Reactions of transition-metal η1-propargyl and η1-allenyl complexes with sulfur dioxide and transition-metal - Carbon bond-cleaving reactions of the cycloadducts which yield cyclic sulfenate esters

Article abstract of DOI:10.1021/om980006l

The preparation of several cyclopentadienyliron dicarbonyl η¹-2-alkynyl and η¹-allenyl complexes is reported. The 3 + 2 cycloaddition reactions of these complexes with sulfur dioxide yielded regioisomeric transition-metal-substituted 1,2-oxathiolen-1-yl oxides (sulfenate esters). One of the η¹-allenyl complex SO₂ cycloadducts has been characterized by X-ray crystallography. The transition metal can subsequently be cleaved from the sulfenate ester containing complexes under oxidative and nonoxidative reaction conditions to produce a variety of new sulfur-containing heterocycles.

Full text of DOI:10.1021/om980006l

2832
Organometallics 1998, 17, 2832-2838
Rea ction s of Tr a n sition -Meta l η1-P r op a r gyl a n d
η1-Allen yl Com p lexes w ith Su lfu r Dioxid e a n d
Tr a n sition -Meta l-Ca r bon Bon d -Clea vin g Rea ction s of
th e Cycloa d d u cts Wh ich Yield Cyclic Su lfen a te Ester s
Allison L. Hurley, Mark E. Welker,*,† and Cynthia S. Day‡
Department of Chemistry, Wake Forest University, P.O. Box 7486,
Winston-Salem, North Carolina 27109
Received J anuary 6, 1998
The preparation of several cyclopentadienyliron dicarbonyl η1-2-alkynyl and η1-allenyl
complexes is reported. The 3 + 2 cycloaddition reactions of these complexes with sulfur
dioxide yielded regioisomeric transition-metal-substituted 1,2-oxathiolen-1-yl oxides (sulfenate
esters). One of the η1-allenyl complex SO2 cycloadducts has been characterized by X-ray
crystallography. The transition metal can subsequently be cleaved from the sulfenate ester
containing complexes under oxidative and nonoxidative reaction conditions to produce a
variety of new sulfur-containing heterocycles.
In tr od u ction
the cycloaddition of cyclopentadienyliron dicarbonyl
2-alkynyl complexes with ketenes as a route to cyclo-
pentenones.4 Five- and six-membered-ring sulfur-
containing heterocycles will presumably begin attracting
increased attention as synthetic targets because of a
recent report that 1,2-dithiolanes and 1,2-dithianes look
particularly promising as inhibitors of HIV type 1
replication.5 This replication inhibition is apparently
a result of their ability to attack the conserved zinc
fingers (presumably via the sulfur of the heterocycle)
of retroviral nucleocapsid proteins causing zinc ejection
from the protein.
Cycloaddition reactions between transition-metal η1-
2-alkynyl (1) and η1-allyl complexes (1) and unsaturated
electrophilic reagents (2) have been studied in detail
over the last 20 years with the pioneering work in this
area having been done by the Rosenblum and Wojcicki
groups.1 These 3 + 2 cycloaddition reactions have been
shown to yield transition-metal-substituted five-mem-
bered-ring heterocycles and carbacycles (3) and offer
alternative approaches to these ring systems when the
metal is subsequently cleaved from the ring.1-3
Several years ago, we reported a variant of this 3 +
2 cycloaddition reaction which yields transition-metal-
substituted five-membered-ring thiosulfinate esters.1a,2
More recently, we have explored an example of this
reaction, first reported by Wojcicki in 1977,3 involving
Exp er im en ta l Section
Gen er a l Meth od s. All nuclear magnetic resonance (NMR)
spectra were obtained using a Varian VXR-200 FT NMR. All
absorptions are expressed in parts per million relative to
tetramethylsilane. Infrared (IR) spectra were obtained using
a Perkin-Elmer 1620 FTIR. All elemental analyses were
performed by Atlantic Microlab, Inc., of Norcross, GA. High-
resolution mass spectral analyses were performed by the
Midwest Center for Mass Spectrometry, University of Ne-
braska-Lincoln. Low-resolution EI mass spectra were ob-
tained on a Hewlett-Packard 5989 GC/MS system. Melting
points were determined on a Mel-Temp apparatus and are
reported uncorrected. Tetrahydrofuran and diethyl ether were
distilled from sodium/benzophenone under nitrogen immedi-
ately prior to use. Dichloromethane was distilled from calcium
hydride immediately prior to use. All reactions were carried
out under an atmosphere of dry nitrogen unless otherwise
noted. Cyclopentadienyliron dicarbonyl dimer was purchased
from Strem Chemicals and used as received. Phenyllithium
and methyllithium solutions, propargyl methyl ether, and
copper iodide were purchased from Aldrich Chemical Co. and
† Henry Dreyfus Teacher-Scholar Awardee (1994-99). E-mail:
welker@wfu.edu.
‡ To whom correspondence concerning X-ray crystallography should
be addressed.
(1) For recent reviews of transition-metal mediated 3 + 2 cycload-
ditions see: (a) Welker, M. E. Chem. Rev. 1992, 92, 97. (b) Chan, D.
M. T. Comprehensive Organic Syntheses; Trost, B. M., Ed., Pergamon
Press: New York, 1991, Vol. 5, p 271. (c) Wojcicki, A. Coord. Chem.
Rev. 1990, 105, 35. (d) Rosenblum, M. J . Organomet. Chem. 1986, 300,
191.
(2) (a) Fulcher, B. C.; Hunter, M. L.; Welker, M. E. Synth. Commun.
1993, 23, 217. (b) Raseta, M. E.; Mishra, R. K.; Cawood, S. A.; Welker,
M. E.; Rheingold, A. L. Organometallics 1991, 10, 2936. (c) Powell, K.
R.; Elias, W. J .; Welker, M. E. J . Organomet. Chem. 1991, 407, 81. (d)
Brown, D. S.; Owens, C. F.; Wilson, B. G.; Welker, M. E.; Rheingold,
A. L. Organometallics 1991, 10, 871. (e) Urove, G. A.; Welker, M. E.;
Eaton, B. E. J . Organomet. Chem. 1990, 384, 105. (f) Raseta, M. E.;
Cawood, S. A.; Welker, M. E.; Rheingold, A. L. J . Am. Chem. Soc. 1989,
111, 8268. (g) Urove, G. A.; Welker, M. E. Organometallics 1988, 7,
1013.
(4) Stokes, H. L.; Ni, L. M.; Belot, J . A.; Welker, M. E. J . Organomet.
Chem. 1995, 487, 95.
(5) (a) Rice, W. G.; Baker, D. C.; Schaeffer, C. A.; Graham, L.; Bu,
M.; Terpening, S.; Clanton, D.; Schultz, R.; Bader, J . P.; Buckheit, R.
W.; Field, L.; Singh, P. K.; Turpin, J . A. Antimicrob. Agents Chemother.
