A combined experimental-theoretical study on the lithiation/electrophilic quench sequence of (η5-cyclohexadienyl)Mn(CO)3 complexes

Article abstract of DOI:10.1021/om7010529

An easy and versatile functionalization of (η⁵- cyclohexadienyl)Mn(CO)₃ complexes by a lithiation/electrophilic quench sequence is described. Using TMSCl as a model electrophile, the reactivity of the series of substrates 1-5 was studied. In addition to the regiochemistry control by ortho-directing groups, such as OMe or Cl, the results suggest a strong influence of the Mn(CO)₃ tripod conformation on the regioselectivity of the lithiation. In order to gain a better understanding of the reactivity features of the cyclohexadienyl ligand in the η⁵ complex, a theoretical investigation was undertaken. It indicates that the regioselectivity relies mainly on the intrinsic stabilities of the deprotonated intermediates, the species lithiated at C², eclipsed by a Mn-CO bond, being the most stable one. The synthetic methodology was finally successfully extended to a representative range of electrophiles, giving access in good to excellent yields to η⁵ derivatives substituted by various heteroatoms (iodine, sulfur, or stannyl groups) or functions, such as ketone, ester, amide, or alcohols, α to the π system.

Full text of DOI:10.1021/om7010529

626
Organometallics 2008, 27, 626–636
A Combined Experimental-Theoretical Study on the Lithiation/
Electrophilic Quench Sequence of (η5-Cyclohexadienyl)Mn(CO)3
Complexes
Béatrice Jacques,† Alina Chanaewa,† Murielle Chavarot-Kerlidou,*,†
Françoise Rose-Munch,*,† Eric Rose,† and Hélène Gérard‡
Laboratoire de Chimie Organique (UMR CNRS 7611), Institut de Chimie Moléculaire (FR 2769), Case
181, UniVersité Pierre et Marie Curie-Paris 6, 4 Place Jussieu, F-75252 Paris Cedex 05, France, and
Laboratoire de Chimie Théorique (UMR CNRS 7616), Case 137, UniVersité Pierre et Marie Curie-Paris
6, 4 Place Jussieu, F-75252 Paris Cedex 05, France
ReceiVed October 19, 2007
An easy and versatile functionalization of (η5-cyclohexadienyl)Mn(CO)3 complexes by a lithiation/
electrophilic quench sequence is described. Using TMSCl as a model electrophile, the reactivity of the
series of substrates 1–5 was studied. In addition to the regiochemistry control by ortho-directing groups,
such as OMe or Cl, the results suggest a strong influence of the Mn(CO)3 tripod conformation on the
regioselectivity of the lithiation. In order to gain a better understanding of the reactivity features of the
cyclohexadienyl ligand in the η5 complex, a theoretical investigation was undertaken. It indicates that
the regioselectivity relies mainly on the intrinsic stabilities of the deprotonated intermediates, the species
lithiated at C2, eclipsed by a Mn-CO bond, being the most stable one. The synthetic methodology was
finally successfully extended to a representative range of electrophiles, giving access in good to excellent
yields to η5 derivatives substituted by various heteroatoms (iodine, sulfur, or stannyl groups) or functions,
such as ketone, ester, amide, or alcohols, R to the π system.
Scheme 1. Reactivity Features of the (η6-Arene)-
Introduction
tricarbonylmanganese Complexes
The coordination of a transition metal to an arene modifies
the reactivity of the arene ligand in several distinct ways. Among
them, the increased acidity of the ring protons, which strongly
facilitates direct proton abstraction from the arene, is remarkable.
The first lithiation of the arene in an (η6-arene)Cr(CO)3 complex
was reported in 1968,1 and since then, this reaction has seen
extensive development and has been the subject of several
reviews.2 Very surprisingly, no report exists on isoelectronic
tricarbonylmanganese complexes, although these have become
increasingly important in organometallic and organic syntheses.3
The lithiation is only known in the close family of (η5-
cyclopentadienyl)Mn(CO)3 complexes, namely, the cymantrene
derivatives,4 where this reaction has found significant applica-
tions.5 The reactivity features of the (η6-arene)tricarbonylman-
ganese complexes are the following: ipso chloride substitution
allows a clean nucleophile introduction (Scheme 1, path a), but
such a strategy is restricted to amino, oxo, and thio nucleophiles,
thus limiting its scope.6
All the attempts we made to functionalize an η6 complex by
any other direct route, such as palladium-catalyzed cross-
couplings7 or lithiation, failed. One major limitation in the
chemistry of such cationic complexes is the poor solubility of
most of them in the usual organic solvents; in order to
circumvent this problem, we developed an anion-exchange
procedure giving access to tetraarylborate salts.8 These new
substrates are soluble in reaction solvents such as THF and can
be purified by chromatography; nevertheless, the nature of the
counteranion does not contribute to their reactivity. Finally, the
* Corresponding author. Fax: (+33) (0)1-44-27-55-04. E-mail: chavarot@
ccr.jussieu.fr; rosemun@ccr.jussieu.fr.
† Laboratoire de Chimie Organique.
‡ Laboratoire de Chimie Théorique.
(1) Nesmeyanov, A. N.; Kolobova, N. E.; Anisimov, K. N.; Markarov,
Y. V. IzV. Akad. Nauk. SSSR Ser. Khim. 1968, 2665.
(2) For reviews, see: (a) Semmelhack, M. F. In ComprehensiVe
Organometallic Chemistry II, Vol. 12; Abel. E. W., Stone F. G. A.,
Wilkinson G., Eds.; Pergamon Press: Oxford, 1995; pp 1017. (b) Rose-
Munch, F.; Rose, E. Curr. Org. Chem. 1999, 3, 445. (c) Berger, A.; Djukic,
J.-P.; Michon, C. Coord. Chem. ReV. 2002, 225, 215. (d) Semmelhack,
M. F.; Chlenov, A. Top. Organomet. Chem. 2004, 7, 21.
(4) Nesmeyanov, A. N.; Anisimov, K. N.; Kolobova, N. E.; Markarov,
Y. V. IzV. Akad. Nauk. SSSR Ser. Khim. 1968, 686.
(3) For recent reviews, see: (a) McDaniel, K. F. In ComprehensiVe
Organometallic Chemistry II, Vol. 6; Abel E. W., Stone F. G. A., Wilkinson
G., Eds.; Pergamon Press: Oxford, 1995; pp 93. (b) Pike, R. D.; Sweigart,
D. A. Coord. Chem. ReV. 1999, 187, 183. (c) Pape, A. R.; Kaliappan, K. P.;
Kündig, E. P. Chem. ReV 2000, 100, 2917. (d) Rose-Munch, F.; Rose, E.
Eur. J. Inorg. Chem. 2002, 1269. (e) Rose-Munch, F.; Rose, E. In Modern
Arene Chemistry; Astruc D., Ed.; Wiley-VCH: New York, 2002; Chapter
11, p 368. (f) Sweigart, D. A.; Reingold, J. A.; Son, S. U. In ComprehensiVe
Organometallic Chemistry III, Vol. 5; Crabtree R. H., Mingos D. M. P.,
Eds.; Elsevier Science Ltd: Oxford, 2006; pp 761.
(5) See for example: (a) Kudis, S.; Helmchen, G. Angew. Chem. Int.
Ed 1998, 37, 3047. (b) Ferber, B.; Top, S.; Vessières, A.; Welter, R.; Jaouen,
G. Organometallics 2006, 25, 5730, and references therein.
(6) (a) Pauson, P. L.; Segal, J. A. J. Chem. Soc., Dalton Trans. 1975,
1677. (b) Pearson, A. J.; Shin, H. J. Org. Chem. 1994, 59, 2314, and
references therein.
(7) Carpentier, J. F.; Castanet, Y.; Brocart, J.; Mortreux, A.; Rose-
Munch, F.; Suzanne, C.; Rose, E. J. Organomet. Chem. 1995, 493, C22.
(8) Schott, D.; Pregosin, P. S.; Jacques, B.; Chavarot, M.; Rose-Munch,
F.; Rose, E. Inorg. Chem. 2005, 44, 5941.
10.1021/om7010529 CCC: $40.75
2008 American Chemical Society
Publication on Web 01/23/2008

(η5-Cyclohexadienyl)Mn(CO)3 Complexes
Organometallics, Vol. 27, No. 4, 2008 627
Scheme 2. Reactivity Features of the (η5-Cyclohexadienyl)-
tricarbonylmanganese Complexes
Figure 1. η5-Cyclohexadienyl)Mn(CO)3 complexes used as sub-
strates in this study.
well-documented for many years.13 Based on similar reactivity
properties between the η5-cyclohexadienyl Mn and η6-arene Cr
series, our present work reports the conditions of lithiation of
(η5-cyclohexadienyl)Mn(CO)3 complexes and provides a new
strategy further extending the scope of applications of the
organomanganese family. Part of this work was the subject of
a preliminary communication.14
most useful reaction for the cationic η6 complexes is the
nucleophilic addition (Scheme 1, path b).9 Indeed, the increased
electrophilic character of these cationic complexes, compared
to neutral ones, allows the arene to be attacked by a broad range
of nucleophiles, leading to neutral and stable (η5-cyclohexadi-
enyl)Mn(CO)3 complexes, which have become increasingly
attractive, in the past decade, to establish efficient functional-
ization pathways.
The (η5-cyclohexadienyl)Mn(CO)3 complexes proved to be
useful synthetic intermediates,3,10 which could lead, after
nucleophilic addition, to the corresponding dienes (Scheme 2,
path a) with total control of the stereochemistry.10a-c In the
specific case of the (η5-oxocyclohexadienyl)Mn(CO)3 com-
plexes, the addition of a nucleophile allowed the synthesis of
disubstituted η5 derivatives.10d-f Thus, a chemistry at the η5
system without loss of the metal was developed. The first cine
and tele nucleophilic substitutions of (η5-cyclohexadienyl)Mn-
(CO)3 complexes (Scheme 2, path b) were developed in 1996
by treatment with hydrides and a proton source,11 and their
mechanism is very close to the cine and tele SNAr described
for (η6-arene)Cr(CO)3 complexes.3d The discovery of Pd cross-
coupling reactions in the η5-cyclohexadienyl manganese series12a
enables easy access to a large variety of substituted η5
complexes, bearing double or triple bonds, aryl or keto groups
linked to the π system (Scheme 2, path c).12b,c Moreover, this
procedure represents an indirect functionalization pathway for
(η6-arene)tricarbonylmanganese complexes, via a rearomatiza-
tion step (Scheme 2, path d), applicable to substrates bearing
an exo hydrogen on the sp3 carbon. This work established that
the presence of the tricarbonyl-Mn fragment dramatically
activates the carbon-halogen bonds in η5-cyclohexadienyl Mn
complexes in the same way as the tricarbonyl-Cr entity does in
η6-arene Cr complexes for which Pd-catalyzed reactions are
Results and Discussion
Lithiation Conditions Depending on the Structure of
the Substrates. The (η5-cyclohexadienyl)Mn(CO)3 complexes
1–5 (Figure 1) used as starting materials in this work were
readily obtained by nucleophilic addition of phenylmagnesium
chloride15 or hydride11,16 onto the corresponding [(η6-arene)-
Mn(CO)3]+ complexes. Chloro- and/or methoxy-substituted
arenes were chosen for their good ortho-directing properties,
due either to inductive electron-withdrawing effect (Cl) or to
lithium coordination (OMe), as demonstrated in the lithiation
of (η6-arene)Cr(CO)3 complexes.2 Nucleophilic addition to the
cationic manganese complex of chlorobenzene led to a mixture
of two regioisomers, 2 and 3.11,16 In contrast, due to the strong
mesomeric donor effect of the methoxy group in the anisole or
para-chloroanisole, complexes 1a,b and 4a,b were isolated as
the sole (4a,b) or the major (1a,b) products after regioselective
addition of the nucleophile to the corresponding η6 complexes.
Complexes 5a,b, without any substituent on the cyclohexadienyl
ring, were also prepared from the cationic [(η6-benzene)Mn-
(CO)3]+ complex.
The lithiation/electrophilic quench of these complexes was
effected by reaction with n-butyllithium (nBuLi) at -78 °C,
followed by the addition of the electrophile at the same
temperature. Trimethylsilylchloride (TMSCl) was chosen as the
reference electrophile. The experimental conditions were opti-
mized to achieve the complete conversion of each substrate.
(9) (a) Semmelhack, M. F. In ComprehensiVe Organometallic Chemistry
II, Vol. 12; Abel E. W., Stone F. G. A., Wilkinson G., Eds.; Pergamon
Press: Oxford, 1995; pp 979. (b) Pike, R. D.; Sweigart, D. A. Synlett 1990,
565.
