Molybdenum(II)- and tungsten(II)-catalyzed allylic substitution

Article abstract of DOI:10.1021/jo9821776

The molybdenum(II) complexes Mo(CO)₅(OTf)₂ (7a), [Mo(CO)₄Br₂]₂ (8a), their tungsten(II) congeners 7b and 8b, and bimetallic complex Mo(CO)₃(MeCN)₂(SnCl₃)Cl (9a) have been found to catalyze the C-C bond-forming allylic substitution with silyl enol ethers derived from β-dicarbonyls (e.g., 16 + 30 → 46) or from simple ketones (e.g., 16 + 32 → 50), aldehydes, and esters as nucleophiles under mild conditions (room temperature, 1-2 h). Methanol, as a prototype oxygen nucleophile, reacts in a similar fashion (e.g., 16 + MeOH → 43). Mechanistic and stereochemical experiments are indicative of Lewis-acid catalysis rather than a metal template-controlled process.

Full text of DOI:10.1021/jo9821776

J . Org. Chem. 1999, 64, 2737-2750
2737
Molybd en u m (II)- a n d Tu n gsten (II)-Ca ta lyzed Allylic Su bstitu tion
Andrei V. Malkov,† Ian R. Baxendale,†,‡ Dalimil Dvorˇa´k,†,§ Darren J . Mansfield,| and
Pavel Kocˇovsky´*,†
Department of Chemistry, University of Leicester, Leicester LE1 7RH, U.K., and AgrEvo UK Ltd.,
Chesterford Park, Saffron Walden, Essex, CB10 1XL, U.K.
Received October 29, 1998
The molybdenum(II) complexes Mo(CO)5(OTf)2 (7a ), [Mo(CO)4Br2]2 (8a ), their tungsten(II) congeners
7b and 8b, and bimetallic complex Mo(CO)3(MeCN)2(SnCl3)Cl (9a ) have been found to catalyze the
C-C bond-forming allylic substitution with silyl enol ethers derived from â-dicarbonyls (e.g., 16 +
30 f 46) or from simple ketones (e.g., 16 + 32 f 50), aldehydes, and esters as nucleophiles under
mild conditions (room temperature, 1-2 h). Methanol, as a prototype oxygen nucleophile, reacts in
a similar fashion (e.g., 16 + MeOH f 43). Mechanistic and stereochemical experiments are
indicative of Lewis-acid catalysis rather than a metal template-controlled process.
Sch em e 1
In tr od u ction
The discovery of palladium(0) catalysis in allylic sub-
stitution1 is one of the milestones in organic synthesis,
partly because it helps solve an old problem of classical
organic chemistry, namely the nonselectivity of the
capricious SN2′ reaction.2 The Pd(0)-catalyzed allylic
substitution is stereospecific and occurs via the interme-
diate η3-complex, arising from allylic esters in an anti-
fashion (Scheme 1; 1 f 2; M ) Pd).3,4 The subsequent
reaction with stabilized C-nucleophiles (e.g., malonates)
again proceeds with an anti-mechanism, giving 3, which
corresponds to an overall retention of configuration.3
Several industrial processes are now using this chemistry
either for the formation of a strategic C-C bond5 or to
facilitate selective deprotection of functional groups in
molecules as sensitive as â-lactam antibiotics.6
Although the advent of Pd(0) catalysis has solved a
number of industrial problems, the methodology suffers
from two major limitations: (1) Whereas the η3-Pd
complexes readily react with enolates derived from
â-dicarbonyls and their congeners as nucleophiles,3 cata-
lytic reactions with simple enolates often fail.7 (2) When
the catalytic turnover is low, the cost of Pd becomes
prohibitive for industrial application. Hence, developing
a less expensive catalyst for those cases where Pd is
either ineffective or too costly would be of particular
importance.
* Correspondence author. E-mail: PK10@Le.ac.uk.
† University of Leicester.
‡ Current address: Department of Chemistry, University of Cam-
bridge, Cambridge CB2 1EW, U.K.
§ On leave from the Department of Organic Chemistry, Prague
Technical University, 16628 Prague 6, Czech Republic.
| AgrEvo UK Ltd.
(1) (a) Hata, H.; Takahashi, K.; Miyake, A. J . Chem. Soc., Chem.
Commun. 1970, 1392. (b) Hata, H.; Takahashi, K.; Miyake, A. Bull.
Chem. Soc. J pn. 1972, 45, 230. (c) Atkins, K. E.; Walker, W. E.;
Maniyik, R. M. Tetrahedron Lett. 1970, 3821. (d) Tsuji, J .; Takahashi,
H.; Morikawa, M. Tetrahedron Lett. 1965, 4387.
(2) (a) Magid, R. M. Tetrahedron 1980, 36, 1901. (b) Paquette, L.
A.; Stirling, C. J . M. Tetrahedron 1992, 48, 7383.
(3) (a) Trost, B. M.; Strege, P. E. J . Am. Chem. Soc. 1975, 97, 2534.
(b) Trost, B. M.; Verhoeven, T. R. J . Org. Chem. 1976, 41, 3215. (c)
Hayashi, T.; Hagihara, T.; Konishi, M.; Kumada, M. J . Am. Chem. Soc.
1983, 105, 7767. For reviews, see: (d) Trost, B. M. Tetrahedron 1977,
33, 371. (e) Trost, B. M. Acc. Chem. Res. 1980, 13, 385. (f) Tsuji, J .
Tetrahedron 1986, 42, 4361. (g) Frost, C. G.; Howarth, J .; Williams, J .
M. J . Tetrahedron: Asymmetry 1992, 3, 1089. (h) Trost, B. M.; Van
Vranken, D. L. Chem. Rev. 1996, 96, 395.
(4) The syn-mechanism (1 f 4) has been observed in two instances
as a result of precoordination of Pd(0) to the leaving group (Ph2PCH2-
CO2 or Cl): (a) Stary´, I.; Kocˇovsky´, P. J . Am. Chem. Soc. 1989, 111,
4981. (b) Stary´, I.; Zaj´ıcˇek, J .; Kocˇovsky´, P. Tetrahedron 1992, 48, 7229.
(c) Kurosawa, H.; Ogoshi, S.; Kawasaki, Y.; Murai, S.; Miyoshi, M.;
Ikeda, I. J . Am. Chem. Soc. 1990, 112, 2813. (d) Kurosawa, H.;
Kajimaru, H.; Ogoshi, S.; Yoneda, H.; Miki, K.; Kasai, N.; Murai, S.;
Ikeda, I. J . Am. Chem. Soc. 1992, 114, 8417. Precoordination to a
neighboring group can also enforce the syn mechanism: (e) Farthing,
C. N.; Kocˇovsky´, P. J . Am. Chem. Soc. 1998, 120, 6661.
Aside from (Ph3P)4Pd and related Pd(0) catalysts,
group 6 complexes have also been shown to exhibit
catalytic activity in allylic substitution and to give
products of overall retention of configuration (1 f 3).8,9
(7) Attempts at developing the Pd(0)-catalyzed reaction of allylic
esters with silyl enol ethers derived from simple ketones, as an
extension of the established reactions with stabilized C-nucleophiles,
have only met with modest success. In the examples reported to date,
the more reactive carbonates (rather than acetates) have been em-
ployed and some of these reactions seem to work efficiently only as
intramolecular processes: (a) Tsuji, J .; Minami, I.; Shimizu, I. Chem-
istry Lett. 1983, 1325. (b) Tsuji, J .; Minami, I.; Shimizu, I. Tetrahedron
Lett. 1983, 24, 1793. (c) Shimizu, I.; Minami, I.; Tsuji, J . Tetrahedron
Lett. 1983, 24, 1797. (d) Tsuji, J .; Takahashi, K.; Minami, I.; Shimizu,
I. Tetrahedron Lett. 1984, 25, 4783. For successful examples employing
allylic acetates, see: (e) Fiaud, J .-C.; Malleron, J . J . Chem. Soc., Chem.
Commun. 1981, 1159. (f) Saitoh, A.; Achiwa, K.; Morimoto, T.
Tetrahedron Asymmetry 1998, 9, 741.
(8) (a) Trost, B. M.; Lautens, M. J . Am. Chem. Soc. 1982, 104, 5543.
(b) Trost, B. M.; Lautens, M. J . Am. Chem. Soc. 1983, 105, 3343. (c)
Trost, B. M.; Lautens, M. Organometallics 1983, 2, 1687. (d) Trost, B.
M.; Lautens, M.; Peterson, B. Tetrahedron Lett. 1983, 24, 4525. (e)
Trost, B. M.; Lautens, M. J . Am. Chem. Soc. 1987, 109, 1469. (f) Trost,
B. M.; Lautens, M. Tetrahedron 1987, 43, 4817. (g) Trost, B. M.; Merlic,
C. A. J . Am. Chem. Soc. 1990, 112, 9590.
(5) (a) Hegedus, L. S. Transition Metals in the Synthesis of Complex
Organic Molecules; University Science Books: Mill Valley, CA, 1994.
(b) Harrington, P. J . Transition Metals in Total Synthesis; J . Wiley &
Sons: New York, 1990. (c) Davies, S. G. Organotransition Metal
Chemistry. Applications to Organic Synthesis; Pergamon: Oxford, U.K.,
1982. For an overview of industrial applications of Pd, see: (d) Tsuji,
J . Synthesis 1990, 739.
(6) Greene, T. W.; Wuts, P. G. M. Protective Groups in Organic
Synthesis; J . Wiley & Sons: New York, 1991; pp 108 and 331-333.
10.1021/jo9821776 CCC: $18.00 © 1999 American Chemical Society
Published on Web 03/20/1999

2738 J . Org. Chem., Vol. 64, No. 8, 1999
Malkov et al.
Sch em e 2
Ch a r t 1a
a
TfO ) CF3SO3.
by analogy with other transition metal complexes, the
Lewis acidity of Mo could be increased by replacing some
of the CO groups in the complex by weakly coordinating
ligands, such as trifluoromethanesulfonate, and/or by
increasing the oxidation state of the metal.15-17
Herein, we present a study of three variants of M(II)
catalysts, namely complexes 7-9 (Chart 1); their prepa-
ration is discussed in appropriate paragraphs and il-
lustrated in Schemes 3-5.
Interestingly, there is evidence that the mechanism for
the reaction catalyzed by Mo(CO)6 can differ from that
for Pd:10-12 instead of double inversion, we have recently
demonstrated a double retention pathway for Mo (1 f 4
f 3).11 In stoichiometric reactions, the first step has also
been shown to occur with retention of configuration (1
f 4),10,12 but the isolated η3-complex 4 is known to react
with stabilized nucleophiles via inversion.10,12 Although
this dichotomy may offer attractive synthetic applica-
tions, wider use of the group 6 catalysts is held back by
their lower reactivity compared to Pd. Thus, Mo and W
catalysts typically require refluxing in higher-boiling
solvents (e.g., toluene) for several hours,8,9,11 whereas
reflux in THF or even ambient temperature is normally
sufficient for Pd.3,4 This striking difference can be at-
tributed, in part, to the ease of ligand dissociation in the
case of Pd catalysts, e.g., (Ph3P)4Pd f (Ph3P)3Pd + Ph3P,
as opposed to the relative stability of Mo(CO)6, W(CO)6,
and related complexes.5a In view of the relatively low cost
of Mo and W complexes, increasing their reactivity would
be highly desirable.13
Resu lts a n d Discu ssion
P r ep a r a tion of Mo(II) a n d W(II) Com p lexes a s
P oten tia l Ca ta lysts. Group 6 complexes with a weakly
coordinating ligand appeared to us to be promising
candidates for catalysts in allylic substitution (vide
supra). Therefore we first endeavored to prepare the
corresponding triflates.
Sch em e 3a
The mechanism of formation of the η3-Pd complex is
generally accepted to involve a primary coordination of
Pd(0) to the CdC bond followed by extrusion of the
leaving group (5, Scheme 2) as a result of back-donation.3
The different behavior of Mo(0) complexes can be under-
stood if, instead of coordinating to the CdC bond, Mo is
assumed to first associate with the Lewis-basic carbonyl
oxygen of the acetate leaving group, followed by coordi-
nation to the CdC bond (6).11,12 Hence, Mo(CO)6 would
act as a weak Lewis acid and this postulate appears to
be compatible with the effect of altering the Lewis
basicity of the carbonyl oxygen by varying the R in the
leaving group: thus, an electron-donating nitrogen atom
(6, R ) Me2N) accelerates the reaction, whereas an
electron-withdrawing unit (6, R ) CF3) retards the
process.11,14 However, the increase of the reaction rate
observed for carbamates is not dramatic, being in the
range of 1 order of magnitude, so that synthetic benefits
would not be as great as desired.
a
Bn ) PhCH2, TfO ) CF3SO3.
Sch em e 4
Alternatively, the above analysis suggests that en-
hancing the Lewis acidity of the Mo complex should also
result in acceleration of the reaction. We reasoned that,
(9) (a) Trost, B. M.; Hung, M.-H. J . Am. Chem. Soc. 1983, 105, 7757.
(b) Trost, B. M.; Hung, M.-H. J . Am. Chem. Soc. 1984, 106, 6837. (c)
Lloyd-J ones, G. C.; Pfaltz, A. Angew. Chem., Int. Ed. Engl. 1995, 34,
462. (d) Lloyd-J ones, G. C.; Pfaltz, A. Z. Naturforsch. B 1995, 50b, 361.
(e) Lehmann, J .; Lloyd-J ones, G. C. Tetrahedron 1995, 51, 8863. (f)
Frisell, H.; A° kermark, B. Organometallics, 1995, 14, 561.
(10) Faller, J . W.; Linebarrier, D. Organometallics 1988, 7, 1670.
(11) Dvorˇa´k, D.; Stary´, I.; Kocˇovsky´, P. J . Am. Chem. Soc. 1995,
117, 6130.
(12) Ward, Y. D.; Villanueva, L. A.; Allred, G. D.; Liebeskind, L. S.
J . Am. Chem. Soc. 1996, 118, 897.
(13) Replacing some of the carbonyls in Mo(CO)6 and W(CO)6 by
other ligands, such as MeCN, DMF, etc., has been shown to slightly
accelerate the reaction.8 See also: Pearson, A. J .; Schoffers, E.
Organometallics 1997, 16, 5365.
(15) (a) Van Seggen, D. M.; Hurlburt, P. K.; Anderson, O. P.; Strauss,
S. H. Inorg. Chem. 1995, 34, 3453 and references cited therein. (b)
Marks, T. J . Acc. Chem. Res. 1992, 25, 57. (c) Strauss, S. H. Chem.
Rev. 1993, 93, 927.
(16) Dvorˇa´kova´, H.; Dvorˇa´k, D.; Sˇrogl, J .; Kocˇovsky´, P. Tetrahedron
Lett. 1995, 36, 6351.
(14) Note that the opposite effect has been observed for the
substrates in which the syn-mechanism is precluded by a steric bias
so that the anti-mechanism (5) becomes the only possible pathway.11
(17) (a) Malkov, A. V.; Baxendale, I. R.; Mansfield, D. J .; Kocˇovsky´,
P. Tetrahedron Lett. 1997, 38, 4895. (b) Malkov, A. V.; Davis, S. L.;
Mitchell, W. L.; Kocˇovsky´, P. Tetrahedron Lett. 1997, 38, 4899.