1997, 41, 419. For a review see: Rice, W. G.; Turpin, J . A. Rev. Med.
Virol. 1996, 6, 187.
(3) Chen, L. S.; Lichtenberg, D. W.; Robinson, P. W.; Yamamoto,
Y.; Wojcicki, A. Inorg. Chim Acta 1977, 25, 165.
S0276-7333(98)00006-5 CCC: $15.00 © 1998 American Chemical Society
Publication on Web 05/21/1998

η1-Propargyl and η1-Allenyl Complexes with SO2
Organometallics, Vol. 17, No. 13, 1998 2833
used as received. Propargyl tosylate, 3-phenyl-2-propyn-1-ol,
and 2-butyn-1-ol were purchased from Farchan Laboratories
and used as received. 2-butyne-1,4-diol and 3-butyn-2-ol were
purchased from Lancaster and used as received. CpFe(CO)2-
CH2CtCR (6a , R ) CH3)6 and (6b, R ) Ph)6 were synthesized
according to literature procedures via addition of a THF
solution of the CpFe(CO)2 (Fp) anion (5) to a THF solution of
the appropriate 2-alkynyl tosylate (4a ,b). Literature proce-
dures6 typically use 2-alkynyl halides, but the tosylates are
more convenient to work with since they are solids and give
routinely higher yields of iron complex. Allenyl complexes,
CpFe(CO)2CHCdCdCHR (8a ,b, R ) H, Me)6b and CpFe-
3-Tosyl-1-bu tyn e (7b). This compound has been reported
without spectroscopic characterization previously.11 3-Butyn-
2-ol (2.00 g, 0.029 mol), p-toluenesulfonyl chloride (5.16 g, 0.027
mol), and potassium hydroxide (8.00 g, 0.143 mol) were reacted
using the above procedure to yield the product (7b) (4.54 g,
0.020 mol, 71%) as a white solid, mp 50-51 °C. 1H NMR
(CDCl3): 7.79 (d, J ) 8.2 Hz, 2 H), 7.31 (d, J ) 8.2 Hz, 2 H),
5.14 (dq, J ) 6.6, 2.0 Hz, 1 H), 2.42 (s, 3 H), 2.39 (d, J ) 2.0
Hz, 1 H), 1.54 (d, J ) 6.6 Hz, 3 H). Anal. Calcd for
C
11H12O3S: C, 58.91; H, 5.39. Found: C, 59.00; H, 5.41.
1-Tosyl-4-m eth oxy-2-bu tyn e (9a ). 4-Methoxy-2-butyn-1-
ol9 (1.11 g, 0.011 mol), p-toluenesulfonyl chloride (2.01 g, 0.011
mol), and potassium hydroxide (3.11 g, 0.056 mol) were reacted
using the above procedure to yield the product (9a ) (2.28 g,
0.009 mol, 85%) as a light yellow oil. 1H NMR (CDCl3): 7.79
(d, J ) 7.8 Hz, 2 H), 7.33 (d, J ) 7.9 Hz, 2 H), 4.72 (t, J ) 1.4
Hz, 2 H), 3.97 (t, J ) 1.4 Hz, 2 H), 3.25 (s, 3 H), 2.43 (s, 3 H).
Anal. Calcd for C12H14O4S: C, 56.68; H, 5.55. Found: C,
56.61; H, 5.55.
(CO)2CRCdCdCH2 (10a , R ) CH2OMe;7 10b, R ) CH2OBn2b
)
were prepared likewise.
4-Meth oxy-2-bu tyn -1-ol. In an adaptation of a literature
procedure,8 propargyl methyl ether (1.00 g, 14.3 mmol) was
dissolved in diethyl ether (100 mL) and cooled to -78 °C. A
2.5 M n-butyllithium (6.28 mL, 15.7 mmol) solution was added
dropwise. The solution was stirred for 1.5 h at -78 °C, and
then paraformaldehyde (0.856 g, 28.5 mmol) was added. The
reaction mixture was allowed to warm to 25 °C overnight. The
mixture was poured into saturated NH4Cl solution (100 mL)
and then extracted with diethyl ether (3 × 50 mL). The
solution was dried with MgSO4, and the solvent was removed
under reduced pressure. The product, a light yellow oil (1.11
g, 11.1 mmol, 78%), was used without further purification and
proved identical by spectroscopic comparison to previously
reported material.9
1-Tosyl-4-(ben zyloxy)-2-bu tyn e (9b). 4-(Benzyloxy)-2-
butyn-1-ol2b (2.55 g, 0.015 mol), p-toluenesulfonyl chloride (2.62
g, 0.014 mol), and potassium hydroxide (4.06 g, 0.072 mol) were
reacted using the above procedure to yield the product (9b)
(3.93 g, 0.012 mol, 87%) as a light yellow oil. 1H NMR
(CDCl3): 7.80 (d, J ) 8.0 Hz, 2 H), 7.31 (m, 7 H), 4.75 (t, J )
1.4 Hz, 2H), 4.46 (s, 2 H), 4.05 (t, J ) 1.4 Hz, 2 H), 2.39 (s, 3
H). Anal. Calcd for C18H18O4S: C, 65.44; H, 5.49. Found: C,
65.58; H, 5.52.
Gen er a l P r oced u r e for Syn th esis of Ir on Alk yn yl a n d
Allen yl Com p lexes.2,6,7 The iron anion (5) was generated by
stirring a THF solution of [CpFe(CO)2]2 over a 1% sodium
amalgam for 5 h. The anion was then added using a double-
ended needle to a THF solution of the appropriate alkynyl
tosylate cooled to 0 °C. The resulting mixture was allowed to
warm to 25 °C over 1 h. The solvent was removed by rotary
evaporation. The remaining residue was washed with pentane
until the washes were colorless. The pentane was removed
by rotary evaporation. The crude product was vacuum-dried
and purified by column chromatography on alumina.
Cyclop en ta d ien yl(2-bu tyn yl)d ica r bon ylir on (6a ). The
iron anion (5) was generated from [CpFe(CO)2]2 (2.00 g, 5.7
mmol) and then added to a THF solution of 1-tosyl-2-butyne
(4a ) (2.32 g, 10.3 mmol) using the procedure outline above.
The crude product was purified by column chromatography
on deactivated alumina using 20:1 hexane/diethyl ether. The
product (6a ) (1.66 g, 7.2 mmol, 70%) was obtained as a brown
solid, which was identical by spectroscopic comparison to
previously reported material.6b
Cyclop en t a d ien yl(3-p h en yl-2-p r op yn yl)d ica r b on yl-
ir on (6b). The iron anion (5) was generated from [CpFe-
(CO)2]2 (10.00 g, 0.028 mol) and then added to a THF solution
of 1-tosyl-3-phenyl-2-propyne (4b) (15.44 g, 0.054 mol) using
the procedure outlined above. The crude product was purified
by column chromatography on deactivated alumina using 10%
diethyl ether in hexane. The product (6b) (10.44 g, 0.036 mol,
66%) was obtained as a brown solid, which was identical by
spectroscopic comparison to previously reported material.6b
Cyclop en t a d ien yl(p r op a d ien yl)d ica r b on ylir on (8a ).
