Regio- and stereocontrolled nucleophilic addition reactions of a phenylthio-substituted cyclohexadiene-containing η4-molybdenum cationic complex

Article abstract of DOI:10.1021/om960499z

The reaction of a new cationic complex, [Cp-(CO)₂Mo(η⁴-2-SPh-C₆H₇)] ⁺PF₆^- (3), with carbon and sulfur nucleophiles was found to give in most cases the C-4 addition products 4 in good yield. The X-ray crystal structure of one of the addition products 4b confirms the regio- and stereochemistry of the reaction.

Full text of DOI:10.1021/om960499z

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Organometallics 1996, 15, 4113-4115
4113
Regio- a n d Ster eocon tr olled Nu cleop h ilic Ad d ition
Rea ction s of a P h en ylth io-Su bstitu ted
Cycloh exa d ien e-Con ta in in g η4-Molybd en u m Ca tion ic
Com p lex
Shang-Shing P. Chou* and Hui-Tuo Sheng
Department of Chemistry, Fu J en Catholic University, Taipei, Taiwan 242, Republic of China
Received J une 20, 1996X
Summary: The reaction of a new cationic complex, [Cp-
dienyl anion (eq 1).8 The structure of 1 was confirmed
-
(CO)2Mo(η4-2-SPh-C6H7)]+PF6 (3), with carbon and
sulfur nucleophiles was found to give in most cases the
C-4 addition products 4 in good yield. The X-ray crystal
structure of one of the addition products 4b confirms the
regio- and stereochemistry of the reaction.
The control of regio- and stereochemistry in the
carbon-carbon bond formation is one of the central
issues in contemporary organic synthesis.1 The use of
(diene)molybdenum2 and dienyliron3 complexes has
proven to be an important method for controlling the
regio- and stereochemistry using the transition-metal
moiety as a directing template. The addition of nucleo-
philes to cyclic (diene)molybdenum cationic complexes
proceeds stereospecifically trans to the metal.4 Unsym-
metrically substituted dienyliron cationic complexes
have often been used in nucleophilic addition reactions,5
but unsymmetrical (diene)molybdenum complexes have
scarcely been reported.6 In this study we describe the
synthesis of a new cationic molybdenum complex 3
bearing a phenylthio group at C-2 and the regio- and
stereoselectivity in the nucleophilic addition reaction.
by its oxidation with m-CPBA to give the corresponding
sulfone complex 29 in 84% yield, whose structure was
proven by X-ray crystallography (Figure 1).10 The η3-
Mo(CO)2Cp complex 1 was easily converted to the η4-
cationic complex 3 in 67% yield by reaction with a
triphenylmethyl cation (eq 2).11 The structure of 3 was
derived from its spectroscopic data2a and can be inferred
from its subsequent nucleophilic addition reactions.
The η3-2-SPh-cyclohexenyl-Mo(CO)2Cp complex 1 was
prepared in 43% yield by treatment of 3-bromo-2-
(phenylthio)cyclohexene7 with Mo(CO)3(CH3CN)3 in
acetonitrile, followed by the reaction with cyclopenta-
X Abstract published in Advance ACS Abstracts, September 15, 1996.
(1) (a) Mathieu, J .; Weill-Raynal, J .; Formation of C-C Bonds; Georg
Thieme Verlag: Stuttgart, Germany, 1971. (b) Trost, B. M.; Fleming,
I., Eds. Comprehensive Organic Synthesis; Pergamon Press: Oxford,
U.K., 1991.
(2) (a) Faller, J . W.; Murray, H. H.; White, D. L.; Chao, K. H.
Organometallics 1983, 2, 400. (b) Pearson, A. J .; Khan, M. N. I.;
Clardy, J . C.; Cun-heng, H. J . Am. Chem. Soc. 1985, 107, 2478. (c)
Pearson, A. J .; Khetani, V. D. J . Chem. Soc., Chem. Commun. 1986,
1772. (d) Pearson, A. J .; Blystone, S. L.; Nar, H.; Pinkerton, A. A.;
Roden, B. A.; Yoon, J . J . Am. Chem. Soc. 1989, 111, 134. (e) Pearson,
A. J .; Khetani, V. D. J . Am. Chem. Soc. 1989, 111, 6778.
(3) (a) Pearson, A. J .; Kole, S. L.; Ray, T. J . Am. Chem. Soc. 1984,
106, 6060. (b) Pearson, A. J .; Eisenstein, O.; Butler, W. M. Organo-
metallics 1983, 3, 1150. (c) Aumann, R. J . Organomet. Chem. 1973,
47, C28. (d) Edwards, R.; Howell, J . A. S.; J ohnson, B. F. G.; Lewis,
J . J . Chem. Soc., Dalton Trans. 1974, 2105.
