The synthesis of a hydroazulen-2-one skeleton-determination of the diastereoselectivity of [3+2] cycloaddition of tricarbonyl[4,5,6,7-η)-2-methyltropone]iron with E/Z-η1-(crotyl)Fp

Article abstract of DOI:10.1016/S0022-328X(02)01671-6

The diastereoselectivity of [3 + 2] cycloaddition of tricarbonyl[(4,5,6,7-η)-2-methyltropone]iron (2) with an E,Z isomeric mixture of η¹-(crotyl)Fp (4E/4Z) [Fp: C₅H₅Fe(CO)₂ or CpFe(CO)₂] has been stud

Full text of DOI:10.1016/S0022-328X(02)01671-6

Journal of Organometallic Chemistry 659 (2002) 43ꢁ49
/
www.elsevier.com/locate/jorganchem
The synthesis of a hydroazulen-2-one skeleton-determination of the
diastereoselectivity of [3ꢀ2] cycloaddition of tricarbonyl[(4,5,6,7-h)-
-methyltropone]iron with E/Z-h -(crotyl)Fp
/
1
2
a
a,
a
b
Branislav Horv a´ th , Andrej Boh a´ cˇ *, Marta Sali sˇ ov a´ , Eva Sol cˇ a´ niov a´ ,
Myron Rosenblum
c
a
Department of Organic Chemistry, Comenius University, Faculty of Natural Sciences, Mlynsk a´ dolina, 842 15 Bratislava, Slovakia
b
Chemical Institute, Comenius University, Faculty of Natural Sciences, Mlynsk a´ dolina, 842 15 Bratislava, Slovakia
c
Department of Chemistry, Brandeis University, Waltham, MA 02254-9110, USA
Received 10 January 2002; received in revised form 20 May 2002; accepted 14 June 2002
Abstract
The diastereoselectivity of [3ꢀ
/
2] cycloaddition of tricarbonyl[(4,5,6,7-h)-2-methyltropone]iron (2) with an E,Z isomeric mixture
1
of h -(crotyl)Fp (4E/4Z) [Fp: C
are formed. The reaction occurs regioselectively and stereoselectively. The relative configurations of the cycloadducts 5a, 5b and 5c
5
H
5
Fe(CO) or CpFe(CO) ] has been studied. By this cyclopentaanulation, four stereogenic centres
2
2
were assigned on the basis of 2D and NOE NMR experiments. A mechanism for the stereoselective [3ꢀ
proposed. The selectivity of the cycloaddition depends on the difference in steric discrimination approaches of the h -(crotyl)Fp 4E/
Z to the tricarbonyl[(3,4,5,6,7-h)-1-trimethylsilyloxy-2-methyltropylium]iron 3 (repulsion of the methyl and methylene groups of 4
/
2] cycloaddition has been
1
4
1
and the planar skeleton of 3) and also upon the isomeric structure (E or Z) of the h -(crotyl)Fp reactant. The geometrical isomerism
of the reagent (4E/4Z) is preserved in the products 5aꢁc. # 2002 Elsevier Science B.V. All rights reserved.
/
Keywords: Regioselectivity; Stereoselectivity; Cyclopentaanulation; Cycloaddition; 2-Methyltroponeiron tricarbonyl; Ketohydroazulene; (crotyl)Fp;
Reiswigin
1
. Introduction
hydroazulene skeleton which have been isolated from
deepwater marine organism (sponges Epipolasis reiswigi
collected by submersible at 330 m). The Reiswigins have
shown potent in-vitro antiviral activity against Herpes
simplex type I virus and murine A59 hepatitis virus [1].
The present paper reports our studies directed toward
the synthesis of hydroazulene skeletons related to this
sesquiterpene.
The terpenes constitute a large and structurally
diverse group of natural products, many of which
possess biological activity. We are currently involved
in the synthesis of biologically active terpenoids. Re-
iswigin A and B (Scheme 1) are sesquiterpenes with a
Rosenblum described a facile cyclopentaanulation
method for the synthesis of hydroazulenes through
1
[
3ꢀ
/
2] syn cycloaddition of h -1-Fp(prop-2-ene) and
1
h -1-Fp(prop-2-yne) complexes with tricarbonylcyclo-
heptatrienyliumiron tetrafluoroborate [2]. It was subse-
quently shown, that the cycloaddition of E/Z h -
crotyl)Fp on the tropylium salt derived from h -
1
1
4
(
Scheme 1.
tricarbonyltroponeiron proceeds regioselectively. How-
ever, the cycloaddition yielded a mixture of diastereo-
*
Corresponding author. Tel.: ꢀ
6690; www: http://www.fns.uniba.sk/ꢀ
E-mail address: bohac@fns.uniba.sk (A. Boh a´ cˇ ).
/
421-2-602-96409; fax: ꢀ
/
421-2-602-
9
0
/
bohac/
1
1
Synonym: h -1-Fp(but-2-ene).