The iron anion (5) was generated from [CpFe(CO)2]2 (2.00 g,
5.7 mmol) and then added to a THF solution of propargyl
tosylate (7a ) (2.26 g, 10.8 mmol) using the procedure outlined
above. The crude product was purified by column chroma-
tography on deactivated alumina using 50:50 hexane/diethyl
ether. The product (8a ) (1.40 g, 6.5 mmol, 60%) was obtained
as a dark red oil, which was identical by spectroscopic
comparison to previously reported material.6b
Gen er a l P r oced u r e for Syn th esis of Alk yn yl Tosyla tes.
In an adaptation of a literature procedure,10 the propargyl
alcohol was dissolved in diethyl ether (100 mL) and p-
toluenesulfonyl chloride (0.95 equiv) was added. The solution
was cooled to -15 °C, and powdered potassium hydroxide (5.0
equiv) was added 1 equiv at a time over 30-45 min. The
reaction mixture was then allowed to stir at -15 °C for 90
min. Ice water (100 mL) was then added, and the mixture
was extracted with diethyl ether (3 × 50 mL). The solution
was dried with MgSO4, and the solvent was removed under
reduced pressure. The product was then triturated with
petroleum ether (15 mL) and cooled to -78 °C, and the solvent
was decanted. The remaining product was dried under
vacuum.
1-Tosyl-2-bu tyn e (4a ). This compound has been reported
without spectroscopic characterization previously.11 2-Butyn-
1-ol (3.59 g, 0.051 mol), p-toluenesulfonyl chloride (9.34 g, 0.049
mol), and potassium hydroxide (14.4 g, 0.257 mol) were reacted
using the above procedure to yield the product (4a ) (10.47 g,
0.047 mol, 91%) as a light yellow solid, mp 43-44 °C. 1H NMR
(CDCl3): 7.74 (d, J ) 8.2 Hz, 2 H), 7.32 (d, J ) 8.2 Hz, 2 H),
4.64 (q, J ) 2.1 Hz, 2 H), 2.42 (s, 3 H), 1.70 (t, J ) 2.1 Hz, 3
H). Anal. Calcd for C11H12O3S: C, 58.91; H, 5.39. Found: C,
58.87; H, 5.40.
1-Tosyl-3-p h en yl-2-p r op yn e (4b). 3-Phenyl-2-propyn-1-
ol (13.65 g, 0.103 mol), p-toluenesulfonyl chloride (18.5 g, 0.100
mol), and potassium hydroxide (28.90 g, 0.515 mol) were
reacted using the above procedure to yield the product (4b)
(24.86 g, 0.0870 mol, 90%) as a light yellow solid, mp 75-77
°C. 1H NMR (CDCl3): 7.84 (d, J ) 8.4 Hz, 2 H), 7.32-7.23
(m, 7 H), 4.93 (s, 2 H), 2.37 (s, 3 H). Anal. Calcd for
C
16H14O3S: C, 67.11; H, 4.93. Found: C, 67.24; H, 4.94.
(6) (a) Thomasson, J . E.; Robinson, P. W.; Ross, D. A.; Wojcicki, A.
Inorg. Chem. 1971, 10, 2130. (b) Roustan, J . L.; Cadiot, P. C. R. Acad.
Sci. 1969, 268, 734.
(7) Foxman, B.; Marten, D.; Rosan, A.; Raghu, S.; Rosenblum, M.
J . Am. Chem. Soc. 1977, 99, 2160.
(8) Brandsma, L.; Verkruijsse, H. D. Synthesis of Acetylenes, Allenes,
and Cumulenes; Elsevier Publishing Co.: New York, 1981; p 65.
(9) J ones, G. B.; Moody, C. J .; Padwa, A.; Kassir, J . M. J . Chem.
Soc., Perkin Trans. 1 1991, 1721.
Cyclop en t a d ien yl(1,2-b u t a d ien -1-yl)d ica r b on ylir on
(8b). The iron anion (5) was generated from [CpFe(CO)2]2
(1.64 g, 4.6 mmol) and was added to a THF solution of 7b (1.89
g, 8.4 mmol) using the procedure outlined above. The product
(8b) was obtained as a dark red oil (1.46 g, 6.4 mmol, 75%),
(10) Brandsma, L. Preparative Acetylenic Chemistry; Elsevier Pub-
lishing Co.: New York, 1971; p 256.
(11) Marszak-Fleury, A. Ann. Chim. Paris 1958, Ser. 13, 3, 657.

2834 Organometallics, Vol. 17, No. 13, 1998
Hurley et al.
which was identical by spectroscopic comparison to previously
reported material.6b
gum (16b) (0.81 g, 2.0 mmol, 48%). IR (NaCl): 2017, 1966,
1141, 1125, 1090, 1070, 867, 840 cm-1 1H NMR (CDCl3): 7.34
.
(m, 5 H), 4.85 (s, 5 H), 4.60 (s, 2 H), 4.28 (s, 2 H), 3.92 (d, J )
16.6 Hz, 1 H), 3.43 (d, J ) 16.6 Hz, 1 H). 13C NMR (CDCl3):
214.21, 213.70, 146.58, 137.86, 128.38, 128.34, 127.75, 100.94,
85.67, 72.57, 66.19, 53.42. Anal. Calcd for C18H16FeO5S: C,
54.02; H, 4.03. Found: C, 53.13; H, 4.08. FAB HRMS (m/e):
calcd for (M + Na+) (C18H16FeO5SNa), 422.9966; found,
422.9955.