These reactions give efficient access to the silylated products
with yields ranging from 62 to 88% and a high degree of
regiocontrol (Table 1). Although an excess of lithiated base (1.4
to 2 equiv) is necessary for complete conversion of the various
substrates, the formation of bis-silylated products resulting from
(10) See for example: (a) Pearson, A. J.; Bruhn, P. R. J. Org. Chem.
1991, 56, 7092. (b) Miles, W. H.; Brinkman, H. R. Tetrahedron Lett. 1992,
33, 589. (c) Pearson, A. J.; Shin, H. Tetrahedron 1992, 48, 7527. (d) Lee,
S.-G.; Kim, J.-A.; Chung, Y. K.; Yoon, T.-S.; Kim, N.-J.; Shin, W.
Organometallics 1995, 14, 1023. (e) Son, S. U.; Park, K. H.; Lee, S. J.;
Seo, H.; Chung, Y. K. Chem. Commun. 2002, 1230. (f) Seo, H.; Lee, S.-
G.; Shin, D. M.; Hong, B. K.; Hwang, D. S.; Chung, Y. K. Organometallics
2002, 21, 3417.
(11) Balssa, F.; Gagliardini, V.; Rose-Munch, F.; Rose, E. Organome-
tallics 1996, 15, 4373.
(13) (a) Carpentier, J. F.; Petit, F.; Mortreux, A.; Dufaud, V.; Basset,
J. M.; Thivolle-Cazat, J. J. Mol. Catal. 1993, 81, 1. (b) Prim, D.; Andrioletti,
B.; Rose-Munch, F.; Rose, E.; Couty, F. Tetrahedron 2004, 60, 3325.
(14) Jacques, B.; Chavarot, M.; Rose-Munch, F.; Rose, E. Angew. Chem.,
Int. Ed. 2006, 45, 3481.
(12) (a) Auffrant, A.; Prim, D.; Rose-Munch, F.; Rose, E.; Schouteeten,
S.; Vaissermann, J. Organometallics 2003, 22, 1898. (b) Jacques, B.;
Tranchier, J.-P.; Rose-Munch, F.; Rose, E.; Stephenson, G. R.; Guyard-
Duhayon, C. Organometallics 2004, 23, 184. (c) Schouteeten, S.; Tranchier,
J.-P.; Rose-Munch, F.; Rose, E.; Auffrant, A.; Stephenson, G. R. Organo-
metallics 2004, 23, 4308.
(15) Chung, Y. K.; Williard, P. G.; Sweigart, D. A. Organometallics
1982, 1, 1053.
(16) Pauson, P. L.; Segal, J. A. J. Chem. Soc., Dalton Trans. 1975, 1683.

628 Organometallics, Vol. 27, No. 4, 2008
Jacques et al.
Table 1. Silylation Conditions for Complexes 1–5
Figure 2. Regioselective lithiation of (η5-6-phenylcyclohexadi-
enyl)Mn(CO)3 complex 5a.
yielda
(%)
entry substrate
time
1 h
1 h
1 h
1 h
15 min none
1 h none
15 min none
2 h
additive
product
position
1b
2
1a
1b
2a
TMEDA 6a
TMEDA 6b
none
none
C3
86
66
62
81
88
82
75
66
degradation during the lithiation step, which therefore needs to
be carefully monitored. This was clearly observed for substrates
2b, 3b, and 5b, for which poor yields were obtained and were
not optimized. The 2-methoxy derivative 1a, which gives the
3-trimethylsilylated complex 6a (Table 1, entry 1), is less
reactive than the chloro-substituted ones 2a and 3a, which afford
the 2- and the 3-trimethylsilylated complexes 7a and 8a (Table
1, entries 3 and 4): thus, in the case of 1a, addition of
tetramethylethylenediamine (TMEDA) was needed to ensure
complete conversion of the substrate. Complex 4a appears to
be the most reactive η5-cyclohexadienyl complex, probably due
to a synergic effect of the two activating groups: the reaction
required only 15 min at -78 °C without TMEDA for complete
conversion of this substrate (Table 1, entry 5). When both the
C1 and C3 positions are available adjacent to the C2 substituent,
as in 1a or 3a, the competition between C1 and C3 is fully
controlled for selectiVe lithiation at the C3 position (Table 1,
entries 1 and 4). Furthermore, when two ortho-directing groups
are present as in 4a, there is a substantial preference for lithiation
at C2, ortho to the chlorine atom (Table 1, entries 5 and 6).
Theoretical Investigation on the Lithiation of Substrates
5. It is important to highlight that the lithiation is still efficient
without any activating group on the substrate. Indeed, the
cyclohexadienyl complex 5a has been silylated in 66% yield
(Table 1, entry 8), although stronger conditions were required:
reaction with 2 equiv of nBuLi and TMEDA for 2 h before
addition of the electrophile. Two regioisomers, resulting from
the lithiation at C2,4 or at C3, were isolated in a 80:20 ratio,
respectively; again, no lithiation was observed on the C1,5
positions of the cyclohexadienyl (Figure 2). This selectivity
should arise from the greater sp2 character of the C2,4 and C3
carbon atoms with respect to the C1,5 carbons, the five C-H
bonds of the metal-complexed cyclohexadienyl being not
equivalent toward deprotonation.
Furthermore, conformational effects might be put forward to
explain the high selectivity for the lithiation at the C2,4 positions;
it is indeed well-known that, in all the structures of η5 complexes
described in the literature, the Mn(CO)3 tripod adopts a
conformation eclipsing the C2, C4, and C6 carbons,12a as justified
from a molecular orbital point of view.21 A similar tripod
conformation was also obtained from geometry optimization
for isoelectronic and isostructural tricarbonylchromium22 and
tricarbonyliron23 analogues. A computational study was per-
formed on complex 5b starting from the opposite conformation,
in which the C6 center is anti-eclipsed with respect to the CO
ligands. This structure is found to be a transition state (TS)
connecting two eclipsed structures. The associated rotational
barrier is 9.9 kcal/mol, which is consistent with a slow rotation
movement and is marginally higher that the value reported in
C3
3b
4b
5b
6
7a
8a
9a + 9′a
9a + 9′a
9b + 9′b
C2
3a
C3
4a
C2 + C3c
C2 + C3e
C2 + C3f
4ad
4b
5ag
7
8
TMEDA 10a + 10′a C2 + C3h
a Isolated yield, unless otherwise specified. b Reference 14. c Ratio )
90:10 determined by 1H NMR analysis of the crude mixture. d LDA
instead of nBuLi. e Ratio ) 75:25. f Ratio ) 60:40. g 2 equiv of nBuLi
and TMEDA, 2.5 equiv of TMSCl. h Ratio ) 80:20.
a double deprotonation has never been observed.17 The ef-
ficiency of the cyclohexadienyl lithiation, based on the use of
nBuLi at -78 °C, is in sharp contrast with the nucleophilic
addition of methyl- or aryl-lithium reagents to a carbonyl Mn
ligand at higher temperature, leading first to acylmetalate
species, then to the corresponding carbene complexes after an
alkylation step.18
For complexes 1–4, substituted by ortho-directing groups,
NMR characterization of products 6–9 confirmed that the
trimethylsilyl group is, in all cases, located ortho to the Cl or
OMe substituent.19 When a chlorine atom is present on the
complex (Table 1, entries 3–7), no competing halogen-lithium
exchange was observed, similarly to what has already been
noticed for chloro-substituted (η6-arene) metal complexes.2d,20
In order to determine the most efficient procedure, we tested
the lithiation of complex 4a, the para-chloroanisole derivative,
with the milder base lithium diisopropylamide (LDA) (Table
1, entry 6). We were pleased to observe that LDA is able to
deprotonate the metal-coordinated cyclohexadienyl moiety.
However, whereas the reaction time was 15 min in the case of
nBuLi (Table 1, entry 5), 1 h was required for a complete
conversion to give the silylated derivatives in 82% yield. The
lithiation/electrophilic quench sequence was also tested in Et2O,
instead of THF. The lithiation step is nevertheless slower in
this solvent; longer reaction times were therefore needed, leading
to partial degradation of the lithiated species.
We can compare the substituent effects on the reactivity from
the series of complexes 1–5: complexes a, bearing a phenyl
group on the exo position, give the silylated products with better
overall yields than the corresponding complexes b, with an exo
hydrogen on C6. These latter ones seem more sensitive to
(17) Multiple metalated species can indeed be generated if more than
one equivalent of base is employed in the lithiation of (η6-arene)Cr(CO)3
complexes: Gibson, S. E.; Steed, J. W.; Sur, S. J. Chem. Soc., Perkin
Trans.1 2001, 636, and references therein.
(18) (a) Padda, R. S.; Sheridan, J. B.; Chaffee, K. J. Chem. Soc., Chem.
Commun. 1990, 1226. (b) Sheridan, J. B.; Padda, R. S.; Chaffee, K.; Wang,
C.; Huang, Y.; Lalancette, R. J. Chem. Soc., Dalton Trans. 1992, 1539. (c)
Yu, Y.; Chen, J.; Wang, X.; Wu, Q.; Liu, Q. J. Organomet. Chem. 1996,
516, 81.
(19) The directed ortho-metalation is a well-known methodology in
organic synthesis; see for example: (a) Hartung, C. G.; Snieckus, V. In
Modern Arene Chemistry; Astruc, D., Ed.; Wiley-VCH: New York, 2002;
Chapter 11, pp 330. (b) Whisler, M. C.; MacNeil, S.; Snieckus, V.; Beak,
P. Angew. Chem., Int. Ed. 2004, 43, 2206.
(21) Albright, T. A; Hofmann, P.; Hoffmann, R. J. Am. Chem. Soc. 1977,
99, 7546.
(22) A rotational barrier of 7.5 kcal · mol-1 was calculated for the anionic
(η5-cyclohexadienyl)Cr(CO)3 complex with a methyl group at C6: Pfletsch-
inger, A.; Koch, W.; Schmalz, H.-G. New J. Chem. 2001, 25, 446.
(23) Carvalho, F. N. N.; Lemos, A. N. D. A.; Veiros, L. F.; Stephenson,
G. R. J. Organomet. Chem. 2001, 632, 49.
(20) Bodes, G.; Heinemann, F. W.; Jobi, G.; Klodwig, J.; Neumann,
S.; Zenneck, U. Eur. J. Inorg. Chem. 2003, 281.

(η5-Cyclohexadienyl)Mn(CO)3 Complexes
Organometallics, Vol. 27, No. 4, 2008 629
Table 2. Energies (kcal/mol) with Respect to the Most Stable
Regioisomer (for definition of LH-Me, see text)
Table 3. Functionalization of 1a by Various Electrophiles
entry
EX
E-
product
yielda (%)
1b
2
MeI
CD3OD
nBu3SnCl
I(CH2)2I
ClCO2Et
Me-
11a
12a
13a
14a
15a
16a
82
96
87
95
72
50c
D-
3b
4b
5b
6
nBu3Sn-
I-
EtO2C-
Me2N(O)C-
ClC(O)N(Me)2
a Isolated yield, unless otherwise specified. b Reference 14. c 2.5
equiv of EX and 2.5 h at -78 °C before warming at rt.
the literature22 for the anionic (η5-cyclohexadienyl)Cr(CO)3
complex. This represents, to the best of our knowledge the first
computational study dealing with (η5-cyclohexadienyl)Mn(CO)3
complexes since the work by R. Hoffmann et al.24 They reported
on the charge densities of the π system carbons calculated for
the cyclohexadienyl anion as well as the (η5-cyclohexadi-
enyl)Mn(CO)3 complex in the course of a study dealing with
the origin of the geometrical deformation of the cyclohexadienyl
ring upon complexation.
Figure 3. Representation of the lithiated species in position C2 (left)
and C3 (center and right): Li+ cation alone (left), Li+ cation
coordinated to LH-H (see text for notation, center), and the retained
model of a Li+ cation coordinated to LH-Me (right). Distances of
the undesired interactions are given in Å.
tonated species. It is well-known that the structure of lithiated
compounds in solution most often involves aggregation, so that
the species computed in this case are not exactly portraying
the species present in solution. It can nevertheless be assumed
that the relative stability of the regioisomers in the monomeric
species is similar to that in the aggregated form. However, the
sole replacement of the hydrogen by a naked Li appears to be
a too rough modeling. Indeed, geometry optimizations lead to
strongly distorted species since, in the absence of any explicit
solvent representation, the lithium cation is seaking to complete
its coordination sphere. It thus builds chemically unrelevant
interactions with its neighbors, namely, the CO ligands (Figure
3). A chemical model of TMEDA was thus coordinated to the
lithium cation in order to get closer to the experimental system.