Mo(II)- and W(II)-Catalyzed Allylic Substitution
J . Org. Chem., Vol. 64, No. 8, 1999 2739
Sch em e 5
year (vide infra), they should be stored under nitrogen
in a freezer (-20 °C). During our frequent preparations
of 8a ,b, we obtained more active and pure complexes by
removal of the solvent (CH2Cl2) at low temperature (-78
°C; see Experimental Section for details). By contrast,
warming the mixture to ambient temperature prior to
the solvent removal20 often resulted in the formation of
black-brown solid or tar. Although the latter substances
still showed characteristic IR signals20 of the desired
product, additional impurities could also be detected;
these products proved to be less stable and of low
catalytic activity.
Interestingly, adding THF to either of the complexes
8a ,b is known to trigger a fast exchange of CO for THF,
generating complexes 15a ,b, respectively.20 The impor-
tance of the ease of the latter reaction for development
of a catalytic process, though not recognized earlier, can
easily be envisaged: if a ligand as weak as THF experi-
ences no difficulty in entering the coordination sphere of
the metal, then other eligible ligands, such as an allylic
acetate and/or a nucleophile, should also be successful.
This, indeed, proved to be the case, as shown below.
(c) Bim eta llic Com p lex. Another suitable Mo(II)
candidate was identified in the orange-red complex 9a ,
which can be prepared by oxidative addition of SnCl4 to
Mo(CO)3(MeCN)3 (Scheme 5).21-23 Pure 9a is moderately
stable and can be stored in the dark under nitrogen at
room temperature; its solutions rapidly decompose when
exposed to air. Although the crude product can be used
directly in our catalytic reactions, recrystallization from
acetonitrile is highly recommended as it gives more stable
and more reactive species.
Mod el Su bstr a tes for Allylic Su bstitu tion . All the
complexes 7-9 possess labile ligands (TfO- in 7a ,b, CO
in 8a ,b, and MeCN in 9a ) that can easily dissociate in
solution, offering vacant coordination sites, potentially
capable of accommodating an allylic substrate and/or a
nucleophile.24 To investigate their reactivity as catalysts
for allylic substitution, we employed a set of allylic
acetates (Chart 2) and two types of nucleophiles: metha-
nol, as a prototype O-nucleophile, and enolate-type
C-nucleophiles (Chart 3).
O-Nu cleop h iles. In a preliminary account,16 we have
shown that 7a catalyzed substitution of an allylic acetoxy
group with MeOH. Thus, 16 and 18 readily underwent
the reaction at room temperature25 to give methoxy
derivatives 43 and 44, respectively (Scheme 6; Table 1,
entries 1, 6), accompanied by elimination products. By
contrast, 23 (an allylic isomer of 22) was found to react
(a ) Tr ifla te Com p lexes. To prepare triflate complexes
of Mo, we examined the reaction of silver triflate with
chloromolybdate 11a which, in turn, can be readily
obtained from Mo(CO)6 on heating with a tetraalkylam-
monium chloride (Scheme 3).18 Although replacement of
the chloride with TfOAg is a standard technique in
transition metal chemistry,15 in the case of 11a the
reaction turned out to be more complex.19 As expected,
on treatment with TfOAg, the chloride in 11a was,
indeed, replaced by TfO- (11a f 12a ). However, the
reaction proceeded with concomitant oxidation of Mo(0)
to Mo(I) (12a f 13a ). The latter species proved to be
unstable and underwent disproportionation to give 12a
and Mo(II) complex 7a . In practice, 3 equiv of TfOAg was
required to drive the reaction to completion.16,19 The
resulting complex 7a can be expected to behave like a
weak Lewis acid in view of its oxidation state (+2) and
the presence of a weakly coordinating TfO- group. The
corresponding tungsten complex 7b was generated in situ
from chlorotungstenate 11b in a similar way.19
Preliminary investigations of the catalytic activity of
complexes 7a ,b toward allylic substrates, employing both
oxygen16 and carbon nucleophiles,17 were promising (vide
infra). Control experiments demonstrated that neither
Mo(0)/W(0) nor TfOAg was capable of catalyzing allylic
substitution under the same conditions, suggesting that
Mo(II) and/or W(II) are, indeed, responsible for the
reactivity. However, the complexes themselves are not
ideal catalysts as they have to be generated from chlo-
romolybdates 10a ,b prior to each reaction and cannot be
stored. The latter instability, in conjunction with the
requirement for 3 equiv of TfOAg for the in situ genera-
tion of the active species, renders this method rather
clumsy and expensive so that development of a simpler
and less expensive alternative was desirable.
(b) [Mo(CO)4Br 2]2 a n d [W(CO)4Br 2]2 Com p lexes. In
view of the disadvantages of 7a ,b , it was desirable to
investigate related complexes that would be more stable
and easier to handle. Since preliminary experiments
suggested M(II) to be the reactive species, we endeavored
to oxidize M(0) to M(II) by other means.
One of the methods for preparation of a potentially
useful Mo(II) complex relies on titration of Mo(CO)6 with
1 equiv of bromine (Scheme 4)20 at low temperature in a
noncoordinating solvent (e.g., CH2Cl2) under inert atmo-
sphere; the resulting product 14a (a 16 electron species)
is stabilized as dimer 8a (an 18 electron species).20 The
corresponding tungsten complex 8b can be prepared from
W(CO)6 in the same way.20 The dimeric complexes 8a ,b
are orange powders and, when dry, can be handled in
air. However, to retain their catalytic activity for >0.5
(21) (a) Baker, P. K.; Bury, A. J . Organomet. Chem. 1989, 359, 189.
(b) Baker, P. K.; Quinlan, A. J . Inorg. Chim. Acta 1989, 162, 179.
(22) (a) Miguel, D.; Perez-Martinez, J . A.; Garcia-Granda, S. Poly-
hedron 1991, 10, 1717. (b) Barrado, G.; Miguel, D.; Perez-Martinez, J .
A.; Riera, V. J . Organomet. Chem. 1993, 463, 127.
(23) Cano, M.; Panizo, M.; Campo, J . A.; Tornero, J .; Menendez, N.
J . Organomet. Chem. 1993, 463, 121.
(24) Interestingly, when crystallized from acetone, 9a undergoes a
ligand exchange to produce Mo(CO)3(MeCN)(Me2CO)(SnCl3)Cl, dem-
onstrating the lability of the MeCN ligand.22
(25) The reactions were typically carried out in CH2Cl2 at room
temperature with 2-5 mol % of the catalyst and a slight excess (1.1
equiv) of the nucleophile. The reaction times and yields are given in
Tables 1-6. All yields refer to “isolated” yields rather than “GC yields”.
(26) For a similar catalytic effect of Ce(IV) and/or Ce(III) on the
transformation of allylic acetates or alcohols into the corresponding
ethers on reaction with alcohols, see: (a) Iranpoor, N.; Mothaghineghad,
E. Tetrahedron 1994, 50, 1859 and 7299. (b) Uzarewicz, A.; Dresler,
R. Pol. J . Chem. 1997, 71, 181. The same effect has been reported for
(Ph3P)2PtCl2-SnCl2 as catalyst: Sakamaki, H.; Kameda, N.; Iwadare,
T.; Ichinohe, Y. Bull. Chem. Soc. J pn 1995, 68, 3491.
(18) (a) Ganorkar, M. C.; Stiddard, M. H. B. J . Chem. Soc. 1965,
3494. (b) Abel, E. W.; Butler, I. S.; Red, J . G. J . Chem. Soc. 1964, 2068.
(c) Sˇrogl, J .; Kocˇovsky´, P. Tetrahedron Lett. 1992, 33, 5991.
(19) Abbott, A. P.; Malkov, A. V.; Zimmermann, N.; Raynor, J . B.;
Ahmed, G.; Steele, J .; Kocˇovsky´, P. Organometallics 1997, 16, 3690.
(20) (a) Bowden, J . A.; Colton, R. Aust. J . Chem. 1968, 21, 2657. (b)
Cotton, F. A.; Falvello, L. R.; Meadows, J . H. Inorg. Chem. 1985, 24,
514. (c) Cotton, F. A.; Poli, R. Inorg. Chem. 1987, 26, 1514.

2740 J . Org. Chem., Vol. 64, No. 8, 1999
Malkov et al.
Ch a r t 2
Sch em e 6a
a
For conditions and yields, see Table 1.
Ta ble 1. Allylic Su bstitu tion a w ith MeOH a s
Nu cleop h ile
allylic
compd
catalyst
(mol %)
time
(h)
yield
(%)b
entry
product
1
2
3
4
5
6
7
8
9
16
16
16
17
17
18
22
22
23
23
23
7a (5)
7b (5)
8a (5)
8a (5)
9a (5)
7a (5)
8a (2)
9a (5)
7a (5)
8a (2)
9a (5)
4
20
4
24
24
4
4
2.5
4
43
43
43
44
44
44
45
45
45
45
45
20c
10
60
20
19
25c
55
92
12
63
94
sluggishly (Table 1, entry 9), and 19 and 24 proved inert,
suggesting a substantial SN1 component in the initial
ionization of the substrate. Analogous reactivity was
observed for tungsten catalyst 7b (Table 1, entry 2).26
Dibromo-catalyst 8a proved to react in a similar way
as documented by conversion of 16, 17, and 22 into the
corresponding methoxy derivatives (Table 1, entries 3,
4, and 7). For acetate 23 (which reacted sluggishly in the
presence of 7a ), this catalyst turned out to be clearly
superior (compare entries 9 and 10 in Table 1).
Bimetallic complex 9a was also found to catalyze the
reaction of 22 and of 23 with MeOH (Scheme 6) to give
45 in excellent yields (compare entries 8 and 11 with
entries 7, 9, and 10 in Table 1). Note, in particular, the
high conversion of 23 into 45, which gave the best yield
with 9a (Table 1, entry 12). By contrast, conversion of
17 into 44 gave low yield (Table 1, entry 5), mainly due
to predominant elimination.
10
11
4
2.5
a
The reactions were carried out in CH2Cl2 at room temperature
unless stated otherwise. Isolated yield. c Conversion was quan-
b
titative.
to develop a C-C bond-forming reaction. However, initial
attempts employing dimethyl lithiomalonate as the nu-
cleophile failed under a range of conditions: the starting
allylic acetates (Chart 2) either proved inert or underwent
a slow elimination to give rise to the corresponding dienes
and further decomposition products. This failure can be
attributed to deactivation of the catalyst via a strong
chelation of the metal by the â-dicarbonyl enolate,27
suggesting that anionic nucleophiles should be avoided.
(a ) Silyl En ol Eth er s Der ived fr om â-Dica r bon yls.
We reasoned that neutral silyl enol ethers might be less
detrimental to the catalyst activity which, indeed, proved
to be the case. Initial experimentation (Scheme 7) with
acetate 16 and the malonate-derived silyl enol ether 30
met with modest success, affording the desired compound
46 accompanied by a substantial proportion of elimina-
tion products; under optimized conditions, 46 was ob-
tained at ambient temperature in 48% isolated yield
(Table 2, entry 1). The less reactive acetate 19 furnished
the corresponding product 49 in only 16% yield (Table 2,
entry 5). Finally, tertiary acetate 18 proved moderately
reactive, affording 47 (55%) on reaction with 30 (Table
2, entry 4). In the presence of either 8a or 9a , silyl enol
ether 31 (derived from methyl acetoacetate) produced 48
in high yields (Table 2, entries 2 and 3).
C-Nu cleop h iles. Inspired by the successful and ready
allylic substitution with O-nucleophiles, we endeavored
Ch a r t 3
(27) Enolates of â-dicarbonyls are known to form relatively stable
chelate complexes with Mo(II): Brower, D. C.; Winston, P. B.; Tonker,
T. L.; Templeton, J . L. Inorg. Chem. 1986, 25, 2883. See also refs 8e,f.

Mo(II)- and W(II)-Catalyzed Allylic Substitution
J . Org. Chem., Vol. 64, No. 8, 1999 2741
Ta ble 3. Allylic Su bstitu tion a w ith Keton e- a n d
Ald eh yd e-Der ived Nu cleop h iles
Sch em e 7a
allyllic nucleo- catalyst
product yield
entry compd phile (mol %) time product ratiob (%)c
1
2
3
4
5
6
7
8
9
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
17
17
17
17
17
17
17
17
17
17
17
17
17
18
18
18
18
19
19
19
19
19
19
20
20
21
21
21
21
21
21
32
32
32
32
32
33
33
34
34
35
35
36
36
37
37
38
38
32
32
32
34
34
35
35
36
36
37
37
38
38
32
32
32
33
32
32
32
32
37
37
32
32
32
32
33
33
35
35
7a (5) 1.5 h
7b (5) 2 h
50
50
50
50
50
56d
56d
54
54
60
60
61
61
62
62
68
68
51
51
51
55
55
63
63
64
64
65
65
69
69
51
51
51
53
52
52
52
52
66
66
57
57
58
58
59
59
67
67
65
59
89
86
80
76
81
79
82
73
80
72
80
74
91
92
83
89
80
89
84
86
75
62
88
91
78
86
80
90
84
68
91
81
14
42
35
75
74
86
54
53
86
81
74
80
56
57
8a (2) 20 min
8b (5) 45 min
9a (5) 25 min
8a (5) 20 min
9a (5) 20 min
8a (5) 30 min
9a (5) 30 min
8a (5) 25 min
9a (5) 25 min
8a (5) 10 min
9a (5) 10 min
8a (5) 20 min
9a (5) 15 min
8a (5) 15 min
9a (5) 15 min
8a (5) 30 min
8b (5) 45 min
9a (5) 25 min
8a (5) 30 min
9a (5) 30 min
8a (5) 1.75 h
9a (5) 1.75 h
8a (5) 10 min
9a (5) 10 min
8a (5) 15 min
9a (5) 15 min
8a (5) 15 min
9a (5) 15 min
8a (2) 30 min
8b (5) 40 min
9a (5) 50 min
7a (5) 1.5 h
7a (5) 24 h
8a (2) 24 h
8b (5) 24 h
9a (5) 2 h
8a (5) 30 min
9a (5) 30 min
8a (5) 10 min
9a (5) 10 min
8a (5) 20 min
9a (5) 20 min
8a (5) 20 min
9a (5) 20 min
8a (5) 4 h
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
96:4e
97:3e
94:6e
a
For conditions and yields, see Tables 2 and 3.
Ta ble 2. Allylic Su bstitu tion a w ith â-Dica r bon yl-Der ived
Nu cleop h iles
allyllic
catalyst
yield
entry compd nucleophile (mol %)
time
product (%)b
1
2
3
4
5
16
17
17
18
19
30
31
31
30
30
7a (5)
8a (5)
9a (5)
7a (5)
7a (5)
1 h
46
48
48
47
49
48
86
80
55
16
45 min
30 min
1 h
9a (5) 4 h
a
The reactions were carried out in CH2Cl2 at room temperature.
The isomer ratios were determined by 1H NMR. c Isolated yield.
A 60:40 mixture of diastereoisomer ratio was formed. e A regio-
b
d
20 h
a
The reactions were carried out in CH2Cl2 at room temperature.
isomer was formed as byproduct, as revealed by 1H NMR spec-
troscopy.
b
Isolated yield.
(b) Keton e-Der ived Silyl En ol Eth er s. Since the
reacted sluggishly again to afford 52 in mere 14% yield
(Table 3, entry 35). The difference in the reactivity of 16
and 17 vs 19 further supports the notion that a substan-
tial SN1 component attends the transition state of the
reaction. Increasing the steric bulk of the nucleophile
turned out to have little effect on the reactivity, as
demonstrated by the high yield of 53 from the reaction
of 18 with 33 (Table 3, entry 34). Tungsten complex 7b
proved slightly less reactive (compare entries 1 and 2 in
Table 3).
reaction of 16 with silylated malonate 30 proved reason-
ably efficient, being the first example of C-C bond
formation catalyzed by Mo(II), it was of interest to
establish whether simple silyl enol ethers, such as 32,
could also be used as nucleophiles (Chart 3).28 If success-
ful, these M(II) catalysts would present a substantial
advantage over their Pd(0) counterparts by offering a
broader scope of reactivity. In practice, 32 turned out to
be more efficient than 30 on reaction with 16 (Scheme
7), giving the corresponding product 50 in 65% yield
(Table 3, entry 1) with 7a as catalyst. On the other hand,
allylic acetate 19 with a disubstituted double bond
Complexes 8a ,b have proven to be superior to triflates
7a ,b. Thus, reactions of allylic acetates 16-18 with 32
(Scheme 7) proceeded to completion in 20-45 min at
room temperature, giving excellent isolated yields (typi-
cally 80-90%) of the expected products (Table 3, entries
3, 4, 18, 19, 31, and 32). The yields were dramatically
(28) The silyl enol ethers were prepared from the corresponding
ketones via deprotonation with LDA or LiHMDS in THF followed by
quenching the intermediate enolate with Me3SiCl.

