Studies of the stereoselective allylation of chiral benzaldimine chromium tricarbonyl complexes

Article abstract of DOI:10.1016/S0022-328X(99)00601-4

Highly stereoselective allylation of a series of chiral tricarbonylchromium benzaldimine complexes (2a-c) was achieved at -20°C and homoallyl amine complexes (4a-c) were isolated in good yields. In the case of homoallyl amine 4c, obtained in 75% d.e., the degree of stereoselection depends on the catalyst and the reaction conditions. The crystal structure of the major diastereoisomer of racemic 4c was determined by X-ray diffraction, which showed a (S,S) or (R,R) configuration, in agreement with the stereochemical model operating for the ortho-substituted tricarbonylchromium arene complexes. Furthermore, the new tricarbonylchromium complex of N-(2-methoxybenzyliden)diphenyl phosphinamide 3 was prepared. This substrate is a stable analog of the normally unviable ammonia imine.

Full text of DOI:10.1016/S0022-328X(99)00601-4

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 593–594 (2000) 380–387
Studies of the stereoselective allylation of chiral benzaldimine
chromium tricarbonyl complexes
Stefano Maiorana a,*, Clara Baldoli a,1, Paola Del Buttero a, Emanuela Licandro a,
Antonio Papagni b, Maurizio Lanfranchi c, Antonio Tiripicchio c
a Dipartimento di Chimica Organica e Industriale, Uni6ersity of Milan and CNR Centro Studio Sintesi e Stereochimica Speciali Sistemi Organici,
Via C. Golgi, 19, I-20133 Milan, Italy
b Dipartimento di Scienza dei Materiali, Uni6ersity of Milan (Bicocca), Via R. Cozzi, 53, I-20125 Milan, Italy
c Dipartimento di Chimica Generale ed Inorganica, Chimica Analitica, Chimica Fisica,
Uni6ersity of Parma and Centro di Studio per la Strutturistica Diffrattometrica del CNR, Parco Area delle Scienze 17A, I-43100 Parma, Italy
Received 7 July 1999; accepted 4 October 1999
Dedicated to Professor Fausto Calderazzo on the occasion of his 70th birthday.
Abstract
Highly stereoselective allylation of a series of chiral tricarbonylchromium benzaldimine complexes (2a–c) was achieved at
−20°C and homoallyl amine complexes (4a–c) were isolated in good yields. In the case of homoallyl amine 4c, obtained in 75%
d.e., the degree of stereoselection depends on the catalyst and the reaction conditions. The crystal structure of the major
diastereoisomer of racemic 4c was determined by X-ray diffraction, which showed a (S,S) or (R,R) configuration, in agreement
with the stereochemical model operating for the ortho-substituted tricarbonylchromium arene complexes.
Furthermore, the new tricarbonylchromium complex of N-(2-methoxybenzyliden)diphenyl phosphinamide 3 was prepared. This
substrate is a stable analog of the normally unviable ammonia imine. © 2000 Elsevier Science S.A. All rights reserved.
Keywords: Tricarbonylchromium arenes; Stereoselective allylation; Imines; Homoallylamines
1. Introduction
bonyl(benzaldimine) chromium complexes have been
widely used for the usually very highly stereoselective
synthesis of various organic and organometallic com-
pounds [2,3]. The addition of organometallic reagents
to chiral arylimine complexes was studied some years
ago by Solladie´-Cavallo [3a], but to the best our knowl-
edge no examples of the addition of allylic
organometallics to such imines have yet been reported.
Because enantiopure homoallyl amines are molecules of
considerable interest, we decided to study the addition
reaction of allylic organometallic reagents to chiral
benzaldimine complexes.
Optically active amines are important organic com-
pounds that can be used as chiral building blocks,
chiral auxiliaries or ligands for catalysts in the field of
asymmetric synthesis. Furthermore, amines with an
a-stereocenter are widely represented in bioactive and
pharmacologically interesting molecules.
The stereoselective 1,2-nucleophilic addition of
organometallic reagents to imines is a useful method for
the synthesis of primary and secondary enantiopure
amines [1]. In particular, the use of allylic organometal-
lic compounds provides a route to homoallyl amines,
which are valuable molecules due to the different possi-
ble transformations of the double bond. Chiral tricar-
2. Results and discussion
We report here the results of the stereoselective addi-
tion of allyl magnesium bromide to a series of chiral
imine complexes 2 and 3 (Fig. 1).
* Corresponding author. Fax: +39-02-2364-369.
