Titanocene-promoted eliminations on epoxy alcohols and epoxy esters

Article abstract of DOI:10.1002/ejoc.200901222

The reaction of a series of 2,3-epoxy alcohols and the corresponding formates, acetates, and benzoates promoted by Cp₂TiCl has been studied. The different outcome of the reaction of epoxy derivatives has been rationalized in terms of mechanistically biased processes. After homolytic oxirane cleavage, four main types of reaction were found: dehydroxylation, decarboxylation, dehydrogenation, and deoxygenation. The reaction products varied according to the substitution pattern. The radical nature of these eliminations is demonstrated.

Full text of DOI:10.1002/ejoc.200901222

FULL PAPER
DOI: 10.1002/ejoc.200901222
Titanocene-Promoted Eliminations on Epoxy Alcohols and Epoxy Esters
Alfonso Fernández-Mateos,*[a] Soledad Encinas Madrazo,[a] Pablo Herrero Teijón,[a] and
Rosa Rubio González[a]
Keywords: Radical reactions / Titanium / Elimination / Epoxides / Alcohols / Oxygen heterocycles
The reaction of a series of 2,3-epoxy alcohols and the corre-
sponding formates, acetates, and benzoates promoted by
Cp2TiCl has been studied. The different outcome of the reac-
tion of epoxy derivatives has been rationalized in terms of
mechanistically biased processes. After homolytic oxirane
cleavage, four main types of reaction were found: dehydrox-
ylation, decarboxylation, dehydrogenation, and deoxygen-
ation. The reaction products varied according to the substitu-
tion pattern. The radical nature of these eliminations is dem-
onstrated.
It has been shown that in the absence of radical acceptors
1,2-disubstituted epoxides (Scheme 2, R = H) can be deoxy-
genated by treatment with Cp2TiCl. This deoxygenation has
been explained in terms of homolytic cleavage of the oxir-
ane, followed by reduction of the secondary incipient radi-
cal with TiIII and further anionic β-elimination.[6]
Introduction
Epoxides are a convenient source of functionalized radi-
cals. The method based on the titanocene-mediated opening
of epoxides through single-electron transfer introduced by
Nugent and RajanBabu,[1] and the catalytic version devel-
oped by Gansäuer et al.,[2] have been the object of many
interesting applications in synthesis.[3] The radicals, gener-
ated by the reaction of epoxides with paramagnetic Cp2TiCl
(Scheme 1), can be trapped, in both intramolecular and
intermolecular addition reactions, by acceptors such as hy-
drogen,[1–3] alkenes,[1–3] carbonyls,[4] and nitriles.[5] In a sec-
ond way, the radicals could be reduced by TiIII to an alkyl-
titanium complex.[1–3]
Scheme 2. Reactions of disubstituted and trisubstituted epoxides.
We also found that trisubstituted epoxides, with at least a
methyl substituent (Scheme 2, R = Me) give allylic alcohols
through the elimination of a hydrogen atom instead of de-
oxygenation.[4a,7] This dehydrogenation method has been
applied to the synthesis of a variety of exo-methylene allylic
alcohols from epoxy carvone derivatives.[8]
The different kinds of behavior of trisubstituted epoxides
with respect to disubstituted ones would be due to the in-
cipient tertiary radical, which is sterically hindered in com-
parison with the secondary radicals. The methyl hydrogen
atoms of these intermediates are more accessible for the
TiIII organometallic reagent.[4a,9]
Regarding this issue, a new type of selective elimination
of a hydroxy group has been provided by Yadav et al.[10]
from the reaction of 2,3-epoxy primary alcohols with
Cp2TiCl. The proposed mechanism (Scheme 3) consists of
Scheme 1. Addition reactions induced by titanocene on epoxides.
[a] Departamento de Química Orgánica, Facultad de CC. Quím-
icas, Universidad de Salamanca,
Plaza de los Caídos 1-5, 37008 Salamanca, Spain
Fax: +34-923-294574
E-mail: afmateos@usal.es
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.200901222.