022-328X/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 3 2 8 X ( 0 2 ) 0 1 6 7 1 - 6

44
B. Horv a´ th et al. / Journal of Organometallic Chemistry 659 (2002) 43ꢁ49
/
heating dicyclopentadiene and Fe(CO)5 with gentle
reflux for 16 h, (yield 90%) [6]. The FpNa salt was
obtained from Fp and NaHg in situ in THF at room
2
x
temperature, then cooled to ꢂ80 8C and treated with
/
crotyl bromide to give a 4E/4Z mixture (70/30, respec-
1
tively, determined by Cp singlet from H-NMR). It is
known that the isomeric impurity, 3-bromobut-1-ene,
present in commercial crotyl bromide is converted by
treatment with FpNa to its FpR compound, which
1
rearranges spontaneously to the desired mixture of h -
(crotyl)Fp 4E/4Z [7] (Scheme 3).
Tricarbonyl[(4,5,6,7-h)-2-methyltropone]iron 2 was
converted in situ to the fluxional tropyliumiron tricar-
bonyl salt 3 [3] by treatment with trimethylsilyl triflate.
This electrophilic organoiron salt yielded ketohydroa-
zulene cycloadducts in 80% yield on treatment with the
Scheme 2. Reagents and conditions: (a) (1) Et
CCHClCOCl, ꢂ5 8C, 75 min; (3) overnight from ꢂ
b) reflux, 119 h, NaOAc, HOAc, H O, then r.t., NaOH, pH 10, 33%
overall yield; (c) Fe (CO) 2.49 mol eq., C , 40 8C, 3 h, 74% of 2
and 8% of diiron by product.
3
N, n-hexane, 0 8C; (2)
H
3
/
/5
8C to r.t.;
(
2
2
9
6
H
6
1
mixture of 4E/4Z h -(crotyl)Fp complexes. The crude
product consisted of a mixture of the three diastereo-
isomers 5a, 5b and 5c in the ratio of (57:26:17,
respectively) (Scheme 4).
isomers. The ratio of the diastereoisomers and their
structures were not known [3]. As part of our research,
The relative configurations of products 5aꢁc were
/
we focused our study on the stereoselectivity of [3ꢀ2]
/
1
determined by a combination of NOE and 2D NMR
experiments and by use of the Karplus equation
cycloaddition of h -(crotyl)Fp (4) with the tropylium-
iron tricarbonyl salt derived from 2-methyltropone (1).
(
correlation between coupling constants and estimated
torsion angles of the rigid skeleton) [8]. The assignment
of the relative configuration of the structures 5aꢁc was
/
2
. Discussion
complex because of the different observed conformation
of the five-membered ring in the skeleton of the
diastereoisomers. The proposed structures and esti-
2-Methyltropone (1) was prepared from cyclopenta-
,3-diene through the intermediate 7exo-chloro-7endo
1
methylbicyclo[3.2.0]hept-2-ene-6-one following the
-
mated conformations (on the basis of observed coupling
1
constants from H-NMR in CDCl at room tempera-
3
work of Brady and Hieble [4] in 33% overall yield.
ture) of the diastereoisomers 5aꢁ
. The results and conclusions of the NOE NMR
experiments are summarised in Table 1.
The NOE experiments confirm that [3ꢀ
/
c are shown in Scheme
The
desired
tricarbonyl[(4,5,6,7-h)-2-methyltropo-
ne]iron (2) was obtained in 74% yield by reaction of 1
5
with Fe (CO) in degassed dry benzene at 40 8C,
2
9
/2] cycloaddi-
according to the described procedure [3]. A by-product,
isolated after FLC was assigned as hexacarbonyl[m-
tion, involving successive nucleophilic attack on the
1
fluxional organoiron salt 3 by h -(crotyl)Fp (4), fol-
[
[
(2,3,4-h:5,6,7-h)-2-methyltropone]]diiron in 8% yield
5] (Scheme 2).
1
The E,Z mixture of h -(crotyl)Fp (4) was prepared
from the commercially available crotyl bromide contain-
ing ca. 12% isomeric 3-bromobut-1-ene. h -Dicarbo-
nylcyclopentadienyliron dimer Fp was prepared by
2
Crotyl bromide, pract. ca. 85% (GC) Fluka (cat. no. 28100)
containing: E-isomer (72%), Z-isomer (16%) and 3-bromobut-1-ene
2
5
1
12%) (determined by H-NMR). All the isomers above gave after the
(
1
reaction with FpNa desired products: h -(crotyl)Fp 4E/4Z.
2
Scheme 3. Reagents and conditions: (a) FpNa in situ from Fp
0/30).
2
and NaHg
x
, ꢂ80 8C, 1 h, then r.t., distillation 150 8C/5 Pa, yield 22%, 4E/4Z (E/Z
/
7

B. Horv a´ th et al. / Journal of Organometallic Chemistry 659 (2002) 43ꢁ
/49
45
reacting components are shown in Schemes 6 and 7
below and appear to give good account of the relative
proportions of products observed in the reaction.