(4) Pearson, A. J . Synlett 1990, 10 and references cited therein.
(5) (a) Birch, A. J .; Bandara, B. M. R.; Chamberlain, K.; Chauncy,
B.; Dahler, P.; Day, A. I.; J enkins, I. D.; Kelly, L. D.; Khor, T.-C.;
Kretschmer, G.; Liepa, A. J .; Narula, A. S.; Raverty, W. D.; Dizzardo,
E.; Sell, C.; Stephenson, G. R.; Thompson, D. J .; Williamson, D. H.
Tetrahedron 1981, 37, 289. (b) Pearson, A. J . Science 1984, 223, 895.
(c) Chou, S. S. P.; Hus, C. H.; Yeh, M. C. P. Tetrahedron Lett. 1992,
33, 643. (d) Chou, S. S. P.; Hus, C. H. Tetrahedron Lett., in press.
(6) (a) Pearson, A. J .; Babu, M. K. M. Organometallics 1994, 13,
2539. (b) Liebeskind, L. S.; Hansson, S.; Miller, J . F. J . Am. Chem.
Soc. 1990, 112, 9660. (c) Liebeskind, L. S.; Bombrun, A. J . Am. Chem.
Soc. 1991, 113, 8736. (d) Liebeskind, L. S.; Almudena, R. J . Am. Chem.
Soc. 1993, 115, 891. (e) Liebeskind, L. S.; Hansson, S.; Yu, R. H.;
McCallum, J . S. Organometallics 1994, 13, 1476.
(8) The preparation of η3-2-SPh-cyclohexenyl-Mo(CO)2Cp (1) was
readily accomplished by using the procedure described by Faller et
al.2a The modified condition is that 3-bromo-2-phenylthiocyclohexene7
was added to a refluxing solution of Mo(CO)3(CH3CN)3 in acetonitrile
for 20 min. The unstable bright yellow crystals of [(CH3CN)2MoBr-
(η3-SPh-C6H8)] could be obtained in 51% yield. The complex 1 was
synthesized by adding lithium cyclopentadienide to the solution of
[(CH3CN)2MoBr(η3-SPh-C6H8)] at -78 °C. This was slowly warmed
to room temperature. The solvent was removed in vacuo. The crude
product was purified by flash column chromatography using EtOAc/
hexane (1:3) as eluent to give 1 in 84% yield: Rf 0.68 (EtOAc/hexane,
1:3); mp 130-131 °C (dec); IR (νmax, CH2Cl2) 1943, 1865 cm-1; 1H NMR
(CDCl3, 300 MHz, 25 °C) δ 7.51-7.20 (5 H, m), 5.45 (5 H, s), 3.67 (2 H,
br s), 2.06-1.95 (2 H, m), 1.88-1.81 (2 H, m), 1.07-0.99 (1 H, m), 0.51-
0.34 (1 H, m); 13C NMR (CDCl3, 75 MHz, 25 °C) δ 232.1, 143.1, 128.9,
127.9, 126.1, 93.0, 70.5, 64.4, 24.0, 18.3; HRMS calcd (98Mo) 408.0078,
found 408.0085.