856
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Titanocene-Promoted Eliminations on Epoxy Alcohols and Epoxy Esters
the formation of TiIII–alkoxide, as an initial step, followed
Reactions were carried out by adding two equivalents of
by homolytic oxirane cleavage to afford the incipient radi- titanocene dichloride to one equivalent of the function-
cal, which subsequently participates intramolecularly with alized epoxide in tetrahydrofuran at room temperature. The
the unfilled d orbital of TiIII to form an oxetane intermedi- regiochemical outcome of the cleavage reaction is in agree-
ate, which then evolves into an alkene and titanocene oxide. ment with what has been observed previously with nonsym-
metrical oxiranes.[13] Epoxide opening is directed by non-
bonding interactions during electron transfer. In almost all
cases, the formation of allylic alcohols was observed.
We carried out the work with a series of acyclic epoxy
alcohols and epoxy esters, which were prepared by known
procedures from heptanal. The first series of primary
alcohol 1 and its derived esters and related compounds is
summarized in Table 1.
Table 1. Cp2TiCl-induced eliminations on epoxy alcohol 1 and its
esters.
Scheme 3. Dehydroxylation of 2,3-epoxy alcohols with TiIII
.
Two related selective eliminations of formyloxyl and ace-
toxyl groups from the formates and acetates of the 2,3-ep-
oxy primary alcohols have been found by our group.[4c]
Also, a β-scission of CN from β,γ-epoxy nitriles has been
reported recently.[9b] The kinetics of all these fragmenta-
tions corresponds to radical reactions, as we have demon-
strated with our radical clock based on pinene derivatives
(Scheme 4).[11]
Scheme 4. Elimination radical clocks.
The selective β-fragmentation mediated by titanocene
chloride would be a powerful route to allylic alcohols. Tak-
ing the reactions described above as a starting point, here
we investigated the mechanism, kinetics, and scope of those
elimination reactions. To the best of our knowledge, little
attention has been devoted to this topic,[12] apart from the
few papers reported above.
The reaction of titanocene chloride with epoxy alcohol 1
and epoxy formate 3 afforded exclusively allylic alcohol 2
in good yield. The first result is in agreement with previous
experiments reported by Yadav[10] with 1,2-disubstituted ep-
oxides. Unlike formate 3, the reaction of acetate 4 and ben-
zoate 6 provided a mixture of alcohol 2 and hydroxy esters
5 and 7, respectively, in different ratios. In both cases, the
major product resulted from β-hydrogen elimination. The
evolution of the disubstituted epoxides was different:
whereas epoxy formate 8 gave deoxygenation and deformyl-
ation products, 9 and 10, epoxy acetate 11 only gave deoxy-
genation product 12. A tentative graphical explanation of
the results shown in Table 1 is given in Scheme 6.
Results and Discussion
Here we report our findings on the reactions between
functionalized
(Scheme 5).
epoxides
and
titanocene
chloride
The eliminations induced by titanocene chloride took
place following several competitive pathways (Schemes 3
and 6). The mechanism proposed by Yadav[10] (Scheme 3)
explains the behavior of epoxy alcohol 1. In the reaction of
epoxy formate 3 (Scheme 6, R = H) the initial step would
be the well-documented titanocene-mediated opening of ep-
oxides, which afforded β-alkoxy radical A. In this interme-
Scheme 5. Eliminations induced by titanocene.
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Table 2. Cp2TiCl-induced eliminations on epoxy alcohol 13 and its
esters.
Scheme 6. Elimination pathways.
diate, the carbonyl group must be coordinated to TiIII and
further evolves to diradical B, which undergoes β-fragmen-
tation to give C and D. The hydrolysis step finally provided
the allylic alcohol and the titanocene oxide.
For epoxy esters 4 and 6, an alternative pathway from
radical A would also operate; that is, the transfer of a hy-
drogen from the methyl group[4a,7,9] to Cp2TiCl to give E.