Diastereomer 5d is not formed in the reaction. This is
best accounted for by the significantly greater steric
interactions (methyl and methylene) of 4Z with the
complex tropylium ion in the first step of the cycloaddi-
tion reaction, which would give rise to this diastereomer.
3. Conclusions
1
The [3ꢀ2] cycloaddition reactions h -(crotyl)Fp (4)
/
with complex tropylium ion 3 provides facile entry into
the substituted hydroazulene skeleton, and has been
shown to be highly diastereoselective at the four new
stereogenic centers formed in these reactions. This
stereoselectivity is accounted for in terms of known
stereoelectronic demands of both organoiron reagents
1
and of steric demands of the h -(crotyl)Fp reagent.
Further study of these cycloaddition reactions and their
application in sesquiterpene synthesis is in progress.
4. Experimental
4.1. General data
Scheme 4. Reagents and conditions: (a) TMSTf, CH
h; (b) (1) FpCH CHCH (E/Z 70/30), ꢂ80 8C, 1 h, then 40 8C,
CHÄ
h; (2) THF, NaHCO aq., r.t., 30 min, yield: 80%.
2
Cl
2
, ꢂ80 8C, 3
/
2
/
3
/
Dicyclopentadiene, 2-chloropropionyl chloride, crotyl
bromide, trimethylsilyl triflate and Fe(CO) are com-
3
3
5
mercially available. NaHgx, cyclopentadiene and
Fe (CO) [10] were prepared according to the known
2
9
lowed by ring closure, proceeds regioselectively at C(3)
and C(2) of the complex cation. The reaction also
proceeds trans-stereoselectively at these centers with
3
procedures. All reactions were carried out under
nitrogen or argon. The reaction apparatus was purged
with argon prior to use. Benzene and THF were dried
over sodium and redistilled under argon from sodium
benzophenone ketyl. Triethylamine, dichloromethane
and diethyl ether were dried over and distilled from
respect to the bulky Fe(CO) group. In this manner,
3
syn-stereogenic centers in the products 5aꢁc at C(1) and
/
C(7) are formed. Finally, each of these steps (nucleo-
philic attack and also ring closure) occurs anti-peripla-
nar with respect to the activating Fp group [9]. Thus, the
CaH under argon. Solvents were bubbled with argon
2
4
for 15 min, prior to use [11]. Hexsol is a commercial
two remaining stereogenic centers in 5aꢁc at C(8) and at
/
C(9) are formed under this control as well as the effect of
steric interactions associated with the reacting compo-
nents. While the E-isomer gives a mixture of two
products (5a and 5b), the Z-isomer yields a single
stereoisomer (5c). The relevant interactions of the
3
Diiron nonacarbonyl was prepared by photolysis of iron
pentacarbonyl in glacial acetic acid with a low pressure Hg lamp.
4
‘The transferable gas container (TGC)’ for introducing an inert
gas into a reaction mixture, a solvent or a solution. TGC attached to a
syringe allows convenient degassing of liquids.
Scheme 5.

46
B. Horv a´ th et al. / Journal of Organometallic Chemistry 659 (2002) 43ꢁ49
/
Table 1
The most important NOE NMR results confirming the assignment of the relative configurations of the diastereoisomers 5a, 5b and 5c
Diastereoisomer Irradiated
signal
Corresponding NOE
a
signals
Structure conclusions
5a
Meꢁ
/
C(1)
Hꢁ
/
C(9)
Fp*
MeꢁC(8)*
MeꢁC(8)*
/
down
Hꢁ/C(6)
Hꢁ
/
C(8)
/
/
up
Hꢁ/C(9)
Meꢁ
/C(1), Meꢁ
/
C(8),
/
/
up, Fp*
/
down and an exact assignment for HMe ꢁ C(1)
ꢁC(10)
/
Me ꢁ C(1)
/
H
ꢁ
C(10)
5
b
c
Hꢁ
/
C(6)
Meꢁ
HꢁC(8)
HꢁC(6), Hꢁ
MeꢁC(8)
/
C(8)
Meꢁ
Meꢁ
Meꢁ
Meꢁ
/
C(8)*
C(8)*
C(8)*
C(8) and Fp are in the syn arrangement
/
down
Hꢁ
/
C(7)
/
/
/down
Meꢁ
Cp from Fp
/C(8)
/
/
C(9)
/
/down, Fp*up
/
5
/
/
group
Hꢁ/C(7)
Meꢁ
/
C(8) and also Hꢁ
/
C(8) The Fp preferred group conformation brings the Meꢁ
one another in 5c. NOE signals for both groups at C(8) are observed when Hꢁ
is irradiated. MeꢁC(8) up, Fpꢁup.
/
C(8) and Meꢁ
/
C(1) close to
/
C(7)
/
/
a
Upper index assigning nucleus for example HMe ꢁ C(1)
ꢁ/
C(10) means: the hydrogen at C(10) oriented towards to Meꢁ
/
C(1) (or looking at Meꢁ
/
C(1)); nomenclature introduced by Prof. Camille Ganter, ETH, Z u¨ rich, Switzerland.