Cyclop en ta d ien yl(4-m eth oxy-1,2-bu ta d ien -3-yl)d ica r -
bon ylir on (10a ). The iron anion (5) was generated from
[CpFe(CO)2]2 (1.66 g, 4.7 mmol) and was added to a THF
solution of 9a (2.28 g, 9.0 mmol) using the procedure outlined
previously. The product was obtained as a dark red oil (10a )
(1.85 g, 7.3 mmol, 79%), which was identical by spectroscopic
comparison to previously reported material.7
Cyclop en ta d ien yl(4-(ben zyloxy)-1,2-bu ta d ien -3-yl)d i-
ca r bon ylir on (10b). The iron anion (5) was generated from
[CpFe(CO)2]2 (1.17 g, 3.3 mmol) and was added to a THF
solution of 9b (2.00 g, 6.1 mmol) using the procedure outline
previously. The product was obtained as a dark red oil (10b)
(1.69 g, 5.0 mmol, 83%), which was identical by spectroscopic
comparison to previously reported material.7
Gen er a l P r oced u r e for th e Syn th esis of Meta llo-
su lfen a te Ester s. The appropriate iron allenyl or propargyl
complex was dissolved in CH2Cl2 (10-15 mL), purged with
nitrogen, and cooled to -78 °C. Sulfur dioxide (10 mL) was
condensed at -78 °C into the iron complex solution. The
reaction mixture was allowed to warm to 25 °C under nitrogen
to allow evaporation of excess sulfur dioxide. The solvent was
removed by rotary evaporation, and the remaining solid was
vacuum-dried. The crude product was purified by recrystal-
lization or column chromatography. Cyclopentadienyl(1-oxo-
5-phenyl-1,2-oxathiol-4-en-4-yl))dicarbonyliron (12b) and cy-
clopentadienyl(1-oxo-5-methyl-1,2-oxathiol-4-en-4-yl)dicar-
bonyliron (12a ) were purified by recrystallization from CHCl3/
hexane and were identical by spectroscopic comparison to
previously reported material.3
Cr ysta llogr a p h ic Str u ctu r e Deter m in a tion of Com -
p lex 14a . Single crystals of CpFe(CO)2(C3H3SO2) (14a ) are,
at 293 K, monoclinic, space group P21/c-C5 (No. 14), with a
2h
) 10.3532(9) Å, b ) 9.5692(7) Å, c ) 22.708(2) Å, â ) 97.931-
(6)°, V ) 2228.2(3) Å3, and Z ) 8 [dcalcd ) 1.670 g cm-3; µa(Mo
KR) ) 1.534 mm-1]. A total of 4336 independent absorption-
corrected reflections having 2θ(Mo KR) < 50.8° (the equivalent
of 0.8 limiting Cu KR sphere) were collected on a computer-
controlled Siemens P4 autodiffractometer using ω scans and
graphite-monochromated Mo KR radiation. The structure was
solved using direct methods” techniques with the Siemens
SHELXTL-PC (version 5.0) software package. The resulting
structural parameters have been refined to convergence [R1
(unweighted, based on F) ) 0.050 and wR2 (weighted, based
on F2) ) 0.085 for 2449 independent reflections having 2θ(Mo
KR)< 50.8° and I > 2σ(I); R1 (unweighted, based on F) ) 0.110
and wR2 (weighted, based on F2) ) 0.106 for all 4096 reflec-
tions; R1 (unweighted, based on F) ) 0.083 and wR2 (weighted,
based on F2) ) 0.095 for 3566 independent reflections having
2θ(Mo KR) < 50.8° and I > 0] using counterweighted full-
matrix least-squares techniques and a structural model which
incorporated anisotropic thermal parameters for all non-
hydrogen atoms and isotropic thermal parameters for the
hydrogen atoms. The hydrogen atoms were included in the
structure factor calculations as idealized atoms (assuming sp3
or sp2 hybridization of the carbon atoms and a C-H bond
length of 0.98 Å) “riding” on their respective carbon atoms.
The isotropic thermal parameters for the hydrogen atoms were
fixed at values 1.2 times the equivalent isotropic thermal
parameters of the carbon atoms to which they are covalently
bonded. All calculations were performed using the SHELXTL-
PC (version 5) interactive software package (G. Sheldrick,
Siemens, Madison, WI).
Cyclop en ta d ien yl(1-oxo-1,2-oxa th iol-3-en -4-yl))d ica r -
bon ylir on (14a ). The iron allenyl complex 8a (2.09 g, 9.7
mmol) was treated with SO2 to generate the crude product,
which was purified by column chromatography on silica gel
using 50:50 ethyl acetate/pentane to yield a brown solid (14a )
(1.26 g, 4.5 mmol, 48%): mp 70-71 °C (dec). IR (NaCl): 2016,
1965, 1130, 1094, 934, 847, 833 cm-1 1H NMR (CDCl3): 5.78
.
(d, J ) 2.4 Hz, 1 H), 4.89 (s, 5 H), 3.79 (dd, J ) 16.3, 2.8 Hz,
1 H), 3.32 (d, J ) 16.3 Hz, 1 H). 13C NMR (CDCl3): 215.0,
214.05, 136.64, 99.03, 85.40, 75.65. DEPT (CDCl3): 136.64
(CH), 99.03 (C), 85.40 (CH), 75.65 (CH2). Anal. Calcd for C10
H8FeO4S: C, 42.89: H, 2.89. Found: C, 42.86; H, 2.89.
-
Rea ction of 12b w ith HCl To P r od u ce tr a n s-Cin n a m yl
Ch lor id e (17). Complex 12b (0.100 g, 0.28 mmol) was
dissolved in CH2Cl2 (12 mL) and cooled to 0 °C. Concentrated
HCl (0.047 mL, 0.56 mmol) was added, and the reaction
mixture was allowed to warm to 25 °C overnight. The solution
was washed with saturated NaHCO3 (20 mL). The aqueous
layer was extracted with CH2Cl2 (2 × 10 mL). The organic
extracts were combined and dried with anhydrous MgSO4. The
solvent was removed by rotary evaporation and the remaining
material vacuum-dried. The crude product was purified by
column chromatography on silica gel using 1:1 diethyl ether/
hexane to elute trans-cinnamyl chloride (17) (0.030 g, 0.20
Cyclop en ta d ien yl(1-oxo-5-m eth yl-1,2-oxa th iol-3-en -4-
yl))d ica r bon ylir on (14b). The iron allenyl complex 8b (1.54
g, 6.5 mmol) was treated with SO2 to generate the crude
product, which was purified by column chromatography on
silica gel using 50:50 ethyl acetate/pentane to yield a brown
gum (14b) (0.56 g, 1.9 mmol, 29%) as a mixture of syn and
anti diastereomers. IR (NaCl): 2017, 1966, 1115, 912, 847
cm-1
.
1H NMR (CDCl3): syn, 5.54 (d, J ) 3.0 Hz, 1H), 4.91
(s, 5 H), 3.60 (dq, J ) 7.4, 3.0 Hz, 1 H), 1.42 (d, J ) 7.4 Hz, 3
H); anti, 5.45 (d, J ) 0.8 Hz, 1 H), 4.89 (s, 5 H), 3.31 (dq, J )
7.5, 0.8 Hz, 1 H), 1.22 (d, J ) 7.5 Hz, 3 H). FAB HRMS (m/e):
calcd for (MH+) (C11H11FeO4S) 294.9728, found 294.9726.
Cyclopen tadien yl(1-oxo-3-m eth ylm eth oxy-1,2-oxath iol-
3-en -4-yl)d ica r bon ylir on (16a ). The iron allenyl complex
10a (0.75 g, 2.9 mmol) was reacted with SO2 to generate the
crude product, which was purified by column chromatography
on silica gel using 100% ethyl acetate to yield a dark red gum
(16a ) (0.48 g, 1.5 mmol, 51%). IR (NaCl): 2016, 1958, 1123,
1
mmol, 70%) (identified by H NMR spectroscopic comparison
to an authentic sample (Acros)) followed by 1:1 CH2Cl2/pentane
to elute cyclopentadienyldicarbonyliron chloride (18) (0.022 g,
0.10 mmol, 37%) (also identified by spectroscopic comparison
to an authentic sample).12
Syn th esis of Su lfen a te Ester s (19). Gen er a l P r oce-
d u r e. The metallosulfenate ester (12a ,b) (150 mg) was
dissolved in CH2Cl2 (10 mL) and purged with carbon monoxide.