The subsequent hydrolysis afforded the corresponding un-
saturated hydroxy ester.
It is worth noting that hydrogen elimination is faster than
decarboxylation on epoxy esters 4 and 6. The rate of ester
elimination decreased from formate 3 to benzoate 6 and this
is consistent with the results found with the radical clock
method.[11] This means that dehydrogenation mediated by
titanocene chloride is a radical reaction. With respect to
disubstituted epoxy esters 8 and 11, the mechanism pro-
posed in Scheme 2 (R = H) would operate for deoxygen-
ation and the one proposed in Scheme 6 would operate for
deformylation; the reduction in the incipient secondary rad-
ical with TiIII is much faster than β-scission of acetate. In
the case of epoxy formate 8, the reduction of the secondary
radical with TiIII is only slightly faster than β-scission of
formate.
Epoxy formate 16 provided deformylation product 14 as
the only product in an identical way to primary isomer 3.
However, secondary acetate 17 and benzoate 19, although
affording decarboxylation and dehydrogenation products
such as primary isomers 4 and 6, did not give similar ratios.
Whereas for epoxy acetate 17 deacetoxylation was the pre-
dominant reaction, debenzoylation and dehydrogenation
were almost equal for epoxy benzoate 19. This means that
the decarboxylation of secondary alcohol esters 17 and 19,
promoted by TiIII, is faster than for the primary ones 4 and
6. The behavior of epoxy benzyl alcohol 21 with TiIII was
different from that of alkyl analogue 13; only the dehydrox-
ylation product was obtained. The phenyl group appeared
to activate the elimination of the hydroxy group.
In order to understand the influence of the substitution
pattern of the epoxy alcohols on this reaction, we subjected
the tertiary epoxy alcohols shown in Table 3 to the reaction
with titanocene chloride.
Table 3. Cp2TiCl-induced eliminations on functionalized epoxides.
The scope and limitations of the elimination reaction
shown above were studied with a new series constituted by
secondary epoxy alcohol 13 and its ester derivatives, which
could react with titanocene chloride through alternative
competing pathways. The results are summarized in Table 2.
The reaction of titanocene chloride with epoxy alcohol
13 afforded a mixture with a similar ratio of dehydroxyl-
ation 14, dehydrogenation 2, and deoxygenation 15 prod-
ucts. This result is quite different from that found for pri-
mary epoxy alcohol 1, and it suggests that the secondary
hydroxy group is the worst leaving group. Thus, the rate
constant for β-scission of secondary hydroxy groups must
be lower than that of primary ones and close to that of β-
hydrogen scission.
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Titanocene-Promoted Eliminations on Epoxy Alcohols and Epoxy Esters
The reaction of tertiary epoxy alcohol 23 with titanocene irane cleavage would afford 35B, which could evolve, by re-
afforded expected dehydroxylation product 24 and dehydro- duction with TiIII, to give 35C, or by elimination of CH2O-
genation product 25. However, the major product was de- TiIV in a similar manner as the diradical B in Scheme 6, to
oxygenation product 26. This compound would not arise give 35D.[15] The 31A/35A equilibrium was displaced to 35A
by oxirane cleavage and further reduction and elimination because the ratio of products 33+34 was always higher than
(see Scheme 2) because the incipient tertiary radical would 32.
not be reduced in this way, as has been demonstrated.[9]
The reduction rate was too low. Therefore, we suggest
that the deoxygenation process could be explained in terms
Conclusions
of an equilibrium between the starting epoxy alcohol and
the regioisomer through a six-membered TiIV intermedi-
ate.[14] In this case, the equilibrium was clearly displaced to
the right (Scheme 7).
The reaction of a series of 2,3-epoxy alcohols and the
corresponding formates, acetates, and benzoates, promoted
by Cp2TiCl has been studied. The different outcome of the
reaction of epoxy derivatives has been rationalized in terms
of mechanistically biased processes. After homolytic oxir-
ane cleavage, four main types of reaction were found: dehy-
droxylation, decarboxylation, dehydrogenation, and deoxy-
genation. The reaction products varied according to the
substitution pattern.
