
/
628 [6]), while the vanadatranes 3 (d ꢀ
and ꢀ392.7, respectively) compare well with the un-
substituted parent compound (d ꢀ
/
380.6, ꢀ
/
400.4,
/
O groups of triethanolamine has been
/
15
/
383.5 [2]). N and
17
O NMR data were determined for the limonene-
derived compound 3a. The nitrogen chemical shift (d
9.2, CDCl ) is clearly distinguished from the uncoor-
(
optically active) vanadatranes are known [3]. In this
5
3
work, we whish to present three new enantiopure chiral
vanadatranes which are easily accessible from terpenes
from the chiral pool. The ligands 2a, 2b and 2c were
prepared by ring opening of the corresponding homo-
chiral epoxides 1a, 1b or 1c with diethanolamine as
previously described [4]. Their reaction with triethoxy
vanadate in ethanol solution occurs smoothly at room
dinated ligand (d 26.4) and reflects the presence of the
vanadiumꢀnitrogen bond, just as in the parent vanada-
trane (d 54.8, d -DMSO) and the corresponding free
/
6
1
5
51
/
ligand triethanolamine (d 24.7) [7]. The Nꢀ V
coupling is not resolved in the vanadatranes, but a
coupling to the hydrogen atoms of the neighbouring
methylene groups can be observed (5.5 Hz; parent
1
7
vanadatrane: 3.2 Hz [7]). Up to now, O NMR data
*
Corresponding author. Tel.: ꢂ
/
44-1483-686 831
of vanadatranes have always been measured in D O
2
0020-1693/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 0 - 1 6 9 3 ( 0 2 ) 0 0 8 4 7 - 2

148
G. Wagner et al. / Inorganica Chimica Acta 336 (2002) 147ꢁ150
/
Fig. 2. NMR numbering of the atoms of 3a and conformation in
solution.
able is the absence of strain in these molecules, since all
ring systems are in conformations very similar to those
in the parent terpenes. The main differences are due to
the stronger deshielding effect of the vanadium(V) unit
1
3
as compared to silicon; thus, in the C spectra, the
carbon atoms attached to oxygen show considerably
higher deshielding in the vanadatranes (Dd 13, . . ., 20
ppm), while those attached to nitrogen are affected to a
lesser extent (Dd 1, . . ., 3 ppm), and all other carbon
Fig. 1. Synthesis of the vanadatranes 3a, 3b and 3c.
1
7
preferably enriched in O). As a result, rapid exchange
(
of oxygen between vanadatrane and the solvent oc-
curred, and two signals of the same intensity were
observed (d 980, Dn 275 Hz (line width at half height); d
atoms do not suffer any changes (Dd 5
/
9
/
1 ppm). An
analogous effect is observed in the H spectra, where the
deshielding of protons in the OꢀCH units is more
pronounced in the vanadium complexes (Dd 0.5, . . ., 0.8
ppm), whereas protons in NꢀCH feel less influence (Dd
.1, . . ., 0.3 ppm). Interestingly, all signals of the terpene
moieties show a tendency towards higher shielding in the
vanadatranes (Dd ꢀ0.2, . . ., 0.0 ppm for 3a and 3c, Dd
0.1, . . ., ꢀ0.4 ppm for 3b). The greater difference in
1
/
9
54, Dn 305 Hz) [5,8]. This observation was explained by
partial hydrolysis of the vanadatrane in aqueous solu-
tion. One of the triethanolamine arms is detached and
leaves behind an anionic vanadium complex with two
oxygen atoms in non-equivalent positions which are
responsible for the two signals observed. The oxygen
atoms of the triethanolamine moiety do not exchange
/
0
/
ꢀ
/
/
the pinane residue in 3b suggests that the conformation
may be somewhat different from the corresponding
silicon compound. The similarity of the NMR spectra of
the vanadatranes and the silatranes includes the occur-
ence of a very characteristic NOE effect in 3a between
17
with O labelled water and are therefore not observed.