Ceric ammonium nitrate (4-8 equiv) was dissolved in metha-
nol or ethanol (15-20 mL) and also purged with carbon
monoxide. Both solutions were cooled to -78 °C. The ceric
ammonium nitrate solution was then added to the metallo-
sulfenate ester solution by a double-ended needle using CO
pressure. The resulting reaction mixture was allowed to warm
1086, 839 cm-1 1H NMR (CDCl3): 4.94 (s, 5 H), 4.20 (s, 2 H),
.
3.93 (d, J ) 16.6 Hz, 1 H), 3.43 (d, J ) 16.4 Hz, 1 H), 3.42 (s,
3 H). 13C NMR (CDCl3): 214.28, 213.97, 146.56, 100.87, 85.78,
68.65, 58.38, 43.45. FAB HRMS (m/e): calcd for MH+ (C12H13
-
FeO5S): 324.9885, found 324.9841.
Cyclopen tadien yl(1-oxo-3-m eth ylben zyloxy-1,2-oxath i-
ol-3-en -4-yl)d ica r bon ylir on (16b). The iron allenyl complex
10b (1.43 g, 4.3 mmol) was treated with SO2 to generate the
crude product, which was purified by column chromatography
on silica gel using 3:1 ethyl acetate/pentane to yield a brown
(12) Piper, T. S.; Cotton, F. A.; Wilkinson, G. J . Inorg. Nucl. Chem.
1955, 1, 165.

η1-Propargyl and η1-Allenyl Complexes with SO2
Organometallics, Vol. 17, No. 13, 1998 2835
to 25 °C and stir 30 min under a balloon of carbon monoxide.
Water (50 mL) was then added and extracted with ethyl
acetate (3 × 30 mL). The organic layers were combined and
dried with anhydrous Na2SO4. The solvent was removed by
rotary evaporation.
15.5 Hz, 1 H), 5.17 (d, J ) 15.2 Hz, 1 H), 1.99 (s, 3 H). 13C
NMR (CDCl3): 144.0, 140.32, 129.02, 128.96, 128.87, 128.61,
84.72, 11.06. Anal. Calcd for C10H10O2S: C, 61.83; H, 5.19.
Found: C, 62.08; H, 5.21.
1-Meth oxy-3-(cyclop en ta d ien yld ica r bon ylfer r io)-3-bu -
ten -2-on e (22a ) fr om 16a a n d Ce(IV)/Meth a n ol. Complex
16a (0.100 g, 0.31 mmol) was treated with ceric ammonium
nitrate (0.51 g, 0.93 mmol) in methanol/CH2Cl2 under a CO
atmosphere as described above for 19. The crude product was
purified by column chromatography on silica gel using 1:1 ethyl
acetate/pentane to yield the product as a red-brown oil (0.010
g, 0.036 mmol, 12%). IR (NaCl): 2016 (s), 1952 (s), 1685 (m),
4-(Ca r bom eth oxy)-5-m eth yl-1,2-oxa th iol-4-en -1-yl Ox-
id e (19a ). Complex 12a (0.154 g, 0.53 mmol) was treated with
ceric ammonium nitrate (1.45 g, 2.65 mmol) in methanol. The
crude product was purified by chromatography on a silica gel
column at 0 °C using 100% diethyl ether to yield the product
as a light yellow oil (0.030 g, 0.17 mmol, 33%). IR (NaCl):
1728, 1437, 1271, 1130, 964, 746, 689 cm-1
.
1H NMR
1120 (m) cm-1 1H NMR (CDCl3): 5.87 (s, 1 H), 5.59 (s, 1 H),
.
(CDCl3): 5.67 (dq, J ) 15.2, 2.4 Hz, 1 H), 5.35 (dq, J ) 15.2,
2.4 Hz, 1 H), 3.82 (s, 3 H), 2.41 (t, J ) 2.4 Hz, 3 H). 13C NMR
(CDCl3): 162.34, 155.77, 129.99, 82.18, 52.52, 10.85. Anal.
Calcd for C6H8O4S: C, 40.90; H, 4.58; Found: C, 41.71; H, 4.48.
4-(Ca r bom eth oxy)-5-p h en yl-1,2-oxa th iol-4-en -1-yl Ox-
id e (19b). Complex 12b (0.150 g, 0.42 mmol) was treated with
ceric ammonium nitrate (1.84 g, 3.36 mmol) in methanol. The
crude product was purified by chromatography on a silica gel
prep plate using 3:1 hexane/ethyl acetate to yield the product
as a light yellow gum (0.020 g, 0.08 mmol, 20%). IR (NaCl):
4.89 (s, 5 H), 4.23 (s, 2 H), 3.42 (s, 3 H). EI HRMS (m/z): calcd
for (M+ - CO) (C11H12O3Fe), 248.0136; found (M+ - CO)
248.0132, (M+ - 2CO) 220.0183. FAB LRMS (m/z): calcd for
(MH+) (C12H13O4Fe) 277.0, found 277.1.
1-(Ben zyloxy)-3-(cyclop en ta d ien yld ica r bon ylfer r io)-3-
bu ten -2-on e (22b) fr om 16b a n d Ce(IV)/Meth a n ol. Com-
plex 16b (0.100 g, 0.25 mmol) was treated with ceric ammo-
nium nitrate (0.41 g, 0.75 mmol) in methanol/CH2Cl2 under a
CO atmosphere as described above for 19. The crude product
was purified by column chromatography on silica gel using
1:1 ethyl acetate/pentane to yield the product as a red oil (0.020
g, 0.057 mmol, 23%). IR (NaCl): 2017 (s), 1959 (s), 1713 (m),
1737, 1436, 1275, 1215, 1133, 967, 695 cm-1
.
1H NMR
(CDCl3): 7.47 (m, 5 H), 5.90 (d, J ) 15.7 Hz, 1 H), 5.58 (d, J
) 15.7 Hz, 1 H), 3.73 (s, 3 H). 13C NMR (CDCl3): 161.9, 156.39,
130.33, 129.97, 129.03, 128.57, 127.16, 83.01, 52.56. EI HRMS
(m/e): calcd for M+ (C11H10O4S) 238.0316, found 238.0300.
4-(Ca r boeth oxy)-5-p h en yl-1,2-oxa th iol-4-en -1-yl Oxid e
(19c). Complex 12b (0.150 g, 0.42 mmol) was treated with
ceric ammonium nitrate (1.84 g, 3.36 mmol) in ethanol. The
crude product was purified by chromatography on a silica gel
prep plate (1 mm) using 1:1 diethyl ether/hexane to yield the
product as a light yellow gum (0.010 g, 0.040 mmol, 9%). 1H
NMR (CDCl3): 7.40-7.54 (m, 5 H), 5.90 (d, J ) 15.8 Hz, 1 H),
5.58 (d, J ) 15.7 Hz, 1 H), 4.18 (q, J ) 7.1 Hz, 2 H), 1.15 (t, J
) 7.1 Hz, 3 H). Anal. Calcd for C12H12O4S: C, 57.13; H, 4.79.