E-mail address: maior@icil64.cilea.it (S. Maiorana)
1 Also corresponding author.
0022-328X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00601-4

S. Maiorana et al. / Journal of Organometallic Chemistry 593–594 (2000) 380–387
381
Fig. 1.
N-Phenyl benzaldimines 2a–c, were prepared from
the parent benzaldehyde complexes 1a–c as previously
described [2b,f]. The Cr(CO)3 complex of N-
diphenylphosphinylimine (3), prepared as reported be-
low, is a new complex and particularly interesting
substrate as it provides a stable analog of normally
unviable ammonia imine [4].
We first studied the addition of allyl magnesium
bromide to racemic N-phenyl benzaldimine complexes
2a–c. The reaction was run in THF at −20°C in the
presence of ZnCl2 (0.1 equivalent). The color of the
solution immediately changed from orange to yellow
after the Grignard addition and the reaction was com-
plete in about 20 min. Homoallyl amine complexes
4a–c were isolated in very good yields (Scheme 1):
Fig. 2. View of the structure of the (S,S) enantiomer of the major
diastereoisomer of racemic 4c.The ellipsoids are drawn at the 30%
probability level.
Complexes 4a and 4b were obtained with complete
diastereoselection as determined by 1H-NMR on the
crude reaction mixture. Compound 4c (R=OCH3)
showed a lower d.e. value (75%, Scheme 1), but the
major diastereoisomer of racemic 4c, was easily ob-
tained after chromatographic separation of the crude
reaction mixture. Furthermore (−)-4c was also ob-
tained in enantiopure form, starting from optically pure
(+)-1(S)-2c (see Section 4). Decomplexation of (−)-4c
by means of air and sunlight gave the corresponding
enantiopure homoallylimine (+)-5c in quantitative
yields. (Scheme 2)
The determination of the crystal structure of 4c by a
X-ray diffraction showed that the configuration of the
major diastereoisomer of 4c is C4-(S), C10-(S) or C4-
(R), C10-(R). The structure of the enantiomer C4-(S),
C10-(S) is shown in Fig. 2 together with the atomic
numbering system. Selected bond distances and angles
in 4c are given in Table 1.
Scheme 1.
4
R
Yield (%)
D.e.
a
b
c
CH3
Cl
OCH3
80
90
88
98
98
75
The coordination around the Cr atom is of three
legged piano stool type with the metal interacting in a
Scheme 2.

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S. Maiorana et al. / Journal of Organometallic Chemistry 593–594 (2000) 380–387
Table 1
with respect to the arene C5, C7, C9 carbon atoms, as
shown by the torsion angle C1–Cr–CE–C9= −
10.3(3)°, C2–Cr–CE–C5= −11.1(3)° and C3–Cr–
CE–C7= −13.5(3)° (CE is the centroid of the arene).
The eclipsed orientation of the Cr(CO)3 tripod with
respect to the OMe substituent is in accord with litera-
ture results for arene complexes bearing electron donat-
ing groups. [5]
The 75% d.e obtained in the case of complex 4c is
lower than the d.e. usually reported in the literature
when adding different nucleophiles to 2-methoxyben-
zaldehyde (85–100% [2a,c,f,5e] or 2-methoxyben-
zaldimine complexes (85–98%, [2b,c,f,6]), and so we
decided to investigate further the stereochemical out-
come of the reaction on 2-methoxybenzaldimine com-
plex 2c.
On the basis of the stereochemical model for the
addition of a nucleophile to a prostereogenic unit of an
ortho-substituted complex [6], the major (or exclusive)
diastereoisomer is generated by the approach of the
Grignard reagent from the opposite side to that of the
Cr(CO)3 group on the favourite conformation A of
imine, in which the CꢀN group is anti with respect to
the ortho-substituent (Fig. 3).
Considering the 1S enantiomer of 2c (in which the
Si-face is the favourite), the Grignard addition to con-
former A leads to an S configuration for the new
stereocenter, in agreement with the result of the X-ray
analysis of 4c. On the other hand, a possible Lewis acid
chelation between the imine nitrogen and the oxygen of
OCH3 could stabilize the minor conformer B, thus
leading to the formation of a certain amount of the
opposite diastereoisomer.