2742 J . Org. Chem., Vol. 64, No. 8, 1999
Malkov et al.
Sch em e 8a
Sch em e 9a
a
For conditions and yields, see Table 3.
Ta ble 4. Allylic Su bstitu tion a w ith Ester -Der ived
Nu cleop h iles
allyllic nucleo- catalyst
product yield
entry compd phile (mol %) time product ratiob (%)c
1
2
3
4
5
6
7
8
9
10
11
12
13
14
16
16
16
17
17
17
17
17
19
19
20
20
21
21
40
40
40
39
39
40
40
40
40
40
40
40
40
40
8a (5) 20 min
8b (5) 35 min
9a (5) 15 min
8a (5) 45 min
9a (5) 45 min
8a (5) 20 min
8b (5) 25 min
9a (2) 20 min
8a (5) 2.5 h
70
70
70
71
71
72
72
72
73
73
74
74
75
75
87:13d
91:9d
85
89
89
75
77
77
89
93
83
89
46
50
82
83
86:14d
92:8d
87:13d
83:17d
a
For conditions and yields, see Table 3.
9a (5) 2.5 h
8a (5) 15 min
9a (5) 15 min
8a (5) 30 min
9a (5) 30 min
improved even in the case of acetate 19 (up to 42%),
although this reaction required 24 h and considerable
decomposition of the starting materials was detected
(Table 3, entries 36 and 37). Again, the steric bulk of the
nucleophile proved to have little effect, as revealed by
the reaction of 16 or 17 with 34, which furnished 54 and
55, respectively (Table 3, entries 8 and 21). Reaction of
16 with 33 also proceeded readily, furnishing 56 (Table
3, entry 6).
The reactivity pattern for bimetallic complex 9a turned
out to be similar to that exhibited by other M(II) catalysts
(vide supra). Thus, on reaction with 32, acetates 16-19
afforded the respective products 50-52 in comparable
or improved yields (Scheme 7) but often in a shorter
period of time than the other M(II) catalysts (Table 3,
entries 5, 20, 33, and 38). Sterically hindered enol ethers
33 and 34 gave essentially the same yields of 54-56,
respectively, on reaction with both 16 and 17, as in the
presence of 8a ,b (Table 3, compare entries 6 vs 7, 8 vs 9,
and 21 vs 22).
The cyclopentene-derived allylic acetate 20 was readily
converted into the expected ketone 57 on reaction with
32 in the presence of 8a (Table 3, entry 41). Even 21,
lacking the additional methyl group, gave the corre-
sponding product 58 in excellent yield (Table 3, entry 43),
demonstrating the higher reactivity of the cyclopentene
series. By analogy, 59 was readily produced on reaction
of 21 with 33 (Table 3, entry 45). Similar reactivity was
observed for complex 9a (Scheme 7; Table 3, entries 42,
44, and 46).
To assess the effect of the aromatic ring (as in 32-34)
on the reactivity, nonaromatic silyl enol ethers 35-37
were screened as nucleophiles (Scheme 8). The cyclohexyl
derivative 35, lacking the stabilizing effect of the aro-
matic ring but having greater steric demand, gave rise,
on reaction with 16 in the presence of 8a , to the expected
product 60 in high yield (Table 3, entry 10). The acetone-
derived silyl enol ether 36 and even its tert-butyl ana-
logue 37 reacted in the same way to furnish 61 and 62,
respectively, in excellent yields (Table 3, entries 12 and
14), showing that steric effects do not prevent the reaction
from occurring. Acetate 17 exhibited the same reactivity
a
The reactions were carried out in CH2Cl2 at room temperature.
The isomer ratios were determined by 1H NMR. c Isolated yield.
b
d
A regioisomer was formed as byproduct, as revealed by 1H NMR
spectroscopy.
toward 35-37, producing 63-65, respectively (Table 3,
entries 23, 25, and 27). Even the least reactive allylic
acetate 19 turned out to be a suitable substrate in the
reaction with 37 (Table 3, entry 39). Cyclopentyl deriva-
tive 21 followed the trend, affording 67 on reaction with
35 (Table 3, entry 47). Similar yields of the respective
products were attained with catalyst 9a on reactions of
16, 17, 19, and 21 (Table 3, entries 11, 13, 15, 24, 26, 28,
40, and 48). On the other hand, the silyl enol ethers
derived from cyclohexanone or cyclopentanone proved
inert. In this instance, rather than undergoing substitu-
tion, the starting allylic acetates were either recovered
or found to be partly converted into elimination products
and polymers; the silyl enol ethers slowly reverted into
the corresponding carbonyl compounds.
(c) Ald eh yd e-Der ived Silyl En ol Eth er . In view of
the successful reactions of allylic acetates with a number
of ketone-derived silyl enol ethers, it was of interest to
establish the suitability of other silyl enol ethers, such
as those generated from aldehydes. Indeed, 38 was found
to react with both 16 and 17 (Scheme 9) giving the
corresponding products 68 and 69, respectively, in the
presence of either of the catalysts 8a and 9a (Table 3,
entries 16, 17, 29, 30).
(d ) Silyl E n ol E t h er s Der ived fr om E st er s a n d
Am id es. Ketene acetals 39 and 40 also proved reactive
toward acetates 16 and 17 in the presence of 8a (Scheme
10). Thus, 39 gave 71 as a single product on reaction with
17 (Table 4, entry 4), whereas formation of mixtures of
regioisomers was observed with 40, in which the major
products 70 and 72, respectively, originated from the
attack on the less substituted carbon (6:1 to 10:1; Table
entries 1, 2, 6, and 7). The usually less reactive allylic
substrate 19 gave 73 in very good yield on reaction with

Mo(II)- and W(II)-Catalyzed Allylic Substitution
J . Org. Chem., Vol. 64, No. 8, 1999 2743
Sch em e 11a
40 (Table 4, entry 9). The cyclopentane-derived allylic
acetate 20 proved more regioselective than its cyclohex-
ane congeners, affording 74 as a single isomer (Table 4,
entry 11); its de-methyl analogue 21 gave the expected
product 75 (Table 4, entry 13).
A practically identical pattern was observed for com-
plex 9a : whereas 39 afforded 71 as a single regioisomer
on reaction with 17 (Table 4, entry 5), its analogue 40
reacted with 16 and 17 to give regioisomeric mixtures,
in which 70 and 72 prevailed (Table 4, entries 3 and 8);
under the same conditions, cyclohexenyl acetate 19
produced 73 in high yield (Table 4, entry 10). Cyclopen-
tane derivatives 20 and 21 reacted with similar efficiency
(Table 4, entries 12 and 14). In contrast to the reactivity
of ketene acetals, attempts at introducing the related
amide nucleophiles, namely 41 and 42, failed even with
the most reactive acetates 16 and 17.
Regioselectivity. Methanol, as a representative O-
nucleophile, exhibited excellent regioselectivity with the
nonsymmetrically substituted allylic substrates 16, 18,
22, and 23 (Scheme 6): the attack occurred exclusively
at the less substituted carbon in the case of 16 and 18.
Remarkably, even the reaction of the allylic system
flanked by Ph at one terminus and by Me at the other
(22 and 23) gave the single methoxy derivative 45 (Table
1, entries 9-11). In all these instances, formation of the
product was independent of the original position of the
leaving group (compare 16 vs 18 and 22 vs 23; Table 1,
entry 3 vs 6 and 7, 8 vs 9-11).
a
For conditions and yields, see Table 5.
Ta ble 5. Regioselectivity of Allylic Su bstitu tion a w ith
Sch em e 10a
C-Nu cleop h iles
allylic nucleo- catalyst
product yield
entry compd phile (mol %) time products ratiob (%)c
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
22
22
22
22
23
23
23
23
23
23
23
24
24
25
25
30
32
32
33
30
32
32
32
32
32
40
32
32
32
32
7a (5) 1 h
7a (5) 1 h
76 + 77 43:57
78 + 81 40:60
59
54
65
80
92
65
87
97
89
79
91
76
75
85
80
8a (2) 30 min 78 + 81 50:50
7a (2) 30 min 79 + 82 42:58
8a (2) 1 h
76 + 77 43:57
8a (2) 30 min 78 + 81 43:57
8b (5) 30 min 78 + 81 50:50
9a (5) 20 min 78 + 81 50:50
9a (5) 2 hd
78 + 81 67:33
9b (25) 50 min 78 + 81 44:56
9a (5) 20 min 86 + 87 50:50
8a (5) 1 h
9a (5) 1 h
8a (5) 2 h
8a (5) 2 h
80 + 83 80:20
80 + 83 75:35
84 + 85 78:22
84 + 85 75:25
a
The reactions were carried out in CH2Cl2 at room temperature
b
unless stated otherwise. The isomer ratios were determined by
1H NMR spectra of the crude mixtures. c Isolated yield. Carried
d
out at -20 °C.
a
For conditions and yields, see Table 4.
33, or 40 (Scheme 11); the ratio of the isomeric products
76/77, 78/81, 79/82, and 86/87 oscillated between 1:1 and
1:1.4 (Table 5, entries 1-11). Lowering the reaction
temperature from 20 to -20 °C rendered the reaction of
23 with 32 slightly more selective in favor of the methyl
terminus (Table 5, entry 9). For comparison, the Mo(0)-
catalyzed reaction of 23 with NaCH(CO2Me)2 is known8,11
to produce a ∼1:2 mixture of 76 and 77, whereas the Pd-
(0)-catalyzed process affords 76 with excellent regiose-
lectivity (up to 20:1).29 On the other hand, employing
more Lewis-acidic Pd(0) catalysts, i.e., those with TME-
DA or (PhO)3P ligands, has been reported to result in
The reactivity of C-nucleophiles initially seemed to
follow the same pattern. Thus, on reaction with the
ketone-derived silyl enol ethers 32 or 33, allylic acetates
16-18 afforded either exclusively or with high preference
the products corresponding to the attack at the less
substituted carbon of the allyl moiety (Scheme 7; Table
3, entries 1-5, 18-20, and 31-34). The reactions with
ketene silyl acetal 40 (Scheme 10) were slightly less
regioselective, but only minute amounts of the regioiso-
mers were detected (Table 4, entries 1-3 and 6-8). By
contrast, the reactivity of phenyl-substituted substrates
22 and 23 turned out to be dramatically different as there
was little preference observed on reactions with 30, 32,
(29) Hayashi, T.; Yamamoto, A.; Hagihara, T. J . J . Org. Chem. 1986,
51, 723.

2744 J . Org. Chem., Vol. 64, No. 8, 1999
Malkov et al.
Sch em e 12a
Sch em e 13a
a
For conditions and yields, see Table 6.
axial epimer 27 reacted faster but gave a larger amount
of the corresponding diene as byproduct. Complex 8a
exhibited essentially the same behavior though the
isolated yields of the methoxy derivatives were even
lower owing to the predominant elimination (Table 6,
entries 5 and 8). By contrast, in the C-C bond-forming
reaction with 32, the axial ketone 91 was found to arise
as the major product from both 26 and 27 (Table 6,
entries 6 and 9), which is indicative of a common
intermediate.
To further investigate the stereochemical course of
these catalytic reactions, we employed another pair of
epimeric allylic acetates, namely 28 and 29 (Scheme 13).
Our previous experiments have demonstrated that exo-
acetate 28 readily reacted with LiCH(CO2Me)2 in the
presence of Mo(CO)6, whereas its endo-epimer 29 was
inert;11 this behavior was used as an argument in favor
of the syn,syn-mechanism of the Mo(0)-catalyzed allylic
substitution (Scheme 1).11 It is pertinent to note that the
latter outcome is in sharp contrast to the reactivity of
Pd(0), where exo-epimer 28 is inert (note that the
required anti-approach by Pd is sterically hindered),
while endo-acetate 29 readily forms the corresponding
η3-Pd complex.4a,b,31 With 8a as catalyst, exo-epimer 28
proved to react much faster: thus, with MeOH, 28 gave
methoxy derivative 92 in 5 h (Table 6, entry 10), whereas
29 was practically inert (Table 6, entry 12). With 32 as
nucleophile, exo-acetate 28 produced exo-ketone 93 in 30
min (Table 6, entry 11), while its endo-counterpart 29
required 14 h (Table 6, entry 13). Hence, M(II) catalysts
seemed to follow the pattern previously observed11 for
Mo(0) catalysts.32
a
For conditions and yields, see Table 6.
Ta ble 6. Ster eoch em istr y of Allylic Su bstitu tion
allylic nucleo- catalyst
product yield
entry compd phile (mol %) time
products
ratiob (%)c
1
2
3
4
5
6
7
8
9
10
11
12
13
(R)-23 MeOH 8a (2) 4 h
(()-45
65
(R)-23 30
(R)-23 30
7a (5) 2 h
8a (2) 20 min (() 76 + 77 42:58
(() 76 + 77 40:60
77
95
51
25d
87
46
30d
99
55
88
26 MeOH 7a (5) 4 h
26 MeOH 8a (2) 4 h
26 32 8a (2) 4 h
27 MeOH 7a (5) 2 h
27 MeOH 8a (2) 2 h
88 + 89
88 + 89
90 + 91
88 + 89
88 + 89
69:31
55:45
29:71
19:81
35:65
22:78
27 32
28 MeOH 8a (2) 5 h
29 32 8a (2) 30 min 93
29 MeOH 8a (2) 24 h
29 32 8a (2) 14 h
8a (2) 30 min 90 + 91
92
no reaction
93
88
a
The reactions were carried out in CH2Cl2 at room temperature.
The isomer ratios were determined by 1H NMR spectra of the
b
crude mixtures. c Isolated yield. The conversion was >90%, giv-
d
ing mainly elimination product.
less selective reaction.3g,30 In contrast to the lack of
regioselectivity in the case of 22 and 23, cinnamyl acetate
24 gave ∼4:1 to ∼3:1 ratios of regioisomers 80 and 83 in
the presence of catalysts 8a and 9a , respectively (Scheme
11; Table 5, entries 12 and 13). The nonaromatic ana-
logue 25 produced a 3:1 mixture of 84 and 85 (Scheme
11; Table 5, entries 14 and 15).
Ster eoch em istr y. The stereochemistry of the transi-
tion metal-catalyzed allylic substitution has recently been
shown to be dependent on the metal used (Scheme 1).11
It was therefore of interest to establish the stereochem-
istry of the present Mo(II)- and W(II)-catalyzed reactions.
To this end, we first investigated the pair of epimeric
acetates 26 and 27 (Scheme 12). With MeOH, the
reaction catalyzed by 7a turned out to proceed predomi-
nantly with retention of configuration, as documented by
the ratios of the resulting methoxy derivatives 88 and
89 (Table 6, entries 4 and 7), but was substantially
attended by competing elimination.16 As expected, the
To eliminate any conformational effects associated with
the nature of the six-membered ring (i.e., the axial/
equatorial relationship) and the general steric effects,
which attend the use of steroid derivatives 26 and 27 and
tricyclic acetates 28 and 29, the reactivity of O- and
C-nucleophiles was further investigated with the aid of
(31) Fiaud, J .-C.; Legros, J .-Y. J . Org. Chem. 1987, 52, 1907.
(32) Whereas partial epimerization of the starting allylic substrate
has occasionally been observed for Pd(0)-catalyzed reactions,4a,e this
is not the case with our Mo(II) catalysts, as revealed by analysis of
the reaction mixtures at ∼50% conversion of 26 and 27 with MeOH
and with 32. Hence, our results are not distorted by isomerization prior
to the substitution reaction.
(30) (a) A° kermark, B.; Hansson, S.; Krakenberger, B.; Vitagliano,
A.; Zetterberg, K. Organometallics 1984, 3, 679. (b) A° kermark, B.;
Krakenberger, B.; Hansson, S.; Vitagliano, A. Organometallics 1987,
6, 620.