Scheme 7. Equilibration of intermediates.
The primary alcohol trisubstituted epoxide system and
its formate led to hydroxy or formyloxyl elimination. The
corresponding epoxy acetate and epoxy benzoate mainly
provided the elimination of hydrogen. The disubstituted ep-
oxides mainly afforded the deoxygenation product. The sec-
ondary alcohol trisubstituted epoxide system and its esters
mainly afforded products from dehydroxylation or decar-
boxylation. The tertiary alcohol trisubstituted epoxide sys-
tem afforded deoxygenation as the major product when the
gem substituents to hydroxy were alkyl groups, and the de-
hydroxylation product when they were phenyl groups. An-
other conclusion is that elimination of the hydroxy groups
is faster for primary alcohols. Among the esters, the for-
myloxyl was the fastest leaving group. The acetate and ben-
zoate of the secondary alcohols were eliminated faster than
the primary ones. A rare reaction of radical CH2OTiCp2Cl
elimination has been found.
Phenyl methyl epoxy alcohol 27 gave dehydroxylation
product 28 and dehydrogenation product 29, as expected;
unsaturated diol 30 was also obtained. The first and second
products would arise through the incipient radical from ox-
irane cleavage, and further titanocene oxide or titanocene
hydride elimination, respectively. The formation of diol 30
would be explained by epoxide isomerization, followed by
regioselective oxirane cleavage and dehydrogenation.
Finally, diphenyl epoxy alcohol 31 provided mainly dehy-
droxylation product 32, diol 33, and methyl ketone 34. The
formation of the latter two products could be explained in
terms of the interconversion of epoxy alcohol 31 into iso-
mer 35. To test this interconversion, already proposed in
Scheme 7, epoxy alcohol 35 was treated with titanocene
chloride. The products obtained from this reaction were ex-
actly the same as from 31, although in a different ratio.
Accordingly, a mechanistic hypothesis can be proposed for
the reaction of 31 and 35 with TiIII, depicted in Scheme 8.
After the formation of TiIII–alkoxide, as an initial step, the
interconversion of 31A into 35A would occur through a six-
membered TiIV intermediate (see Scheme 7), followed by re-
gioselective oxirane cleavage to 31B, and elimination of ti-
Experimental Section
1
General Remarks: Melting points are uncorrected. H NMR spec-
tra were measured at either 200 or 400 MHz and 13C NMR spectra
tanocene epoxide to give 31C. From 35A, regioselective ox- were measured at 50 or 100 MHz in CDCl3 and referenced to sol-
Scheme 8. Proposed mechanism for reaction of epoxy alcohols 31 and 35 with Cp2TiCl.
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vent, except where otherwise indicated. IR spectra were recorded
for neat samples on NaCl plates, unless otherwise noted. Standard
mass spectrometry data were acquired by using a GC–MS system
in EI mode with a maximum m/z range of 600. When required, all
solvents and reagents were purified by standard techniques: tetra-
hydrofuran (THF) was purified by distillation from sodium and
benzophenone and degassed before use. All reactions were con-
ducted under a positive pressure of argon by using standard bench-
top techniques for the handling of air-sensitive materials. Chroma-
tographic separations were carried out under pressure on silica gel
using flash column techniques on Merck silica gel 60 (0.040–
0.063 mm). Unless otherwise mentioned yields reported are for
chromatographically pure isolated products.
(CH2), 31.6 (CH2), 36.9 (CH2), 73.0 (CH), 114.1 (CH2), 141.3 (CH)
ppm. HRMS (ESI): calcd. for C9H18ONa 165.1255; found
165.1259. C9H18O (142.14): calcd. C 76.00, H 12.76; found C 76.08,
H 12.74.