In contrast, we have measured the spectrum in CDCl at
3
1
7
natural O concentration and found two well-resolved
signals in a 3:1 ratio (d 386, Dn 1870 Hz (VꢀO); d 1209,
Dn 370 Hz (VꢁO)), while the free ligand gives rise only
to a very broad hump in the range of ꢂ10ꢁ 100 ppm.
/
/
the methyl group 11H and one proton of the Nꢀ
/CH2
/
/
ꢀ
/
group (6H) which proves the puckering of the five-
membered rings as depicted in Fig. 2 (right). Since signal
overlap is more of a problem in the compounds 3b and
3c, one cannot draw the same conclusions about ring
puckering with certainty in these cases.
As for almost all oxygen atoms connected to another
element by a double bond, a higher deshielding of the
Vꢁ
/
O oxygen atom in combination with a narrower line
width is observed.
The structure of the terpene-derived part of com-
1
c was studied by H and
13
pounds 3aꢁ
/
C NMR
techniques, including two-dimensional shift correla-
tions, and NOE determinations. Despite the compara-
1
tively strong overlap of the H signals, the assignment
2
. Experimental
The chiral triethanolamines 2a, 2b and 2c were
including stereochemical aspects is complete for com-
pound 3a, and close to complete for 3b and 3c. Fig. 2
shows the numbering of the atoms quoted in the NMR
spectra (see Section 2) for the limonene-derived com-
pound 3a. The numbering of 3b and 3c was made
analogously and is consistent with that of the corre-
sponding silatranes obtained with the same ligands [4].
As a rule, the conformations closely resemble those of
the corresponding silatranes. Most of the conclusions
drawn about their structures also apply here. Remark-
prepared as described [4]. C, H and N elemental analyses
were carried out by the Microanalytical Service of the
Instituto Superior T e´ cnico. Optical rotations were
measured with a PerkinꢁElmer 241 M polarimeter and
/
ꢀ
1
2
deg cm g . Mass spectra were
ꢀ1
are quoted in 10
obtained on a Trio 2000 instrument in EI mode. IR
ꢀ
1
400 cm ) were recorded on a Mattson
1
7000 FTIR instrument in KBr pellets. H, C, N, O,
spectra (4000ꢁ
/
13
15
17
5
1
and V NMR spectra were measured on Varian
UNITY 300, Bruker AM 360 and Bruker DRX 500

G. Wagner et al. / Inorganica Chimica Acta 336 (2002) 147ꢁ
/
150
149
17
1
spectrometers, all nuclei except O at room temperature
7
1
5
(150 Hz). N NMR (CDCl ): d 59.2 (5.5 Hz).
3
O
1
7
(
r.t.), whereas O was measured at 50 8C. For assign-
NMR (CDCl ): d 1209 (370 Hz, Vꢁ
/
O), 386 (1870 Hz, 3
0.58, C H O). EIꢁMS: m/z 321
3
1
13
24
O). [a]
D
ment of the H and C signals and conformational
analysis, H,H-COSY with double quantum filter, HET-
COR, HMQC, HMBC, and one dimensional NOE
Vꢀ
/
ꢂ
/
89.78 (cꢃ
/
/
3
6
ꢂ
ꢂ
ꢂ
[M] , 303 [Mꢀ
/
H O] , 291 [MꢀCH O] , 273 (100%)
/
2
2
ꢂ
2 14 24 4
[MꢀH OꢀCH O] . Anal. Calc. for C H NO V: C,
/
/
2
5
1
difference spectra were used. V chemical shifts are
52.34; H, 7.53; N, 4.36. Found: C, 52.51; H, 7.75; N,
4.31%.