1
Scheme 6. Proposed mechanism for the stereoselective cycloaddition of the E-h -(crotyl)Fp 4E on the organoiron salt 3.
5
name for light hexane fraction of petrol (bp 62ꢁ
TLC was carried out on silica plates and spots were
detected by UV (lꢃ254 nm light), or in the iodine
/
658C).
4.2. 2-Methyltropone (1)
/
2-Methyltropone was prepared following the proce-
dure from the literature [4]. Yield: 11.8 g (98.2 mmol,
33% based on the starting cyclopentadiene), Kugelrohr
vapours. Flash liquid chromatography FLC was per-
formed on SiO2 (40/100 mesh). NMR spectra were
recorded on a Varian Gemini 2000 spectrometer at 300
MHz for protons and 75 MHz for carbons, in CDCl3
unless otherwise noted. TMS was used as an internal
standard. Listed coupling constants are in Hz. The
Hetcor, HMQC and NOE techniques were used for
exact assignments of the relative configuration of the
distillation: oven temperature 105 8C (0.5 Torr) (lit. b.p.
1
70ꢁ
7.17ꢁ
C(3), Hꢁ
J(3,MeꢁC(2))ꢃ
187.4 (s, C(1)Ä
133.8 and 132.5 (5ꢄ
22.8 (q, MeꢁC(2)). Anal. Calc. for C
/
72 8C/1 Torr) [4a]. H-NMR (CDCl
) 7.36ꢁ
m, Hꢁ
(7)), 2.28 (3H, d,
/
7.30,
3
/
7.04 and 7.00ꢁ
C(4), Hꢁ
1.0, Meꢁ
/
6.87 (1H, 2H and 2H, 3ꢄ
/
/
/
/
C(5), Hꢁ
/
C(6), Hꢁ
/
1
3
/
/
/
C(2)).
C-NMR (CDCl )
3
/
O), 152.5 (s, C(2)), 139.9, 135.5, 135.1,
d, C(3), C(4), C(5), C(6) and C(7)),
O (120.15): C,
products 5aꢁ
/
c. IR spectra were recorded on a Perkinꢁ
/
/
Elmer spectrophotometer in 0.1 mm NaCl cell with the
ꢂ1
/
8
H
8
scale in cm . Melting points were determined on a
79.97; H, 6.71. Found: C, 79.57; H 6.79%.
Kofler hot stage and are uncorrected. Elemental ana-
lyses (C, H, N) were performed on a Carlo Erba
Instrumentazione analyzer.
5
Synonym: 2-methylcyclohepta-2,4,6-trien-1-one.

B. Horv a´ th et al. / Journal of Organometallic Chemistry 659 (2002) 43ꢁ
/49
47
1
Scheme 7. Proposed mechanism for the stereoselective cycloaddition of the Z-h -(crotyl)Fp 4Z on the organoiron salt 3.
6
4
.3. Tricarbonyl[(4,5,6,7-h)-2-methyltropone]iron (2)
4.50 (1H, ddd, J(6,7)ꢃ
HꢁC(6)), 3.38 (1H, dd, J(6,7)ꢃ
C(7)), 1.63 (3H, s, Meꢁ
(s, 6ꢄCO from 2ꢄFe(CO)
(d, C(3)), 75.9 (s, C(2)), 74.4 (d, C(6)) 62.9 (d, C(5)), 61.7
(d, C(7)), 57.1 (d, C(4)), 23.0 (q, MeꢁC(2)). IR (CHCl ):
070, 2025, 2010, 1590 (C(1)ꢃO), 590, 580, 555. Anal.
Calc. for C H Fe O (399.90): C, 42.05; H, 2.02.
/
7.7, J(5,6)ꢃ
7.7, J(5,7)ꢃ
C(2)). C-NMR (CDCl ) 210.2
/
6.9, J(4,6)ꢃ
/
1.0,
/
/
/
1.4, Hꢁ
/
1
3
2
-Methyltropone irontricarbonyl was prepared fol-
lowing the procedure from the literature [3]. Yield: 7.63
g (29.3 mmol, 74%), red crystals, m.p. 68.5ꢁ70.0 8C
/
3
/
/
), 189.6 (s, C(1)Ä
/
O), 78.4
3
/
1
[
hexsol/Et O] (lit. 84%, m.p. 64 8C) [3]. H-NMR
/
3
2
2
/
(
CDCl ) 6.39 (1H, dq, J(3,4)ꢃ
/
8.2, J(Me,3)ꢃ
7.6, J(5,6)ꢃ4.7, J(4,6)ꢃ
C(6)), 6.30 (1H, ddd, J(4,5)ꢃ7.3, J(5,6)ꢃ4.7,
J(5,7)ꢃ1.4, HꢁC(5)), 3.17 (1H, dd, J(6,7)ꢃ
J(5,7)ꢃ1.4, HꢁC(7)), 2.68 (1H. ddd, J(3,4)ꢃ
J(4,5)ꢃ7.3, J(4,6)ꢃ1.5, Hꢁ
J(Me,3)ꢃ1.5, MeꢁC(2)). C-NMR (CDCl ) 208.2 (s,
CO from Fe(CO) ), 198.9 (s, C(1)Ä
/
1.5, Hꢁ
/
3
C(3)), 6.32 (1H, ddd, J(6,7)ꢃ
1
/
/
/
14
8
2
7
Found: C, 42.50; H, 2.04%.