(9) A solution of 1 (1.00 g, 2.46 mmol) and m-CPBA (1.87 g, 50%,
5.4 mmol) in CH2Cl2 (50 mL) was stirred at 0 °C for 15 min. It was
then washed with 10% Na2S2O3 and then 5% NaHCO3, dried (MgSO4),
and evaporated under vacuum. The crude product was purified by
flash column chromatography using hexane/EtOAc (3:1) as eluent to
give 2 (0.906 g, 84% yield), which was recrystallized from hexane/
CH2Cl2: mp 139-141 °C (dec); IR (νmax, CH2Cl2) 1947, 1870 cm-1 1H
;
NMR (CDCl3, 300 MHz, 25 °C) δ 8.01-7.97, 7.63-7.59 (5 H, m), 5.69
(5, H, s), 3.67 (2 H, br s), 1.67-1.61 (2 H, m), 1.42-1.32 (2 H, m), 0.87-
0.80 (1 H, m), 0.42-0.32 (1 H, m); 13C NMR (CDCl3, 75 MHz, 25 °C) δ
229.1, 144.4, 132.8, 129.3, 127.1, 93.5, 85.8, 52.1, 21.4, 18.7; HRMS
(7) (a) Trost, B. M.; Lavoie, A. C. J . Am. Chem. Soc. 1983, 105, 5075.
(b) Liebeskind, L. S.; Baysdon, S. L. Tetrahedron Lett. 1984, 25, 1747.
calcd
MoO4S: C, 52.06; H, 4.14. Found: C, 52.33; H, 4.20.
( -
98Mo) 439.9976, found 439.9984. Anal. Calcd for C19H18
S0276-7333(96)00499-2 CCC: $12 00 © 1996 American Chemical Society

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4114 Organometallics, Vol. 15, No. 20, 1996
Communications
Ta ble 1. Nu cleop h ilic Ad d ition Rea ction s of
Com p lex 3
reacn
yields
entry
nucleophilea
conditionb products (%)c
1
2
3
4
5
NaSPh
NaSO2Ph
NaCH(CN)2
NaCH(CO2Me)2
NaCH(SO2Ph)CO2Me
A
B
C
C
C
4a
4b
4c
68
85
81
68
75
4d
4ed
6
7
NaC(CO2Me)COCH2CH2CH2
NaCH(COMe)CO2Me
A
C
4fd
82
76
4ge + 5g
(3.3:1)
a
b
equiv of the nucleophile was used. All reactions were carried
out in THF. Method A: rt, 0.5 h. Method B: rt, 4 h. Method C:
0 °C, 0.5 h. c Isolated yields of purified products. The ratio of
d
diastereomers was 1.3:1. e The ratio of diastereomers was 1.1:1.
F igu r e 1. Crystallographic structure of complex 2, Cp-
(CO)2Mo(η3-2-SO2Ph-C6H8). Selected bond lengths (Å) and
bond angles (deg): Mo-C1 ) 1.947(3), Mo-C2 ) 1.945(3),
Mo-C3 ) 2.349(3), Mo-C4 ) 2.149(3), Mo-C5 ) 2.332(3),
S-C4 ) 1.758(3), C1-Mo-C2 ) 84.67(12); C1-Mo-C3 )
structure of 4b was confirmed by the X-ray analysis
(Figure 2) which not only proves its regio- and stereo-
chemistry13 but also correlates with the structures of
other addition products 4. The reaction of 3 with active
methylene compounds (entries 3-6) gave only the C-4
addition products 4c-f, with the exception that methyl
sodioacetoacetate (entry 7) also yielded small amount
of the C-1 addition product 5g. From these results it
can be seen that the regio- and stereoselectivity of the
reaction are very good and are probably attributable to
the C-2 phenylthio group.
68.30(1), C1-Mo-C4
111.13(11), C2-Mo-C3 ) 109.23(11), C2-Mo-C4 )
105.93(11), C2-Mo-C5 ) 70.88(11), C3-Mo-C4
) 104.00(11), C1-Mo-C5 )
)
36.56(10), C3-Mo-C5 ) 62.07(9), C4-Mo-C5 ) 36.82(9),
Mo-C3-C4 ) 64.03(14), Mo-C4-S ) 124.71(13), Mo-
C4-C3 ) 79.40(16), Mo-C4-C5 ) 78.60(15), S-C4-C3
) 120.72(19), S-C4-C5 ) 121.48(20), C3-C4-C5 )
115.77(23), Mo-C5-C4
121.52(19).