It leads to a tricoordinated lithium, which is consistent with
recent theoretical data26 for this cation in the presence of steric
hindrance. For the sake of computational cost, the methyl groups
were replaced by H substituents, and ethylenediamine (referred
as LH-H ) H2N-C2H4-NH2) was used. Nevertheless the obtained
structures using this model are still not satisfying since H-bonds
are being built during the optimization process between the
amine groups of LH-H and the carbonyl ligands, interactions that
are not relevant since the hydrogens are modeling Me groups
(Figure 3). The most suitable model was finally the dimethyl-
ethylenediamine ligand, LH-Me ) MeHN-C2H4-NHMe, the
methyl being added only on the endo side of the molecule, in
order to avoid any H bonds with the CO ligands (Figure 3).
Conformational effects have already been observed for the
lithiation of the (η6-dimethylaniline)Cr(CO)3 complex, giving
the meta substitution as the major product, whereas the lithiation
of the uncomplexed dimethylaniline is selective of the ortho
position.25 The authors have proposed that the chelation of the
alkyllithium base by the oxygen of a CO ligand could be at the
origin of this unusual selectivity. In the cyclohexadienyl
complexes 5a,b, such a coordination between nBuLi and a
carbonyl ligand could also be involved in the selective lithiation
at C2,4 carbons. It is nevertheless not the only regiodirector effect
that can be proposed for this system due to the inequivalence
of the five hydrogen atoms. Deprotonation and lithiation of (η5-
cyclohexadienyl)Mn(CO)3 complexes 5a and 5b were thus
computationally examined in detail in order to determine the
origin of the experimentally observed regioselectivity. The
species deprotonated in position C2 (Table 2, entries 1 and 2)
are found to be the most stable in both cases. No major effect
of the phenyl substituent in position C6 could be observed: the
unsubstituted 5b was thus used as a model in the following
study in order to limit the computational cost. Rotational barriers
for the species deprotonated in C1, C2, and C3 are respectively
8.8, 9.9, and 6.0 kcal/mol, indicating that the conformational
preference of the complex is not affected upon deprotonation,
whatever the deprotonation site is. This is consistent with the
fact that deprotonation alters the σ skeleton of the cyclohexa-
dienyl ligand, whereas coordination to the metal relies on the
π orbitals.
The lithium sphere being completed with LH-Me in the lithiated
form of 5b, the lithiated species at C2 is found to be the most
stable regioisomer (Table 2, entry 3). It thus appears that the
preference for position C2 obtained in the anionic species (Table
2, entry 2) is maintained even when the negative charge is
The study of the relative stability of the lithiated form of 5b
was then undertaken in order to examine the effect of the
counterion coordination on the relative stabilities of the depro-
(24) Hoffmann, R.; Hofmann, P. J. Am. Chem. Soc. 1976, 98, 598.
(25) (a) Card, R. J.; Trahanovsky, W. S. J. Org. Chem. 1980, 45, 2560.
(b) Masters, N. F.; Widdowson, D. A. J. Chem. Soc., Chem. Commun. 1983,
955.
(26) See for recent examples: (a) De la Lande, A.; Fressigné, C.; Gérard,
H.; Maddaluno, J.; Parisel, O. Chem. Eur. J. 2007, 13, 3459. (b) Pratt, L. M.;
Truhlar, D. G.; Cramer, C. J.; Kass, S. R.; Thompson, J. D.; Xidos, J. D.
J. Org. Chem. 2007, 72, 2962, and references therein.

630 Organometallics, Vol. 27, No. 4, 2008
Jacques et al.
Table 4. Functionalization of 4a by Various Electrophiles
stabilized by coordination to a lithium center. The experimen-
tally observed preference for functionalization at C2 can thus
be fully justified on the basis of the stability of the intermediate
carbolithiated moiety, stability that is found to be similar to
that of the carbanionic complex. Moreover, the stability of the
final silylated product cannot be at the origin of the experimen-
tally observed 80:20 ratio for C2:C3. Indeed, computations on
the SiH3 addition products (Table 2, entry 4), models for the
SiMe3 complexes experimentally obtained, gave the C3-func-
tionalized species as the most stable and therefore the major
product.
yielda
entry
EX
E-
product
17a
(%) C2:C3b
1
2
MeI
Me-
80
100:0
(-C(Me)2O)2B- (-C(Me)2O)2B- 18a
70c 100:0
In addition to the preference for position C2, the results of
the computations are also in line with the reactivity of position
C3, for which the carbolithiated species is found to be only 1.4
kcal/mol above the reference. This is fully in line with the
experimental observation for the formation of 20% of 10′a
(Table 1, entry 8), the regioisomer substituted at position C3.
On the other side, the species lithiated at position C1 is
significantly higher in energy (Table 2, entry 3) and is therefore
not expected to be formed. In order to bring forward the role
played by the Mn(CO)3 tripod on the regioselectivity, we
examined the deprotonation of a “virtual” unbound anionic
OiPr
3
4
5
6
7
ClCO2Et
(CH3)3COCl
PhS-SPh
I(CH2)2I
nBu3SnCl
EtO2C-
(CH3)3CO-
PhS-
19a + 19′a 84
80:20
74:26
65:35
62:38
57:43
20a + 20′a 86
21a + 21′a 73
22a + 22′a 86
23a + 23′a 86
I-
nBu3Sn-
a Isolated yield, unless otherwise specified. b Determined by 1H NMR
analysis of the crude mixture. c Conversion, determined by 1H NMR
analysis of the crude mixture.
Table 5. Energies (kcal/mol) with Respect to the Most Stable
Regioisomers (for definition of LH-Me, see text)
2-
cyclohexadienyl ligand, C6H6 (Table 2, entry 5); such a
comparison with an uncoordinated ligand has also proven its
usefulness in the computational studies of aryl27 or benzyl28
anions, radicals, and cations of (η6-arene)Cr(CO)3 complexes
in order to understand their chemical properties. The results
show that positions C1 and C2 are very close in energy, whereas
position C3 is much more destabilized. This is in sharp contrast
with the complexed analogue 5b- (Table 2, entry 2) and thus
with the experimental results. In conclusion, whereas a slight
preference for position C2 is intrinsic to the cyclohexadienyl
ligand, the strong destabilization of position C1, and thus the
regioselectivity of the lithiation, is thermodynamically due to
+
its coordination to the Mn(CO)3 moiety. In these conditions,
the strong conformational preference of the Mn(CO)3+ moiety
is likely to play an important role in the selectivity of the
reaction.
reactivity toward Pd-catalyzed coupling reactions under a CO
atmosphere.12a In the present work, the procedure does not affect
the substituents of the starting material, and consequently, when
a chlorine atom is present as in 2, 3, or 4, it remains available
for a subsequent functionalization. This new approach is
therefore complementary to the Pd-catalyzed method published
in this series a few years ago. More strategically important
products were formed by reaction with tributyltin chloride and
1,2-diiodoethane, introducing tributylstannyl (complexes 13a
and 23–23′a) and iodo (complexes 14a and 22–22′a) groups in
high yields (86–95%). Monocrystals of complex 14a were
readily obtained and the corresponding crystal structure was
previously described.14 The synthesis of the boronated η5
complex 18a was also attempted (Table 4, entry 2); although
the expected product was formed with a good conversion (70%)
in the crude mixture, we failed to isolate it in a pure form. As
far as further transformations are concerned, such functionalized
complexes could be involved in halogen-metal or metal-metal
exchange30 and also in palladium cross-coupling procedures.
Indeed, the methodology previously developed in our group
allowed efficient functionalization at the C1 and C2 positions
of the cyclohexadienyl ring. Thanks to the lithiation/electrophilic
quench sequence, new precursors bearing suitable functions at
C3 can now be synthesized.
Extension to a Wide Range of Electrophiles. Having
investigated Me3SiCl as an electrophile for functionalization of
various η5 complexes, we carried out further investigations using
a large panel of electrophiles, complexes 1a (Table 4) and 4a
(Table 5) being chosen as model substrates. The results
established the general applicability of the lithiation/electrophilic
quench sequence, which led to a large variety of derivatives in
moderate to excellent yields (50 to 95%). Most of the functional
groups presented in Tables 4 and 5 are incompatible with the
arene complexation procedures29 and therefore need to be
introduced subsequently by efficient synthetic procedures.
This reaction is efficient not only to label the cyclohexadienyl
ring by a deuterium (Table 3, entry 2) but also to introduce
alkyl groups (Tables 3 and 4, entry 1) and thioether (Table 4,
entry 5), ketone (Table 4, entry 4), and ester (Table 3, entry 5;
Table 4, entry 3) functions. An amide derivative (Table 3, entry
6) was also prepared, but in a relatively lower yield, using a
carbamoyl chloride as the electrophile. In an earlier study, we
already introduced ketone, ester, and amide groups on (η5-
chlorocyclohexadienyl)Mn(CO)3 complexes by using the C-Cl
The regioselectivity of the lithiation/electrophilic quench
process for the para-chloroanisole derivatives 4a,b deserves
much more comment. Indeed, as two ortho-directing groups are
(27) Merlic, C. A.; Miller, M. M.; Hietbrink, B. N.; Houk, K. N. J. Am.
Chem. Soc. 2001, 123, 4904.
(28) Merlic, C. A.; Walsh, J. C.; Tantillo, D. J.; Houk, K. N. J. Am.
Chem. Soc. 1999, 121, 3596.
(29) Jackson, J. D.; Villa, S. J.; Bacon, D. S.; Pike, R. D.; Carpenter,
G. B. Organometallics 1994, 13, 3972.
(30) See for example: Ariffin, A.; Blake, A. J.; Ewin, R. A.; Li, W.-S.;
Simpkins, N. S. J. Chem. Soc., Perkin Trans. 1 1999, 3177.

(η5-Cyclohexadienyl)Mn(CO)3 Complexes
Organometallics, Vol. 27, No. 4, 2008 631
Table 6. Selective Access to Variously Substituted (η5-hydroxymethylcyclohexadienyl)Mn(CO)3 Complexes
entry
substrate
R-
EX
E-
product
yielda (%)
C2:C3b
1c
2
3
4
5
1a
1a
4a
4a
4a
H-
H-
Cl-
Cl-
Cl-
Ph2CO
PhCHO
Ph2CO
PhCHO
(CH3)2CO
Ph2C(OH)-
PhCH(OH)-
Ph2C(OH)-
PhCH(OH)-
(CH3)2C(OH)-
24a
83
93
64
87
31f
C3 only
C3 only
60:40
66:34
65:35
25ad
26a + 26′a
27a + 27′ae
28a + 28′a
a Isolated yield, unless otherwise specified. b Determined by 1H NMR analysis of the crude mixture. c Reference 14. d Four diastereoisomers (2 pairs
of enantiomers) in a 56:44 ratio. e Four diastereoisomers (2 pairs of enantiomers) in a 52:48 ratio for 27a, a 75:25 ratio for 27′a. f Conversion of 46%
determined by 1H NMR analysis of the crude mixture.
present, two regioisomers are isolated from the lithiation either
ortho to the methoxy group or ortho to the chlorine atom. We
have not been able to separate all the regioisomers by chroma-
tography on silica gel, depending on the polarity of the resulting
η5 complexes. The different results are summarized in Table 1
(entries 5–7) and in Table 4. The first comment is that there is
a substantial preference for the functionalization at C2, ortho
to the chlorine atom. From Table 4, it also clearly appears that
the regioselectivity is highly dependent on the electrophile
introduced. While a unique regioisomer is isolated using
iodomethane (C2:C3 ) 100:0; Table 4, entry 1), two regioiso-
mers are obtained in C2:C3 ratios varying from 90:10 for
Me3SiCl (Table 1, entry 5) to 57:43 for tributyltin chloride
(Table 4, entry 7). This variation according to the electrophile
suggests that the regioselectivity is not fully determined at the
end of the deprotonation step; depending on the electrophilic
quench kinetics, an isomerization of the lithiated η5 anion might
occur. Equilibration processes have also been observed with
This could be explained by simple inductive attractor effects
on the σ skeleton localized minus charge: indeed, the methoxy
group electronegativity (3.7)33a is higher than the chloride one
(2.8).33b
In contrast, the C2-lithiated form, stabilized by coordination
of the Li cation to MeNHCH2CH2NHMe (LH-Me) as in the case
of the unsubstituted η5 complex computations (Table 2, entry
3), was found to be the most stable by 2.6 kcal/mol (Table 5,
entry 2). The C2-substituted form is also found to be the most
stable when the lithium is coordinated to two additional dimethyl
ether molecules in order to model solvation. It highlights the
strong impact of the lithium chelation at the anionic center on
the regiochemical outcome of the reaction for this specific
substrate. In this connection, the stability of the species will
most probably be altered by other factors, among which
aggregation but also chelation to the electrophile. A close
examination of the mechanisms of both lithiation and electro-
philic quench, and especially of the regiochemical stability of
the lithiated intermediates in the presence of the electrophile,
is thus necessary, and a thorough study will be published in
due time.