.5, Hꢁ
/
/
/
/
/
/
7.6,
5
.4. h -Dicarbonylcyclopentadienyliron dimer (Fp )
4
/
/
/
8.2,
2
/
/
/
C(4)), 1.48 (3H, d,
1
3
Fp was prepared following the procedure from the
2
1
literature [6]. Yield: 23.7 g (0.067 mol, 90%). H-NMR
/
/
3
3
ꢄ
/
/
O), 143.0 (d,
C(3)), 129.3 (s, C(2)), 95.1 and 91.3 (d, C(5)) and (d,
C(6)), 61.2 and 51.5 (d, C(4)) and (d, C(7)), 17.0 (q, Meꢁ
C(2)). IR (CHCl ): 2065, 2007, 1993, 1632, 1610, 968,
3
(
80 MHz, CDCl ): 4.78 (10H, s, 2ꢄ
/Cp).
3
/
1
.5. mixture of E/Z h -(crotyl)Fp (4E, 4Z)
8
4
3
ꢂ1
6
07, 600 cm . Anal. Calc. for C H FeO (260.02): C,
11 8 4
A solid NaHgx (21.30 g, containing Na 2.8% w/w,
4.9 mmol, 1.14 mol eq.) was added to the solution of
5
0.81; H, 3.10. Found: C, 49.96; H, 3.00%.
Hexacarbonyl[m-[(2,3,4-h:5,6,7-h)-2-methyltropo-
2
Fp (4.00 g, 11.30 mmol, 1.03 mol eq.) in 65 ml of dry
7
2
ne]]diiron, red crystals, m.p. 112ꢁ
observed as a by product. Yield 1.30 g (3.25 mmol, 8%).
/
120 8C (dec.) was
THF. The mixture was stirred 1 h at room temperature
(r.t.). The solution of FpNa was decanted from the rest
of Hg and HgNa . Crotyl bromide (72% trans, 16% cis,
1
H-NMR (CDCl3) 4.73 (1H, dddd, J(4,5)ꢃ
J(5,6)ꢃ6.9, J(5,7)ꢃ1.4, J(3,5)ꢃ0.8, HꢁC(5)), 4.66
1H, dd, J(3,4)ꢃ7.7, J(3,5)ꢃ0.8, HꢁC(3)), 4.57 (1H,
ddd, J(3,4)ꢃ7.7, J(4,5)ꢃ7.7, J(4,6)ꢃ1.0, HꢁC(4)),
/7.7,
x
/
/
/
/
1
2
2% 3-bromobut-1-ene) (see footnote 2) (2.95 g, 2.25 ml,
1.85 mmol) was added to the ꢂ80 8C cooled solution
(
/
/
/
/
/
/
/
/
of FpNa within 15 min. The stirred mixture was allowed
to warm up to r.t. during 1 h. The precipitate was
removed by centrifugation and then the solid washed
6
Other synonyms: 2-methyltroponeiron tricarbonyl or
tricarbonyl[(4,5,6,-h)-2-methylcyclohepta-2,4,6-trien-1-one]iron; CAS:
[
54931-32-7] and [130853-98-4].
7
8
1
1
Synonym: hexacarbonyl[m-[(2,3,4-h:5,6,7-h)-2-methylcyclohepta-
,4,6-trien-1-one]]diiron.
Other synonyms: E/Z h -1-Fp(but-2-ene) or E/Z dicarbonyl[h -
5
2
(but-2-en-1-yl)-h -cyclopentadienyl]iron.

48
B. Horv a´ th et al. / Journal of Organometallic Chemistry 659 (2002) 43ꢁ49
/
with ether (3ꢄ
vacuo. The crude oil was distilled on Kugelrohr
150 8C/5 Pa). Yield: 1.12 g (4.83 mmol, 22.1%) as the
/
30 ml). The solvent was evaporated in
Fraction 1: the diastereoisomeric mixture 5a and 5b
(298 mg, 0.606 mmol)
Fraction 2: the mixture of 5a, 5b and 5c (840 mg,
1.707 mmol)
Fraction 3: the pure diastereoisomer 5c (71 mg, 0.144
mmol)
(
mixture of isomers 4E/4Z (E:Zꢃ
/
70:30 determined by
H-NMR). Obtained brown oil was used in the next step
1
1
without further purification. H-NMR (4E, CDCl3)
Fraction 4: starting material tricarbonyl[(4,5,6,7-h)-
5
.65 (1H, dt, J(2,3)ꢃ
1H, dq, J(2,3)ꢃ15.5, J(3, Me)ꢃ
5H, s, Cp), 2.12 (2H, d, J(1,2)ꢃ8.4, ꢁ
). H-NMR (4Z, CDCl ) 5.70
/
15.5, J(1,2)ꢃ
6.4, Hꢁ
CH2ꢁ
/
8.4, Hꢁ
C(3)), 4.68
), 1.58 (3H,
/
C(2)), 5.31
2
-methyltropone]iron 2 (180 mg, 0.692 mmol)
(
(
/
/
/
/
/
/
The mixture 5a, 5b and 5c (840 mg, 1.707 mmol) was
chromatographed again on silica gel (170 g, 40/100
1
d, J(3, Me)ꢃ
and 5.32 (2H, 2ꢄ
Cp), 2.18 (2H, d, J(1,2):
Me):6.0, Meꢁ).