,
Selected bond lengths (A) and angles (°) for 4c
Bond lengths
Cr–C(1)
Cr–C(2)
Cr–C(3)
Cr–C(4)
Cr–C(5)
Cr–C(6)
Cr–C(7)
Cr–C(8)
Cr–C(9)
O(1)–C(1)
O(2)–C(2)
O(3)–C(3)
O(4)–C(5)
1.850(4)
1.834(3)
1.836(3)
2.280(3)
2.263(3)
2.236(3)
.203(3)
2.217(3)
2.228(3)
1.154(4)
1.147(4)
1.154(4)
1.351(4)
(4)–C(20)
N–C(14)
N–C(10)
1.430(4)
1.392(4)
1.449(4)
1.401(4)
1.433(4)
1.531(4)
1.399(4)
1.417(5)
1.386(6)
1.417(5)
1.552(4)
1.485(5)
1.303(5)
C(4)–C(9)
C(4)–C(5)
C(4)–C(10)
C(5)–C(6)
C(6)–C(7)
C(7)–C(8)
C(8)–C(9)
C(10)–C(11)
C(11)–C(12)
C(12)–C(13)
Bond angles
C(2)–Cr–C(3)
C(2)–Cr–C(1)
C(3)–Cr–C(1)
C(2)–Cr–C(8)
C(1)–Cr–C(6)
C(3)–Cr–C(4)
88.16(15)
88.43(15)
88.29(15)
162.05(14)
165.51(14)
163.07(13)
C(5)–C(4)–C(10)
O(4)–C(5)–C(6)
O(4)–C(5)–C(4)
C(6)–C(5)–C(4)
C(5)–C(6)–C(7)
C(8)–C(7)–C(6)
C(7)–C(8)–C(9)
C(4)–C(9)–C(8)
N–C(10)–C(4)
N–C(10)–C(11)
C(4)–C(10)–C(11)
C(12)–C(11)–C(10)
C(13)–C(12)–C(11)
119.7(3)
124.0(3)
115.2(3)
120.8(3)
119.3(3)
121.0(3)
119.2(3)
121.6(3)
112.7(3)
109.1(2)
109.7(2)
114.1(3)
125.2(4)
C(5)–O(4)–C(20) 118.8(3)
C(14)–N–C(10)
O(1)–C(1)–Cr
O(2)–C(2)–Cr
O(3)–C(3)–Cr
C(9)–C(4)–C(5)
125.5(2)
177.3(3)
179.8(3)
179.0(3)
118.0(3)
C(9)–C(4)–C(10) 122.2(3)
This hypothesis suggests that the amount of the
Lewis acid could be an important factor in driving the
reaction towards one or the other of the two
diastereoisomers (Fig. 3).
Fig. 3.
With the aim of thoroughly investigating the
stereoselectivity of the allylation of 2-methoxyben-
zaldimine complex 2c, the reaction was repeated under
different experimental conditions, by changing the
amount and nature of Lewis acid, as well as the reac-
tion temperature (Scheme 2, Table 2)
In a first set of experiments we studied the influence
of the amount of ZnCl2 on the stereoselectivity, work-
ing again at −20°C (entries 4–6). The reaction was
first run using one equivalent of ZnCl2 (Table 2, entry
4), but only a slight decrease in d.e. (10%) occurred
(compare entry 4 with entry 5). A considerable increase
in d.e. (90%) was found when the reaction was run
without any catalyst (entry 6), but the product was
obtained in lower yield (53%) even after addition of two
further equivalents of Grignard reagent.
Table 2
Allylation of 2c to give 4c
Entry T (°C)
ZnCl2 (equivalents)
% Yield % D.e.
1
2
3
0
0
0
1
0.1
0
90
90
74
62
70
90
4
5
6
−20
−20
−20
1
0.1
0
90
88
53
65
75
90
7
8
−78
−78
0.1
75
79
93
98
BF3·OEt2 (1 equivalent)
slightly asymmetric h6-fashion with the arene (Cr–C
bond lengths in the range 2.203(3)–2.280(3) A). The
three carbonyls adopt a nearly eclipsed conformation
In a second set of experiments, we studied the effect
of temperature on stereoselectivity by working at 0°C
(entries 1–3). The same trend of stereoselection was
,

S. Maiorana et al. / Journal of Organometallic Chemistry 593–594 (2000) 380–387
383
Scheme 3.
Scheme 4.
observed and, in the case of the reaction run in the
absence of ZnCl2 (Table 2, entry 3), the yield was better
than at −20°C again with a good d.e. (90%). Finally,
the reaction with 0.1 equivalent of ZnCl2 was per-
formed at −78°C (entry 7) and 4c was obtained in
higher stereoselection (93%) and quite good yields
(75%).