Application: Synthesis of Unprecedented Alcohol Deriva-
tives and Indirect Functionalization of η6 Complexes. Having
in hand an efficient and general substitution pathway, we turned
our attention to η5 manganese complexes substituted by an
alcohol group, R to the π-system. Such complexes cannot be
prepared from the corresponding cationic complexes, the
benzylic alcohol function being indeed incompatible with the
complexation procedures. For this reason, the first example was
only recently reported in our group34 and was obtained by
hydride reduction of a keto-substituted η5 complex prepared
by a palladium-catalyzed carbonylative coupling. In comparison,
the lithiation/electrophilic quench sequence offers a one-pot
access to alcohol derivatives, provided that an aldehyde or a
ketone is employed as the electrophile. We therefore undertook
the synthesis of variously substituted (η5-hydroxymethylcyclo-
hexadienyl)Mn(CO)3 complexes, starting from either 1a or 4a
and following the previously optimized experimental conditions.
Benzophenone, benzaldehyde, and acetone were chosen as the
electrophiles.
31
lithiated (η6-arene)Cr(CO)3 and have for instance been put
forward to explain the erosion of the ee observed in the
enantioselective lithiation of anisole-type arene chromium
complexes.31c We led several nonconclusive attempts to get
more information about the isomerization process involved in
the lithiated (η5-cyclohexadienyl)Mn(CO)3 complexes. For
instance, allowing the temperature to increase before the
electrophile addition led to the degradation of the lithiated
species instead of their expected thermodynamic equilibration.31a,b
A second reported strategy to demonstrate the occurrence of
an anion equilibration consists in submitting a stannylated
substrate to a metal-metal exchange with nBuLi and then
determining its stability after quenching with an electrophile
such as TMSCl.31c Unfortunately, in our case, we could not
separate the stannylated regioisomers 23a-23′a in order to
obtain a pure substrate.32
Theoretical investigations within the stability of the para-
chloroanisole derivatives evidence the greater complexity of the
regioselectivity issue in this system. The C2 deprotonated species
without any countercation Li+ is found to be disfavored by 1.4
kcal/mol with respect to the C3 one (Table 5, entry 1), whereas
it was favored by 3.0 kcal/mol in the unsubstituted species
(Table 2, entry 2). The potential for lithium coordination to OMe
is therefore not the only origin of its ortho-directing properties.
The expected alcohol derivatives were isolated in good to
excellent yields, except for 28a-28′a (Table 6, entry 5), for
which the poor conversion could be explained by a competitive
(31) (a) Treichel, P. M.; Kirss, R. U. Organometallics 1987, 6, 249. (b)
Schmalz, H.-G.; Volk, T.; Bernicke, D.; Huneck, S. Tetrahedron 1997, 53,
9219. (c) Ewin, R. A.; MacLeod, A. M.; Price, D. A.; Simpkins, N. S.;
Watt, A. P. J. Chem. Soc., Perkin Trans. 1 1997, 401.
(33) (a) Boyd, R. J.; Edgecombe, K. E. J. Am. Chem. Soc. 1988, 110,
4182, and references therein. (b) Alred, A. L.; Rochov, E. G. J. Inorg. Nucl.
Chem. 1958, 5, 264.
(32) The metal-metal exchange was nevertheless attempted on the
mixture of the two stannylated regioisomers (C2:C3 ) 55:45), giving a new
ratio C2:C3 ) 82:18.
(34) Eloi, A.; Rose-Munch, F.; Jonathan, D.; Tranchier, J.-P.; Rose, E.
Organometallics 2006, 25, 4554.

632 Organometallics, Vol. 27, No. 4, 2008
Jacques et al.
+
Table 7. Synthesis of Functionalized (η6-Arene)Mn(CO)3
Complexes by Rearomatization
entry
substrate
E-
product
yielda (%)
1
2
6b
30b
-SiMe3
-I
29
31
78
76
a Isolated yield, unless otherwise specified.
This novel family of metal-complexed benzylic alcohols could
exhibit a rich and varied chemistry, which is currently under
investigation.
The straightforward access to a large panel of functionalized
η5 manganese derivatives opens numerous perspectives for the
chemistry of tricarbonylmanganese complexes. Among them,
+
the indirect functionalization of the cationic (η6-arene)Mn(CO)3
complexes is especially attractive. Indeed, as mentioned before,
most of the functionalized cationic complexes are difficult or
impossible to prepare by direct complexation. Taking advantage
of the rearomatization procedure by exo-hydride abstraction6a
already successfully exploited in the group,12a we have applied
it to two new η5 complexes, 6b and 30b (Table 7), the latter
one being synthesized in 61% yield by lithiation of 4b followed
by an electrophilic quench with diiodoethane; the corresponding
η6 cationic complexes 29 and 31 were isolated in 78 and 76%
yield, respectively.
Figure 4. Molecular structure of complex 24a with thermal
ellipsoids at the 30% probability level. All H atoms are omitted
for clarity. Selected bond lengths (Å): Mn-C1 2.223(2), Mn-C2
2.1979(18), Mn-C3 2.1628(18), Mn-C4 2.149(2), Mn-C5 2.241(2),
C3-C14 1.545(3), C14-O2 1.438(2).
acetone enolization, giving back the substrate 4a. When
benzaldehyde was used as the electrophile, a new stereogenic
center was created during the addition of the lithiated anion.
Although prepared as racemic mixtures, the substrates 1a and
4a indeed present a planar chirality. Four diastereoisomers (two
pairs of enantiomers) were therefore obtained and the diaste-
reoisomeric ratios determined by 1H NMR analysis of the crude
mixtures. The facial stereodiscrimination of the benzaldehyde
CdO bond by the planar chiral anion is not efficient for 25a
(dr ) 56:44) and 27a (dr ) 52:48) and is really limited for
27′a (dr ) 75:25); this lack of diastereoselectivity has been
observed previously in a similar experiment using a planar chiral
(η6-lithio-arene)Cr(CO)3 complex.31c
Whereas (η6-chloroarene)Mn(CO)3+ and their corresponding
η5complexes have been well-documented for many years,
only two syntheses6a,29 of a bromo derivative are mentioned
in the literature to our knowledge, leading to a mixture,
difficult to purify, of the expected (η6-bromobenzene)Mn-
+
(CO)3 complex either with a dehalogenated derivative, the
+ 6a
+ 29
(η6-benzene)Mn(CO)3
,
or with Mn(CO)6
.
As for an
iodo-substituted complex, nothing has been reported up to
now.36 The nucleophilic addition/lithiation/electrophilic quench/
rearomatization sequence represents therefore the only al-
ternative to efficiently prepare the halogeno manganese η6
derivatives.
Pleasingly, monocrystals of complex 24a were readily
obtained to provide a crystal structure of an alcohol-substituted
(η5-cyclohexadienyl)Mn(CO)3 complex.35 The ORTEP view is
presented in Figure 4 as well as some selected bonds. The
diphenylhydroxymethyl group is located adjacent to the methoxy
group, the distance between the two oxygens O1 and O2 being
2.733 Å, suitable for the establishment of a hydrogen bond
between these two functions. The single C14-O2 bond presents
a 1.438(2) Å bond length value very similar to the one (1.398(7)
Å) found in the structure of the η5 complex containing an
alcohol function R to the C1 carbon.34 The two phenyl groups
are oriented in order to minimize the steric hindrance. The η5
structure has not been modified by the functionalization, with
five coplanar sp2 carbons, while the remaining sp3 carbon is
located 38° above this plane. The conformation of the Mn(CO)3
tripod is in agreement with what is usually observed,12a the sp3
C6 carbon being eclipsed by one Mn-CO bond.
Conclusion
We successfully developed a highly efficient and versatile
strategy for easy functionalization of (η5-cyclohexadienyl)Mn-
(CO)3 complexes through a lithiation/electrophilic quench
sequence. The electrophiles examined (methyl iodide, diphe-
nyldisulfide, tributylstannyl chloride, ethyl chloroformiate, piv-
aloyl chloride, . . .) all gave good to excellent yields of the
corresponding substituted η5 complexes. Using benzophenone
or benzaldehyde as electrophiles led to the formation, also in
very good yields, of η5 complexes substituted by alcohol
functions. In all cases the reaction occurred at the π system,
ortho to the directing groups, when OMe or Cl is present, and
no functionalization was detected at the extremity positions C1
and C5 of the cyclohexadienyl moiety. Theoretical investigations
performed on η5 complexes without any substituent on the
conjugated system provided a particularly well-suited example
of the fruitful interplay between theory and experiment. Indeed,
they highlighted the major role of the Mn(CO)3 tripod on the
(35) Crystal data for 24a: C29H23MnO5, M ) 506.43, yellow crystals,
T ) 250 K, monoclinic, space group P21/c, a ) 12.864(3), b ) 11.6069(18),
c ) 17.1408(8) Å, V ) 2533.4(7) Å3, Z ) 4, Fcalcd ) 1.328 g · cm-3, 2θmax
) 64°, µ(Mo KR) ) 5.574 cm-1, 8783 independent reflections, R ) 0.0303,
wR ) 0.0307. The structure was solved by direct methods using SHELXS86
and refined with full-matrix least-squares technique on F using the
CRYSTALS programs. CCDC-650517 and the supporting information
contain the supplementary crystallographic data for this paper.
(36) The complexation of iodobenzene, according to the chlorobenzene
complexation procedure, was unsuccessful in our hands: Chavarot, M.; Rose-
Munch, F.; Rose, E., unpublished results.

(η5-Cyclohexadienyl)Mn(CO)3 Complexes
Organometallics, Vol. 27, No. 4, 2008 633
Typical Procedure for the Lithiation/Electrophilic Quench
Sequence. A solution of (η5-cyclohexadienyl)Mn(CO)3 complex
(0.5 mmol) and freshly distilled TMEDA (0 to 2 equiv; see Table
1) in 5 mL of THF was cooled to -78 °C. A solution of n-BuLi
(1.6 M in hexanes; 1.4 to 2 equiv; see Table 1) was slowly added.
The mixture was stirred for 15 min to 2 h (see Table 1) at -78 °C
before the addition of the electrophile (1.6 to 2.5 equiv; see Table
1). The mixture was stirred for another hour at -78 °C before
warming to room temperature and quenching by addition of H2O.
After extraction of the mixture by Et2O, the combined organic layers
were washed with a saturated aqueous NaCl solution and dried over
MgSO4. After concentration in Vacuo, the crude mixture was
purified by flash chromatography on silica gel to afford the pure
functionalized η5-cyclohexadienyl complex.
regioselectivity of the lithiation/electrophilic quench sequence
which is mainly governed by the stability of the deprotonated
species on the C2 carbon eclipsed by a Mn-CO bond. On the
other hand, the origins of the reaction regioselectivity on the
para-chloroanisole derivatives are less obvious; preliminary
theoretical studies showed that it cannot be anymore explained
by the sole thermodynamic properties of the deprotonated
species.
This new reaction, together with the Pd-catalyzed cross-
couplings that we developed a few years ago, sheds new light
on the applications of (η5-cyclohexadienyl)Mn(CO)3 complexes
in organic and organometallic syntheses.
1
6a (86%). H NMR (400 MHz, CDCl3): δ (ppm) 0.45 (s, 9H,
Experimental Section
SiMe3), 3.38 (s, 3H, OCH3), 3.50 (m, 2H, H1 and H5), 3.97 (tapp
,
J ) 6.0 Hz, 1H, H6), 4.86 (d, J ) 6.4 Hz, 1H, H4), 6.89–6.92 (m,
2H, HPh), 7.12–7.27 (m, 3H, HPh). 13C NMR (100 MHz, CDCl3):
δ (ppm) 0.2 (SiMe3), 42.9 (C6), 44.2 (C1), 54.4 (OCH3), 61.9 (C5),
74.7 (C3), 97.3 (C4), 125.9 (CHPh), 127.1 (CHPh), 128.8 (CHPh),
146.6 (C2 or CPh), 148.0 (C2 or CPh). IR (neat): ν˜ (cm-1) 1913,
2007 (CO (Mn)). HRMS (EI, positive mode): m/z calcd for
C19H21MnO4Si, 396.0590; found, 396.0599 (M+).
Computational Details. Full geometry optimizations were
systematically conducted with no symmetry restraints using the
Gaussian 03 program37 within the framework of the density
functional theory (DFT) using the hybrid B3LYP exchange-
correlation functional38–40 and the 6-31+G** basis set for all atoms.