) 64.58(14), S-C6-C5 )
The reaction of complex 3 with methyl sodiomalonate
at 0 or -78 °C gave the same addition product 4d in
68% and 43% yield, respectively. It is quite remarkable
that in our study the phenylthio group controls the
regiochemistry of the addition reaction of stabilized
nucleophiles independent of the reaction temperatures
used. Our results were different from what Pearson had
recently reported,6a in which the regioselectivity of
organolithiates and Grignard reagents additions to a (2-
methylbutadiene)molybdenum complex was found to be
influenced by the reaction temperature: at -78 °C the
C-4 adduct was dominant, but at higher temperature
the regioselectivity was not good.
The reactions of 3 with various nucleophiles (eq 3)
are shown in Table 1.12 The heteroatom nucleophiles,
thiolate (entry 1) and sulfonate (entry 2), reacted
efficiently at room temperature to give the addition
1
products 4a ,b, respectively in good yield. The H and
13C NMR spectra of 4a ,b agree well with similar data
reported in the literature.2a,b The yellow single crystals
of complex 4b were grown by layering ether on a
dichloromethane solution at -16 °C for 2 days. The
The demetalation reaction of complex 4c with iodine
in acetonitrile at 0 °C gave a regioisomeric mixture of
allylic iodides,2b which, due to its instability, was quickly
passed through a short column of silica gel to remove
the excess iodine. The crude product was then treated
with sodium hydride in THF to give the cyclized product,
7,7-dicyano-2-(phenylthio)bicyclo[4.1.0]hept-2-ene (6) in
(10) Crystal data for C19H18MoO4S (2): fw 438.38, triclinic, space
group P1h, a ) 7.738(3) Å, b ) 8.6647(17) Å, c ) 13.86760(0) Å, R )
96.368(18)°, â ) 105.119(23)°, γ ) 91.6442(21)°, V ) 890.4(3) Å3, Z )
2, µ ) 8.504 cm-1, Mo KR radiation (λ ) 0.709 30 Å), dcalcd ) 1.635
g/cm3, 298 K, F(000) ) 444, Nonius diffractometer, yellow crystal (0.40
× 0.50 × 0.60 mm), 19.00° e 2θ e 23.12°. Absorption correction was
carried out by indexing crystal faces and integration: minimum and
maximum transmission coefficients 0.957 and 1.000. All non-hydrogen
atoms were refined with anisotropic thermal parameters; hydrogen
atoms were included in calculated positions and treated as riding
atoms. Rf ) 0.025, Rw ) 0.026 for 2857 reflections with I > 2σ(I) out
of 3130 unique reflections and 227 parameters (Rf ) ∑(Fo - Fc)/∑Fo,
Rw ) [∑(w(Fo - Fc)2/∑(wFo)2]1/2).
(12) General procedure for nucleophilic addition reactions of 3: A
solution of the nucleophile (0.73 mmol) in THF (2 mL) was treated
with a suspension of sodium hydride (0.72 mmol, 60%) in THF (8 mL).
The diene complex 3 (0.10 g, 0.18 mmol) was then added by a solid
addition funnel in 30 min. The reaction could be monitored by
dissolution of the THF-insoluble complex 3. The mixture was then
poured into water (20 mL) and was extracted with EtOAc (2 × 10 mL).
The combined EtOAc extracts were washed with water (2 × 10 mL),
dried (MgSO4), and evaporated in vacuo to yield the crude product 4,
which was further purified by column chromatography.13 Com-
plex 4a : Rf 0.5 (EtOAc/hexane, 1:3); 68% yield, mp 132-133 °C; IR
(11) To a stirred solution of complex 1 (2.00 g, 4.93 mmol) in dry
CH2Cl2 (20 mL) at 0 °C under nitrogen was added Ph3CPF6 (1.90 g,
4.93 mmol) in one portion. The resulting mixture was stirred for 1.5
h and was then reduced to about one-half of its volume in vacuo. The
crude product 3 was precipitated by addition of dry ether (20 mL),
filtered out, and washed with dry ether (20 mL × 2) giving yellow
product 3 (1.82 g, 67% yield): Mp 125-126 °C; IR (νmax, CH2Cl2) 2200,
(νmax, CH2Cl2) 1936, 1861 cm-1 1H NMR (CDCl3, 300 MHz, 25 °C) δ
;
7.74-7.18 (10 H, m), 5.47 (5 H, s), 3.94 (1 H, dd, J ) 5.5, 2.6 Hz), 3.80
(1 H, t, J ) 2.7 Hz), 3.60 (1 H, t, J ) 4.8 Hz), 2.36-2.26 (1 H, m),
1.85-1.78 (1 H, m), 1.19 (1 H, dd, J ) 15.0, 4.8 Hz), 0.94-0.81 (1 H,
m); 13C NMR (CDCl3, 75 MHz, 25 °C) δ 233.2, 231.9, 140.8, 136.5, 131.0,
128.8, 128.8, 127.3, 126.3, 93.4, 72.8, 66.3, 62.7, 46.1, 24.1, 20.8.