given relative to neat OVCl ꢃ0 ppm, with half height
/
3
1
5
17
line widths in parenthesis. N and O NMR spectra
were measured in natural abundance in direct detection
2.2. (1?R,3S)-5-Aza-6?,6?-dimethyl-1-oxo-1-vanada-
2,8,9-trioxabicyclo[3.3.3]undecane-3-spiro-2?-
bicyclo[3.1.1]heptane (3b)
1
7
mode, using 1.5 M solutions of the compound. For
O
NMR spectra, an aquisition time of 0.031 s and a
relaxation delay of 0.002 s was applied. Chemical shifts
1
5
Yield: 750 mg (78%), m.p. 248 8C. IR (cmꢀ1): 955 s
are given relative to H Oꢃ0 ppm. N spectra were
/
2
1
O). H NMR (CDCl ): d 0.94 (s,
recorded after addition of Cr(acac) (0.03 M) as relaxa-
n(Vꢁ
/
O), 630 m n(Vꢀ
/
3
3
tion reagent, using inverse gated decoupling, an acquisi-
tion time of 1 s and a relaxation delay of 3 s. Chemical
shifts are given relative to nitromethane (50% in
3H, 13H or 14H), 1.24 (s, 3H, 13H or 14H), 1.57 (d, 10.5
Hz, 1H, 12H anti to C8), 1.78 (dm, 8.5 Hz, 1H, 10H),
1.89 (m, 1H, 9H), 1.91 (m, 1H, 10H), 1.96 (m, 1H, 7H),
2.04 (m, 1H, 11H), 2.10 (m, 1H, 11H), 2.14 (m, 1H, 12H
syn to C-8), 3.01 (m, 1H, 4H or 6H), 3.05 (m, 1H, 6H or
4H), 3.07 (m, 1H, 4H or 6H), 3.08 (d, 13.5 Hz, 1H, 2H),
3.17 (m, 1H, 6H or 4H), 3.22 (d, 13.2 Hz, 1H, 2H), 4.56
CDCl )ꢃ379.6 ppm. Chemical shifts from the literature
/
3
are converted to this scale.
A suspension of V O (546 mg, 3 mmol) in dry EtOH
2
5
(
filtered. The solid, assumed to be unchanged V O , was
120 ml) was refluxed overnight, cooled to r.t. and
1
3
(m, 4H, 3H and 5H). C NMR (CDCl ): d 23.8 (C13 or
3
2
5
dried and weighted. From this weight, the amount of
OV(OEt)3 in the filtrate was calculated. Typically,
C14), 24.8 (C10), 27.0 (C12), 27.3 (C13 or C14), 33.8
(C11), 38.2 (C8), 40.1 (C9), 54.9 (C7), 55.9 (C4 or C6),
56.8 (C4 or C6), 66.7 (C2), 73.6 (C3 or C5), 74.5 (C3 or
solutions containing approximately
3
mmol of
OV(OEt) were obtained [9]. They were treated with a
5
1
C5), 89.7 (C1). V NMR (CDCl ): d ꢀ
/
400.4 (174 Hz).
ꢂ
3
3
24
D
solution of one equivalent of the corresponding chiral
triethanolamine in 5 ml of EtOH at r.t. for 2 h. Complex
[a]
303 [Mꢀ
CH O] , 261 [Mꢀ
ꢂ
/
8.08 (cꢃ
/
0.25, C H O). EIꢁ
/
MS: m/z 321 [M] ,
ꢂ
3
6
ꢂ
/
H O] , 291 [Mꢀ
/
CH O] , 273 [Mꢀ
/
H Oꢀ
/
2
2
2
ꢂ
ꢂ
ꢂ
3
b precipitates directly from the reaction mixture as a
/
2CH O] , 183 [Mꢀ
/
pinanone] ,
2
2
ꢂ
colourless powder which is filtered off and dried in
vacuo. The complexes 3a and 3c are obtained as
crystalline pale yellow solids upon slow evaporation of
approximately 90% of the solvent, filtration and drying
in vacuo.