This level of theory has been widely used in modeling arene-
Cr(CO)3 complexes and has proved to give good results from both
geometrical41 and energetic basis.22 NMR chemical shift computa-
tions were carried out using the standard Gaussian03 procedure.
Evaluation of chemical shifts using such gas-phase modeling should
be taken cautiously since long-range environment effects are known
to play an essential role in chemical shifts. Nevertheless, since the
present study is only concerned with trends in series of highly
analogous compounds, we believe the results remain reliable.
General Procedures. All reactions were routinely performed
under a dry nitrogen atmosphere using standard Schlenk techniques.
THF was dried over sodium benzophenone ketyl and distilled.
N,N,N′,N′-Tetramethylethylenediamine (TMEDA) was distilled over
KOH and stored under nitrogen over 4 Å molecular sieves. Acetone
and benzaldehyde were distilled over K2CO3. NMR spectra were
recorded on a Bruker ARX 200 MHz or Avance 400 MHz
spectrometer. Infrared spectra were measured on a Bruker Tensor
27 spectrometer. Elemental analyses were performed by the Service
Central d’Analyze du CNRS. Mass spectra were performed for
MALDI-TOF by the Plate-Forme Spectrométrie de Masse et
Protéomique (IFR83, UPMC), for ES-MS by the Groupe de
Spectrométrie de Masse (UMR 7613, UPMC), and for the EI-MS
by the Service de Spectrométrie de Masse de l’ENS (Chemistry
Dpt, Paris).
1
6b (66%). H NMR (400 MHz, CDCl3): δ (ppm) 0.41 (s, 9H,
SiMe3), 2.19 (d, J ) 12.6 Hz, 1H, H6exo), 2.73–3.01 (m, 3H, H1,
H5 and H6endo), 3.29 (s, 3H, OCH3), 4.75 (d, J ) 7.2 Hz, 1H, H4).
13C NMR (100 MHz, CDCl3): δ (ppm) 0.5 (SiMe3), 27.1 (C6),
36.5 (C1), 54.2 (OCH3), 54.8 (C5), 75.1 (C3), 99.3 (C4), 147.4 (C2),
220.6 (CO (Mn)). IR (neat):ν˜ (cm-1) 1910, 2005 (CO (Mn)).
HRMS (MALDI TOF, positive mode): m/z calcd for C13H16MnO4Si,
319.0198; found, 319.0117 (M + H+).
1
7a (62%). H NMR (400 MHz, CDCl3): δ (ppm) 0.35 (s, 9H,
SiMe3), 3.75 (ddd, J ) 7.0, 6.3, 1.5 Hz, 1H, H5), 4.21 (d, J ) 6.3
Hz, 1H, H6), 4.88 (dd, J ) 7.0, 5.2 Hz, 1H, H4), 5.55 (dd, J ) 5.2,
1.5 Hz, 1H, H3), 6.96–7.00 (m, 2H, HPh), 7.21–7.26 (m, 3H, HPh).
13C NMR (100 MHz, CDCl3): δ (ppm) -0.1 (SiMe3), 52.2 (C6),
60.7 (C5), 80.6 (C3), 86.8 (C1), 95.7 (C4), 103.5 (C2), 126.4 (CHPh),
127.8 (CHPh), 128.6 (CHPh), 144.5 (CPh), 222.2 (CO (Mn)). IR
(neat): ν˜(cm-1) 1920, 2011 (CO (Mn)). HRMS (EI, positive mode):
m/z calcd for C18H18ClMnO3Si, 400.0094; found, 400.0060 (M+).
1
8a (81%). H NMR (400 MHz, CDCl3): δ (ppm) 0.52 (s, 9H,
SiMe3), 3.60 (ddd, J ) 7.3, 5.9, 2.0 Hz, 1H, H5), 3.86 (dd, J )
5.9, 2.0 Hz, 1H, H1), 3.96 (tapp, J ) 5.9 Hz, 1H, H6), 4.75 (d, J )
7.3 Hz, 1H, H4), 6.88–6.94 (m, 2H, HPh), 7.15–7.32 (m, 3H, HPh).
13C NMR (100 MHz, CDCl3): δ (ppm) 0.6 (SiMe3), 43.3 (C6),
62.1 (C5), 64.0 (C1), 83.9 (C3), 97.2 (C4), 121.1 (C2), 126.0 (CHPh),
127.5 (CHPh), 128.9 (CHPh), 146.8 (CPh), 222.0 (CO (Mn)). IR
(neat): ν˜ (cm-1) 1923, 2014 (CO (Mn)). Anal. Calcd: C, 53.94; H,
4.53. Found: C, 53.89; H, 4.65.
Complexes 1a,15 1b,11 2a,16 2b,11 3a,16 3b,11 4a,12a 4b,11 and
5a15 were synthesized according to procedures previously described
in the literature.
(37) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,
M. A.; Cheeseman, J. R.; Montgomery, J. A., Jr.; Vreven, T.; Kudin, K. N.;
Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.; Barone, V.;
Mennucci, B.; Cossi, M.; Scalmani, G.; Rega, N.; Petersson, G. A.;
Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.;
Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Klene, M.; Li,
X.; Knox, J. E.; Hratchian, H. P.; Cross, J. B.; Bakken, V.; Adamo, C.;
Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.;
Cammi, R.; Pomelli, C.; Ochterski, J. W.; Ayala, P. Y.; Morokuma, K.;
Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Zakrzewski, V. G.; Dapprich,
S.; Daniels, A. D.; Strain, M. C.; Farkas, O.; Malick, D. K.; Rabuck, A. D.;
Raghavachari, K.; Foresman, J. B.; Ortiz, J. V.; Cui, Q.; Baboul, A. G.;
Clifford, S.; Cioslowski, J.; Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz,
P.; Komaromi, I.; Martin, R. L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.;
Peng, C. Y.; Nanayakkara, A.; Challacombe, M.; Gill, P. M. W.; Johnson,
B.; Chen, W.; Wong, M. W.; Gonzalez, C.; and Pople, J. A. Gaussian 03,
Revision C.02; Gaussian, Inc.: Wallingford, CT, 2004.
Lithiation of 4a (overall yield: 88%; 9a partly isolated pure;
9′a isolated as a mixture with 9a).
9a. 1H NMR (400 MHz, CDCl3): δ (ppm) 0.37 (s, 9H, SiMe3),
3.45 (s, 3H, OCH3), 3.67 (dd, J ) 6.5, 3.0 Hz, 1H, H5), 4.28 (d, J
) 6.5 Hz, 1H, H6), 5.46 (d, J ) 3.0 Hz, 1H, H3), 6.95–7.00 (m,
2H, HPh), 7.16–7.37 (m, 3H, HPh). 13C NMR (100 MHz, CDCl3):
δ (ppm) -0.1 (SiMe3), 46.7 (C5), 54.7 (C6 or OCH3), 54.9 (C6 or
OCH3), 69.3 (C3), 85.2 (C1), 99.2 (C2), 126.3 (CHPh), 127.8 (CHPh),
128.7 (CHPh), 142.5 (C4 or CPh), 144.7 (C4 or CPh), 221.9 (CO
(Mn)). IR (neat): ν˜(cm-1) 1923, 2013 (CO(Mn)). Anal. Calcd: C,
52.97; H, 4.68. Found: C, 52.92; H, 4.82.
9′a. 1H NMR (400 MHz, CDCl3): δ (ppm) 0.42 (s, 9H, SiMe3),
3.36 (s, 3H, OCH3), 3.61 (d, J ) 6.4 Hz, 1H, H5), 4.30 (dd, J )
6.4, 1.4 Hz, 1H, H6), 5.04 (d, J ) 1.4 Hz, 1H, H2), 6.96–7.00 (m,
2H, HPh), 7.23–7.28 (m, 3H, HPh). 13C NMR (100 MHz, CDCl3):
δ (ppm) 0.1 (SiMe3), 45.6 (C5), 52.6 (C6), 54.9 (OCH3), 71.9 (C3),
83.5 (C1), 96.6 (C2), 126.5 (CHPh), 128.0 (CHPh), 128.8 (CHPh),
(38) Lee, C.; Yang, W.; Parr, R. G. Phys. ReV. B 1988, 37, 785.
(39) Miehlich, B.; Savin, A.; Stoll, H.; Preuss, H. Chem. Phys. Lett.
1989, 157, 200.
(40) Becke, A. D. J. Chem. Phys. 1993, 98, 5648.
(41) Pfleschinger, A.; Dargel, T. K.; Bats, J. W.; Schmalz, H.-G.; Koch,
W. Chem.-Eur. J. 1999, 5, 537, and references therein.

634 Organometallics, Vol. 27, No. 4, 2008
Jacques et al.
144.2 (C4 or CPh), 145.0 (C4 or CPh). IR (neat): ν˜ (cm-1) 1921,
2012 (CO (Mn)).
14a (95%). 1H NMR (400 MHz, CDCl3): δ (ppm) 3.29 (m, 1H,
H5), 3.47 (dd, J ) 6.0, 2.0 Hz, 1H, H1), 3.49 (s, 3H, OCH3), 3.89
(tapp, J ) 6.0 Hz, 1H, H6), 5.45 (d, J ) 7.3 Hz, 1H, H4), 6.89 (d,
J ) 7.5 Hz, 2H, HPh), 7.19 (t, J ) 7.5 Hz, 1H, HPh), 7.26 (tapp, J
) 7.5 Hz, 2H, HPh). 13C NMR (100 MHz, CDCl3): δ (ppm) 39.5
(C3), 40.9 (C1), 42.4 (C6), 55.7 (OCH3), 58.9 (C5), 101.9 (C4), 125.5
(CHPh), 127.3 (CHPh), 128.9 (CHPh), 142.1 (C2 or CPh), 147.0 (C2
or CPh), 222.2 (CO (Mn)). IR (neat): ν˜ (cm-1) 1912, 2009 (CO
(Mn)). Anal. Calcd: C, 42.69; H, 2.69. Found: C, 42.65; H, 2.66.
Lithiation of 4b (overall yield: 75%).
1
9b (49%). H NMR (400 MHz, CDCl3): δ (ppm) 0.38 (s, 9H,
SiMe3), 2,76 (d, J ) 12.0 Hz, 1H, H6exo), 3.14 (m, 2H, H6endo and
H5), 3.43 (s, 3H, OCH3), 5.52 (d, J ) 2.5 Hz, 1H, H3). 13C NMR
(100 MHz, CDCl3): δ (ppm) 0.0 (SiMe3), 39.3 (C5), 39.8 (C6),
54.8 (OMe), 69.6 (C3), 79.2 (C1), 100.8 (C2), 143.5 (C4), 222.1
(CO (Mn)). IR (neat): ν˜(cm-1) 1918, 2010 (CO (Mn)).
1
1
15a (72%). H NMR (400 MHz, CDCl3): δ (ppm) 1.38 (tapp, J
9′b (26%). H NMR (400 MHz, CDCl3): δ (ppm) 0.41 (s, 9H,
) 7.1 Hz, 3H, CH3), 3.49 (s, 3H, OCH3), 3.52 (dd, J ) 6.1, 1.6
Hz, 1H, H1), 3.64 (m, 1H, H5), 3.97 (tapp, J ) 6.1 Hz, 1H, H6),
4.33–4.48 (m, 2H, CH2), 5.73 (d, J ) 7.6 Hz, 1H, H4), 6.93 (d, J
) 7.5 Hz, 2H, HPh), 7.17 (t, J ) 7.5 Hz, 1H, HPh), 7.24 (tapp, J )
7.5 Hz, 2H, HPh). 13C NMR (100 MHz, CDCl3): δ (ppm) 14.5
(CH3), 41.9 (C6), 44.3 (C1), 55.3 (OCH3), 61.5 (CH2), 62.2 (C5),
73.4 (C3), 96.0 (C4), 125.7 (CHPh), 127.4 (CHPh), 128.9 (CHPh),
144.1 (C2 or CPh), 147.0 (C2 or CPh), 167.7 (CO2Et). IR (neat): ν˜
(cm-1) 1725 (CO (CO2Et)), 1920, 2015 (CO (Mn)). HRMS
(MALDI TOF, positive mode): m/z calcd for C19H17MnNaO6,
419.030; found, 418.994 (M + Na+).
SiMe3), 2,72 (d, J ) 11.8 Hz, 1H, H6exo), 3.16 (m, 2H, H6endo and
H5), 3.30 (s, 3H, OMe), 5.02 (s, 1H, H2). 13C NMR (100 MHz,
CDCl3): δ (ppm) 0.4 (SiMe3), 37.2 (C6), 38.8 (C5), 54.8 (OMe),
72.2 (C1 or C3), 76.9 (C1 or C3), 98.4 (C2), 145.9 (C4). IR (neat):
ν˜ (cm-1) 1919, 2011 (CO (Mn)). HRMS (EI, positive mode): m/z
calcd for C13H16ClMnO4Si, 353.9887; found, 353.9894 (M+).