/
6.4, Meꢁ
/
3
/
m, Hꢁ/C(2) and H-C(3)), 4.74 (5H, s,
mesh, hexsol/Et O (1:1)) to give: 5a, 5b (502 mg, 1.020
2
/
9.2, ꢁCH2ꢁ), 1.60 (3H, d, J(3,
/
/
mmol) and 5c (99 mg, 0.201 mmol) (yellow red crystals
/
/
m.p. 168ꢁ172 8C (dec)). Loss of material through
/
decomposition during purification was observed (239
mg, 28% w/w). The pure 5a (pale yellow crystals m.p.
1
77ꢁ
the mixture 5a, 5b in ether/hexsol. The mother liquid
gave enriched 5b (70% 5bꢀ30% 5a).
a: H-NMR (CDCl ) 5.78 (1H, ddd, J(3,4)ꢃ
/
180 8C (dec)) was obtained by crystallisation of
4
.6. [3ꢀ
/
2] Cycloaddition of tricarbonyl[(4,5,6,7-h)-2-
1
methyltropone]iron and E/Z h -(crotyl)Fp (5aꢁ
/
d)
/
1
5
/7.4,
A solution of tricarbonyl[(4,5,6,7-h)-2-methyltropo-
ne]iron (1.00 g, 3.85 mmol) 2 in dry degassed CH Cl (20
3
J(4,5)ꢃ
/
5.3, J(4,6)ꢃ
8.0, J(4,5)ꢃ
5H, s, Cp), 3.17 (1H, dd, J(3,4)ꢃ
C(3)), 3.14 (1H, ddd, J(5,6)ꢃ8.0, J(6,7)ꢃ
J(4,6)ꢃ1.4, HꢁC(6)), 2.50 (1H, ddd, J(9,10 )ꢃ
J(8,9)ꢃ8.8, J(9,10
ddd, J(6,7)ꢃ4.9, J(7,8)ꢃ
C(7)), 1.89 (1H, dd, Jgem
C(10)), 1.84 (1H, dddq, J(8,9)ꢃ
/
1.4, Hꢁ/C(4)), 5.58 (1H, ddd, J
2
2
(5,6)ꢃ
/
/
5.3, J(3,5)ꢃ
/
1.1, Hꢁ/C(5)), 4.74
ml) was stirred and cooled to ꢂ80 8C under argon.
Trimethylsilyl triflate (TMSTf) (0.7 ml, 0.853 g, 3.86
mmol) was added dropwise and the mixture was stirred
/
(
/
7.4, J(3,5)ꢃ/1.1,
Hꢁ
/
/
/
4.9,
Fp
1
/
/
/
12.5,
C(9)), 2.28 (1H,
3
4
h at ꢂ
/
80 8C. The solution of h -(crotyl)Fp (1.12 g,
MeꢁC(1)
/
)ꢃ
/
6.3, Hꢁ
/
.83 mmol, 1.25 mol eq.) 4E/4Z (70/30) in dry CH Cl2
2
MeꢁC(1)
/
/
4.3, J(7,10
)ꢃ
12.5, H
C(8))ꢃ
C(8)), 1.50
6.3, w 2.8,
/
1.4, Hꢁ
/
(
5 ml) was added during 15 min. After stirring at ꢂ
/
Fp
Fp
/
ꢃ
/
12.3, J(9,10 )ꢃ
/
ꢁ
8
0 8C for 1 h the temperature was allowed to warm up
/
8.8, J(8, Meꢁ
/
/
to 40 8C for 3 h. After evaporation of the solvent, the
redꢁbrown residue was disolved in tetrahydrofuran (80
ml). The saturated aqueous NaHCO (20 ml) was added
MeꢁC(1)
6
.9, J(7,8)ꢃ
1H, ddm, Jgem
among others, J(7,10
/
4.3, J(8, 10
ꢃ
):
/
1.4, Hꢁ
/
/
MeꢁC(1)
(
/
12.3, J(9,10
)ꢃ
1.4, J(8, 10
C(10)), 1.15 (3H, d, J(8, MeꢁC(8))ꢃ
C(1)). C-NMR (CDCl3)
CO from Fp), 209.6 (s, 3ꢄCO from
Fe(CO) ), 209.4 (s, C(2)ÄO), 92.2 (d, C(4)), 89.3 (d,
/
ꢃ
/
1/2
MeꢁC(1)
MeꢁC(1)
3
)ꢃ
/
):
/
and the mixture was stirred at r.t. for 30 min. The
organic layer was separated. Water layer was washed
MeꢁC(1)
1
.4, H
MeꢁC(8)), 1.08 (3H, s, Meꢁ
18.0, 217.7 (s, 2ꢄ
ꢁ
/
/
/6.9,
13
/
/
with ether (3ꢄ10 ml). The combined organic layers
/
2
/
/
were dried over magnesium sulphate. After filtration
and evaporation of the solvent, the brown residue (2.28
g) was purified by flash column chromatography (FLC)
/
3
C(5)), 85.8 (s, Cp), 67.0 (d, C(7)), 66.0 (d, C(6)), 61.9 (d,
C(8)), 60.2 (d, C(3)), 56.5 (t, C(10)), 55.3 (s, C(1)), 30.3
on silica gel (450 g, 40/100 mesh, hexsol/Et O (1:1)) to
2
(d, C(9)), 25.6 (q, Meꢁ
/
C(1)), 22.60 (q, MeꢁC(8)). Anal.