153 (100%) [Mꢀ
/
pinanoneꢀ
/
H O] . Anal. Calc. for
2
C H NO V: C, 52.34; H, 7.53; N, 4.36. Found: C,
52.68; H, 7.39; N, 4.50%.
1
4
24
4
2.3. (3S,2?S?,-5?R)-5-Aza-5?-methyl-2?-(1-
methylethyl)-1-oxo-1-vanada-2,8,9-
trioxabicyclo[3.3.3.]undecane-3-spiro-1?-cyclohexane
(3c)
2
1
.1. (3R,6S,8R)-5-Aza-3-methyl-6-(1-methylethenyl)-
-oxo-1-vanada-2,12,13-
3
,8
trioxatricyclo[7.3.3.0] pentadecane (3a)
ꢀ
1
Yield: 770 mg (76%), m.p. 200 8C. IR (cm ): 965 s
ꢀ
1
1
O). H NMR (CDCl ): d 0.76 (m,
Yield: 530 mg (55%), m.p. 214 8C (dec.). IR (cm ):
n(Vꢁ
/
O), 635 m n (Vꢀ
/
3
1
9
(
1
(
65 s n(Vꢁ
s, 3H, 11H), 1.49 (m, 1H, 7H ax.), 1.56 (m, 1H, 8H ax.),
.60 (dm, 10.8 Hz, 1H, 7H eq.), 1.72 (s, 3H, 14H), 1.80
td, 13.2 Hz, 5.7 Hz, 1H, 10H ax.), 1.99 (dm, 10.8 Hz,
/
O), 630 m n(Vꢀ
/
O). H NMR (CDCl ): d 1.39
1H, 9H), 0.79 (d, 6.0 Hz, 3H, 14H or 15H), 0.86 (d, 7.0
Hz, 3H, 12H), 0.88 (d, 6.2Hz, 3H, 14H or 15H), 1.04 (m,
1H, 7H), 1.06 (m, 1H, 11H), 1.46 (dquart., 12.4 Hz, 3.0
Hz, 1H, 8H), 1.55 (dt, 12.9 Hz, 2.7 Hz, 1H, 8H), 1.68 (m,
1H, 9H), 1.71 (m, 1H, 10H), 1.96 (m, 1H, 11H), 1.99 (m,
1H, 13H), 2.92 (d, 14.1 Hz, 1H, 2H), 3.00 (dd, 11.4 Hz,
5.7 Hz, 1H, 4H or 6H), 3.07 (td, 12.3 Hz, 3.6 Hz, 1H, 4H
or 6H), 3.20 (td, 12.1 Hz, 3.2 Hz, 1H, 4H or 6H), 3.26
(m, 1H, 4H or 6H), 3.40 (d, 14.4 Hz, 1H, 2H), 4.49 (br,
1H, 3H§ or 5H§), 4.59 (td, 12.2 Hz, 4.2 Hz, 1H, 3Hƒ or
5Hƒ), 4.60 (br, 1H, 3H§ or 5H§), 4.64 (td, 12.0 Hz,
3
1
1
H, 8H eq.), 2.12 (dm, 13.5 Hz, 1H, 10H eq.), 2.51 (m,
H, 9H eq.), 2.75 (dd, 13.2 Hz, 4.8 Hz, 1H, 6H?), 2.87
(
1
(
td, 12.6 Hz, 5.7 Hz, 1H, 4H), 2.95 (dd, 13.2 Hz, 2.7 Hz,
H, 2H ax.), 3.09 (dd, 12.9 Hz, 3.9 Hz, 1H, 4H?), 3.32
td, 12.6 Hz, 6.6 Hz, 1H, 6H (NOE to 11H)), 4.38 (br,
1
1
1
H, 3H§), 4.57 (br, 1H, 5H§), 4.60 (td, 12.0 Hz, 3.9 Hz,
H, 3Hƒ), 4.74 (td, 12.0 Hz, 4.2 Hz, 1H, 5Hƒ), 4.80 (‘s’,
1
3
H, 13-H trans to CH 14), 4.93 (‘s’, 1H, 13H cis to
1
3.9Hz, 1H, 3Hƒ or 5Hƒ). C NMR (CDCl ): d 18.1