10 (66%; mixture of the two regioisomers). IR (neat): ν˜ (cm-1
)
1908, 2002 (CO (Mn)). HRMS (EI, positive mode): m/z calcd for
C18H19MnO3Si, 366.0484; found, 366.0474 (M+).
10a. 1H NMR (400 MHz, CDCl3): δ (ppm) 0.20 (s, 9H, SiMe3),
3.38 (m, 1H, H1), 3.62 (m, 1H, H5), 3.80 (tapp, J ) 6.0 Hz, 1H,
H6), 4.96 (dd, J ) 7.0, 5.0 Hz, 1H, H4), 5.65 (ddd, J ) 5.0, 1.2,
1.2 Hz, 1H, H3), 6.91–6.94 (m, 2H, HPh), 7.13–7.24 (m, 3H, HPh).
13C NMR (100 MHz, CDCl3): δ (ppm) –1.9 (SiMe3), 39.9 (C6),
59.5 (C1 or C5), 59.6 (C1 or C5), 83.8 (C3), 97.6 (C4), 106.2 (C2),
125.9 (CHPh), 126.9 (CHPh), 128.6 (CHPh), 148.2 (CPh), 223.4
(CO (Mn)).
1
16a (50%). H NMR (400 MHz, CDCl3): δ (ppm) 3.03 (s, 3H,
CH3), 3.11 (s, 3H, CH3), 3.34 (m, 2H, H1 and H5), 3.45 (s, 3H,
OCH3), 3.90 (tapp, J ) 6.0 Hz, 1H, H6), 5.43 (d, J ) 7.0 Hz, 1H,
H4), 6.92 (d, J ) 7.2 Hz, 2H, HPh), 7.13 (t, J ) 7.2 Hz, 1H, HPh),
7.22 (tapp, J ) 7.2 Hz, 2H, HPh). 13C NMR (100 MHz, CDCl3): δ
(ppm) 36.2 (CH3), 38.2 (C1), 38.9 (CH3), 41.2 (C6), 54.6 (C5), 54.9
(OCH3), 89.3 (C3), 95.9 (C4), 125.1 (CHPh), 127.0 (CHPh), 128.8
(CHPh), 141.4 (C2 or CPh), 147.6 (C2 or CPh), 166.5 (C(O)NMe2).
IR (neat): ν˜ (cm-1) 1639 (CO (C(O)NMe2)), 1921, 2014 (CO (Mn)).
HRMS (electrospray): m/z calcd for C19H19MnNO5, 396.0638;
found, 396.0645 (M + H+).
10′a. 1H NMR (400 MHz, CDCl3): δ (ppm) 0.38 (s, 9H, SiMe3),
3.62 (m, 2H, H1,5), 3.80 (t, J ) 6.0 Hz, 1H, H6), 4.84 (d, J ) 7.2
Hz, 2H, H2,4), 6.91–6.94 (m, 2H, HPh), 7.13–7.24 (m, 3H, HPh).
13C NMR (100 MHz, CDCl3): δ (ppm) -0.6 (SiMe3), 40.1 (C6),
62.1 (C1,5), 85.9 (C3), 99.6 (C2,4), 126.1 (CHPh), 127.2 (CHPh),
128.7 (CHPh), 147.7 (CPh), 223.4 (CO (Mn)).
1
17a (80%). H NMR (400 MHz, CDCl3): δ (ppm) 2.22 (s, 3H,
CH3), 3.48 (s, 3H, OCH3), 3.59 (dd, J ) 6.5, 2.8 Hz, 1H, H5), 4.36
(d, J ) 6.5 Hz, 1H, H6), 5.59 (d, J ) 2.8 Hz, 1H, H3), 6.97–6.99
(m, 2H, HPh), 7.20–7.30 (m, 3H, HPh). 13C NMR (100 MHz,
CDCl3): δ (ppm) 21.3 (CH3), 45.5 (C5), 53.7 (C6), 55.0 (OCH3),
67.8 (C3), 81.0 (C1), 105.7 (C2), 126.2 (CHPh), 127.7 (CHPh), 128.8
(CHPh), 141.0 (C4 or CPh), 144.4 (C4 or CPh), 221.7 (CO (Mn)).
IR (neat): ν˜ (cm-1) 1917, 2011 (CO (Mn)). HRMS (EI, positive
mode): m/z calcd for C17H14ClMnO4, 371.9961; found,
371.9951 (M+).
1
11a (82%). H NMR (400 MHz, CDCl3): δ (ppm) 2.48 (s, 3H,
Me), 3.22 (ddd, J ) 7.1, 6.1, 1.7 Hz, 1H, H5), 3.38 (dd, J ) 6.1,
1.7 Hz, 1H, H1), 3.44 (s, 3H, OCH3), 3.87 (tapp, J ) 6.1 Hz, 1H,
H6), 5.06 (d, J ) 7.1 Hz, 1H, H4), 6.91 (d, J ) 7.5 Hz, 2H, HPh),
7.16 (t, J ) 7.5 Hz, 1H, HPh), 7.24 (tapp, J ) 7.5 Hz, 2H, HPh). 13
C
NMR (100 MHz, CDCl3): δ (ppm) 16.0 (CH3), 40.8 (C1), 43.0
(C6), 54.6 (C5 or OCH3), 54.7 (C5 or OCH3), 85.2 (C3), 96.2 (C4),
125.5 (CHPh), 127.0 (CHPh), 128.7 (CHPh), 142.6 (C2 or CPh), 147.9
(C2 or CPh), 223.2 (CO (Mn)). IR (neat): ν˜(cm-1) 1901, 2003 (CO
(Mn)). HRMS (EI, positive mode): m/z calcd for C17H15MnO4,
338.0351; found, 338.0363 (M+).
19 (overall yield: 84%).
1
19a (69%). H NMR (400 MHz, CDCl3): δ (ppm) 1.37 (t, J )
1
7.1 Hz, 3H, CH3), 3.52 (s, 3H, OCH3), 3.60 (dd, J ) 6.6, 2.8 Hz,
1H, H5), 4.3 (m, 3H, H6 and CH2), 5.99 (d, J ) 2.8 Hz, 1H, H3),
7.00 (m, 2H, HPh), 7.19–7.28 (m, 3H, HPh). 13C NMR (100 MHz,
CDCl3): δ (ppm) 14.3 (CH3), 45.3 (C5), 53.7 (C6), 55.3 (OCH3),
63.1 (CH2), 66.2 (C3), 76.1 (C1), 97.4 (C2), 126.1 (CHPh), 127.9
(CHPh), 128.9 (CHPh), 140.0 (C4 or CPh), 143.7 (C4 or CPh), 165.6
(CO2Et), 221.0 (CO (Mn)). IR (neat): ν˜ (cm-1) 1734 (CO (CO2Et)),
1931, 2019 (CO (Mn)). Anal. Calcd: C, 52.98; H, 3.74. Found: C,
52.93; H, 3.86.
12a (96%). H NMR (400 MHz, CDCl3): δ (ppm) 3.37–3.43
(m, 2H, H1 and H5), 3.51 (s, 3H, OCH3), 3.93 (tapp, J ) 6.1 Hz,
1H, H6), 4.97 (d, J ) 7.3 Hz, 1H, H4), 6.94 (d, J ) 7.5 Hz, 2H,
HPh), 7.15 (t, J ) 7.5 Hz, 1H, HPh), 7.23 (tapp, J ) 7.5 Hz, 2H,
HPh). 13C NMR (100 MHz, CDCl3): δ (ppm) 42.3 (C6), 43.8 (C1),
54.6 (OCH3), 58.3 (C5), 67.7 (t, JCD ) 27 Hz, C3), 93.0 (C4), 125.6
(CHPh), 127.0 (CHPh), 128.7 (CHPh), 143.3 (C2 or CPh), 147.7 (C2
or CPh), 222.9 (CO (Mn)). IR (neat): ν˜ (cm-1) 1895, 2001 (CO
(Mn)). HRMS (EI, positive mode): m/z calcd for C16H12DMnO4,
325.0257; found, 396.0243 (M+).
19′a (15%). 1H NMR (400 MHz, CDCl3): δ (ppm) 1.40 (t, J )
7.2 Hz, 3H, CH3), 3.49 (s, 3H, OCH3), 3.65 (d, J ) 6.6 Hz, 1H,
H5), 4.32 (dd, J ) 6.6, 1.7 Hz, 1H, H6), 4.42 (m, 2H, CH2), 5.96
(d, J ) 1.7 Hz, 1H, H2), 7.00 (m, 2H, HPh), 7.23–7.27 (m, 3H,
HPh). 13C NMR (100 MHz, CDCl3): δ (ppm) 14.5 (CH3), 45.4 (C5),
51.9 (C6), 55.9 (OCH3), 61.9 (CH2), 70.0 (C1 or C3), 83.3 (C1 or
C3), 94.9 (C2), 126.4 (CHPh), 128.3 (CHPh), 129.1 (CHPh), 142.8
1
13a (87%). H NMR (400 MHz, CDCl3): δ (ppm) 0.93 (t, J )
7.3 Hz, 9H, nBu3Sn), 1.13–1.22 (m, 6H, nBu3Sn), 1.35–1.45 (m,
6H, nBu3Sn), 1.60–1.69 (m, 6H, nBu3Sn), 3.34 (s, 3H, OCH3), 3.50
(m, 2H, H1 and H5), 3.97 (tapp, J ) 6.0 Hz, 1H, H6), 4.79 (d, J )
7.1 Hz, 1H, H4), 6.95 (d, J ) 7.5 Hz, 2H, HPh), 7.16 (t, J ) 7.5
Hz, 1H, HPh), 7.24 (tapp, J ) 7.5 Hz, 2H, HPh). 13C NMR (100
MHz, CDCl3): δ (ppm) 11.1 (nBu3Sn), 14.1 (nBu3Sn), 27.7
(nBu3Sn), 29.4 (nBu3Sn), 42.9 (C6), 44.3 (C1), 54.4 (OCH3), 61.9
(C5), 73.4 (C3), 98.6 (C4), 125.9 (CHPh), 127.0 (CHPh), 128.7
(C4 or CPh), 143.5 (C4 or CPh), 166.9 (CO2Et). IR (neat): ν˜ (cm-1
)
1729 (CO (CO2Et)), 1937, 2023 (CO (Mn)).
20 (86%; mixture of the two regioisomers). IR (neat): ν˜ (cm-1
)
(CHPh), 146.0 (C2 or CPh), 148.1 (C2 or CPh). IR (neat): ν˜ (cm-1
)
1710 (CO (COtBu)), 1930, 2019 (CO (Mn)). HRMS (EI, positive
mode): m/z calcd for C21H20ClMnO5, 442.0380; found, 442.0392
(M+).
1912, 2009 (CO (Mn)). HRMS (MALDI TOF, positive mode): m/z
calcd for C28H40MnO4Sn, 613.1329; found, 613.0836 (M + H+).

(η5-Cyclohexadienyl)Mn(CO)3 Complexes
Organometallics, Vol. 27, No. 4, 2008 635
1
20a. H NMR (400 MHz, CDCl3): δ (ppm) 1.01 (s, 9H, tBu),
3.65 (d, J ) 6.3 Hz, 1H, H5), 4.32 (dd, J ) 6.3, 1.8 Hz, 1H, H6),
4.98 (d, J ) 1.8 Hz, 1H, H2), 6.99–7.03 (m, 2H, HPh), 7.17–7.28
(m, 3H, HPh). 13C NMR (100 MHz, CDCl3): δ (ppm) 11.3
(nBu3Sn), 14.0 (nBu3Sn), 27.7 (nBu3Sn), 29.4 (nBu3Sn), 45.8 (C5),
54.1 (C6), 55.0 (OCH3), 70.5 (C3), 87.8 (C1), 98.1 (C2), 126.5
(CHPh), 127.8 (CHPh), 128.7 (CHPh), 143.8 (C4), 144.5 (CPh), 222.2
(CO (Mn)).