Mo(II)- and W(II)-Catalyzed Allylic Substitution
J . Org. Chem., Vol. 64, No. 8, 1999 2745
Sch em e 14
Sch em e 15
the enantiomerically pure allylic acetate (R)-(+)-23 (g99%
ee).4b In the reaction catalyzed by 8a (Scheme 14),
methanol was found to produce racemic methoxy deriva-
tive 4533 (Table 6, entry 1) and, similarly, C-nucleophile
30 gave a mixture of racemic regioisomers 76 and 77
(Table 6, entries 2 and 3).
catalyst [M] for another cycle (step c). This scheme can
be applied to all complexes 7-9 as they can dissociate
prior to the reaction by losing a TfO-, CO, or MeCN
ligand, respectively. For MeOH as the nucleophile, the
intermediate complex AcO-[M]- would undergo proto-
nolysis, releasing AcOH (instead of AcOSiMe3) and [M].
The regioselectivity of the methanol attack (e.g., 22 or
23 f 45 and 16 f 43 in Scheme 6) apparently results
from thermodynamic control since, for instance, PhCH-
(OMe)CHdCHMe (allylic isomer of 45) can be converted
into 45 in the presence of the catalyst. By contrast, the
products of the reaction with C-nucleophiles cannot be
equilibrated so that the outcome should reflect the
preferential site of attack. With the substrates possessing
a trisubstituted double bond, e.g., 16, the attack exclu-
sively occurs at the less substituted terminus of the allylic
system (e.g., 16 + 32 f 50; Table 3, entries 1-5).
Cinnamyl acetate 24 also preferentially yields products
of reaction at the less substituted carbon, i.e., 80 (Table
5, entries 12 and 13). On the other hand, its homologue
23, which generates an allylic cation flanked by a Ph
substituent on one terminus and a Me on the other, is
attacked by C-nucleophiles on both termini to give ∼1:1
mixtures (of, e.g., 78 and 81 on reaction with 32; Table
5, entries 6-10). Interesting is the case of the reaction
of 16 with 40, where the expected product 70 is ac-
companied by 9-14% of its allylic isomer (Table 4, entries
1-3). Formation of a new C-C bond between two
quaternary centers (a sterically most disfavored process)
in the latter instance suggests participation of a compet-
ing single electron transfer (SET) mechanism.40 Accord-
ing to this scenario, the electron-rich silyl enol ether 40
would transfer an electron (presumably via the metal
catalyst), generating an allylic radical, whose subsequent
reaction with the radical cation arising from 40 would
afford the allylic byproduct.
Mech a n istic Con sid er a tion s. The stereochemical
experiments with 26-29 have demonstrated that a
common intermediate is involved for each epimeric pair.
Note that the steroidal intermediate preferentially reacts
via axial attack and that, for the tricyclic system, only
the exo-attack is sterically feasible. The difference in the
reaction rates of 28 vs 29 is merely indicative of an easier
ionization of 28 (as compared to 29), presumably due to
the better alignment of the C-OAc σ*-orbital with the
π-system of the CdC bond. This behavior is inconsistent
with the template-directed reaction pathway (Scheme 1)
and suggests an ionic, SN1-like mechanism, which is
further supported by complete racemization of (R)-(+)-
23 with both C- and O-nucleophiles (Scheme 14). In this
respect, the reactivity of catalysts 7-9 parallels that of
LiClO4 (at high concentrations),34 LiCo(B9C2H11)2 (lithium
cobalt bis(dicarbollide)),35 trityl perchlorate,36 and other
Lewis acids.37
In such an ionic mechanism, the corresponding cata-
lytic cycle (Scheme 15) can be assumed to involve
dissociation of [M]L to generate its coordinatively unsat-
urated, Lewis-acidic38 form [M],39 followed by ionization
of the allylic substrate, generating allylic cation and
AcO-[M]- (step a); the allylic species should then react
with silyl enol ether to give the final product (step b).
The Me3Si group is likely to be trapped by the AcO-
released from the complex, thereby regenerating the
(33) Initial experiments actually suggested retention of configuration
since (R)-(+)-23 produced (R)-(+)-45 of g95% ee, as revealed by
comparing the optical rotation of the latter product ([R]D +36.5) with
that of the compound obtained via methylation (Me2SO4, K2CO3, Me2-
CO, room temperature, 6 h) of the enantiomerically pure4b (R)-(+)-4-
phenyl-but-3-en-2-ol ([R]D +36.9; g99% ee). However, this result could
not be reproduced later. Painstaking analysis revealed that one batch
of the starting ennatiomerically pure alcohol, used for the preparation
of acetate (R)-(+)-23, was contaminated by ca. 5% of diisopropyl
tartrate, originating from the Sharpless epoxidation (in kinetic resolu-
tion mode). Apparently, the tartrate, still present in the Mo(II)-
catalyzed reaction, was the source of this error.
(34) (a) Pearson, W. H.; Schkeryantz, J . M. J . Org. Chem. 1992, 57,
2986. (b) Grieco, P. A.; Collins, J . L.; Henry, K. J ., J r. Tetrahedron
Lett. 1992, 33, 4735. (c) Henry, K. J .; Grieco, P. A. J . Chem. Soc., Chem.
Commun. 1993, 510. (d) Smith, C. C.; Rothhaar, R. R.; Thobe, K. J .;
Crago, C. M.; Pekelnicky, P. Microchem. J . 1997, 56, 65.
(35) Grieco, P. A.; DuBay, W. J .; Todd, L. J . Tetrahedron Lett. 1996,
37, 8707.
(36) Mukaiyama, T.; Nagaoka, H.; Oshima, M.; Murakami, M. Chem.
Lett. 1986, 1009.
(37) Yokozawa, T.; Furuhashi, K.; Natsume, H. Tetrahedron Lett.
1995, 36, 5243.
(38) For other examples of Lewis-acidic transition metal complexes,
see, e.g.: Hollis, K.; Odenkirk, W.; Robinson, N. P.; Whelan, J .; Bosnich,
B. Tetrahedron 1993, 49, 5415.
(39) Related Mo(II) and W(II) complexes [M(NO)2(MeCN)4](BF4)2
have also been shown to be Lewis-acidic and, as such, to polymerize
and/or rearrange olefins: Sen, A.; Thomas, R. R. Organometallics 1982,
1, 1251.
Con clu sion s
Powerful, Lewis-acidic Mo(II) and W(II) catalysts 7-9
have been developed to promote C-C bond-forming
allylic substitution under very mild conditions (typically,
at ambient temperature over 1-2 h). Allylic acetates 16-
29 have been found to react with a range of trimethylsilyl
enol ethers, such as those derived from â-dicarbonyls (30
and 31), ketones (32-37), aldehyde (38), and esters (39,
(40) For a recent, detailed discussion of the competing ionic and SET
mechanism in the Mukaiyama-Michael reaction, and its dependence
on the Lewis acid employed and the steric bulk of the reaction partners,
see: Otera, J .; Fujita, Y.; Sakuta, N.; Fujita, M.; Fukuzumi, S. J . Org.
Chem. 1996, 61, 2951.

2746 J . Org. Chem., Vol. 64, No. 8, 1999
Malkov et al.
MgSO4. Petroleum ether refers to the fraction boiling in the
range 40-60 °C. The Mo and W complexes 7a ,b and 11a ,b
were prepared as described in our earlier paper.19 The allylic
acetates 16-29 are known compounds44 and were either
prepared by acetylation of the corresponding allylic alcohols
(Ac2O, Et3N, Et2O, and 4-(dimethylamino)pyridine as catalyst)
or purchased (24, 26); the required allylic alcohols were either
purchased or obtained by reduction of the corresponding
ketones or, as in the case of 22 and 25, by reaction of
crotonaldehyde with the corresponding Grignard reagent. The
enantiomerically pure alcohol (R)-(+)-4-phenylbut-3-en-2-ol,4b
required for the synthesis of (R)-(+)-23, was obtained from the
racemate by Sharpless epoxidation in kinetic resolution mode
and had [R]D +24.5 (c 2.5, CHCl3). Since this sample was of
g99% ee, as revealed by the 1H NMR spectrum recorded in
the presence of Eu(tfc)34b and by chromatography on Chiralcel
OD-H with a 9:1 hexane-2-propanol mixture (retention times
for the racemate: tR ) 15.2 min, tS ) 21.4 min; flow rate 0.5
mL/min), we conclude that the latter optical rotation repre-
sents the maximum, which is in agreement with an early
report;45a another value, reported in the literature,45b namely
[R]D +34.9 (c 5.78, CHCl3), seems to be too high. The silyl enol
40); the amide-derived nucleophiles (41, 42) and the Li
and Na enolates proved inert. Methanol, as a prototype
oxygen nucleophile, reacts in a fashion similar to give
the corresponding methoxy derivatives. Both these C-C
and C-O bond-forming reactions are believed to occur
as Lewis acid-catalyzed (rather than metal template-
directed41,42) processes, which can be stereoselective if
carried out with stereochemically biased allylic sub-
strates (e.g., 25-29); on the other hand, racemization was
observed with (R)-(+)-23. The catalytic cycle is sum-
marized in Scheme 15. In the case of sterically hindered
silyl enol ethers as nucleophiles, participation of a single
electron-transfer pathway has been proposed as a com-
peting process. Since these experiments reveal the Lewis
acidic character of 7-9, application of these complexes
in the reactions prone to Lewis acid catalysis can be
envisaged. To date, preliminary experiements, carried out
in this laboratory in the areas of Diels-Alder and ene
reactions, Michael addition, and aromatic electrophilic
substitution, are particularly promising and will be
reported in due course.43
(45) (a) Kenyon, J .; Partridge, S. M.; Philips, H. J . Chem. Soc. 1936,
85. (b) Goering, H. L.; Kantner, S. S.; Tseng, C. C. J . Org. Chem. 1983,
48, 715.
Exp er im en ta l Section
(46) General references for the silyl enol ether formation (including
32, 35, 39, and 40) include ref 21a and the following: (a) Rathke, M.
W.; Sullivan, D. F. Synth. Commun. 1973, 3, 67. 33: (b) Hnach, M.;
Aycard, J . P.; Zineddine, H. Bull. Soc. Chim. Fr. 1991, 3, 393. 34: (c)
Hans Reich, J .; Carl, A.; Willis, W. W. Tetrahedron 1985, 41, 4771. (d)
Tirpak, R. E.; Rathke, M. W. J . Org. Chem. 1987, 52, 1907. 41: (e)
Woodbury, R. P.; Rathke, M. W. J . Org. Chem. 1978, 43, 881. 42: (f)
McDaniel, R. S.; Peace, B. W.; Wulfman, D. S. Tetrahedron 1976, 32,
1241, 1251, and 1257. For the E/ Z geometry, see: (g) Ireland, R. E.;
Mueller, R. H.; Willard, A. K. J . Am. Chem. Soc. 1976, 98, 2868. (h)
Evans, D. A. Stereoselective Alkylation Reactions of Chiral Metal
Enolates. In Asymmetric Synthesis; Morrison, J . D., Ed.; Academic:
New York, 1984; Vol. 3, p 1.
(47) Methoxy derivatives references are as follows. 43: ref 26 and
(a) House, H. O.; Kniloch, E. F. J . Org. Chem. 1974, 39, 1173. (b)
Hutchins, R. O.; Kanasamy, D. J . Org. Chem. 1975, 40, 2530. (c)
Grandi, R.; Marchesini, A.; Pagnoni, U. M.; Trave, R. J . Org. Chem.
1976, 41, 1755. 44: ref 26 and (d) Zon, G.; Paquette, L. A. J . Am. Chem.
Soc. 1984, 96, 215. (e) Zon, G.; Paquette, L. A. J . Am. Chem. Soc. 1974,
96, 215. (f) Chow, H.-F.; Fleming, I. J . Chem. Soc., Perkin Trans. 1
1984, 1815. (g) Crabtree, R. H.; Davis, M. W. J . Org. Chem. 1986, 51,
2655. 45: (h) Baldry, P. J . J . Chem. Soc., Perkin Trans. 2. 1980, 809.
88 and 89: ref 44i and (i) Henbest, H. B.; Eilson, R. A. L. J . Chem.
Soc. 1957, 1958. (j) Pusset, J .; Beugelmans, R. Tetrahedron 1976, 32,
797. 92: ref 26a and (k) Wu, C.; Bartlett, P. D. J . Org. Chem. 1985,
50, 733.
(48) References for products of the C-C bond formation are the
following. 47: ref 46f. 49: (a) Laidig, G. J .; Hegedus, L. S. Synthesis
1995, 527. (b) Schaefer, J .; Al Azraka, H. Chem. Ber. 1972, 105, 2398.
52: (c) Zhdankin, V. V.; Tykwinski, R.; Caple, R. Tetrahedron. Lett.
1988, 29, 3703. (d) Zhdankin V. V.; Tykwinski, R.; Caple, R.; Mullilin,
M.; Berglund, B. J . Org. Chem. 1989, 54, 2605. (e) Snowden, R. L.,
Schulte-Elte, K.-H. Helv. Chim. Acta 1981, 64, 2193. 58: (f) Morton,
G. O.; Van Lear, G. E.; Fulmor, W. J . Am. Chem. Soc. 1972, 92, 5852.
(g) Morton, G. O.; Van Lear, G. E.; Fulmor, W. J . Am. Chem. Soc. 1970,
92, 2590. (h) Padwa, A.; Eisenberg, W. J . Am. Chem. Soc. 1972, 94,
2590 and 5852. 59: (i) Cagniant, Buu-Hoi; C. R. Hebd. Seances Acad.
Sci. 1943, 217, 26. 64: (j) Burgstahler, A. W.; Nordin, I. C. J . Am.
Chem. Soc. 1961, 83, 198. (k) Grieco, P. A.; Clark, J . D.; J agoe, C. T.
J . Am. Chem. Soc. 1991, 113, 5488 and references therein. 66: refs
48d,e. 67: ref 48f. 72: (l) Barabarich, T. J .; Handy, S. T.; Miller, S.
M.; Anderson, O. P.; Grieco, P. A.; Strauss, S. H.; Organometallics 1996,
15, 3776. (m) Grieco, P. A.; DuBay, W. J .; Todd, L. J .; Tetrahedron
Lett. 1996, 37, 8707. 73: ref 48l. 74: (n) Beereboom, J . J . J . Org. Chem.
1965, 30, 4230. (o) Erman, W. F.; Wenkert, E.; J effs, P. W. J . Org.
Chem. 1969, 34, 2196. (p) Stevens, R. V.; Fitzpatrick, J . M.; Germeraad,
P. B.; Harrison, B. L.; Lapalme, R. J . Am. Chem. Soc 1976, 98, 6313.
75: (q) Patel, S. K.; Paterson, I. Tetrahedron Lett. 1983, 24, 1315. (r)
Stevens, R. V.; Fitzpatrick, J . M.; Germeraad, P. B.; Harrison, B. L.;
Lapalme, R. J . Am. Chem. Soc. 1976, 98, 8, 6313. 76 and 77: (s)
Hayashi, T.; Yamamoto, A.; Hagihara, T. J . Org. Chem. 1986, 51, 723.
78: ref 36. 80: (t) Itoh, I.; Hamaguchi, N.; Miura, M.; Nomura, M.; J .
Chem. Soc., Chem. Perkin Trans. 1 1992, 2833. (u) Ishikawa, N.;
Tokuda, M.; Miyamoto, T.; Fujita, H.; Suginome, H. Tetrahedron 1991,
47, 747. (v) Mukaiyama, T.; Suzuki, K.; Yamada, T.; Tabusa, F.
Tetrahedron 1990, 46, 265. (w) Kubota, T.; Miyashita, S.; Kitazume,
T. J . Org. Chem. 1980, 45, 5052. 81: ref 48r. 83: (x) Takeda, T.; Torii,
K.; Ogura, H. Tetrahedron Lett. 1990, 31, 265. 87: ref 36.
Gen er a l Meth od s. The NMR spectra were recorded in
1
CDCl3, H at 250 MHz and 13C at 62.9 MHz with chloroform-
d1 (δ 7.26, 1H; δ 77.0, 13C) as internal standard; “a” and “b”
are used to distinguish between the two diastereotopic protons.
Various 2D-techniques and DEPT experiments were used to
establish the structures and to assign the signals. The IR
spectra were recorded for a thin film between KBr plates or
using the “golden-gate” technique. The mass spectra (EI and/
or CI) were measured on a dual sector mass spectrometer using
direct inlet and the lowest temperature enabling evaporation.
The GC-MS analysis was performed with RSL-150 column (25
m
× 0.25 mm). All reactions were performed under an
atmosphere of dry, oxygen-free nitrogen in oven-dried glass-
ware twice evacuated and filled with the nitrogen. Solvents
and solutions were transferred by syringe-septum and can-
nula techniques. All solvents for the reactions were of reagent
grade and were dried and distilled immediately before use as
follows: diethyl ether from lithium aluminum hydride; tet-
rahydrofuran (THF) from sodium/benzophenone; dichloro-
methane from calcium hydride. Standard workup of an
ethereal solution means washing 3 × with 5% HCl (aqueous),
water, and 3× with 5% KHCO3 (aqueous) and drying with
(41) For the Mo- and W-template-controlled allylic substitution, see
refs 8-13. For the formation of a stable π-allyl complex on reaction of
allyl chloride with 11a ,b, see: Hull, C. G.; Stiddard, M. H. B. J .
Organomet. Chem. 1967, 9, 519.
(42) For related Fe-template-controlled reactions, see, e.g.: (a) Xu,
Y.; Zhou, B. J . Org. Chem. 1987, 52, 974. (b) Zhou, B.; Xu, Y. J . Org.
Chem. 1988, 53, 4419. (d) Li, Z.; Nicholas, K. M. J . Organomet. Chem.
1991, 402, 105. (c) Green, J .; Carrol, M. K. Tetrahedron Lett. 1991,
32, 1141. (d) J ohannsen, M.; J o¨rgensen, K.-A. J . Org. Chem. 1994, 59,
214. (e) Enders, D.; J andeleit, B.; Raabe, G. Angew. Chem., Int. Ed.
Engl. 1994, 33, 1949.
(43) For catalytic activity of 8 in the Friedel-Crafts-type allylation
of electron rich aromatics, and in the carbonyl ene-type cyclizations,
see: (a) Malkov, A. V.; Davis, S. L.; Baxendale, I. B.; Mitchell, W. L.;
Kocˇovsky´, P. J . Org. Chem. 1999, 64, 2751-2764. (b) Kocˇovsky´, P.;
Ahmed, G.; Sˇrogl, J .; Malkov, A. V.; Steele, J . J . Org. Chem. 1999, 64,
2765-2775.
(44) Allylic acetates references, as follows: 16: (a) Lessard, J .; Tan,
P. V. M.; Martino, R.; Sanders, J . K. Can. J . Chem. 1977, 55, 1015.
17: (b) Ishida, T.; Asakawa, Y.; Okano, M.; Aratani, T. Tetrahedron
Lett. 1977, 18, 2437. 18: (c) Mandrou, A.-M.; Potin, P.; Wylde-
Lanchazette, R. Bull. Chim. Soc. France 1962, 1546. 19: ref 44a. 20:
(d) Masatoshi, A. Bull. Chem. Soc. J pn. 1990, 63, 721. (e) Shono, T.;
Ikeda, A.; J . Am. Chem. Soc. 1972, 94, 7892. 21: (f) Hansson, S.;
Heumann, A.; Rein, T.; Åkermark, B. J . Org. Chem. 1990, 55, 975. 22
and 23: (g) Goering, H. L.; Seits, E. P., J r.; Tseng, C.-C. J . Org. Chem.
1981, 46, 5304. 25: (h) Grummitt, O.; Splitter, J . J . Am. Chem. Soc.
1952, 74, 3924. 27: (i) Shopee, C. W.; Agashe, B. D.; Summers, G. H.
R. J . Chem. Soc. 1957, 3107. 28 and 29: ref 31.