Found: C, 57.29; H, 4.93.
1682 (m) 1568 (m), 1116 (m), 1027 (m) cm-1
.
1H NMR
(CDCl3): 7.29-7.35 (m, 5 H), 5.84 (s, 1 H), 5.56 (s, 1 H), 4.87
(s, 5 H), 4.61 (s, 2 H), 4.29 (s, 2 H). 13C NMR (CDCl3): 214.99,
208.26, 153.62, 137.65, 130.65, 128.39, 127.99, 127.78, 85.54,
73.07, 72.28. DEPT (CDCl3): 130.65 (CH2), 128.39 (CH),
127.99 (CH), 127.78 (CH), 85.54 (CH), 73.07 (CH2), 72.28 (CH2).
EI HRMS (m/z): calcd for (M+ - CO) (C17H16O3Fe) 324.0449,
found (M+ - CO) 324.0440, (M+ - 2CO) 296.0440. FAB LRMS
(m/z): calcd for (MH+) (C18H17O4Fe) 353.0, found 353.1.
1-Meth oxy-3-(cyclop en ta d ien yld ica r bon ylfer r io)-3-bu -
ten -2-on e (22a ) fr om 16a a n d Dim eth ylcu p r a te. Complex
16a (0.106 g, 0.33 mmol) was reacted with dimethylcuprate
generated from the reaction of copper(I) iodide (0.094 g 0.49
mmol) with methyllithium (1.4 M, 0.70 mL, 0.98 mmol) as
described above for 21. The crude product was purified by
column chromatography on silica gel using 1:1 ethyl acetate/
pentane to yield a red-brown oil (0.010 g, 0.036 mmol, 11%)
identical by spectroscopic comparison to the material (22a )
reported above.
Rea ction of 12a w ith Meth yllith iu m to yield 20. 12a
(0.100 g, 0.34 mmol) was dissloved in 10 mL of freshly distilled
THF and was cooled to -78 °C. Methyllithium (1.2 mL, 1.4
M, 1.71 mmol) was added slowly to the flask. The reaction
mixture was allowed to stir for 30 min at -78 °C and then
saturated NaCl solution (20 mL) was added. The aqueous
layer was extracted with diethyl ether (2 × 20 mL). The
organic extracts were combined and dried with anhydrous
magnesium sulfate. The solvent was removed by rotary
evaporation, and the crude product was vacuum-dried, yielding
a dark red gum (0.063 g, 0.20 mmol, 60%). IR (CDCl3): 3155,
2021, 1968, 1436, 1384, 1096, 934, 868, 767. 1H NMR
(CDCl3): 4.93 (s, 5 H), 4.71 (d, J ) 10 Hz, 1 H), 4.42 (d, J )
10 Hz, 1 H), 2.49 (s, 3 H), 2.19 (s, 3 H). FAB HRMS (m/e):
calcd for (M+Na+) (C12H14O4FeSNa), 332.9839, found 332.9862.
4-Met h yl-5-p h en yl-1,2-oxa t h iol-4-en -1-yl Oxid e (21).
Copper(I) iodide (0.160 g, 0.84 mmol) was added to THF (5
mL). The suspension was thoroughly purged with nitrogen
and cooled to -45 °C. Methyllithium (1.4 M, 1.20 mL, 1.68
mmol) was added, and the reaction mixture was allowed to
stir at -45 °C (30 min). In another flask, 12b (0.200 g, 0.56
mmol) was dissolved in THF (10 mL). The solution was purged
with nitrogen and cooled to -45 °C. The THF solution of 12b
was then transferred to the cuprate solution by a double-ended
needle. The resulting mixture was allowed to stir for 30 min
at -45 °C, and then saturated NH4Cl (25 mL) was added. The
aqueous layer was extracted with diethyl ether (3 × 15 mL).
The organic extracts were combined and dried with anhydrous
magnesium sulfate. The solvent was removed by rotary
evaporation, and the remaining oil was vacuum-dried. The
crude product was purified by chromatography (1:1 hexane/
Et2O) on a silica gel prep plate (1 mm) to yield a light yellow
gum (0.040 g, 0.21 mmol, 37%). IR (NaCl): 1123, 970, 760,
1-(Ben zyloxy)-3-(cyclop en ta d ien yld ica r bon ylfer r io)-3-
bu ten -2-on e (22b) fr om 16b a n d Dim eth ylcu p r a te. Com-
plex 16b (0.771 g, 1.93 mmol) was reacted with dimethylcu-
prate generated from the reaction of copper(I) iodide (0.550 g,
2.89 mmol) with methyllithium (1.4 M, 4.13 mL, 5.78 mmol)
as described above for 21. The crude product was purified by
column chromatography on silica gel using 1:1 ethyl acetate/
pentane to yield a red oil (0.184 g, 0.52 mmol, 27%) identical
by spectroscopic comparison to the material (22b ) reported
above.
Resu lts a n d Discu ssion
The propargyl and allenyl complexes used for cycload-
ditions were prepared by addition of the CpFe(CO)2
anion (Fp anion) (5) to solutions of the appropriate
propargyl tosylate.2,6,7 The tosylates were prepared
from the propargyl alcohols using standard conditions.10
4-Methoxy-2-butyne-1-ol used to make 9a was prepared
via condensation of the anion of propargyl methyl ether
with paraformaldehyde.8,9 We have reported the prepa-
ration of 4-benzyl-2-butyn-1-ol used to make 9b pre-
viously.2b Propargyl tosylates of internal alkyl or aryl
substituted alkynes (4a ,b) react with the Fp anion in
SN2 reactions to produce 2-alkynyl complexes (6a ,b ).
695 cm-1 1H NMR (CDCl3): 7.43-7.39 (m, 5 H), 5.60 (d, J )
.

2836 Organometallics, Vol. 17, No. 13, 1998
Hurley et al.
Propargyl tosylates of terminal alkynes (7a ,b) or inter-
nal alkynes containing oxygen substituents (9a ,b) react
with Fp anion in SN2′ reactions to produce allenes (8a ,b
and 10a ,b).
Reaction of iron propargyl complexes (6a ,b) with SO2
was first reported in 1969 by Roustan and Charrier.13
They reported the products to be SO2 insertion products,
and in 1971 Wojcicki et al.6a correctly assigned the
product structures as sultines resulting from a 3 + 2
cycloaddition reaction with SO2. Demetalation to yield
S,O-containing heterocycles has not been studied in
detail previously. We first repeated Wojcicki’s SO2
experiments with the exception of performing them in
CH2Cl2 at -78 °C and isolated the 3 + 2 cycloaddition
products (12a ,b) in excellent yields as expected.