Reaction of 1-(2-Methyloxiran-2-yl)heptan-1-ol (13) with Cp2TiCl:
According to GP1, reaction of 13 (102 mg, 0.58 mmol) with
Cp2TiCl followed by flash chromatography (hexane/diethyl ether,
8:2) furnished 14 (32 mg, 34%), 2 (25 mg, 27%), and (hexane/di-
ethyl ether, 2:8) 15 (23 mg, 23%). Data for 15: IR: ν = 3353, 2932,
˜
1449, 1034 cm–1. 1H NMR (400 MHz, CDCl3): δ = 0.88 (t, J =
6.8 Hz, 3 H, 9-H), 1.2–1.6 (m, 10 H), 4.16 (d, J = 13.2 Hz, 1 H, 1-
H), 4.23 (t, J = 6.8 Hz, 1 H, 3-H), 4.30 (d, J = 13.2 Hz, 1 H, 1-H),
5.09 (s, 1 H, =CH2), 5.12 (s, 1 H, =CH2) ppm. 13C NMR
(100 MHz, CDCl3): δ = 14.0 (CH3), 22.5 (CH2), 25.6 (CH2), 29.1
(CH2), 31.7 (CH2), 35.7 (CH2), 64.0 (CH2), 74.7 (CH), 112.4 (CH2),
149.9 (C) ppm. HRMS (ESI): calcd. for C10H20O2Na 195.1356;
found 195.1355. C10H20O2 (172.15): calcd. C 69.72, H 11.70; found
C 69.67, H 11.68.
General Procedure 1 (GP1): A mixture of Cp2TiCl2 (2.20 mmol)
and Zn (6.60 equiv.) in strictly deoxygenated THF (10 mL) was
stirred at room temperature until the red solution turned green. In
a separate flask, the epoxy compound (1 mmol) was dissolved in
strictly deoxygenated THF (10 mL). The green TiIII solution was
slowly added by cannula to the epoxide solution. After 30 min, an
excess amount of saturated NaH2PO4 was added, and the mixture
was stirred for 20 min. The mixture was filtered to remove insoluble
titanium salts. The product was extracted into ether, and the com-
bined organic layer was washed with saturated NaHCO3 and brine,
dried (Na2SO4), and filtered. After removal of the solvent, the
crude product was purified by flash chromatography.
Reaction of 5-(2-Methyloxiran-2-yl)nonan-5-ol (23) with Cp2TiCl:
According to GP1, reaction of 23 (150 mg, 0.75 mmol) with
Cp2TiCl followed by flash chromatography (hexane/diethyl ether,
9:1) furnished 26 (77 mg, 53%), 24 (35 mg, 27%), and (hexane/
diethyl ether, 1:9) 25 (6 mg, 4%). Data for 24: IR: ν = 3357, 2929,
˜
1
1462, 1134, 1008 cm–1. H NMR (200 MHz, CDCl3): δ = 0.90 (m,
6 H, 7-H, 4Ј-H), 1.2–1.4 (m, 8 H), 1.73 (s, 3 H, Me), 2.00 (m, 4 H),
4.10 (s, 2 H, 1-H) ppm. 13C NMR (50 MHz, CDCl3): δ = 13.8 (2
CH3), 16.0 (CH3), 22.8 (CH2), 29.5 (CH2), 30.5 (CH2), 31.6 (CH2),
31.9 (CH2), 32.3 (CH2), 63.7 (CH2), 127.7 (C), 138.6 (C) ppm.
HRMS (ESI): calcd. for C12H24ONa 207.1719; found 207.1728.