These results suggest that the Lewis acid catalyst
affects reaction yields, but has little effect on
diastereoselectivity; the Zn chelation between OCH3
and CꢀN only plays a marginal role in controlling
stereoselection (as also found by Ku¨ndig [7]). It is likely
that the angular geometry of the methoxy group re-
duces its steric hindrance (see X-ray, Fig. 2) and conse-
quently the discrimination between the two conformers
A and B. In line with this assumption, the bulkier
ortho-substituents, such as CH3 and Cl in 2a and 2b,
gave the corresponding 4a and 4b with complete
stereoselection (see Scheme 1).
The racemic N-diphenylphosphinyl imine complex 3
was prepared in very good yields from tricarbonyl(2-
methoxybenzaldehyde)chromium (1c), following a pro-
cedure described for uncomplexed substrates [8].
(Scheme 3)
The allylation reaction was run at 0°C without ZnCl2
and gave the N-diphenylphosphinyl amine 6 in 80%
yield and with complete stereoselection (Scheme 4)
After decomplexing, the corresponding amine 7 was
recovered in 90% yield.
The complete stereoselection obtained in this case
(for sake of clarity only one enantiomer of 6 is shown)
is probably due to the stereoelectronic effect of the
nitrogen diphenylphospinyl substituent, which only al-
lows an anti disposition of the imino moiety in 3.
3. Conclusions
The importance of the steric effect of the ortho-sub-
stituent is also supported by the result obtained in a
further experiment (entry 8), in which a non-chelating
BF3·OEt2 Lewis acid was used. Product 4c was recov-
ered in good yield and with complete stereoselection.
This is probably due to the fact that the coordination of
BF3 to the methoxy group greatly increases the size of
this group and consequently the conformeric popula-
tion A.
In conclusion we achieved a highly stereoselective
synthesis of aromatic homoallyl amines, which can also
be obtained in enantiomerically pure forms. The new
chromiumtricarbonyl complex of N-diphenylphos-
phinyl imine 3 is a synthon of an ammonia imine and
allows the preparation of primary homoallyl amines,
which are very useful organic intermediates.
Given the promising results obtained for the allyla-
tion of N-phenyl substituted imine complexes 2, the
reaction was extended to the N-phosphinyl imine 3. As
mentioned above, after the removal of the phosphinyl
group, this reaction can provide primary homoally-
lamines that are useful intermediates for the prepara-
tion of more elaborate organic compounds.
4. Experimental
4.1. General methods
All of the reactions were performed under nitrogen,
with the exclusion of direct sunlight. Tetrahydrofuran
was distilled from sodium benzophenone ketyl, and the

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S. Maiorana et al. / Journal of Organometallic Chemistry 593–594 (2000) 380–387
solvents purified according to standard procedures. Un-
less otherwise stated, all of the other reagents were used
as obtained from commercial sources. Melting points
were determined using a Bu¨chi 510 M.P. apparatus and
are uncorrected. The IR spectra were recorded on a
Perkin-Elmer 1725X FTIR; the 1H- and 13C-NMR
spectra were recorded in CDCl3 using a Bruker AC300
spectrometer. Complexes 1 and 2 were prepared as
described in the literature [2a,b,f].
slowly added. After 4 h (TLC: AcOEt:Et3N, 10:1), the
mixture was filtered over Celite® and washed with 30
ml of a saturated solution of NaHCO3. The aqueous
phase was extracted with CH2Cl2 (3×30 ml) and, after
evaporation of the solvent, the red residue was purified
by flash column chromatography (eluent: AcOEt:Et3N,
10:1). Yield: 95%; m.p.: 131–132°C (diisopropyl ether).
1
IR (nujol): w, 1968, 1885, 1605, 1198 cm−1. H-NMR,
l: 3.82 (s, 3H, OCH3), 5.02 (dd, 1H, arom.Cr(CO)3,
J=6.5, 6.4 Hz), 5.06 (d, 1H, arom.Cr(CO)3, J=6.9
Hz), 5.83 (ddd, 1H, arom.Cr(CO)3, J=6.9, 6.4, 1.1
Hz), 6.65 (dd, 1H, arom.Cr(CO)3, J=6.5, 1.1 Hz),
7.4–7.5 (m, 6H, arom.), 7.9 (m, 4H, arom.), 9.4 (d, 1H
CHꢀN, JH–P=30.8 Hz). 31P-NMR, l: 26.37. EI-MS
m/z: 471 (M+), 415 (M+2CO), 387 (M+–3CO).