Mo(II)- and W(II)-Catalyzed Allylic Substitution
J . Org. Chem., Vol. 64, No. 8, 1999 2747
ether reagents 31 and 36-38 were purchased from commercial
suppliers and used without further purification; others were
prepared from the corresponding ketone by means of LDA
deprotonation (THF, -78 °C) followed by quenching with Me3-
SiCl;46 for details, see the Supporting Information. Some of
the products, resulting from the allylic substitution, are known
compounds.36,47,48 Yields are given for isolated product showing
one spot on a TLC plate and no impurities detectable in the
NMR spectrum. The identity of the products prepared by
different methods was checked by comparison of their NMR,
IR, and MS data and by the TLC behavior.
Dibr om om olybd en u m Tetr a ca r bon yl Dim er (8a ). A
solution of bromine (1.36 g; 8.5 mmol) in dichloromethane (10
mL) was added to a suspension of the finely ground molyb-
denum hexacarbonyl (2.24 g; 8.5 mmol) in deoxygenated
dichloromethane (60 mL) at -78 °C; the mixture gradually
evolved carbon monoxide, and the solid dissolved. The solution
was maintained at -78 °C for 1 h, and the solvent was then
evaporated under reduced pressure at -78 °C to yield 8a as
an orange, crystalline solid (3.03 g; 97%). Pure product,
obtained by recrystallization from MeCN which could be stored
in a freezer under nitrogen for several months: IR (CH2Cl2)
ν(CtO) 2100 (s), 2020 (m), 1980 (m), 1960 (m) cm-1 in
accordance with the literature.20
Dibr om otu n gsten Tetr a ca r bon yl Dim er (8b). A solution
of bromine (1.36 g; 8.5 mmol) in dichloromethane (10 mL) was
added to a stirred suspension of the finely ground tungsten
hexacarbonyl (3.0 g; 8.5 mmol) in deoxygenated dichlo-
romethane (60 mL) at -78 °C; the mixture gradually evolved
carbon monoxide, and the solid dissolved. After 1 h at -78
°C, the solution was allowed to warm slowly with stirring to
room temperature to give a dark orange solution, which was
concentrated to ca. 5 mL by evaporating under reduced
pressure at -78 °C to afford an orange/brown, crystalline
precipitate. The resulting green supernatant liquid was re-
moved via cannula, and the precipitate was washed with dry
hexane (20 mL). The residue was dried in a vacuum to furnish
8b (2.41 g; 62%), which could be stored in a freezer under
nitrogen for several months: IR (CH2Cl2) ν(CtO) 2100 (s), 2020
(m), 1975 (m), 1940 (w) cm-1 in accordance with the litera-
ture.20 A more stable and active complex was obtained by
adopting the procedure described for 8a (namely evaporation
at low temperature).
(5 mol %) was added to a solution of the allylic substrate (1
mmol) and the silyl enol ether (1.1-1.4 mmol) or methanol (2
mmol) in dichloromethane (10 mL). The mixture was stirred
at room temperature or at -5 °C until the TLC analysis
indicated disappearance of the starting material or until no
further reaction was observed after 24 h. Aqueous saturated
hydrogen carbonate (15 mL) was then added, and the mixture
was stirred for 15 min, then extracted with ether (2 × 15 mL),
and dried (MgSO4). The solvent was evaporated and the crude
brown residue was purified by flash chromatography on a
column of silica gel. Alternatively, acetic acid (0.5 mL) was
added to the reaction mixture and stirred for 10 min; the
mixture was then diluted with ether and adsorbed on silica
gel (1.5 g), followed by flash chromatography. For details and
the yields see below and Tables 1-6.
1-Meth oxy-3,5,5-tr im eth yl-2-cycloh exen e (43): 1H NMR
δ 5.48 (1 H, br s, 2-H), 3.80 (1 H, m, 1-H), 3.36 (3 H, s, MeO),
1.69 (3 H, s, 3-Me), 0.99 (3 H, s, 5-Me), 0.89 (3 H, s, 5-Me), in
accordance with the literature.26,47a-c
1-Meth oxy-3-m eth yl-2-cycloh exen e (44): 1H NMR δ 5.54
(1 H, br s, 2-H), 3.72 (1 H, m, 1-H), 3.36 (3 H, s, MeO), 1.69 (3
H, s, 3-Me), in accordance with the literature.26,47a-c
(E)-3-Meth oxy-1-p h en yl-1-bu ten e (45): 1H NMR δ 7.15
(m, 5 H, arom), 6.35 (1 H, d, J ) 15 Hz, PhCHdC), 5.92 (1 H,
dd, J ) 15.0 and 7.5 Hz, HCdCHPh), 3.72 (1 H, d, J ) 3.8 Hz,
CHOCH3), 3.18 (3 H, s, OCH3), 1.20 (3 H, d, J ) 3.8 Hz, Me);
13C NMR δ 136.5 (s), 131.3 (d), 131.2 (d), 128.1 (2 × d), 127.8
(d), 126.3 (2 × d), 77.9 (d), 55.9 (q), 21.3 (q); MS (EI) m/z (%)
162 (74, M•+), 147 (100), in accordance with the literature.47h
Dim eth yl (3,5,5-Tr im eth yl-2-cycloh exen -1-yl)m a lon a te
(46): 1H NMR δ 5.10 (1 H, s, 2-H), 3.69 (3 H, s, OMe), 3.67 (3
H, s, OMe), 3.13 (1 H, d, J ) 9.4 Hz, CH(CO2Me)2), 2.87 (1 H,
m, 1-H), 1.78 (1 H, m, 6-Ha), 1.57 (3 H, s, 3-Me), 1.50 (1 H, m,
6-Hb), 1.27 (2 H, m, CH2), 0.88 (3 H, s, 5-Me), 0.81 (3 H, s,
5-Me); 13C NMR δ 168.7 (s), 168.7 (s), 135.2 (s), 119.8 (d), 56.9
(d), 52.1 (2 × q), 43.8 (t), 39.4 (t), 34.4 (d), 31.6 (q), 29.7 (s),
24.9 (q), 23.7 (q); IR (neat) ν 1758, 1735; MS (EI) m/z (%) 254
(45, M•+), 179 (100).
Dim eth yl (3-Meth yl-2-cycloh exen -1-yl)m a lon a te (47):
1H NMR δ 5.15 (1 H, s, 2-H), 3.68 (3 H, s, OMe), 3.66 (3 H, s,
OMe), 3.17 (1 H, d, J ) 10.1 Hz, CH(CO2Me)2), 2.80 (1 H, m,
1-H), 1.82 (2 H, m, CH2), 1.65 (3 H, m, CH2 and 6-Ha), 1.57 (3
H, s, 3-Me), 1.46 (1 H, m, 6-Hb); 13C NMR δ 168.7 (s), 168.7
(s), 136.6 (s), 121.3 (d), 56.9 (d), 52.1 (2 × q), 35.5 (d), 29.7 (t),
26.2 (t), 23.7 (q), 21.0 (t); IR (neat) ν 1735, 1709 cm-1; MS (EI)
m/z (%) 226 (3, M•+), 95 (100), in accordance with the
literature.46f
Meth yl 1-(3′-Meth yl-2′-cycloh exen -1′-yl)-3-oxobu tan oate
(48). Obtained as a 1:1 mixture of diastereoisomers: 1H NMR
δ 4.98 and 4.90 (1 H, s, CdCH), 3.50 and 3.49 (6 H, 2 × s,
OMe), 3.15 and 3.10 (1 H, s, CHCO2Me), 2.68 (1 H, m, CHCd
C), 2.12 and 2.11 (3 H, s, CH3CO), 1.75 (2 H, m, CH2), 1.45 (2
H, m, CH2), 1.40 (3 H, s, 3′-Me), 1.33 (1 H, m, 6′-Ha), 0.96 (1
H, m, 6′-Hb); 13C NMR δ 203.0 (s) and 202.8 (s), 168.3 (s) and
168.3 (s), 137.1 (s) and 136.8 (s), 121.4 and 121.0, 65.4 and
65.3, 52.1 (2×), 35.5 and 35.4, 29.7 and 29.7 (t), 29.6 and 29.5,
26.3 (t) and 26.2 (t), 23.8, 21.5 (t); IR (neat) ν 1730 cm-1; MS
(EI) m/z (%) 210 (4, M•+), 143 (100).
Bis(a ceton itr ile)tr ica r bon ylch lor o(tr ich lor osta n n yl)-
m olybd en u m (9a ). A nitrogen-purged mixture of molybde-
num hexacarbonyl (4.0 g; 15.4 mmol) and dry degassed
acetonitrile (120 mL) was heated under reflux for 24 h to give
a yellow/light brown solution. The solution was cooled to room
temperature, tin(IV) chloride (3.18 g; 15.4 mmol) was added,
the mixture was stirred for 10 min, and the solvent was
removed in a vacuum to give a dark red solid. The latter solid
was redissolved in dry acetonitrile (30 mL) and filtered through
a sintered glass filter, which removed a black tar residue and
gave an orange-red filtrate. Removal of the solvent by evapo-
ration under reduced pressure at <40 °C gave 9a as a red/
orange solid (6.39 g; 79%): IR (CH2Cl2) ν(CtO) 2027 (s), 1990
(s), 1953 (m), 1915 (w), ν(CtN) 2320 (w), 2285 (w) cm-1; IR
(Nujol) ν(CtO) 2030 (m), 1955 (m), 1920 (br), ν(CtN) 2310
(w), 2295 (w) cm-1 in accordance with the literature.21
Gen er a l P r oced u r e A for th e Allylic Su bstitu tion
Rea ction s Ca ta lyzed by Com p lexes 7a ,b. To a stirred
solution of the allylic substrate (1 mmol) and the silyl enol
ether (1.4 mmol) or methanol (2 mmol) in CH2Cl2 (10 mL) at
room temperature was added PhCH2(Et)3N+[M(CO)5Cl]- (M
) Mo or W; 0.05 mmol) in one portion, followed by a solution
of AgOTf (0.15 mmol) in DME (2 mL). The mixture was stirred
under nitrogen at room temperature for 4 h and then diluted
with ether (20 mL), and the ethereal solution was washed
successively with 5% aqueous NaHCO3 and water and dried
with MgSO4. The solvent was evaporated under reduced
pressure to give a crude product, which was purified by flash
chromatography on a silica gel column. For details and the
yields see below and Tables 1-6.
Dim eth yl (2-Cycloh exen -1-yl)m a lon a te (49): 1H NMR
δ 5.76 (1 H, ddd, J ) 10.1, 5.7, 3.5 Hz, 3-H), 5.52 (1 H, br d, J
) 10.1 Hz, 2-H), 3.73 (3 H, s, OMe), 3.72 (3 H, s, OMe), 3.28
(1 H, dd, J ) 9.4, 2.5 Hz, CH(CO2Me)2), 2.90 (1 H, m, 1-H),
1.98 (2 H, m, 4-CH2), 1.70 (2 H, m, CH2), 1.30 (2 H, m, CH2);
13C NMR δ 168.6 (2 × s), 129.3 (d), 127.2 (d), 56.6 (d), 52.0 (2
× q), 35.2 (d), 26.4 (t), 24.7 (t), 20.7 (t); IR (neat) ν 1728 cm-1
accordance with the literature.48a,b
;
MS (EI) m/z (%) 212 (12, M•+), 152 (100, M+ - HCO2Me), in
2-(3′,5′,5′-Tr im eth yl-2′-cycloh exen -1′-yl)-1-oxo-1-p h en -
1
yleth a n e (50): H NMR δ 7.89 (2 H, m, arom), 7.30-7.48 (3
H, m, arom), 5.13 (1 H, s, 2′-H), 2.66 (2 H, m, CH2CO), 2.73 (1
H, m, 1′-H), 1.75 (1 H, br d, J ) 16.9 Hz, 6′-Ha), 1.55 (3 H, s,
3′-Me), 1.45 (1 H, br d, J ) 16.9 Hz, 6′-Hb), 0.90 (2 H, m, CH2),
0.88 (3 H, s, 5′-Me), 0.80 (3 H, s, 5′-Me); 13C NMR δ 199.8 (s),
137.4 (s), 133.7 (s), 132.9 (d), 128.5 (d), 128.1 (2 × d), 123.3 (2
× d), 45.2 (t), 44.1 (t), 42.6 (t), 31.8 (d), 30.4 (t), 30.0 (s), 25.3
Gen er a l P r oced u r e A for th e Allylic Su bstitu tion
Rea ction s Ca ta lyzed by Com p lexes 8a ,b a n d 9a . Catalyst