F igu r e 1. Molecular structures of two crystallographically
independent molecules (a, b) present in 14a .
Ta ble 1. Cr ysta l Da ta a n d Str u ctu r e Refin em en t
for Cp F e(CO)2(C3H3SO2) (14a )
empirical formula
fw
C10H8FeO4S
280.08
temp
293(2) K
Iron allenyl complex cycloaddition chemistry has not
been studied to the extent propargyl chemistry has. In
1971, Wojcicki et al. reported isolating no SO2-contain-
ing products from a variety of reactions of 8a with SO2
at 25 °C or above.6a In the mid 1980s, Rosenblum and
Watkins reported use of 8a in 3 + 2 cyclization ap-
proaches to hydroazulenes.14 We have found that all 4
allenyl complexes reported above (8a ,b and 10a ,b) will
react with SO2 in CH2Cl2 at -78 °C to produce 3 + 2
cycloaddition products (14a ,b and 16a ,b), which are
regioisomers of the complexes formed by the propargyl
cyclizations. These cyclization reactions presumably
proceed via intermediates (13 and 15) analogous to the
one (11) reported for the propargyl cyclizations.6a
The structure of the cyclization product (14a ) from
the simplest allene was confirmed by X-ray crystal-
lography. A single-crystal X-ray structural analysis of
14a revealed that it was composed of two crystallo-
graphically independent molecules of CpFe(CO)2(C3H3-
SO2) as shown in Figure 1a,b. Data collection and
refinement parameters are summarized in Table 1 with
selected bond lengths and angles, averaged for the two
independent molecules, given in Table 2.
wavelength
cryst system
space group
unit cell dimens
0.710 73 Å
monoclinic
P21/c-C5 (No. 14)
2h
a ) 10.3532(9) Å
b ) 9.5692(7) Å, b ) 97.931(6)°
c ) 22.708(2) Å
2228.2(3) Å3, 8
V, Z
D(calcd)
abs coeff
range of rel transm factors
F(000)
1.670 g‚cm-3
1.534 mm-1
0.843-1.000
1136
cryst size
0.35 × 0.40 × 0.40 mm
2θ range for data collcn
limiting indices
reflcns collcd
indepdt reflcns
refinement method
data/restraints/params
goodness-of-fit on F2
final R indices
2449 I > 2σ(I) data
R indices (all 4096 data)
4.5-50.8°
0 e 12, 0 e k e 11, -27 e l e 27
4336
4096 [R(int) ) 0.0216]
full-matrix least-squares on F2
3566/0/290
1.007
R1 ) 0.0499, wR2 ) 0.0846
R1 ) 0.1096, wR2 ) 0.1057
R indices (3566 data, I > 0) R1 ) 0.0828, wR2 ) 0.0952
extinction coeff
largest diff peak and hole
0.0012(2)
0.285 and -0.315 e/Å3
The average Fe-Cvinyl bond length is 1.978(5) Å, in
agreement with values previously observed in other
CpFe(CO)2 complexes containing a sulfur γ to Fe or a
five-membered ring system [1.991(7) Å in CpFe(CO)2-
(CMeCHSO2(C6H5)),15 2.008(7) Å in CpFe(CO)2(C3H2-
(C6H5)S2O),2b and 1.997(8) Å in CpFe(CO)2(C4H5SO2)16].
(13) Roustan, J .-L.; Charrier, C. C. R. Acad. Sci. Ser. C, 1969, 268,
2113.
(14) Rosenblum, M.; Watkins, J . C. J . Am. Chem. Soc. 1990, 112,
6316 and references therein.

η1-Propargyl and η1-Allenyl Complexes with SO2
Organometallics, Vol. 17, No. 13, 1998 2837
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg) in Cr ysta llin e Cp F e(CO)2(C3H3SO2) (14a )a
Ta ble 3. 1H NMR Ch em ica l Sh ifts of Meth yl a n d
Meth in e P r oton s in 14b-a n ti a n d -syn
param
valueb
param
valueb
δ
δ w/Eu
(CDCl3) (FOD)3 ∆δ
Bond Lengths
Fe1-C6-10
Fe1-Cp
Fe1-C4
Fe1-C1
1.749(6,4,8,4)
1.978(5,7,7,2)
2.081(6,15,41,10)
1.724(-,2,2,2)c
14b-anti methyl (d, J ) 7.5 Hz)
14b-anti methine (dq, J ) 7.5, 0.8 Hz)
14b-syn methyl (d, J ) 7.4 Hz)
1.22
3.31
1.42
3.60
1.55
4.60
2.27
3.98
0.33
1.29
0.85
0.38
S1-O1
S1-O2
S1-C3
O1-C2
C1-C2
1.635(4,3,3,2)
1.466(4,2,2,2)
1.806(5,2,2,2)
1.428(6,7,7,2)
1.301(6,1,1,2)
O3-C4
1.143(5,2,4,4)
14b-syn methine (dq, J ) 7.4, 3.0 Hz)
C6-C7
1.371(10,24,46,10)
1.512(6,3,3,2)
C1-C3
Bond Angles
CpFe1C1
CpFe1C4
C4Fe1C5
C4Fe1C1
121.3(-,14,14,2)c
125.5(-,3,5,4)c
94.5(2,5,5,2)
O1S1O2
O2S1C3
O1S1C3
C2O1S1
108.1(2,5,5,2)
105.9(3,7,7,2)
91.9(2,2,2,2)
109.9(3,1,1,2)
the anti orientation of the oxygen and methyl groups
as proven by shift reagent studies (Table 3).17 The
methine proton in the major diastereomer shifted down-
field by 1.29 ppm when treated with Eu(FOD)3, whereas
the methyl only shifted downfield by 0.33 ppm. The syn
diastereomer showed the exact opposite trend in shifts
(methyl moved downfield more than the methine) as
expected. Allylic coupling from the alkene H to the
methine was much larger in the syn (14b) (allylic J )
3.0 Hz) compared to the anti (14b) (allylic J ) 0.8 Hz)
diastereomer. In our earlier thiosulfinate ester synthe-
ses,2b we had seen some effect of Lewis acid additives
on 3 + 2 cycloaddition stereochemistry so we also tried
the cycloaddition to produce 14b in the presence of
MgBr2 (-78 °C to -45 °C). The cyclization still oc-
curred, but the stereochemistry was little affected (1.9:1
anti/ syn).
90.0(2,16,27,4)
Fe1C4O3
Fe1C1C2
Fe1C1C3
178.8(5,5,10,4)
128.8(4,9,9,2)
122.3(3,7,7,2)
C2C1C3
C7C6C10
C1C3S1
C1C2O1
108.9(5,2,2,2)
108.0(7,9,17,10)
106.0(3,2,2,2)
118.4(5,1,1,2)
a
Bond lengths and angles have been averaged for the two
crystallographically-independent molecules. Entries in the table
b
are labeled in agreement with Figure 1a, molecule 1. The first
number in parentheses followed an average value of a bond length
or angle is the root-mean-square estimated standard deviation of
an individual datum. The second and third numbers are the
average and maximum deviation from the average value, respec-
tively. The fourth number represents the number of individual
measurements which are included in the average light. c The
symbol Cp is used to represent the center of gravity for the
cyclopentadienyl ring designated by carbon atoms C6-C10 in
Figure 1a and carbon atoms C16-C20 in Figure 1b. These values
are therefore listed without estimated standard deviations.