Anal. Calcd for C25H22MoO2S2: C, 58.36; H, 4.31. Found: C, 58.53;
H, 4.50.
1950 cm-1 1H NMR (C3D6O, 300 MHz, 25 °C) δ 7.61-7.41 (5 H, m),
,
6.29 (1 H, dd, J ) 7.6, 2.7 Hz), 6.03 (5 H, s), 4.68 (1 H, dd, J ) 5.3, 2.7
Hz), 4.41 (1 H, dt, J ) 7.6, 3.0 Hz), 2.45-2.14 (4 H, m); 13C NMR
(C3D6O, 75 MHz, 25 °C) δ 218.3, 216.7, 135.2, 132.5, 130.9, 129.8, 100.0,
95.8, 89.9, 87.0, 74.3, 28.5, 23.9; HRMS calcd (98Mo) 551.9642, found
551.9643. Anal. Calcd for C19H17MoF6O2PS: C, 41.47; H, 3.11.
Found: C, 41.58; H, 3.19.
(13) The spectroscopic data for compounds 4b-g and 5g can be
found in the Supporting Information.

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Communications
Organometallics, Vol. 15, No. 20, 1996 4115
in directing the addition almost solely at the C-4
position trans to the metal to give products 4 in good
yield. The demetalation and cyclization of product 4c
with iodine and sodium hydride provided the bicyclic
product 6, which could be treated with another nucleo-
phile to give a trans-disubstituted cyclohexene product
7.
Ack n ow led gm en t. Financial support of this work
by the National Science Council of the Republic of China
(NSC 85-2113-M-030-001) is gratefully acknowledged.
F igu r e 2. Crystallographic structure of complex 4b,
Cp(CO)2Mo(η3-2-SPh-4-SO2Ph-C6H7). Selected bond lengths
(Å) and bond angles (deg): Mo-C1 ) 1.953(7), Mo-C2 )
1.956(7), Mo-C3 ) 2.368(6), Mo-C4 ) 2.213(6), Mo-C5
) 2.347(6), S2-C4 ) 1.781(6), S1-C6 ) 1.811(6); C1-Mo-
C2 ) 82.9(3), C1-Mo-C3 ) 108.71(24), C1-Mo-C4 )
Su p p or tin g In for m a tion Ava ila ble: Text giving spec-
troscopic data for complexes 4b-g and 5g and tables giving
the structure determination summary, positional and thermal
parameters, bond distances, and bond angles for 2 and 4b (14
pages). Ordering information is given on any current mast-
head page.
107.86(24), C1-Mo-C5 ) 74.22(24), C2-Mo-C3
69.30(25), C2-Mo-C4 ) 105.30(24), C2-Mo-C5
113.02(24), C3-Mo-C4 ) 36.55(22), C3-Mo-C5
)
)
)
60.99(21), C4-Mo-C5 ) 35.84(21), Mo-C3-C4 ) 65.9(3),
Mo-C4-S2 ) 113.1(3), Mo-C4-C3 ) 77.6(3), Mo-C4-
C5 ) 77.3(3), S2-C4-C3 ) 122.5(4), S2-C4-C5 ) 123.5(5),
C3-C4-C5 ) 114.0(5), Mo-C5-C4 ) 66.9(3), S1-C6-C5
) 112.1(4), S1-C6-C7 ) 106.7(4), C5-C6-C7 ) 114.5(5).
OM960499Z
(15) Complex 4c (0.28 g, 0.596 mmol) was treated with iodine (0.47
g, 1.788 mmol) in acetonitrile (5 mL) at 0 °C for 20 min, followed by
passing through a short column of silica gel to remove the excess iodine
using ether as the eluent. The solvent was then removed in vacuo.