24a (83%). 1H NMR (400 MHz, CDCl3): δ (ppm) 3.16 (m, 1H,
H5), 3.37 (s, 3H, OCH3), 3.51 (dd, J ) 6.3, 1.5 Hz, 1H, H1), 3,99
(tapp, J ) 6.3 Hz, 1H, H6), 4.20 (d, J ) 7.3 Hz, 1H, H4), 4.97 (s,
1H, OH), 7.00 (d, J ) 7.5 Hz, 2H, HPh), 7.21 (t, J ) 7.5 Hz, 2H,
HPh), 7.26–7.38 (m, 7H, HPh), 7.43–7.50 (m, 4H, HPh). 13C NMR
(100 MHz, CDCl3): δ (ppm) 40.8 (C6), 41.8 (C1), 53.3 (C5), 55.6
(OCH3), 80.3 (C(OH)Ph2), 95.7 (C4), 100.5 (C3), 125.2 (CHPh),
126.9 (CHPh), 127.5 (CHPh), 127.9 (CHPh), 128.0 (CHPh), 128.6
(CHPh), 128.7 (CHPh), 141.3 (C2 or CPh), 143.3 (C2 or CPh), 147.4
(C2 or CPh), 147.7 (C2 or CPh). IR (neat): ν˜ (cm-1) 1919, 2011
(CO (Mn)). Anal. Calcd: C, 68.78; H, 4.58. Found: C, 68.99; H,
4.40.
3.47 (dd, J ) 6.3 Hz, J ) 2.8 Hz, 1H, H5), 3.61 (s, 3H, OCH3),
4.41 (d, J ) 6.3 Hz, 1H, H6), 5.54 (d, J ) 2.8 Hz, 1H, H3),
7.08–7.11 (m, 2H, HPh), 7.26–7.34 (m, 3H, HPh). 13C NMR (100
MHz, CDCl3): δ (ppm) 27.5 (C(CH3)3), 43.0 (C5), 46.2 (C(CH3)3),
53.3 (C6), 55.3 (OCH3), 64.6 (C3), 76.2 (C1), 116.7 (C2), 126.9
(CHPh), 128.2 (CHPh), 128.7 (CHPh), 138.6 (C4 or CPh), 142.1 (C4
or CPh), 205.2 (COtBu), 221.3 (CO (Mn)).
1
20′a. H NMR (400 MHz, CDCl3): δ (ppm) 1.37 (s, 9H, tBu),
3.45 (s, 3H, OCH3), 3.54 (d, J ) 6.8 Hz, 1H, H5), 4.34 (dd, J )
6.8, 1.5 Hz, 1H, H6), 5.43 (d, J ) 1.5 Hz, 1H, H2), 7.08–7.11 (m,
2H, HPh), 7.26–7.34 (m, 3H, HPh). 13C NMR (100 MHz, CDCl3):
δ (ppm) 27.5 (C(CH3)3), 41.3 (C5), 45.9 (C(CH3)3), 51.6 (C6), 55.3
(OCH3), 76.9 (C1), 90.5 (C3), 94.2 (C2), 126.0 (CHPh), 128.0
(CHPh), 128.9 (CHPh), 139.8 (C4 or CPh), 143.6 (C4 or CPh), 207.6
(COtBu).
21 (overall yield: 73%; 21a partly isolated pure; 21′a isolated
as a mixture with 21a).
21a. 1H NMR (400 MHz, CDCl3): δ (ppm) 3.34 (s, 3H, OCH3),
3.56 (dd, J ) 6.6, 2.3 Hz, 1H, H5), 4.42 (d, J ) 6.6 Hz, 1H, H6),
5.20 (d, J ) 2.3 Hz, 1H, H3), 6.99 (d, J ) 7.3 Hz, 2H, HPh),
7.22–7.31 (m, 3H, HPh), 7.44–7.49 (m, 3H, HPh), 7.61 (d, J ) 7.3
Hz, 2H, HPh). 13C NMR (100 MHz, CDCl3): δ (ppm) 45.7 (C5),
54.1 (C6), 55.0 (OCH3), 65.9 (C3), 76.4 (C1), 115.5 (C2), 126.2
(CHPh), 127.8 (CHPh), 128.9 (CHPh), 129.6 (CPh), 130.3 (2 x CHPh),
135.7 (CHPh), 140.0 (C4 or CPh), 143.6 (C4 or CPh). IR (neat): ν˜
(cm-1) 1922, 2013 (CO (Mn)). HRMS (EI, positive mode): m/z
calcd for C22H16ClMnO4S, 465.9838; found, 465.9835 (M+).
21′a. 1H NMR (400 MHz, CDCl3): δ (ppm) 3.46 (s, 3H, OCH3),
3.64 (d, J ) 6.6 Hz, 1H, H5), 4.35 (dd, J ) 6.6, 1.8 Hz, 1H, H6),
5.60 (d, J ) 1.8 Hz, 1H, H2), 6.94–6.97 (m, 2H, HPh), 7.23–7.26
(m, 3H, HPh), 7.27–7.33 (m, 3H, HPh), 7.47–7.49 (m, 2H, HPh).
13C NMR (100 MHz, CDCl3): δ (ppm) 43.4 (C5), 52.2 (C6), 55.8
(OCH3), 78.1 (C1 or C3), 80.3 (C1 or C3), 100.6 (C2), 126.2 (CHPh),
127.4 (CHPh), 128.1 (CHPh), 128.9 (CHPh), 129.5 (CHPh), 129.6
(CHPh), 138.0 (CPh), 143.1 (C4 or CPh), 143.5 (C4 or CPh).
25a (overall yield: 93%).
25a-dia1 (45%). 1H NMR (400 MHz, CDCl3): δ (ppm) 2.41 (d,
J ) 2.6 Hz, 1H, OH), 3.29–3.36 (m, 2H, H1 and H5), 3.39 (s, 3H,
OCH3), 3,85 (tapp, J ) 5.8 Hz, 1H, H6), 5.36 (d, J ) 7.4 Hz, 1H,
H4), 6.34 (d, J ) 2.6 Hz, 1H, CH(OH)Ph), 6.64 (d, J ) 7.1 Hz,
2H, HPh), 7.03–7.08 (m, 3H, HPh), 7.35–7.43 (m, 3H, HPh), 7.61
(d, J ) 7.3 Hz, 2H, HPh). 13C NMR (100 MHz, CDCl3): δ (ppm)
41.8 (C1), 43.0 (C6), 54.8 (OCH3), 57.0 (C5), 69.6 (CH(OH)Ph),
90.1 (C4), 94.5 (C3), 125.9 (CHPh), 126.6 (CHPh), 127.1 (CHPh),
128.2 (CHPh), 128.6 (CHPh), 128.9 (CHPh), 141.1 (C2 or CPh), 143.3
(C2 or CPh), 147.2 (C2 or CPh), 223.1 (CO (Mn)). IR (neat): ν˜
(cm-1) 1916, 2008 (CO (Mn)).
25a-dia2 (48%). 1H NMR (400 MHz, CDCl3): δ (ppm)
3.19–3.24 (m, 2H, H5 and OH), 3.44 (d, J ) 6.1 Hz, 1H, H1), 3.47
(s, 3H, OCH3), 3,88 (tapp, J ) 6.1 Hz, 1H, H6), 4.71 (d, J ) 7.5
Hz, 1H, H4), 6.30 (d, J ) 4.8 Hz, 1H, CH(OH)Ph), 6.95 (d, J )
7.6 Hz, 2H, HPh), 7.17–7.27 (m, 3H, HPh), 7.33–7.44 (m, 3H, HPh),
7.65 (d, J ) 7.4 Hz, 2H, HPh). 13C NMR (100 MHz, CDCl3): δ
(ppm) 42.7 (C1), 42.9 (C6), 55.0 (OCH3), 56.6 (C5), 72.2
(CH(OH)Ph), 93.0 (C3), 93.1 (C4), 125.9 (CHPh), 127.3 (CHPh),
128.2 (CHPh), 128.6 (CHPh), 128.9 (CHPh), 141.2 (C2 or CPh), 141.8
(C2 or CPh), 147.4 (C2 or CPh). IR (neat): ν˜ (cm-1) 1911, 2008
(CO (Mn)). HRMS (electrospray): m/z calcd for C23H19MnNaO5,
453.0505; found, 453.0542 (M + Na+).
22 (83%; mixture of the two regioisomers). IR (neat): ν˜ (cm-1
)
1927, 2016 (CO (Mn)). HRMS (EI, positive mode): m/z calcd for
C16H11ClIMnO4, 483.8771; found, 483.8759 (M+).
22a. 1H NMR (400 MHz, CDCl3): δ (ppm) 3.48 (s, 3H, OCH3),
3.66 (dd, J ) 6.6, 2.8 Hz, 1H, H5), 4.53 (d, J ) 6.6 Hz, 1H, H6),
6.16 (d, J ) 2.8 Hz, 1H, H3), 6.94–6.97 (m, 2H, HPh), 7.22–7.31
(m, 3H, HPh). 13C NMR (100 MHz, CDCl3): δ (ppm) 46.1 (C5),
53.7 (C6), 55.4 (OCH3), 75.5 (C2), 76.2 (C3), 79.9 or 82.4 (C1),
126.2 (CHPh), 128.0 (CHPh), 129.0 (CHPh), 140.2 (C4 or CPh), 143.6
(C4 or CPh), 221.3 (CO (Mn)).
26 (overall yield: 64%).
1
26a (44%). H NMR (400 MHz, CDCl3): δ (ppm) 3.47 (s, 3H,
OCH3), 3.50 (dd, J ) 6.3, 2.8 Hz, 1H, H5), 4.04 (s, 1H, OH), 4.42
(d, J ) 6.3 Hz, 1H, H6), 5.01 (d, J ) 2.8 Hz, 1H, H3), 6.80 (m,
4H, HPh), 7.05 (m, 3H, HPh), 7.32–7.38 (m, 6H, HPh), 7.47 (m,
2H, HPh). 13C NMR (100 MHz, CDCl3): δ (ppm) 43.2 (C5), 54.8
(C6 or OCH3), 55.0 (C6 or OCH3), 71.4 (C3), 76.8 (C1), 80.9
(C(OH)Ph2), 118.7 (C2), 126.9 (CHPh), 127.1 (CHPh), 127.3 (CHPh),
128.0 (CHPh), 128.1 (CHPh), 128.2 (CHPh), 128.7 (CHPh), 128.8
(CHPh), 139.3 (C4 or CPh), 141.6 (C4 or CPh), 142.1 (C4 or CPh),
145.5 (C4 or CPh), 221.5 (CO (Mn)). IR (neat): ν˜ (cm-1) 1928,
2016 (CO (Mn)). HRMS (electrospray): m/z calcd for
C29H22ClMnNaO5, 563.0428; found, 563.0417 (M + Na+).
22′a. 1H NMR (400 MHz, CDCl3): δ (ppm) 3.47 (s, 3H, OCH3),
3.61 (d, J ) 6.6 Hz, 1H, H5), 4.26 (dd, J ) 6.6, 1.8 Hz, 1H, H6),
5.71 (d, J ) 1.8 Hz, 1H, H2), 6.94–6.97 (m, 2H, HPh), 7.22–7.31
(m, 3H, HPh). 13C NMR (100 MHz, CDCl3): δ (ppm) 34.9 (C3),
41.8 (C5), 52.4 (C6), 56.2 (OCH3), 79.9 or 82.4 (C1), 100.8 (C2),
126.2 (CHPh), 128.2 (CHPh), 129.1 (CHPh), 140.7 (C4 or CPh), 143.3
(C4 or CPh), 221.3 (CO (Mn)).
23 (86%; mixture of the two regioisomers). IR (neat): ν˜ (cm-1
)
1921, 2010 (CO (Mn)). HRMS (EI, positive mode): m/z calcd for
C28H38ClMnO4, 648.0861; found, 648.0837 (M+).
23a. 1H NMR (400 MHz, CDCl3): δ (ppm) 0.87 (t, J ) 7.3 Hz,
9H, nBu3Sn), 1.11–1.67 (m, 18H, nBu3Sn), 3.49 (s, 3H, OCH3),
3.60 (dd, J ) 6.6, 2.8 Hz, 1H, H5), 4.32 (d, J ) 6.6 Hz, 1H, H6),
5.40 (d, J ) 2.8 Hz, 1H, H3), 6.99–7.03 (m, 2H, HPh), 7.17–7.28
(m, 3H, HPh). 13C NMR (100 MHz, CDCl3): δ (ppm) 12.0
(nBu3Sn), 13.9 (nBu3Sn), 27.6 (nBu3Sn), 29.0 (nBu3Sn), 46.1 (C5),
52.7 (C6), 54.9 (OCH3), 70.9 (C3), 83.5 (C1), 103.0 (C2), 126.5
(CHPh), 127.7 (CHPh), 128.6 (CHPh), 144.3 (C4 or CPh), 144.5 (C4
or CPh), 222.2 (CO (Mn)).