We then proceeded to investigate methods for the
cleavage of the iron-carbon bonds in complexes 12, 14,
and 16. The methods most often used by organometallic
chemists to remove organic ligands from CpFe(CO)(L)-
(R) complexes are protonolysis, halogenolysis, and oxi-
dative carboxylation18 so these methods were investi-
gated here first. Protonolysis of 12b did produce iron-
carbon bond cleavage but also resulted in SO2 extrusion
to produce trans-cinnamyl chloride (17, 70%) as well as
recovered iron in the form of CpFe(CO)2Cl (18, 37%).12
Related ring-opening reactions of sultines have been
reported previously.19
The average Fe-C(carbonyl) distance is 1.749(6) Å and
the average Fe-Cp centroid distance is 1.724 Å in
agreement with those previously observed.2b,15,16 The
average CdC bond of the cyclized ring is 1.301(6) Å,
shorter than the values of 1.336(9) and 1.330(10) Å in
CpFe(CO)2(CMeCHSO2(C6H5))15 and CpFe(CO)2(C3H3-
(C6H5)S2O),2b respectively, and similar to the value of
1.312(12) Å in CpFe(CO)2(C4H5SO2).16 The average
C-C bond length for the two isomers is 1.512(6) Å,
within the range observed for similar five-membered
ring complexes (1.485(12)-1.503(9) Å).2b,16 Both mol-
ecules also exhibit large exocyclic angles at the vinyl
carbon (127.9(4) and 123.0(3)° for molecule 1 and 129.6-
(4) and 121.6(3)° for molecule 2) with the larger angle
involving the methine carbon and the smaller angle
involving the methylene carbon of the ring.
Oxidative carboxylation of 12a ,b did produce the
desired esters (19), but the isolated yields were not as
high as we had hoped for. The known susceptibility of
cyclic sulfinate esters to alcohol-induced ring open-
ings19,20 is most likely responsible for the lower than
expected yields of esters (19).
(17) (a) Kato, A.; Numata, M. Tetrahedron Lett. 1972, 203. (b) Legler,
L. E.; J indal, S. L.; Murray, R. W. Tetrahedron Lett. 1972, 3907. (c)
Yanagawa, H.; Kato, T.; Kitahara, Y. Tetrahedron Lett. 1973, 1073.
(18) For some recent relevant examples and a review (e) see: (a)
Reger, D. L.; Mintz, E.; Lebioda, L. J . Am. Chem. Soc. 1986, 108, 1940.
(b) Barrett, A. G. M.; Mortier, J .; Sabat, M.; Sturgess, M. A. Organo-
metallics 1988, 7, 2553. (c) Reger, D. L.; Klaeren, S. A.; Babin, J . E.;
Adams, R. D. Organometallics 1988, 7, 181. (d) Liebeskind, L. S.;
Welker, M. E.; Fengl, R. W. J . Am. Chem. Soc. 1986, 108, 6328. (e)
J ohnson, M. D. Acc. Chem. Res. 1978, 11, 57.
Complex 14b was produced as a 2.3:1 mixture of
diastereomers. The major diastereomer (14b-anti) had
(19) Liskamp, R. M. J .; Zeegers, H. J . M.; Ottenheijm, H. C. J . J .
Org. Chem. 1981, 46, 5408.
(20) J ung, F.; Sharma, N. K.; Durst, T. J . Am. Chem. Soc. 1973, 95,
3420.
(15) Patel, P. P.; Welker, M. E.; Liable-Sands, L. M.; Rheingold, A.
L. Organometallics 1997, 16, 4519.
(16) Churchill, M. R.; Wormald, J . J . Am. Chem. Soc. 1971, 93, 1971.

2838 Organometallics, Vol. 17, No. 13, 1998
Hurley et al.
We then investigated nonoxidative demetalations by
analogy to cyclopentenone demetalations we had re-
ported in 1995.4 We examined reactions of 12a ,b with
nucleophiles such as alkyllithiums and cuprates. When
12a was treated with MeLi, ring opening to produce
sulfone (20) occurred. This is an expected result on the
basis of analogy to reported reactions of alkyllithiums
and Grignard reagents with cyclic sulfenate esters.21
from initial nucleophilic ring opening of the sulfenate
esters (16a ,b).19-21 Loss of a sulfur-containing species
from the â-position of 23 would account for the observed
products (22a ,b).
In summary, Fp propargyl and allenyl complexes
react with sulfur dioxide in 3 + 2 cycloaddition reac-
tions. These cycloaddition reactions produce regioiso-
meric transition-metal-substituted sulfenate esters in
good yields. The iron-substituted sulfenate esters can
be demetalated under oxidative and nonoxidative reac-
tion conditions to produce unusual, sulfur-containing
heterocycles. The biological activities of these hetero-
cycles will be reported in due course.
However, when 12b was treated with a cuprate
generated from MeLi or MeMgBr, we were able to
isolate the demetalated cyclic sulfenate ester (21).
Isolated yields again were probably diminished to some
extent by competitive ring-opening reactions of 12b and
21 that these nucleophilic conditions might induce.21
Ack n ow led gm en t. We thank the NIH NIGMS and
the Camille and Henry Dreyfus Foundation (Henry
Dreyfus Teacher-Scholar Award to M.E.W, 1994-99) for
their support. Low-resolution mass spectra were ob-
tained on an instrument purchased with the partial
support of NSF (Grant CHE-9007366). The Nebraska
Center for Mass Spectrometry (NSF Grant DIR9017262)
performed high-resolution mass spectral analyses.
Last, we investigated demetalation of the cycload-
ducts (16a ,b) prepared from the allenyl complex cy-
clizations. To our surprise, these complexes reacted
with Ce(IV) in methanol and dimethylcopper lithium to
produce identical, new R,â-unsaturated acyl complexes
(22a ,b). We propose that these complexes (22a ,b) result
Su p p or tin g In for m a tion Ava ila ble: Tables giving de-
tails of the X-ray structure determinations, atomic coordinates
and isotropic thermal parameters, bond lengths and bond
angles, and anisotropic displacement parameters for 14a (16
pages). Ordering information is given on any current masthead
page.
(21) (a) Harpp, D. N.; Vines, S. M.; Montillier, J . P.; Chan, T. H. J .
Org. Chem. 1976, 41, 3987. (b) Squires, T. G.; Venier, C. G.; Hodgson,
B. A.; Chang, L. W. Davis, F. A.; Panunto, T. W. J . Org. Chem. 1981,
46, 2373.
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