4.2. Tricarbonyl[N-(p6-2-methylbenzylidene)-
aniline]chromium (2a)
1
M.p. 80–81°C (pentane). H-NMR, l: 2.42 (s, 3H,
CH3), 5.15 (d, 1H, arom.Cr(CO)3, J=6.4 Hz,), 5.3 (dd,
1H, arom.Cr(CO)3, J=6.6, 6.3 Hz), 5.58 (dd, 1H,
arom.Cr(CO)3, J=6.3, 6.4 Hz), 6.41 (d, 1H,
arom.Cr(CO)3, J=6.6 Hz,), 7.1–7.42 (m, 5H, arom.),
8.3 (s, 1H, CHꢀN). Anal. Calc. for C17H13CrNO3: C,
61.63; H, 3.95; N, 4.23. Found: C, 61.65; H, 3.95; N,
4.24.
4.6. Allylation of benzaldimine complexes. General
procedure
Allyl magnesium bromide (1 mmol, 1 ml of 1 M sol.
in Et2O) was added dropwise to a solution of the
proper imine complex 2a–c (0.6 mmol) and ZnCl2 (see
Table 1) in THF (6 ml) cooled to the appropriate
temperature. The color of the solution rapidly changed
from orange to yellow and, after 20 min (TLC:
CH2Cl2:petroleum ether, 1:1), the mixture was
quenched by adding 15 ml of 1/1, H2O/MeOH solution.
The mixture was passed through a pad of Celite®,
extracted with CH2Cl2 (3×15 ml), and the solvent was
evaporated. The crude mixture was purified by means
of column chromatography (eluent: petroleum
ether:Et2O, 3:2) affording complexes 4a–c as yellow
solids.
4.3. Tricarbonyl[N-(p6-2-chlorobenzylidene)aniline]-
chromium (2b)
1
M.p. 83–84 °C (pentane). H-NMR, l: 5.20 (dd, 1H,
arom.Cr(CO)3, J=6.4, 6.3 Hz), 5.46 (d, 1H,
arom.Cr(CO)3, J=6.5 Hz,), 5.58 (ddd, 1H,
arom.Cr(CO)3, J=6.5, 6.3, 1.0 Hz), 6.56 (dd, 1H,
J=6.5, 1.0 Hz, arom.Cr(CO)3), 7.15–7.45 (m, 5H,
arom.), 8.53 (s, 1H, CHꢀN). Anal. Calc. for
C16H10ClCrNO3: C, 54.64; H, 2.86; N, 3.98. Found: C,
54.71; H, 2.88; N, 3.97.
4.4. Tricarbonyl[N-(p6-2-methoxybenzylidene)-
aniline]chromium (2c)
4.7. Tricarbonyl[N-1-((p6-2-methylphenyl)-but-3-enyl)
aniline]chromium (4a)
1
M.p. 138–140°C (pentane). H-NMR, l: 3.81 (s, 3H,
Yield: 80%; m.p.: 103–104°C (diisopropyl ether). IR
OCH3), 5.05 (dd, 1H, arom.Cr(CO)3, J=6.4, 6.5Hz),
5.13 (d, 1H, arom.Cr(CO)3, J=6.8 Hz,), 5.74 (ddd, 1H,
arom.Cr(CO)3, J=6.8, 6.4, 1.2 Hz,), 6.65 (dd, 1H,
aromCr(CO)3, J=6.5, 1.2 Hz), 7.35–7.5 (m, 5H,
arom.), 8.5 (s, 1H, CHꢀN). Anal. Calc. for
C17H13CrNO4: C, 58.79; H, 3.77; N, 4.03. Found: C,
58.49; H, 3.79; N, 4.05. (+)-1(S)-2c, [h]D= +390
(c=0.1, CHCl3).
1
(nujol): w, 3410, 1880, 1860, 1600 cm−1. H-NMR, l:
2.3 (s, 3H, CH3,), 2.5 (m, 2H, CH2), 3.75 (brs, 1H,
NH), 4.38 (t, 1H, CHN, J=6.1 Hz), 4.98 (d, 1H,
arom.Cr(CO)3,
J=6.2
Hz),
5.06
(dd,
1H,
arom.Cr(CO)3, J=6.4, 6.3 Hz), 5.15 (d, 1H, CH2ꢀ,
J=17.0 Hz), 5.16 (d, 1H, CH2ꢀ, J=10.7 Hz) 5.49 (dd,
1H, arom.Cr(CO)3, J=6.3, 6.2 Hz), 5.73 (m, 1H,
CHꢀ), 5.76 (d, 1H, arom.Cr(CO)3, J=6.4 Hz), 6.75 (m,
3H, arom.), 7.2 (m, 2H, arom.). Anal. Calc. for
C20H19CrNO3: C, 64.34; H, 5.13; N, 3.75. Found: C,
64.40; H, 5.15; N, 3.77.