2748 J . Org. Chem., Vol. 64, No. 8, 1999
Malkov et al.
(q), 23.9 (q); IR (neat) ν 1670 cm-1; MS (EI) m/z (%) 242 (7,
M•+), 105 (100).
1′-H), 3.02 (1 H, dd, J ) 16.4, 6.6 Hz, Ha of CH2CO), 2.91 (1
H, dd, J ) 16.4, 7.9 Hz, Hb of CH2CO), 2.25 (2 H, m, CH2),
2.22 (1 H, m, 5′-Ha), 1.79 (3 H, s, 3′-Me), 1.50 (1 H, m, 5′-Hb);
13C NMR δ 199.7 (s), 140.8 (s), 137.1 (s), 132.6 (d), 128.1 (d),
127.9 (d), 127.8 (d), 44.9 (t), 41.5 (d), 36.0 (t), 31.0 (t), 16.4 (q);
IR (neat) ν 1715 cm-1; MS (EI) m/z (%) 200 (20, M•+), 80 (100).
2-(2′-Cyclop en ten -1′-yl)-1-oxo-1-p h en yleth a n e (58): 1H
NMR δ 7.94 (2 H, m, arom), 7.49 (3 H, m, arom), 5.76 (2 H, m,
HCdCH), 3.31 (1 H, m, 1′-H), 3.09 (1 H, dd, J ) 16.4, 6.7 Hz,
Ha of CH2CO), 2.97 (1 H, dd, J ) 16.4, 7.9 Hz, Hb of CH2CO),
2.40 (2 H, m, CH2), 2.21 (1 H, m, 5′-Ha), 1.45 (1 H, m, 5′-Hb);
13C NMR δ 199.6 (s), 137.1 (s), 134.1 (d), 132.4 (d), 131.1 (d),
128.4 (d), 128.0 (d), 44.7 (t), 47.3 (d), 31.7 (t), 29.9 (t); IR (neat)
ν 1682 cm-1; MS (EI) m/z (%) 186 (16, M•+), 105 (100), in
accordance with the literature.48f-l
2-(3′-Me t h y l-2′-c y c lo h e x e n -1′-y l)-1-o x o -1-p h e n y l-
eth a n e (51): 1H NMR δ 7.96 (2 H, m, arom), 7.55-7.40 (3 H,
m, arom), 5.30 (1 H, d, J ) 2.5 Hz, 2′-H), 2.89 (2 H, d, J ) 7.5
Hz, CH2COPh), 2.83-2.70 (1 H, m, 1′-H), 1.76 (2 H, m, CH2),
1.65 (3H, s, 3′-Me), 1.54 (2 H, m, CH2), 1.16 (2 H, m, CH2); 13
C
NMR δ 199.5 (s), 137.1 (s), 134.8 (s), 132.7 (d), 128.7 (2 × d),
128.1 (2 × d), 124.7 (d), 44.9 (t), 31.7 (d), 29.8 (t), 28.7 (t), 23.7
(q), 21.3 (t); IR (neat) ν 1680 cm-1; MS (EI) m/z (%) 214 (6,
M•+), 77 (100).
2-(2′-Cycloh exen -1′-yl)-1-oxo-1-p h en yleth a n e (52): 1H
NMR δ 7.95 (2 H, m, arom), 7.58-7.40 (3 H, m, arom), 5.72 (1
H, m, J ) 10.1, 3.5 Hz, 3′-H), 5.58 (1 H, dd, J ) 10.1 and 1.9
Hz, 2′-H), 2.94 (2 H, m, CH2CO), 2.81 (1 H, m, 1′-H), 1.99 (2
H, m, CH2), 1.86 (1 H, m, 6′-Ha), 1.78-1.48 (2 H, m, CH2), 1.30
(1 H, m, 6′-Hb); 13C NMR 199.6 (s), 137.4 (s), 132.9 (d), 130.8
(d), 128.6 (2 × d), 128.1 (2 × d), 127.9 (d), 44.8 (t), 31.6 (d),
29.1 (t), 25.1 (t), 21.1 (t); IR (neat) ν 1676 cm-1; MS (EI) m/z
(%) 200 (28, M•+), 105 (100, PhCO), in accordance with the
literature.48c-e
2-(2′-Cyclopen ten -1′-yl)-1-oxo-1-ph en ylpr opan e (59). Ob-
1
tained as a 1:1 mixture of diastereoisomers: H NMR δ 7.95
(4 H, m, arom), 7.69-7.40 (6 H, m, arom), 5.85-5.70 (3 H, m,
HCdCH), 5.55 (1 H, m, CHdC), 3.43 and 3.42 (1 H, m,
CHCH3), 3.14 and 3.13 (1 H, m, 1′-H), 2.31 and 2.30 (2 H, m,
4′-CH2), 2.02 (1 H, m, 5′-Ha for diastereoisomer A), 1.97 (1 H,
m, 5′-Hb for diastereoisomer A), 1.60 (1 H, m, 5′-Ha for
diastereoisomer B), 1.45 (1 H, m, 5′-Hb for diastereoisomer B),
1.19 and 1.15 (3 H, d, J ) 7.2 Hz, CH3CH); 13C NMR δ 204.2
(s), 204.1 (s), 136.9 (2 × s), 133.0 (d), 132.7 (2 × d), 132.2 (d),
131.9 (d), 131.5 (d), 128.5 (2 × d), 128.2 (2 × d), 48.7 (d), 48.2
(d), 45.5 (d), 45.2 (d), 32.0 (2 × t), 28.6 (t), 26.4 (t), 15.2 (q),
14.7 (q); IR (neat) ν 1678 cm-1; MS (EI) m/z (%) 200 (8, M•+),
105 (100).
2-(3′-Met h yl-2′-cycloh exen -1′-yl)-1-oxo-1-p h en ylp r o-
p a n e (53). Obtained as a 1.7:1 mixture of diastereoisomers:
1H NMR (diastereoisomer A): δ 7.93 (2 H, m, arom), 7.48 (3
H, m, arom), 5.34 (1 H, s, 2′-H), 3.41 (1 H, m, CHCO), 2.63 (1
H, m, 1′-H), 1.95 (2 H, m, CH2), 1.93 (1 H, m, 6′-Ha), 1.79 (3
H, s, 3′-Me), 1.63 (1 H, m, 6′-Hb), 1.48 (2 H, m, CH2), 1.28 (3
1
H, d, J ) 6.9 Hz, 2-Me); H NMR (diastereoisomer B) δ 7.93
(2 H, m, arom), 7.48 (3 H, m, arom), 5.17 (1 H, s, 2′-H), 3.41 (1
H, m, CHCO), 2.63 (1 H, m, 1′-H), 1.95 (2 H, m, CH2), 1.93 (1
H, m, 6′-Ha), 1.72 (3 H, s, 3′-Me) 1.61 (1 H, m, 6′-Hb), 1.48 (2
H, m, CH2), 1.23 (3 H, d, J ) 6.9 Hz, 2-Me); 13C NMR δ 204.4
(s), 204.3 (s), 137.1 (s), 137.0 (s), 136.0 (s), 135.4 (s), 132.7 (2
× d), 128.5 (2 × d), 128.2 (d), 128.1 (d), 124.3 (d), 121.9 (d),
45.5, 44.9, 38.3, 38.2, 29.9 (2 × t), 27.6 (t), 24.8 (t), 24.0, 23.8
(q), 21.9 (2 × q), 13.9 (q), 13.5 (q); IR (neat) ν 1674 cm-1; MS
(EI) m/z (%) 228 (22, M•+), 95 (100).
2-(3′,5′,5′-Tr im eth yl-2′-cycloh exen -1′-yl)-1-cycloh exyl-
1-oxoeth a n e (60): 1H NMR δ 5.01 (1 H, s, 2′-H), 2.52 (1 H,
m, 1′-H), 2.23 (3 H, m, CH2CO, 1-H-cyclo), 1.80-1.52 (6 H, m,
3 × CH2), 1.51 (3 H, s, 3′-Me), 1.46-1.00 (8 H, m, 4 × CH2),
0.83 (3 H, s, 5′-Me), 0.75 (3 H, s, 5′-Me); 13C NMR δ 213.5 (s),
133.4 (s), 123.5 (d), 51.2 (d), 47.4 (t), 44.1 (t), 42.5 (t), 31.8 (d),
29.9 (s), 29.7, 27.9 (2 × t), 26.0 (t), 25.9 (2 × t), 25.7 (q), 25.3
(q); IR (neat) ν 1705 cm-1; MS (EI) m/z (%) 248 (15, M•+), 165
(100).
1-(3′,5′,5′-Tr im et h yl-2′-cycloh exen -1′-yl)p r op a n -2-on e
(61): 1H NMR δ 5.15 (1 H, br s, 2′-H), 2.63 (1 H, m, 1′-H),
2.41 (1 H, m, Ha of CH2CO), 2.31 (1 H, m, Hb of CH2CO), 2.14
(3 H, d, J ) 1.9 Hz, CH3CO), 1.79 (1 H, br d, J ) 17.3 Hz,
6′-Ha), 1.62 (3 H, s, 3′-Me), 1.54 (1 H, br d, J ) 17.3 Hz, 6′-Hb),
1.41 (1 H, m, 4′-Ha), 0.94 (3 H, s, 5′-Me), 0.88 (3 H, s, 5′-Me),
0.87 (1 H, m, 4′-Hb); 13C NMR δ 208.4 (s), 133.7 (s), 129.9 (d),
50.4 (t), 44.0 (t), 42.3 (t), 31.7 (q), 30.4 (q), 29.9 (d), 29.8 (s),
25.2 (q), 23.8 (q); IR (neat) ν 1712 cm-1; MS (EI) m/z (%) 180
(22, M•+), 107 (100).
2-Meth yl-2-(3′,5′,5′-tr im eth yl-2′-cycloh exen -1′-yl)-1-oxo-
1-p h en ylp r op a n e (54): 1H NMR δ 7.66 (2 H, m, arom), 7.40
(3 H, m, arom), 5.21 (1 H, m, 2′-H), 2.86 (1 H, m, 1′-H), 1.80 (1
H, br d, J ) 17.3 Hz, 6′-Ha), 1.64 (3 H, s, 3′-Me), 1.52 (1 H, d,
J ) 17.3 Hz, 6′-Hb), 1.30 (3 H, s, 2-Me), 1.18 (3 H, s, 2-Me),
1.05 (2 H, m, CH2), 0.93 (3 H, s, 5′-Me), 0.80 (3 H, s, 5′-Me);
13C NMR δ 209.5 (s), 139.5 (s), 134.8 (s), 130.5 (d), 127.9 (2 ×
d), 127.5 (2 × d), 119.9 (d), 50.5 (s), 44.0 (t), 40.4 (d), 36.8 (t),
32.0 (q), 29.8 (s), 25.1 (q), 24.1 (q), 22.8 (q), 22.3 (q); IR (neat)
ν 1670 cm-1; MS (EI) m/z 270 (3, M•+), 123 (100).
2-Meth yl-2-(3′-m eth yl-2′-cycloh exen -1′-yl)-1-oxo-1-ph en -
ylp r op a n e (55): 1H NMR δ 7.66 (2 H, d, J ) 1.6 Hz, arom),
7.39 (3 H, m, arom), 5.20 (1 H, d, J ) 1.0 Hz, 2′-H), 2.82 (1 H,
m, 1′-H), 1.84 (2 H, m, CH2), 1.75 (1 H, m, 6′-Ha), 1.64 (3 H, s,
3′-Me), 1.45 (1 H, m, 6′-Hb), 1.25 (3 H, s, 2-Me), 1.21 (3 H, s,
2-Me), 1.18 (2 H, m, CH2); 13C NMR δ 209.7 (s), 139.6 (s), 136.3
(s), 130.6 (d), 128.0 (2 × d), 127.6 (2 × d), 121.7 (d), 51.0 (s),
42.6 (d), 30.0 (t), 24.1 (q), 23.9 (t), 22.7 (t), 22.6 (q), 22.4 (q);
IR (neat) ν 1726 cm-1; MS (EI) m/z (%) 242 (11, M•+), 95 (100).
2-(3′,5′,5′-Tr im eth yl-2′-cycloh exen -1′-yl)-1-oxo-1-p h en -
ylp r op a n e (56). Obtained as a 15:1 mixture of diastereoiso-
mers: 1H NMR (diastereoisomer A) δ 7.94 (2 H, m, arom), 7.48
(3 H, m, arom), 5.32 (1 H, s, 2′-H), 3.36 (1 H, m, CHCO), 2.58
(1 H, m, 1′-H), 1.79 (1 H, m, 6′-Ha), 1.63 (3 H, s, 3′-Me), 1.51
(1 H, m, 6′-Hb), 1.27 (2 H, m, CH2), 1.17 (3 H, d, J ) 6.9 Hz,
2-Me), 0.90 (3 H, s, 5′-Me), 0.82 (3 H, s, 5′-Me); 1H NMR
(diastereoisomer B) δ 7.94 (2 H, m, arom), 7.48 (3 H, m, arom),
5.11 (1 H, s, 2′-H), 3.36 (1 H, m, CHCO), 2.58 (1 H, m, 1′-H),
1.79 (1 H, m, 6′-Ha), 1.58 (3 H, s, 3′-Me), 1.51 (1 H, m, 6′-Hb),
1.27 (2 H, m, CH2), 1.11 (3 H, d, J ) 6.9 Hz, 2-Me), 0.94 (3 H,
s, 5′-Me), 0.79 (3 H, s, 5′-Me); 13C NMR δ 204.5 (s), 204.2 (s),
137.2 (s), 134.8 (s), 134.2 (s), 132.8, 128.6, 128.3, 128.2, 122.7,
120.2, 45.7 (s), 44.8 (t), 44.2 (t), 44.1 (s), 40.9 (t), 38.3 (t), 36.4,
32.1, 31.9, 30.0, 29.9, 25.2 (2×), 24.1 (q), 23.9, 13.8, 13.7; IR
(neat) ν 1725 cm-1; MS (EI) m/z (%) 256 (13, M•+), 105 (100).
2-(3′-Me t h y l-2′-c y c lo p e n t e n -1′-y l)-1-o x o -1-p h e n y l-
eth a n e (57): 1H NMR δ 7.94 (2 H, m, arom), 7.57-7.38 (3 H,
m, arom), 5.30 (1 H, dq, J ) 1.6, 1.6 Hz, 2′-H), 3.23 (1 H, m,
1-(3′,5′,5′-Tr im eth yl-2′-cycloh exen -1′-yl)-3,3-d im eth yl-
bu ta n -2-on e (62): 1H NMR δ 5.05 (1 H, s, 2′-H), 2.64 (1 H,
m, 1′-H), 2.37 (2 H, d, J ) 12.5 Hz, CH2CO), 1.74 (1 H, m,
6′-Ha), 1.58 (3 H, s, 3′-Me), 1.51 (1 H, m, 6′-Hb), 1.35 (2 H, m,
4′-CH2), 1.09 (9 H, s, t-Bu), 0.90 (3 H, s, 5′-Me), 0.85 (3 H, s,
5′-Me); 13C NMR δ 214.8 (s), 133.2 (s), 123.6 (d), 44.1 (t), 43.9
(s), 43.1 (t), 42.3 (t), 31.8 (d), 29.8 (s), 29.4, 26.2 (3 × q), 25.2
(q), 23.8 (q); IR (neat) ν 1732 cm-1; MS (EI) m/z (%) 222 (9,
M•+), 165 (100).
2-(3′-Met h yl-2′-cycloh exen -1′-yl)-1-cycloh exyl-1-oxo-
eth a n e (63): 1H NMR δ 5.17 (1 H, m, 2′-H), 2.59 (1 H, m,
1′-H), 2.38 (2 H, m, CH2CO), 2.30 (1 H, m, 1-H-cyclo), 1.93-
1.65 (10 H, m, 5 × CH2), 1.65 (3 H, s, 3′-Me), 1.55 (1 H, m,
6′-Ha), 1.40 (4 H, m, 2 × CH2), 1.08 (1 H, m, 6′-Hb); 13C NMR
δ 213.6 (s), 134.8 (s), 125.0 (d), 51.2 (d), 47.3 (t), 31.2 (d), 30.0
(t), 28.4 (t), 28.3 (t), 25.9 (t), 25.7 (t), 23.8 (q), 21.5 (t); IR (neat)
ν 1703 cm-1; MS (EI) m/z (%) 220 (28, M•+), 137 (100).
1-(3′-Meth yl-2′-cycloh exen yl)pr opan -2-on e (64): 1H NMR
δ 5.29 (1 H, br s, 2′-H), 2.59 (1 H, m, 1′-H), 2.38 (2 H, d, J )
6.6 Hz, CH2CO), 2.13 (3 H, s, CH3CO), 1.87 (2 H, m, CH2),
1.71 (2 H, m, CH2), 1.63 (3 H, s, 3′-Me), 1.52 (1 H, m, 6′-Ha),
1.12 (1 H, m, 6′-Hb); 13C NMR δ 208.3 (s), 134.9 (s), 124.4 (d),
50.2 (t), 31.3 (d), 30.2 (q), 29.8 (t), 28.6 (t), 23.6 (q), 21.3 (t); IR
(neat) ν 1709 cm-1; MS (EI) m/z (%) 152 (17, M•+), 94 (100), in
accordance with the literature.48j,k
1-(3′-Meth yl-2′-cycloh exen -1′-yl)-3,3-d im eth ylbu ta n -2-
on e (65): 1H NMR δ 5.18 (1 H, s, 2′-H), 2.63 (1 H, m, 1′-H),