To a solution of the crude product (0.124 g) in THF (2 mL) was added
a suspension of sodium hydride (2.4 mmol) in THF (5 mL) at 0 °C for
10 min. After general workup and purification by flash column
chromatography, compound 6 was obtained in 54% yield: Rf 0.35
(EtOAc/hexane, 1:3), IR (νmax, neat) 2280, 1475 cm-1; 1H NMR (CDCl3,
300 MHz, 25 °C) δ 7.49-7.38 (5 H, m), 6.27 (1 H, t, J ) 4.4 Hz), 2.50
(1 H, d, J ) 9.2 Hz), 2.46-2.40 (1 H, m), 2.34-2.27 (2 H, m), 2.15-
2.08 (2 H, m); 13C NMR (CDCl3, 75 MHz, 25 °C) δ 132.7, 132.6, 131.7,
129.5, 128.4, 124.8, 114.8, 112.3, 31.8, 30.9, 22.1, 15.7, 13.0; HRMS
calcd for 252.0722, found 252.0713. Anal. Calcd for C15H12N2S: C,
71.39; N, 11.10; H, 4.79. Found: C, 71.39; N, 11.12; H, 4.98.
54% yield (eq 4).14 The cis-fused configuration of com-
pound 6 was confirmed by comparing its proton NMR
spectrum with that of 2-norcarene analogues.15 Reac-
tion of bicyclic compound 6 with sodium benzenethiolate
provided the trans ring-opening product 7 in 66% yield
(eq 5).16
In summary, the 2-phenylthio group on the diene
molybdenum cationic complex 3 plays an important role
(16) Paquette, L. A.; Wilson, S. E. J . Org. Chem. 1972, 37, 3849.
(17) To a solution of compound 6 (52 mg, 0.21 mmol) in THF (2 mL)
was added a suspension of sodium benzenethiolate (0.24 mmol) at 0
°C. After general workup and purification by flash column chroma-
tography, trans-4-dicyanomethyl-2,3-bis(phenylthio)cyclohexene (7)
was obtained in 66% yield: Rf 0.41 (EtOAc/hexane, 1:3), IR (νmax, neat)
(14) Crystal data for C25H22MoO4S2 (4b): fw 546.50, orthorhombic,
space group Pna21, a ) 16.896(3) Å, b ) 8.0125(10) Å, c ) 16.899(3)
Å, R ) 90°, â ) 90°, γ ) 90°, V ) 2287.8(6) Å3, Z ) 4, µ ) 7.632 cm-1
,
Mo KR radiation (λ ) 0.7107 Å), dcalcd ) 1.587 g/cm3, 298 K, F(000) )
1106, Nonius diffractometer, yellow crystal (0.13 × 0.35 × 0.40 mm),
17.00° e 2θ e 30.80°. Absorption correction was carried out by
indexing crystal faces and integration: minimum and maximum
transmission coefficients 0.905 and 1.000. All non-hydrogen atoms
were refined with anisotropic thermal parameters; hydrogen atoms
were included in calculated positions and treated as riding atoms. Rf
) 0.029, Rw ) 0.030 for 1740 reflections with I g 2σ(I) out of 2082
2300, 1565 cm-1 1H NMR (CDCl3, 300 MHz, 25 °C) δ 7.47-7.35 (10
;
H, m), 5.98 (1 H, t, J ) 3.8 Hz), 4.04 (1 H, d, J ) 8.3 Hz), 3.68 (1 H,
d, J ) 4.8 Hz), 2.45-2.30 (2 H, m), 2.22-2.14 (2 H, m), 1.91-1.85 (1
H, m); 13C NMR (CDCl3, 75 MHz, 25 °C) δ 133.2, 132.6, 132.4, 132.3,
130.9, 129.5 (×2), 129.4, 128.4, 128.3, 111.7, 111.1, 49.8, 41.0, 24.9,
22.8, 20.6; HRMS calcd for 362.0913, found 362.0908. Anal. Calcd
for C21H18N2S2: C, 69.58; N, 7.73; H, 5.00. Found: C, 69.53; N, 7.61;
H, 5.09.
unique reflections and 289 parameters (Rf ) ∑(Fo - Fc)/∑Fo, Rw
)
[∑(w(Fo - Fc)2)/∑(wFo)2]1/2).