4.5. Tricarbonyl[N-(p6-2-methoxybenzylidene)-
diphenylphosphinamide]chromium (3)
Triethylamine (0.74 ml, 4.4 mmol) was added drop-
wise to a stirred solution of tricarbonyl(2-methoxyben-
zaldehyde) chromium (1c) (0.4 g, 1.47 mmol) and
N-diphenylphosphinamide (0.38 g, 1.76 mmol) in
CH2Cl2 (6 ml). The mixture was cooled to 0°C and
TiCl4 (0.88 mmol, 0.88 ml of 1 M sol. in CH2Cl2) was
4.8. Tricarbonyl[N-1-(p6-2-chlorophenyl)-but-3-enyl)
aniline]chromium (4b)
Yield: 90%; m.p.: 94–95°C (pentane). IR (nujol): w,
1
3393, 1971, 1874, 1650, 1048 cm−1. H-NMR, l: 2.5

S. Maiorana et al. / Journal of Organometallic Chemistry 593–594 (2000) 380–387
385
(m, 1H, CH2), 2.65 (m, 1H, CH2), 3.85 (brs, 1H, NH),
4.72 (m, 1H, CHN), 4.9 (dd, 1H, arom.Cr(CO)3, J=
6.2, 6.1 Hz), 5.16 (d, 1H, CH2ꢀ, J=17.6 Hz), 5.18 (d,
1H, CH2ꢀ, J=10.1 Hz), 5.28 (d, 1H, arom.Cr(CO)3,
J=6.2 Hz), 5.5 (dd, 1H, arom.Cr(CO)3, J=6.1, 6.4
Hz), 5.73 (m, 1H, CHꢀ), 5.75 (d, 1H, arom.Cr(CO)3,
J=6.4 Hz), 6.75 (m, 3H, arom.), 7.2 (m, 2H, arom.).
Anal. Calc. for C19H16ClCrNO3: C, 57.54; H, 4.09; N,
3.57. Found: C, 57.90; H, 4.05; N, 3.57.
m/z: 389 (M+), 361 (M+–CO), 333 (M+–2CO), 305
(M+–3CO). From (+)-1(S)-2c: (−)-(S,S)-4c, m.p.
114°C (pentane), [h]D= −302 (c=0.12, CHCl3).
4.10. N-(1-(-2-methoxyphenyl)-but-3-enyl) aniline (5c)
A solution of racemic 4c in CH2Cl2 was exposed to
air and sunlight until the yellow color had completely
disappeared. The solvent was evaporated and the
residue, taken up with Et2O, was filtered over a pad of
Celite® to yield 5c as nearly analitically pure colorless
4.9. Tricarbonyl[N-1-(p6-2-methoxyphenyl)-but-3-enyl)
aniline]chromium (4c)
oil. IR (neat): w, 3410, 3075, 3050,1600 cm−1 1H-
.
NMR, l: 2.45 (m, 1H, CH2), 2.64 (m, 1H, CH2), 3.9 (s,
3H, OCH3), 4.20 (brs, 1H, NH), 4,8 (dd, 1H, CHNH,
6
Yield: 88% (Table 1, entry 5). After column chro-
matography (eluent: petroleum ether:Et2O, 3:2).
J=7.8, 4.9 Hz), 5.1 (d, 1H, CH2ꢀ, J=10.1 Hz), 5.15
(d, 1H, CH2ꢀ, J=17.2 Hz), 5.78 (m, 1H, CHꢀ), 6.45–
6.65 (m, 3H, arom.), 6.83–7.31(m, 6H, arom.). From
(−)-(S,S)-4c: (+)-(S)-5c, [h]D= −302 (c=0.12,
4.9.1. I diast.
(S*,R*) (r.f. 0.36), yield: 12%; m.p.: 157°C
dec.(diisopropyl ether). IR (nujol): w, 3435, 1940, 1856,
1
CHCl3). (e.e.]98, by H-NMR, using Eu(hfc)3 as chi-
ral shift reagent).