Mo(II)- and W(II)-Catalyzed Allylic Substitution
J . Org. Chem., Vol. 64, No. 8, 1999 2749
2.49 (1 H, m, Ha of CH2CO), 2.37 (1 H, m, Hb of CH2CO), 1.87
(2 H, m, CH2), 1.75 (2 H, m, CH2), 1.69 (1 H, m, 6′-Ha), 1.57 (3
H, s, 3′-Me), 1.50 (1 H, m, 6′-Hb), 1.14 (9 H, s, t-Bu); 13C NMR
δ 215.2 (s), 134.6 (s), 125.2 (d), 44.0 (s), 43.0 (t), 30.9 (d), 30.0
2-Me); 13C NMR δ 178.3 (s), 129.0 (d), 127.6 (d), 51.5 (q), 45.2
(s), 43.0 (d), 25.3 (t), 24.2 (t), 23.0 (t), 22.3 (q), 22.2 (q); IR (neat)
ν 1728 cm-1; MS EI m/z (%) 182 (8, M•+), 102 (100), in
accordance with the literature.48l
Meth yl 2,2-d im eth yl-2-(3′-m eth yl-2′-cyclop en ten -1′-yl)-
a ceta te (74): 1H NMR δ 5.17 (1 H, m, J ) 1.9, 1.6 Hz, 2′-H),
3.65 (3 H, s, OMe), 2.98 (1 H, m, 1′-H), 2.19 (2 H, br t, J ) 6
Hz, 4′-CH2), 1.88 (1 H, m, 5′-Ha), 1.72 (3 H, s, 3′-Me), 1.56 (1
H, m, 5′-Hb), 1.11 (3 H, s, 2-Me), 1.07 (3 H, s, 2-Me′); 13C NMR
δ 178.4 (s), 142.2 (s), 124.7 (d), 53.9, 51.5, 45.4 (s), 36.6 (t),
25.9 (t), 22.6 (q), 21.6 (q), 16.6 (q); IR (neat) ν 1712 cm-1; MS
(EI) m/z (%) 182 (6, M•+), 81 (100), in accordance with the
literature.48m-p
Met h yl 2,2-d im et h yl-2-(2′-cyclop en t en -1′-yl)a cet a t e
(75): 1H NMR δ 5.76 (1 H, m, J ) 5.7, 4.4, 2.5 Hz, 2′-H), 5.55
(1 H, m, J ) 5.7, 2.2, 2.2 Hz, 3′-H), 3.62 (3 H, s, OMe), 2.99 (1
H, m, J ) 2.5, 1.6 Hz, 1′-H), 2.24 (2 H, m, J ) 2.5, 1 Hz, 4′-
CH2), 1.86 (1 H, m, J ) 13.5, 8.5, 6.6 Hz, 5′-Ha), (1 H, m, J )
13.5, 8.5, 6.6 Hz, 5′-Hb), 1.09 (3 H, s, 2-Me), 1.05 (3 H, s, 2-Me);
13C NMR δ 176.2 (s), 132.4 (d), 131.0 (d), 53.7, 51.5, 45.1 (s),
32.3 (t), 25.0 (t), 22.7 (q), 21.7 (q); IR (neat) ν 1718 cm-1; MS
(EI) m/z (%) 168 (2, M•+), 102 (100), in accordance with the
literature.48q,r
(E)-Dim eth yl (4-P h en yl-3-bu ten -2-yl)m a lon a te (76). Ob-
tained as a 1:1.3 mixture with 80; the spectrum was measured
for the mixture: 1H NMR δ 7.03-7.22 (5 H, m, arom), 6.32 (1
H, d, J ) 15.7 Hz, 4-H), 5.99 (1 H, dd, J ) 15.8, 8.3 Hz, 3-H),
3.61 (3 H, s, OMe), 3.53 (3 H, s, OMe), 3.27 (1 H, d, J ) 9.1
Hz, 2′-H), 2.99 (1 H, m, 2-H), 1.06 (3 H, d, J ) 6.6 Hz, Me), in
accordance with the literature.48s
(t), 28.7 (t), 24.8 (3 × q), 23.8, 21.5 (t); IR (neat) ν 1705 cm-1
;
MS EI m/z (%) 194 (15, M•+), 123 (100).
1-(2′-Cycloh exen -1′-yl)-3,3-dim eth ylbu tan -2-on e (66): 1H
NMR δ 5.61 (1 H, ddd, J ) 10.1, 5.7, 2.2 Hz, 3′-H), 5.41 (1 H,
dd, J ) 10.1, 2.2 Hz, 2′-H), 2.64 (1 H, m, 1′-H), 2.43 (1 H, dd,
J ) 20.8, 7.2 Hz, Ha of CH2CO), 2.36 (1 H, dd, J ) 20.8, 6.9
Hz, Hb of CH2CO), 1.92 (2 H, m, 4′-CH2), 1.77-1.43 (4 H, m,
2 × CH2), 1.07 (9 H, s, t-Bu); 13C NMR δ 214.5 (s), 131.0 (d),
127.4 (d), 44.0 (s), 42.7 (t), 30.6 (d), 28.9 (t), 26.1 (3 × q), 25.0
(t), 21.0 (t); IR (neat) ν 1701 cm-1; MS (EI) m/z (%) 180 (9,
M•+), 81 (100), in accordance with the literature.48f,g
2-(2′-Cyclop en ten -1′-yl)-1-cycloh exyl-1-oxoeth a n e (67):
1H NMR δ 5.73 (1 H, m, J ) 5.7, 2.2 Hz, CdCH), 5.62 (1 H, m,
J ) 5.7, 2.2, 1.9 Hz, CdCH), 3.10 (1 H, m, 1′-H), 2.53 (1 H, dd,
J ) 16.7, 7.3 Hz, Ha of CH2CO), 2.47 (1 H, dd, J ) 16.7, 8.3
Hz, Hb of CH2CO), 2.32 (2 H, m, CH2), 2.11 (1 H, m, CHCO
cyclohexyl), 1.80-1.63 (6 H, m, CH2), 1.30-1.10 (7 H, m,
cyclohexyl); 13C NMR δ 213.5 (s), 134.2 (d), 130.9 (d), 50.9 (d),
46.8 (t), 40.8 (d), 31.7 (t), 29.9 (t), 28.3 (2 × t), 25.8 (t), 25.6 (2
× t); IR (neat) ν 1701 cm-1; MS (EI) m/z (%) 192 (13, M•+), 109
(100), in accordance with the literature.48h
2-Meth yl-2-(3′,5′,5′-tr im eth yl-2′-cycloh exen -1′-yl)pr opan -
1-a l (68): 1H NMR δ 9.50 (1 H, s, CHO), 5.17 (1 H, s, 2′-H),
2.37 (1 H, m, 1′-H), 1.79 (1 H, br d, J ) 17.1 Hz, 5′-Ha), 1.64
(3 H, s, 3′-Me), 1.54 (1 H, d, J ) 17.1 Hz, 5′-Hb), 1.26 (1 H, m,
4′-Ha), 1.08 (1 H, m, 4′-Hb), 1.01 (6 H, s, CMe2), 0.96 (3 H, s,
5′-Me), 0.87 (3 H, s, 5′-Me); 13C NMR δ 206.7 (d), 135.4 (s),
119.1 (d), 48.2 (s), 43.9 (t), 38.9 (d), 36.5 (t), 32.0 (q), 29.8 (s),
25.0 (q), 24.0 (q), 18.9 (q), 18.4 (q); IR (neat) ν 1724 cm-1; MS
(EI) m/z (%) 194 (20, M•+), 123 (100).
2-Meth yl-2-(3′-m eth yl-2′-cycloh exen en -1′-yl)p r op a n -1-
a l (69): 1H NMR δ 9.50 (1 H, s, CHO), 5.18 (1 H, s, 2′-H),
2.32 (1 H, m, 1′-H), 1.86 (2 H, m, CH2), 1.79 (1 H, m), 1.72 (1
H, m), 1.65 (3 H, s, 3′-Me), 1.49 (1 H, m), 1.15 (1 H, m), 1.01
(6 H, s, CMe2); 13C NMR δ 206.8 (d), 136.7 (s), 120.7 (d), 48.6
(s), 40.9 (d), 29.8 (t), 23.9 (q), 23.6 (t), 22.5 (t), 18.8 (q), 18.3
(q); IR (neat) ν 1724 cm-1; MS (EI) m/z (%) 166 (10, M•+), 95
(100).
(E)-Dim eth yl (1-P h en yl-2-bu ten -1-yl)m a lon a te (77). Ob-
tained as a 1.3:1 mixture with 79; the spectrum was measured
for the mixture: 1H NMR δ 7.03-7.22 (5 H, m, arom), 5.46 (2
H, m, 2-H, 3-H), 3.91 (1 H, dd, J ) 11.0, 6.9 Hz, 1-H), 3.69 (1
H, d, J ) 11.0 Hz, 2′-H), 3.60 (3 H, s, OMe), 3.34 (3 H, s, OMe),
1.50 (3 H, d, J ) 4.7 Hz, Me), in accordance with the
literature.48s
(E)-1,5-Dip h en yl-3-m et h yl-1-oxo-4-p en t en e (78). Ob-
tained as a mixture with 81, which was separated on a
Dynamax 60 Å column (C18, 250 × 41.4 mm i.d.) using a 40:
60 H2O-MeCN mixture, flow rate 50 mL min-1, detection UV
1
at 210 nm; 78 was the less polar fraction (t ) 18.18 min): H
Meth yl 2,2-d im eth yl-2-(3′,5′,5′-tr im eth yl-2′-cycloh exen -
1′-yl)a ceta te (70): 1H NMR δ 5.10 (1 H, s, 2′-H), 3.66 (3 H, s,
OMe), 2.45 (1 H, m, 1′-H), 1.72 (1 H, d, J ) 17.3 Hz, 6′-Ha),
1.69 (3 H, s, 3′-Me), 1.42 (1 H, d, J ) 17.3 Hz, 6′-Hb), 1.10 (2
H, m, CH2), 1.07 (3 H, s, 2-Me), 1.05 (2 H, m, CH2), 1.01 (3 H,
s, 2-Me), 0.89 (3 H, s, 5′-Me), 0.79 (3 H, s, 5′-Me); 13C NMR δ
178.6 (s), 134.7 (s), 120.1 (d), 51.6 (q), 45.1 (s), 44.0 (t), 41.1
(d), 36.7 (t), 32.2 (q), 29.9 (s), 25.2 (q), 24.1 (q), 21.8 (q), 21.7
(q); MS (EI) m/z (%) 224 (13, M•+), 123 (100).
Meth yl 2-(3′-Meth yl-2′-cycloh exen -1′-yl)pr opion ate (71).
Obtained as a 1:1 mixture of diastereoisomers: 1H NMR δ 5.35
and 5.15 (1 H, s, 2′-H), 3.68 and 3.66 (3 H, s, OMe), 2.45 and
2.45 (1 H, m, 1′-H), 2.05 and 2.05 (1 H, m, CHCO), 1.89-1.71
(10 H, m, CH2), 1.68 and 1.68 (1 H, m, 6′-Ha), 1.64 and 1.64 (3
H, s, 3′-Me), 1.55 and 1.55 (1 H, m, 6′-Hb), 1.16 and 1.11 (3 H,
d, J ) 9 Hz, CH3CHCO); 13C NMR δ 176.7 (s), 176.6 (s), 136.0
(s), 135.7 (s), 123.5 (d), 122.0 (d), 51.3 (2 × q), 44.5, 44.3, 38.4,
29.9 (t), 29.9 (t), 27.0 (t), 25.0 (q), 23.9 (2 × q), 21.9 (t), 21.7
(t), 13.7 (q), 13.6 (q); IR (neat) ν 1728 cm-1; MS (EI) m/z (%)
182 (9, M•+), 95 (100).
NMR δ 7.94 (2 H, m, ArCO), 7.56-7.38 (3 H, m, ArCO), 7.35-
7.12 (5 H, m, Ar), 6.41 (1 H, d, J ) 16 Hz, PhHCdC), 6.22 (1
H, dd, J ) 16, 6.3 Hz, PhHCdCH), 3.34-2.90 (3 H, m, CHMe
and CH2), 1.18 (3 H, d, J ) 6.3 Hz, HCMe); 13C NMR δ 199.0
(s), 137.4 (s), 137.2 (s), 134.8 (d), 132.9 (d), 128.5 (d), 128.4
(d), 128.1 (d), 128.0 (d), 127.0 (d), 126.1 (d), 45.4 (t), 33.0 (d),
20.1 (q); IR (neat) ν 1686 cm-1; MS (EI) m/z (%) 250 (20, M•+),
105 (100), in accordance with the literature.36
(E)-2,3-Dim eth yl-1,5-diph en yl-1-oxo-4-pen ten e (79). Ob-
tained from 22 and 33 as a 1:1.4 mixture of regioisomers with
82; each regioisomer was represented by a 1:1 mixture of
diastereoisomers. All spectra were recorded for the mixture
of all isomers: 1H NMR (79; ∼1:1 mixture of diastereoisomers)
δ 0.85 and 0.98 (3 H, 2 × d, J ) 7.7 Hz, CHdCHCHMe), 1.10
and 1.13 (3 H, 2 × d, J ) 7.7 Hz, COCHMe), 2.68 (1 H, m,
MeCHCO), 3.33 and 3.47 (1 H, 2 × m, CHdCHCHMe), 6.04
(1 H, m, CHdCHCH), 6.27 and 6.29 (1 H, 2 × d, J ) 16.0 and
15.7 Hz, PhCHdCH), 7.01-7.88 (10 H, m, arom); IR ν 1682
cm-1; MS (EI) m/z (%) 264 (4, M•+), 105 (100).
1,5-Dip h en yl-1-oxo-4-p en ten e (80): 1H NMR δ 8.05 (2 H,
m, arom), 7.65-7.17 (8 H, m, arom), 6.51 (1 H, d, J ) 16.1 Hz,
PhCH), 6.32 (1 H, dt, J ) 16.1, 6.7 Hz, PhCHdCH), 3.17 (2 H,
t, J ) 7.3 Hz, COCH2), 2.69 (2 H, dt, J ) 7.3, 6.7 Hz, dCCH2);
13C NMR δ 199.2 (s), 137.3 (s), 136.8 (s), 132.9 (d), 130.7 (d),
129.0 (d), 128.4 (d), 127.9 (d), 127.6 (d), 126.9 (d), 125.9 (d),
38.1 (t), 27.4 (t); IR (neat) ν 1693, 1640 cm-1; MS (EI) m/z (%)
236 (9, M•+), 105 (100), in accordance with the literature.48t-v
(E)-1,3-Dip h en yl-1-oxo-4-h exen e (81). Obtained as a
mixture with 78, which was separated by HPLC (see above);
Meth yl 2,2-d im eth yl-2-(3′-m eth yl-2′-cycloh exen -1′-yl)-
a ceta te (72): 1H NMR δ 5.10 (1 H, br d, J ) 1 Hz, 2′-H), 3.65
(3 H, s, OMe), 2.45 (1 H, m, 1′-H), 1.81 (2 H, m, CH2), 1.75 (1
H, m, 6′-Ha), 1.63 (3 H, s, 3′-Me), 1.30 (2 H, m, CH2), 1.14 (3
H, s, 2-Me), 1.05 (3 H, s, 2-Me); 13C NMR δ 178.3 (s), 135.9 (s),
121.6 (d), 51.4 (q), 45.3 (s), 43.1 (d), 29.9 (t), 23.9 (q), 23.8 (t),
22.5 (t), 21.5 (2 × t); IR (neat) ν 1728 cm-1; MS EI m/z (%) 196
(26, M•+), 95 (100), in accordance with the literature.48l,m
Met h yl
2,2-d im et h yl-2-(2′-cycloh exen -1′-yl)a cet a t e
(73): 1H NMR δ 5.72 (1 H, br. m, J ) 10.1 Hz, CdCH), 5.42
(1 H, br m, J ) 10.1 Hz, CdCH), 3.62 (3 H, s, OMe), 2.45 (1
H, m, 1′-H), 1.91 (2 H, m, CH2), 1.75 (1 H, m), 1.60 (1 H, m),
1.47 (1 H, m), 1.23 (1 H, m), 1.10 (3 H, s, 2-Me), 1.06 (3 H, s,
81 was eluted as the more polar fraction (t ) 20.84 min): H
1
NMR δ 7.91 (2 H, m, ArCO), 7.57-7.38 (3 H, m, ArCO), 7.32-
7.13 (5 H, m, Ar), 5.65 (1 H, ddq, J ) 15.4, 7.1, 1.3 Hz, HCd
CHMe), 5.45 (1 H, ddq, J ) 15.4, 6.2, 1 Hz, HCdCHMe), 4.06