6
/
9
give 5: (1.209 g, 2.457 mmol, 64% yield, 78% conversion
Calc. for C H Fe O (492.08): C, 53.70; H, 4.10.
Found: C, 53.35; H, 4.01%.
2
2
20
2
calculated on the used starting material). The ratio of
the diastereoisomers in the crude product was deter-
1
5b: H-NMR (CDCl ) 5.69ꢁ
/
5.62 (2H, m, Hꢁ
C(5)), 4.70 (5H, s, Cp), 3.13 (1H, dd, J(3,4)ꢃ
J(3,5)ꢃ1.7, HꢁC(3)), 2.93 (1H, ddd, J(5,6)ꢃ
J(6,7)ꢃ4.3, J(4,6)ꢃ2.1, HꢁC(6)), 2.54 (1H, ddm,
J(7,8)ꢃ5.8, J(6,7)ꢃ 1.9, HꢁC(7)), 2.21
1H, dd, J(9,10
C(9)), 2.14 (1H, dq, J(8, Meꢁ
HꢁC(8)), 2.06 (1H, ddm, Jgemꢃ
w1/2
J(9,10)ꢃ
MeꢁC(1)), 1.10 (3H, d, J(8, Meꢁ
C-NMR (CDCl ) 217.5 and 217.2 (s, 2ꢄ
/
C(4), Hꢁ
6.6,
7.6,
/
3
1
mined by H-NMR (CDCl ) based on the singlets of Cp
/
3
signals of the Fp groups 5a, 5b, 5c, 5d in the ratio
5
/
/
/
7:26:17:0%; 4.74 d (5H, s, 5aꢁ
/
Cp) 4.70 d (5H, s, 5bꢁ
/
/
/
/
/
/
4.3, w1/2
:
/
/
Cp), 4.77 d (5H, s, 5cꢁCp), ? d (5H, s, 5dꢁ
/
/Cp),
HꢁC(9)
MeꢁC(1)
(
)ꢃ
/
9.6, J(9,10
C(8)ꢃ
14.2, J(9,10)ꢃ
)ꢃ
6.1, J(7,8)ꢃ
/
8.8, Hꢁ
5.8,
9.6,
/
respectively. The diastereoisomer 5d was not observed.
Part of the starting material 2 was also recovered (180
mg, 0.692 mmol, 18% mol).
/
/
/
/
/
/
C(9)
:/1.8, H
ꢁ
/
C(10)), 1.21 (1H, ddm, Jgemꢃ
/14.2,
MeꢁC(1)
/8.8, w1/2
:/1.5, H
ꢁ
/
C(10)), 1.13 (3H, s,
/
/
C(8))ꢃ
/
6.1, Meꢁ
CO from
CO from Fe(CO) ), 209.2 (s, C(2)ÄO),
d, C(4) and C(5)), 86.0 (s, Cp), 63.7
(d, C(7)), 59.1 (2ꢄd, C(3) and C(6)), 54.5 (t, C(10)),
/
C(8)).
1
3
/
3
Fp), 209.5 (s, 3ꢄ
/
/
3
9
1
91.2 and 90.2 (2ꢄ
/
When 1.86 mol eq. of h -(crotyl)Fp (instead of 1.25 mol eq.) was
used the yield of cycloadducts increased from 64 to 80%.
/

B. Horv a´ th et al. / Journal of Organometallic Chemistry 659 (2002) 43ꢁ
/49
49
5
4.0 (s, C(1)), 51.7 (d, C(8)), 27.3 (q, Meꢁ
C(9)), 17.0 (q, MeꢁC(8)).
c: H-NMR (CDCl ) 5.66 (1H, ddd, J(3,4)ꢃ
/
C(1)), 26.7 (d,
The Comenius University, UK/135/2002 and UK/136/
2002 is also gratefully acknowledged.