1
1642 cm−1. H-NMR, l: 2.35 (ddd, 1H, CH2, J=14.7,
5.1, 3.7 Hz), 2.9 (ddd, 1H, CH2, J=14.7, 8.7, 10.1 Hz),
3.88 (s, 3H, OCH3), 3.98 (brs, 1H, NH), 4,38 (dd, 1H,
CHN, J=3.7, 10.1 Hz), 4.7 (dd, 1H, arom.Cr(CO)3,
J=6.3, 6,4 Hz), 5.05 (d, 1H, arom.Cr(CO)3, J=6.8
Hz), 5.18 (d, 1H, CH2ꢀ, J=10.2 Hz), 5.25 (d, 1H,
CH2ꢀ, J=17.1), 5.58 (ddd, 1H, arom.Cr(CO)3, J=6.4,
6.5, 1,0 Hz), 5.87 (dddd, 1H, CHꢀ, J=10.2, 17.1, 8.7,
5.1 Hz), 5.97 (dd, 1H, arom.Cr(CO)3, J=6.5, 1.0 Hz),
6.45 (d, 2H, arom., J=9.4 Hz), 6.7 (t, 1H, arom.,
J=8.0 Hz), 7.1 (t, 1H, arom., J=9.4 Hz). 13C-NMR,
l: 44.25 (CH2), 50.18 (CHN), 55.87 (OCH3), 72.44,
82.86, 95.46, 97.69, (CH, arom.Cr(CO)3), 103.94 (Cq,
arom.Cr(CO)3), 113.23 (CH, arom.), 117.96 (CH,
arom.), 118.38 (CH2ꢀ), 129.23 (CH, arom.), 135.1
(CHꢀ), 141.9 (Cq, arom.Cr(CO)3), 146.5 (Cq, arom.),
233.38 (CO). EI-MS m/z:389 (M+), 361 (M+–CO),
333 (M+–2CO), 305 (M+–3CO). From (+)-1(S)-2c:
(+)-(S,R)-4c, 161–163°C (pentane), [h]D= +76 (c=
0.12, CHCl3).
4.11. Tricarbonyl[N-(1-(p6-2-methoxyphenyl)-but-
3-enyl)diphenylphosphinamide (6)
M.p. 106–107°C (dec.) (diisopropyl ether). IR (nu-
1
jol): w, 3160, 1970, 1955, 1867, 1183 cm−1. H-NMR,
l: 2.34 (dd, 1H, NH, J=3.5, 10.1 Hz), 2.62–2.88 (m,
2H, CH2), 3.7 (s, 3H, OCH3), 4.3 (m, 1H, CHNH), 4.78
(dd, 1H, arom.Cr(CO)3, J=6.2, 6.3 Hz), 4.94 (d, 1H,
arom.Cr(CO)3, J=6.5 Hz), 5.1 (d, 1H, CH2ꢀ, J=10.9
Hz), 5.12 (d, 1H,CH2ꢀ, J=15.0 Hz), 5.54 (d, 1H,
arom.Cr(CO)3,
J=6.2
Hz),
5.56
(dd,
1H,
arom.Cr(CO)3, J=6.3, 6.5 Hz), 5.65 (m, 1H, CHꢀ),
7.1–7.6 (m, 6H, arom.), 7.8–8.05 (m, 4H, arom). 13C-
NMR, l: 42.7 (CH2), 50.8 (CHN), 55.7 (OCH3), 72.6,
83.4, 94.9, 95.7, (CH, arom.Cr(CO)3), 103 (Cq,
arom.Cr(CO)3), 119.6, (CH2ꢀ), 128.6, 128.7, 131.8, 132,
132.5, 132.6, (CH, arom.), 133.4 (CHꢀ), 141.6 (Cq,
arom.Cr(CO)3), 151.5 (Cq, arom.), 233 (CO). Anal.
Calc. for C26H24CrNO5P: C, 60.82; H, 4.71; N, 2.73.
Found: C, 60.89; H, 4.72; N, 2.73.
4.9.2. II diast.
(S*,S*) (r.f. 0.26), yield: 80%; m.p.: 103°C (pentane).