3
3
3
CH 14). C NMR (CDCl ): d 22.6 (C14), 23.3 (C11),
3
(C14 or C15), 21.1 (C8), 22.2 (C14 or C15), 23.6 (C12),
26.6 (C13), 27.8 (C10), 34.3 (C9), 48.5 (C7), 51.9 (C11),
3
2
5
1
5.1 (C10), 25.9 (C8), 38.6 (C9), 39.2 (C7), 50.7 (C6),
3.2 (C4), 62.6 (C2), 74.3 (C3), 75.5 (C5), 89.7 (C1),
56.8 (C4 or C6), 59.3 (C4 or C6), 62.6 (C2), 74.3 (C3 or
51
5
1
11.2 (C13), 145.6 (C12). V NMR (CDCl ): d ꢀ
/
380
C5), 74.9 (C3 or C5), 95.1 (C1). V (CDCl ): d ꢀ392
/
3
3

150
G. Wagner et al. / Inorganica Chimica Acta 336 (2002) 147ꢁ150
/
2
D
4
(
3
181 Hz). [a]
ꢂ
ꢀ
/
83.38 (cꢃ
/
0.12, C H O). EIꢁ
/
MS: m/z
ꢂ
References
3
6
ꢂ
37 [M] , 319 [Mꢀ
CH O] , 277 [Mꢀ
menthone] , 153 (100%) [Mꢀ
/
H O] , 307 [MꢀCH O] , 289
/
2
2
ꢂ
ꢂ
[1] (a) M.G. Voronkov, A.F. Lapsin, Khim. Geterotsikl. Soedin.
(1966) 357;
[
Mꢀ
/
H Oꢀ
/
/
2CH O] , 183 [Mꢀ
/
2
2
2
ꢂ
ꢂ
/
menthoneꢀH O] .
/
2
(b) M.G. Voronkov, G.I. Seltschan, A. Lapsina, W.A. Pestuno-
witsch, Z. Chem. 8 (1968) 214.
Anal. Calc. for C H NO V: C, 53.40; H, 8.37; N,
4
1
5
28
4
.15. Found: C, 53.66; H, 8.29; N, 4.03%.
[2] D.C. Crans, H. Chen, O.P. Anderson, M.M. Miller, J. Am. Chem.
Soc. 115 (1993) 6769.
[
[
3] W.A. Nugent, R.L. Harlow, J. Am. Chem. Soc. 116 (1994) 6142.
4] G. Wagner, B. Pedersen, R. Herrmann, W. Scherer, Z. Natur-
forsch. 56b (2001) 25.
Acknowledgements
[5] D.C. Crans, P. Shin, Inorg. Chem. 27 (1988) 1797.
[
[
6] W. Priebsch, D. Rehder, Inorg. Chem. 24 (1985) 3058.
7] E.E. Liepinsh, A.F. Lapsinya, G.I. Zelchan, E.Y. Lukevics, Latv.
PSR Zinat. Akad.Vestis. Kim. Ser. (1980) 371.
The authors wish to thank the European Community
and the Funda c¸ a˜ o para a Ci eˆ ncia e Tecnologia, Portu-
gal, for grants (TMR Erbfmeict 972008, Praxis xxi BPD/
[
[
8] D.C. Crans, P. Shin, J. Am. Chem. Soc. 116 (1994) 1305.
9] C.R. Cornman, J. Kampf, M.S. Lah, V.L. Pecoraro, Inorg. Chem.
31 (1992) 2035.
1
1779/97, BPD/1638/2000 and BCC/20261/99).