/
1
5
/7.4,
3
J(4,5)ꢃ
J(5,6)ꢃ
5H, s, Cp), 3.30 (1H, dd, J(3,4)ꢃ
/
5.2, J(4,6)ꢃ
/
1.7, Hꢁ
/
C(4)), 5.53 (1H, ddd,
/
8.0, J(4,5)ꢃ
/
5.2, J(3,5)ꢃ
/
1.2, Hꢁ/C(5)), 4.77
(
/
7.4, J(3,5)ꢃ
/
1.2,
MeꢁC(1)
References
Hꢁ
J(9,10
ddd, J(5,6)ꢃ
.50 (1H, dd, J(6,7)ꢃ
dqm, J(8, MeꢁC(8))ꢃ
C(8)), 1.84 (1H, dddm, Jgemꢃ
/
C(3)), 3.24 (1H, ddd, J(9,10
)ꢃ
/
12.9,
HꢁC(9)
)ꢃ
8.0, J(6,7)ꢃ
5.6, J :
/
8.1, J(8,9)ꢃ
5.6, J(4,6)ꢃ
0.6, HꢁC(7)), 1.97 (1H,
7.0, w1/2 3, Hꢁ
/
7.0, Hꢁ
/
C(9)), 3.23 (1H,
[1] Y. Kashman, S. Hirsch, F. Koehn, S. Cross, Tetrahedron Lett. 28
/
/
/
1.7, HꢁC(6)),
/
(
1987) 5461.
2
/
/
/
[2] N. Greco, D. Marten, S. Raghu, M. Rosenblum, J. Am. Chem.
Soc. 98 (1976) 848.
/
/
7.5, J(8,9)ꢃ
/
:
/
/
HꢁC(9)
[3] M. Rosenblum, J.C. Watkins, J. Am. Chem. Soc. 112 (1990)
6316.
/
14.2, J(9,10
)ꢃ
/
HꢁC(9)
8
1
1
7
.1, w1/2
4.2, J(9,10
.27 (3H, s, Meꢁ
ꢃ
/
1.8, H
ꢁ
/
C(10)), 1.52 (1H, ddm, Jgemꢃ
/
[4] (a) W.T. Brady, J.P. Hieble, J. Am. Chem. Soc. 94 (1972)
MeꢁC(1)
MeꢁC(1)
/
)ꢃ
C(1)), 1.11 (3H, d, J(8, Meꢁ
3
/
12.9, w1/2
ꢃ
/1.2, H
ꢁ
C(10)),
C(8))ꢃ
C(8)). C-NMR (CDCl ) 217.8 and 217.4 (2ꢄ
4
279;
/
/
/
(
b) W.T. Brady, J.P. Hieble, Tetrahedron Lett. 37 (1970) 3205.
1
.5, Meꢁ
CO from Fp), 209.5 (s, 3ꢄ
08.8 (s, C(2)ÄO), 91.1 (d, C(4)), 88.8 (d, C(5)), 85.8 (s,
Cp), 66.5 (d, C(6)), 64.3 (d, C(7)), 62.3 (d, C(3)), 56.6 (d,
C(8)), 54.7 (t, C(10)), 54.5 (s, C(1)), 29.7 (q, MeꢁC((1)),
2.6 (d, C(9)), 22.5 (q, MeꢁC(8)). Anal. Calc. for
C H Fe O (492.08): C, 53.70; H, 4.10. Found: C,
/
/
[5] N. Morita, T. Asao, A. Tajiri, H. Sotokawa, M. Hatano, Chem.
Lett. (1985) 1879.
3
s, 2ꢄ
/
/CO from Fe(CO)3),
[6] R.B. King, Organometallic Syntheses: Transition Metal, vol. 1,
Academic Press, New York, 1965, p. 90.
2
/
[7] (a) A. Cutler, D. Ehntholt, W.P. Giering, P. Lennon, S. Raghu, A.
Rosan, M. Rosenblum, J. Tancrede, D. Wells, J. Am. Chem. Soc.
/
2
/
9
8 (1976) 3495;
2
2
20
2
6
(b) A. Bucheister, P Klemarczyk, M. Rosenblum, Organometal-
lics 1 (1982) 1679.
5
3.48; H, 4.08%.
[
[
8] E. Pretsch, T. Clerc, J. Seibl, W. Simon, Tables of Spectral Data
for Structure Determination of Organic Compounds, Springer-
Verlag, Berlin, 1983, p. H25.
Acknowledgements
9] M. Rosenblum, J. Organometal. Chem. 300 (1986) 191.
[10] G. Brauer, Handbuch der Pr a¨ parativen Anorganischen Chemie,
Financial support by The Slovak Grant Agency
VEGA 1/4167/97, VEGA 1/7013/20, also by grants of
vol. 3, Ferdinand Enke Verlag, Stuttgart, 1981, p. 1827.
[11] A. Boh a´ cˇ , J. Chem. Educ. 72 (1995) 263.