26′a (20%). 1H NMR (400 MHz, CDCl3): δ (ppm) 3.35 (s, 3H,
OCH3), 3.64 (d, J ) 6.8 Hz, 1H, H5), 4.42 (dd, J ) 6.8, 1.8 Hz,
1H, H6), 4.48 (d, J ) 1.8 Hz, 1H, H2), 4.83 (s, 1H, OH), 7.10 (m,
2H, HPh), 7.25 (m, 2H, HPh), 7.29–7.39 (m, 7H, HPh), 7.49–7.51
(m, 4H, HPh). 13C NMR (100 MHz, CDCl3): δ (ppm) 43.3 (C5),
51.1 (C6), 56.2 (OCH3), 75.7 (C1), 80.2 (C(OH)Ph2), 95.4 (C2),
97.2 (C3), 126.0 (CHPh), 127.8 (CHPh), 128.0 (CHPh), 128.2 (CHPh),
128.4 (CHPh), 128.5 (CHPh), 128.9 (CHPh), 139.9 (C4 or CPh), 142.6
(C4 or CPh), 143.8 (C4 or CPh), 146.7 (C4 or CPh). IR (neat): ν˜
(cm-1) 1930, 2017 (CO (Mn)). Anal. Calcd: C, 64.40; H, 4.10.
Found: C, 64.38; H, 4.21.
23′a. 1H NMR (400 MHz, CDCl3): δ (ppm) 0.93 (t, J ) 7.3 Hz,
9H, nBu3Sn), 1.11–1.67 (m, 18H, nBu3Sn), 3.32 (s, 3H, OCH3),

636 Organometallics, Vol. 27, No. 4, 2008
Jacques et al.
1
27 (overall yield: 87%).
28′a. H NMR (400 MHz, CDCl3): δ (ppm) 1.77 (s, 3H, CH3),
1.87 (s, 3H, CH3), 3.13 (s, 1H, OH), 3.46 (s, 3H, OCH3), 3.53 (d,
J ) 6.7 Hz, 1H, H5), 4.25 (dd, J ) 6.7, 1.6 Hz, 1H, H6), 5.53 (d,
J ) 1.6 Hz, 1H, H2), 6.98–7.02 (m, 2H, HPh), 7.22–7.31 (m, 3H,
HPh). 13C NMR (100 MHz, CDCl3): δ (ppm) 29.7 (CH3), 32.7
(CH3), 43.3 (C5), 52.7 (C6), 55.4 (OCH3), 71.5 (C(CH3)2OH), 78.9
(C1), 91.8 (C2), 95.1 (C3), 126.3 (CHPh), 128.1 (CHPh), 128.9
(CHPh), 139.2 (C4 or CPh), 143.7 (C4 or CPh).
27a-dia 1 (mixture with 27′a-dia 1). 1H NMR (400 MHz,
CDCl3): δ (ppm) 3.15 (d, J ) 4.8 Hz, 1H, OH), 3.33 (s, 3H, OCH3),
3.69 (dd, J ) 6.6, 2.8 Hz, 1H, H5), 4.36 (d, J ) 6.6 Hz, 1H, H6),
5.15 (d, J ) 2.8 Hz, 1H, H3), 5.58 (d, J ) 4.8 Hz, 1H, CH(OH)Ph),
7.04–7.66 (m, 10H, HPh). 13C NMR (100 MHz, CDCl3): δ (ppm)
47.6 (C5), 54.4 (C6 or OCH3), 55.0 (C6 or OCH3), 67.6 (C3), 74.9
(CH(OH)Ph), 76.5 (C1), 111.1 (C2), 126.4 (CHPh), 128.0 (CHPh),
128.4 (CHPh), 128.9 (CHPh), 129.0 (CHPh), 129.1 (CHPh), 139.5
(C4 or CPh), 143.0 (C4 or CPh), 143.6 (C4 or CPh), 221.5 (CO (Mn)).
27′a-dia 1 (mixture with 27a-dia 1). 1H NMR (400 MHz,
CDCl3): δ (ppm) δ ) 2.37 (d, J ) 3.0 Hz, 1H, OH), 3.39 (s, 3H,
OCH3), 3.51 (d, J ) 6.5 Hz, 1H, H5), 4.20 (dd, J ) 6.5, 1.8 Hz,
1H, H6), 5.66 (d, J ) 1.8 Hz, 1H, H2), 6.27 (d, J ) 3.0 Hz, 1H,
CH(OH)Ph), 6.67 (m, 2H, HPh), 7.04–7.66 (m, 8H, HPh). 13C NMR
(100 MHz, CDCl3): δ (ppm) 43.3 (C5), 53.0 (C6), 55.3 (OCH3),
69.4 (CH(OH)Ph), 79.4 (C1), 89.6 (C2), 90.9 (C3), 126.5 (CHPh),
127.9 (CHPh), 128.6 (CHPh), 128.8 (CHPh), 129.1 (CHPh), 140.0
(C4 or CPh), 143.5 (C4 or CPh), 145.2 (C4 or CPh), 221.5 (CO (Mn)).
30b (61%). 1H NMR (400 MHz, CDCl3): δ (ppm) 2.17 (d, J )
11.9 Hz, 1H, H6exo), 2.65–2.88 (m, 3H, H6endo, H5 and H1), 3.42
(s, 3H, OCH3), 5.34 (d, J ) 7.3 Hz, 1H, H4). 13C NMR (100 MHz,
CDCl3): δ (ppm) 0.5 (SiMe3), 27.0 (C6), 33.0 (C1), 40.3 (C3), 52.1
(C5), 55.6 (OCH3), 103.6 (C4), 142.9 (C2). IR (neat): ν˜ (cm-1
)
1924, 2012 (CO (Mn)).
Typical Rearomatization Procedure. A solution of triphenyl-
carbenium tetrafluoroborate (0.70 mmol, 3 equiv) in CH2Cl2 (4 mL)
was added to a solution of η5 complex (0.23 mmol, 1 equiv) in
CH2Cl2 (5 mL). After stirring at room temperature for 1.5 h, 50
mL of freshly distilled Et2O was added to induce precipitation of
the expected cationic η6 complex. The resulting yellow powder
was isolated by filtration and washed with Et2O.
1
27a-dia 2 (28%). H NMR (400 MHz, CDCl3): δ (ppm) 2.42
(d, J ) 3.5 Hz, 1H, OH), 3.54 (s, 3H, OCH3), 3.64 (dd, J ) 6.5
Hz, 3.0 Hz, 1H, H5), 4.26 (d, J ) 6.5 Hz, 1H, H6), 5.55 (d, J )
3.5 Hz, 1H, CH(OH)Ph), 6.14 (d, J ) 3.0 Hz, 1H, H3), 6.53 (m,
2H, HPh), 6.93–7.46 (m, 8H, HPh). 13C NMR (100 MHz, CDCl3):
δ (ppm) 45.7 (C5), 53.6 (C6), 55.2 (OCH3), 63.0 (C3), 72.4
(CH(OH)Ph), 75.5 (C1), 111.5 (C2), 125.9 (CHPh), 127.3 (CHPh),
127.5 (CHPh), 128.5 (CHPh), 128.9 (CHPh), 140.8 (C4 or CPh), 141.1
(C4 or CPh), 143.6 (C4 or CPh). IR (neat): ν˜ (cm-1) 1924, 2014
(CO (Mn)). HRMS (electrospray): m/z calcd for C23H18ClMnNaO5,
487.0115; found, 487.0107 (M + Na+).
1
29 (78%). H NMR (400 MHz, (CD3)2CO): δ (ppm) 0.53 (s,
9H, SiMe3), 4.30 (s, 3H, OCH3), 6.26 (ddd, J ) 6.3, 6.3, 0.8 Hz,
1H, H4), 6.54 (dd, J ) 7.6, 0.8 Hz, 1H, H6), 7.12 (dd, J ) 6.3, 1.5
Hz, 1H, H3), 7.37 (ddd, J ) 7.6, 6.3, 1.5 Hz, 1H, H5). 13C NMR
(100 MHz, (CD3)2CO): δ (ppm) -0.5 (SiMe3), 59.5 (OCH3), 81.1
(C6), 90.8 (C4), 95.6 (C2), 108.6 (C5), 112.8 (C3), 155.8 (C1), 217.7
(CO (Mn)). IR (neat): ν˜ (cm-1) 2002, 2068 (CO (Mn)). HRMS
(MALDI TOF, positive mode): m/z calcd for C13H16MnO4Si,
319.0198; found, 319.0215 (M - BF4-).
1
27′a-dia 2 (23%). H NMR (400 MHz, CDCl3): δ (ppm) 3.00
1
31 (76%). H NMR (400 MHz, (CD3)2CO): δ (ppm) 4.33 (s,
(d, J ) 4.7 Hz, 1H, OH), 3.48 (s, 3H, OCH3), 3.60 (d, J ) 6.6 Hz,
1H, H5), 4.23 (dd, J ) 6.6, 1.6 Hz, 1H, H6), 4.95 (d, J ) 1.6 Hz,
1H, H2), 6.28 (d, J ) 4.7 Hz, 1H, CH(OH)Ph), 7.00 (m, 2H, HPh),
7.21–7.28 (m, 3H, HPh), 7.36–7.49 (m, 3H, HPh), 7.64 (m, 2H, HPh).
13C NMR (100 MHz, CDCl3): δ (ppm) δ ) 44.2 (C5), 52.9 (C6),
55.5 (OCH3), 71.7 (CH(OH)Ph), 78.9 (C1), 89.8 (C3), 92.4 (C2),
126.5 (CHPh), 127.2 (CHPh), 128.1 (CHPh), 128.6 (CHPh), 128.8
(CHPh), 129.0 (CHPh), 140.3 (C4 or CPh), 140.6 (C4 or CPh), 143.7
(C4 or CPh). IR (neat): ν˜ (cm-1) 1922, 2011 (CO (Mn)). HRMS
(electrospray): m/z calcd for C23H18ClMnNaO5, 487.0115; found,
487.0106 (M + Na+).
3H, OMe), 6.23 (dtapp, J ) 6.6, 1.0 Hz, 1H, H5), 6.67 (dd, J ) 7.1,
1.0 Hz, 1H, H3), 7.17 (dtapp, J ) 7.1, 1.3 Hz, 1H, H4), 7.69 (dd, J
) 6.6, 1.3 Hz, 1H, H6). 13C NMR (100 MHz, (CD3)2CO): δ (ppm)
60.8 (OMe), 81.2 (C3), 92.9 (C5), 106.0 (C4), 115.6 (C6), 149.5
(C1 or C2), 150.8 (C2 or C1), 217.3 (CO (Mn)). IR (neat): ν˜ (cm-1
)
1991, 2067 (CO (Mn)). HRMS (FAB, positive mode): m/z calcd
for C10H7IMnO4, 372.8770; found, 372.8778 (M - BF4-).
Acknowledgment. P. Herson (CIM2, UMR 7071, Uni-
versité P. et M. Curie, Paris) is acknowledged for performing
the X-ray structure analysis. A. Eloi is acknowledged for
his involvement in the DFT calculations. The calculations
have been performed at the CCRE of the University Pierre
et Marie Curie (F. 75252, Paris, France) and at the CRIHAN
(F. 76800 Saint-Etienne-du-Rouvray, France) Regional Su-
percomputing Centre.
28 (overall yield: 31%; 28a partly isolated pure; 28′a isolated
as a mixture with 28a).
1
28a. H NMR (400 MHz, CDCl3): δ (ppm) 1.55 (s, 3H, CH3),
1.65 (s, 3H, CH3), 2.94 (s, 1H, OH), 3.49 (s, 3H, OCH3), 3.61 (dd,
J ) 6.5, 2.7 Hz, 1H, H5), 4.23 (d, J ) 6.5 Hz, 1H, H6), 5.85 (d, J
) 2.7 Hz, 1H, H3), 6.98–7.02 (m, 2H, HPh), 7.21–7.26 (m, 3H,
HPh). 13C NMR (100 MHz, CDCl3): δ (ppm) 28.6 (CH3), 30.1
(CH3), 46.0 (C5), 55.1 (OCH3), 55.8 (C6), 65.9 (C3), 72.7
(C(CH3)2OH), 76.1 (C1), 115.3 (C2), 126.5 (CHPh), 128.1 (CHPh),
128.7 (CHPh), 139.8 (C4 or CPh), 144.0 (C4 or CPh), 221.6 (CO
(Mn)). IR (neat): ν˜ (cm-1) 1920, 2012 (CO (Mn)). HRMS
(electrospray): m/z calcd for C19H18ClMnNaO5, 439.0115; found,
439.0107 (M + Na+).
Supporting Information Available: Full experimental proce-
dures, 13C NMR spectra of all new compounds, and crystal data
for 24a. This material is available free of charge via the Internet at
http:/pubs.acs.org.
OM7010529