2750 J . Org. Chem., Vol. 64, No. 8, 1999
Malkov et al.
(1 H, m, PhHC), 3.49 (1 H, dd, J ) 16.4, 7.6 Hz, Ha of CH2-
CO), 3.31 (1 H, dd, J ) 16.4, 6.6 Hz, Hb of CH2CO), 1.62 (3 H,
d, J ) 6.2 Hz, dCHMe); 13C NMR δ 198.5 (s), 144.1 (s), 137.3
(s), 133.6 (d), 132.9 (d), 128.5 (2 × d), 128.4 (d) 128.1 (2 × d),
127.6 (2 × d), 126.4 (d), 125.5 (d), 44.7 (t), 43.9 (d), 17.9 (q); IR
(Nujol) ν 1683 cm-1; MS (EI) m/z (%) 250 (11, M•+), 105 (100),
in accordance with the literature.48s
(E)-2-Meth yl-1,3-diph en yl-1-oxo-4-h exen e (82). Obtained
from 22 and 33 as a 1.4:1 mixture of regioisomers with 79;
each regioisomer was represented by a 1:1 mixture of diaste-
reoisomers. The spectra were recorded for the mixture of all
isomers: 1H NMR (82; ∼1:1 mixture of diastereoisomers) δ
1.34 and 1.57 (3 H, 2 × d, J ) 6.1 Hz, CHdCHMe), 1.05 and
1.08 (3 H, 2 × d, J ) 7.8 Hz, CHMe), 3.60 (1 H, m, CHCO),
3.77 (1 H, m, PhCH), 5.48 (2 H, m, CHdCH), 7.01-7.88 (10
H, m, 2 × Ph).
HPLC (see above); 87 was eluted as the less polar fraction (t
) 27.44 min): 1H NMR δ 7.3-7.13 (5 H, m, Ar), 5.85 (1 H,
ddq, J ) 15.1, 9.8, 1.6 Hz, 2-H), 5.57 (1 H, ddq, J ) 15.1, 6.5,
1 Hz, 3′-H), 3.60 (3 H, s, OMe), 3.54 (1 H, d, J ) 9.8 Hz, 1′-H),
1.67 (3 H, dd, J ) 6.5, 1.6 Hz, 3′-H), 1.15 (3 H, s, 2-Me), 1.09
(3 H, s, 2-Me); 13C NMR δ 177.6 (s), 141.1 (s), 129.4 (d), 129.3
(2 × d), 129.1 (d), 128.2 (2 × d), 127.9 (d), 126.6 (d), 56.7 (d),
51.3 (q), 47.1 (s), 23.1 (q), 22.3 (q), 18.1 (q); IR (neat) ν 1730
cm-1; MS (EI) m/z (%) 232 (1, M•+), 131 (100), in accordance
with the literature.36
3â-Meth oxy-4-ch olesten e (88): 1H NMR δ 5.34 (1 H, d, J
) 1.4 Hz, 4-H), 3.73 (1 H, br m, 3R-H), 3.37 (3 H, s, MeO),
1.04 (3 H, s, 19-H), 0.67 (3 H, s, 18-H), in accordance with the
literature.44i,47i,j
1
3r-Meth oxy-4-ch olesten e (89): H NMR δ 5.46 (1 H, br
d, J ) 4.8 Hz, 4-H), 3.56 (1 H, m, 3â-H), 3.34 (3 H, s, MeO),
1.02 (3 H, s, 19-H), 0.67 (3 H, s, 18-H), in accordance with the
literature.44i,47i,j
1,3-Dip h en yl-1-oxo-4-p en ten e (83): 1H NMR δ 7.82 (2 H,
m, arom), 7.49-7.26 (3 H, m, arom), 7.22 (5 H, m, arom), 5.94
(1 H, ddd, J trans ) 17.0, J cis ) 10.4, 6.8 Hz, CHdCH), 4.96 (1
H, ddd, J cis ) 10.4, J gem ) 1.25, J allylic ) 1.25 Hz, Hcis), 4.92 (1
H, ddd, J trans ) 17.0, J gem ) 1.25, J allylic ) 1.25 Hz, Htrans), 4.03
(1 H, ddd, J ) 6.9, 6.8, 1.25 Hz, Hallylic), 3.32 (1 H, dd, J )
16.5, 6.9 Hz, Ha of CH2CO), 3.26 (1 H, dd, J ) 16.5, 7.0 Hz, Hb
of CH2CO); 13C NMR δ 198.2 (s), 143.1 (s), 139.6 (d), 137.1 (s),
132.9 (d), 128.5 (2 × d), 128.0 (d), 127.6 (d), 126.5 (d), 114.6
(t), 44.5 (d), 44.0 (t); IR (neat) ν 1692 cm-1; MS (EI) m/z (%)
236 (37, M•+), 105 (100), in accordance with the literature.48x
(E)-1-P h en yl-3-m et h yl-5-cycloh exyl-1-oxop en t -4-en e
(84). Obtained as a mixture with 85, which was separated on
a Dynamax 60 Å column (C18, 250 × 41.4 mm i.d.) using an
85:15 MeCN-H2O mixture, flow rate 50 mL min-1, detection
by UV at 230 nm. Analysis of the mixture was performed on
a HP 1050 Dynamax 60 Å column (C18, 250 × 4.6 mm 8 m
i.d.) using an 80:20 MeCN-H2O mixture, flow rate 1 mL min-1
at 2.30 kpsi; 84 was the more polar fraction (t ) 28.47): 1H
NMR δ 7.92 (2 H, m, Ar), 7.60-7.37 (3 H, m, Ar), 5.35 (2 H,
m, CHdCH), 3.02-2.74 (3 H, m, 2-CH2 and CH of cyclohexyl),
1.85 (1 H, m, 3-H), 1.75-1.55 (5 H, m, CH2-cyclohexyl), 1.30-
0.90 (8 H, m), 1.06 (3 H, d, J ) 6.2 Hz, Me); 13C NMR 199.8
(s), 137.5 (s), 135.2 (d), 132.8 (d), 131.9 (d), 128.5 (2 × d), 128.1
(2 × d), 46.0 (t), 40.5 (d), 33.2 (d), 33.1 (t), 26.2 (t), 26.0 (2 × t),
20.6 (q); MS (EI) m/z (%) 256 (8, M•+), 105 (100).
3â-(Ben zoylm et h yl)-4-ch olest en e (90). Obtained along
with 91 as a 1:3.5 mixture of diastereoisomers: 1H NMR δ
(recorded for a mixture with 91) 7.89 (2 H, d, J ) 6.9 Hz, 2′-
H, 6′-H), 7.46 (1 H, t, J ) 7.2 Hz, 4′-H), 7.38 (2 H, t, J ) 7.2
Hz, 3′-H, 5′-H), 5.08 (1 H, br s, 4-H), 2.82 (2 H, dd, J ) 7.2,
2.8 Hz, COCH2), 2.67 (1 H, m, 3R-H).
3r-(Ben zoylm eth yl)-4-ch olesten e (91). Obtained along
with 90 as a 3.5:1 mixture of diastereoisomers: 1H NMR δ
(recorded for a mixture with 90) 7.89 (2 H, d, J ) 6.9 Hz, 2′-
H, 6′-H), 7.46 (1 H, t, J ) 7.2 Hz, 4′-H), 7.38 (2 H, t, J ) 7.2
Hz, 3′-H, 5′-H), 5.20 (1 H, br d, J ) 4.1 Hz, 4-H), 2.88 (2 H,
dd, J ) 7.1, 2.3 Hz, COCH2), 2.67 (1 H, m, 3â-H), 0.94 (3 H, s,
19-H), 0.61 (3 H, s 18-H); IR (thin film) ν 1690 cm-1; MS (EI)
m/z (%) 488 (20, M•+), 105 (100).
1-Meth oxy-3a ,4,5,6,7,7a -h exa h yd r o-(1r,3a r,4r,7r,7a r)-
4,7-m eth a n o-1H-in d en e (92): 1H NMR δ 5.89 (1 H, dd, J )
5.7, 1.9 Hz, 2-H), 5.77 (1 H, dt, J ) 5.7, 2.0 Hz, 3-H), 4.23 (1
H, br s, 1-H), 3.23 (3 H, s, OMe), 3.05 (1 H, m, 3a-H), 2.26 (3
H, m, 4-H, 7-H, 7a-H), 1.04-1.46 (6 H, m, 3 × CH2); 13C NMR
δ 140.5 (d), 130.7 (d), 86.8 (q), 55.8 (d), 52.5 (d), 50.7 (d), 42.0
(t), 40.4 (d), 39.5 (d), 25.2 (t), 23.7 (t), identical with the known
compound.26a,47k
1-(Be n zoylm e t h yl)-3a ,4,5,6,7,7a -h e xa h yd r o-(1r,3a r,
4r,7r,7a r)-4,7-m eth a n o-1H-in d en e (93). Colorless oil: 1H
NMR δ 7.94 (2 H, d, J ) 7.1 Hz, 2′-H, 6′-H), 7.54 (1 H, t, J )
6.9 Hz, 4′-H), 7.44 (2 H, t, J ) 6.9 Hz, 3′-H, 5′-H), 5.63 (2 H,
m, CHdCH), 3.13 (1 H, m, 1-H), 3.07 (1 H, dd, J ) 16.5, 5.8
Hz; COCHH), 3.01 (1 H, m, 3a-H), 2.89 (1 H, dd, J ) 16.5, 8.3
Hz, COCHH), 2.28 (2 H, m, 4,7-H), 2.09 (1 H, dt, J ) 10.1, 3.1
Hz, 7a-H), 1.25 (6 H, m, 3 × CH2); 13C NMR δ 199.8 (CO),
137.3 (1′-C), 134.0 (4′-CH), 133.9 and 132.9 (2,3-CH), 128.5 and
128.0 (2′,3′,5′,6′-CH), 52.1 and 50.7 (1,3a-CH), 45.9 (COCH2),
41.0 (8-CH2), 40.9 and 39.4 (4,7,7a-CH), 25.0 and 22.9 (5,6-
CH2); IR (thin film) ν 1674 cm-1; MS (EI) m/z (%) 252 (13, M•+),
105 (100).
(E)-1-P h en yl-3-cycloh exyl-1-oxo-h ex-4-en e (85). Ob-
tained as a mixture with 84, which was separated by prepara-
tive HPLC (vide supra); 85 was the less polar fraction (t )
23.89 min): 1H NMR δ 7.98 (2 H, m, Ar), 7.40-6.62 (3 H, m,
Ar), 5.30 (2 H, m, CHdCH), 2.99 (2 H, m, 2-CH2), 2.55 (1 H,
m, 3-H), 1.90-1.60 (4 H, m), 1.62 (3 H, d, J ) 5.0 Hz, Me),
1.40-0.80 (6 H, m, CH2 of cyclohexyl); 13C NMR δ 200.4 (s),
137.6 (s), 132.6 (d), 132.2 (d), 128.4 (2 × d), 128.1 (2 × d), 126.0
(d), 44.6 (d), 42.0 (d), 41.6 (t), 31.0 (t), 29.7 (t), 26.5 (3 × t),
17.8 (q); MS (EI) m/z (%) 256 (7, M•+), 105 (100).
Meth yl 2,2-Dim eth yl-2-(4′-p h en yl-3′-bu ten -2′-yl)a ceta te
(86). Obtained as a mixture with 87, which was separated on
a Dynamax 60 Å column (C18, 250 × 41.4 mm id) using a 40:
60 H2O-MeCN mixture, flow rate 50 mL min-1, detection UV
at 210 nm; 86 was the more polar fraction (t ) 33.92 min):
1H NMR δ 7.38-7.13 (5 H, m, Ar), 6.39 (1 H, d, J ) 15.7 Hz,
PhHCd), 6.08 (1 H, dd, J ) 15.7, 8.8 Hz, PhHCdCH), 3.67 (3
H, s, OMe), 2.64 (1 H, dq, J ) 8.8, 6.9 Hz, MeCH), 1.17 (3 H,
s, 2-Me), 1.15 (3 H, s, 2-Me), 1.03 (3 H, d, J ) 6.9 Hz, CHMe);
13C NMR δ 177.9 (s), 140.9 (s), 137.5 (d), 131.6 (d), 130.9 (2 ×
d), 128.4 (d), 127.0 (2 × d), 126.1 (d), 51.5 (s), 45.9 (s), 44.7
(d), 23.2 (q), 21.1 (q), 15.7 (q); IR (neat) ν 1728 cm-1; MS (EI)
m/z (%) 232 (4, M•+), 131 (100).
Ack n ow led gm en t. We thank the EPSRC for Grants
No. GR/H92067 and GR/K07140 and EPSRC and AgrE-
vo UK Ltd. for a CASE award to I.R.B.
Su p p or tin g In for m a tion Ava ila ble: Detailed experi-
mental procedures, including the preparation of silyl enol
ethers and their spectral characterization, IR, MS, and HRMS
spectral characteristics, and elemental analyses, and 1H and
13C NMR spectra for the new compounds. This material is
available free of charge via the Internet at http://pubs.acs.org.
Meth yl 2,2-Dim eth yl-2-(1′-p h en yl-2′-bu ten -1′-yl)a ceta te
(87). Obtained as a mixture with 86, which was separated by
J O9821776