4.12. N-(1-(2-methoxyphenyl)-but-3-enyl)-
diphenylphosphinamide (7)
1
IR (nujol): w, 3047, 1956, 1875, 1639 cm−1. H-NMR,
l: 2.6 (m, 2H, CH2), 3.78 (s, 1H, NH), 3.82 (s, 3H,
OCH3), 4,67 (dd, 1H, CHN, J=7.2, 4.7 Hz), 4.78 (t,
1H, arom.Cr(CO)3, J=6.2 Hz), 4.98 (d, 1H,
arom.Cr(CO)3, J=6.8 Hz), 5.14 (m, 2H, CH2ꢀ), 5.52
(dd, 1H, arom.Cr(CO)3, J=6.2, 6.8 Hz), 5.73 (dddd,
1H, CHꢀ, J=2.5, 7.0, 9.9, 13.6 Hz), 5.8 (d, 1H,
arom.Cr(CO)3, J=6.2 Hz), 6.75 (m, 3H, arom.), 7.18
(m, 2H, arom.). 13C-NMR, l: 41.58 (CH2), 51.08
(CHN), 55.72 (OCH3), 72.57, 83.23, 94.73, 94.78, (CH,
arom.Cr(CO)3), 102.14 (Cq, arom.Cr(CO)3), 114.02
(CH, arom.), 118.13 (CH, arom.), 118.84 (CH2ꢀ),
129.14 (CH, arom.), 133.68 (CHꢀ), 141.3 (Cq,
arom.Cr(CO)3), 146.5 (Cq, arom.), 232.91 (CO). EI-MS
A solution of racemic 6 in CH2Cl2 was exposed to air
and sunlight until the yellow color had completely
disappeared. The solvent was evaporated and the
residue, taken up with Et2O, was filtered over a pad of
Celite® to yield 7 as white solid (90%): m.p. 119–120°C
(diisopropyl ether). IR (nujol): w, 3138, 1600, 1493,
1
1245, 1194 cm−1. H-NMR, l: 2.7 (m, 2H, CH2), 3.72
(s, 3H, OCH3), 3.94 (dd, 1H, NH, J=11.0, 8.2 Hz),
4.32–4.46 (m, 1H, CHN), 4.95 (d, 1H, CH2ꢀ, J=8.2
Hz), 5.0 (d, 1H, CH2ꢀ, J=15.4 Hz), 5.5–5.64 (m, 1H,
CHꢀ), 6.8–7.0 (m, 3H, arom.), 7.2–7.5 (m, 8H, arom.),
7.7–7.9 (m, 3H, arom.).

386
S. Maiorana et al. / Journal of Organometallic Chemistry 593–594 (2000) 380–387
Table 3
di Studio per la Strutturistica Diffrattometrica’ del
CNR, Parma.
Crystal data and structure refinement for 4c
Empirical formula
Formula weight
Temperature (K)
C20H19CrNO4
389.36
293(2)
0.71073
5. Supplementary material
,
Wavelength (A)
Crystal system, space group
Monoclinic, P21/n
Unit cell dimensions
The supplementary material for the structure includes
the lists of atomic coordinates for the non-H atoms, of
coordinates for the hydrogen atoms, and of anisotropic
thermal parameters. Crystallographic data for the
structure reported in this paper have been deposited
with the Cambridge Crystallographic Data Centre,
CCDC No. 130237. Copies of this information may be
obtained free of charge from The Director, CCDC, 12
Union Road, Cambridge, CB2 1EZ, UK (Fax: +44-
1223-336033; e-mail: deposit@ccdc.cam.ac.uk or www:
http://www.ccdc.cam.ac.uk).
,
a (A)
12.257(5)
9.338(2)
17.143(6)
105.29(2)
1892.7(11)
4, 1.366
0.628
808
,
b (A)
,
c (A)
i (°)
3
,
Volume (A )
Z, calculated density (Mg m−3
)
Absorption coefficient (mm−1
F(000)
)
Crystal size (mm)
q range for data collection (°)
Index ranges
0.15×0.25×0.38
3.22–30.03
−175h516,
05k513, 05l524
5675/5518 [Rint=0.0318]
3130
Reflections collected/unique
Reflections observed [I\2|(I)]
Refinement method
Data/restraints/parameters
Goodness-of-fita on F2
Final R indices [I\2|(I)]
R indices (all data)
Full-matrix least-squares on F2
5518/0/255
Acknowledgements
1.150
R1b=0.0475, wR2c=0.1230
R1=0.1188, wR2=0.1850
We gratefully acknowledge financial support from
the Ministero dell’Universita` e della Ricerca Scientifica
e Tecnologica (MURST) and Consiglio Nazionale delle
Ricerche (CNR).
Largest difference peak and hole 0.404 and −0.872
−3
,
(e A
)
a GoF=[ꢀ[w(F2o−F2c)2]/(n−p)]1/2
b R1=ꢀꢁꢁFoꢁ−ꢁFcꢁꢁ/ꢀꢁFoꢁ.
.
c wR2=[ꢀ[w(Fo2−Fc2)2]/ꢀ[w(F2o)2]]1/2
.
w=1/[|2(F2o)+(aP)2+bP],
where P=[max(F2o,0)+2Fc2]/3.
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The crystallographic data are summarized in Table 3.
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randomly distributed and carefully centered reflections
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monitored every 100 measurements, no significant de-
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thermal parameters for all the non-hydrogen atoms. All
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default-distances calculated positions and refined ‘rid-
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out on the DIGITAL AlphaStation 255 of the ‘Centro
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.