Reaction of (3-Hexyl-2-methyloxiran-2-yl)methanol (1) with Cp2-
TiCl: According to GP1, reaction of 1 (87 mg, 0.50 mmol) with
Cp2TiCl followed by flash chromatography (hexane/diethyl ether,
8:2) furnished 2 (67 mg, 85%). IR: ν = 3370, 2957, 2930, 2859,
˜
1653, 1458, 1377, 1262, 1113, 1030 cm–1. 1H NMR (400 MHz,
CDCl3): δ = 0.88 (t, J = 7.0 Hz, 3 H, 9-H), 1.2–1.6 (m, 10 H), 1.72
(s, 3 H, Me), 4.05 (t, J = 6.5 Hz, 1 H, 3-H), 4.83 (s, 1 H, 1-H), 4.93
(s, 1 H, 1-H) ppm. 13C NMR (100 MHz, CDCl3): δ = 14.0 (CH3),
17.4 (CH3), 22.5 (CH3), 25.5 (CH3), 29.2 (CH3), 31.7 (CH3), 34.9
(CH3), 76.0 (CH3), 110.8 (CH3), 147.7 (C) ppm. MS (EI): m/z (%)
= 156 (3) [M+], 113 (11), 99 (11), 94 (12), 86 (18), 71 (100), 55 (20).
HRMS (ESI): calcd. for C10H20ONa 179.1412; found 179.1401.
C10H20O (156.15): calcd. C 76.86, H 12.90; found C 76.98, H 12.94.
C12H24O (184.18): calcd. C 78.20, H 13.12; found C 78.38, H 13.16.
1
Data for 25: IR: ν = 3364, 2935, 1455, 1128, 999 cm–1. H NMR
˜
(200 MHz, CDCl3): δ = 0.88 (m, 6 H, 7-H, 4Ј-H), 1.2–1.7 (m, 12
H), 4.15 (s, 2 H, 1-H), 4.98 (s, 1 H, =CH2), 5.17 (s, 1 H, =CH2)
ppm. 13C NMR (50 MHz, CDCl3): δ = 13.9 (2 CH3), 23.0 (2 CH2),
25.5 (2 CH2), 40.7 (2 CH2), 65.0 (CH2), 77.5 (C), 111.4 (CH2),
148.1 (C) ppm. HRMS (ESI): calcd. for C12H24ONa 207.1719;
found 207.1726. C12H24O (184.18): calcd. C 78.20, H 13.12; found
C 78.08, H 13.15.
Reaction of (3-Hexyl-2-methyloxiran-2-yl)methyl Acetate (4) with
Cp2TiCl: According to GP1, reaction of 4 (103 mg, 0.51 mmol)
with Cp2TiCl followed by flash chromatography (hexane/diethyl
ether, 8:2) furnished 2 (22 mg, 25%) and 5 (64 mg, 64%). Data for
Reaction of (2-Methyloxiran-2-yl)diphenylmethanol (31) with
Cp2TiCl: According to GP1, reaction of 31 (103 mg, 0.42 mmol)
with Cp2TiCl followed by flash chromatography (hexane/diethyl
ether, 7:3) furnished 34 (16 mg, 18%), 32 (39 mg, 39%), and 33
5: IR: ν = 3436, 2929, 2857, 1742, 1461, 1373, 1238, 1038, 912 cm–1.
˜
(28 mg, 28%). Data for 34: IR: ν = 2900, 1705, 1451, 1353,
˜
1H NMR (400 MHz, CDCl3): δ = 0.87 (m, 3 H, 9-H), 1.1–1.6 (m,
10 H), 2.08 (s, 3 H, Me), 4.16 (t, J = 6.5 Hz, 1 H, 3-H), 4.60 (d, J
= 13.4 Hz, 1 H, 1-H), 4.66 (d, J = 13.4 Hz, 1 H, 1-H), 5.14 (br. s,
1 H, =CH2), 5.20 (br. s, 1 H, =CH2) ppm. 13C NMR (100 MHz,
CDCl3): δ = 14.0 (CH3), 20.9 (CH3), 22.5 (CH2), 25.6 (CH2), 29.1
(CH2), 31.7 (CH2), 35.5 (CH2), 63.9 (CH2), 73.4 (CH), 113.6 (CH2),
146.2 (C), 170.8 (C) ppm. MS (EI): m/z (%) = 196 (1) [M+ – 18],
154 (1), 129 (50), 113 (6), 97 (21), 87 (95), 69 (55), 55 (100). HRMS
(ESI): calcd. for C12H22O3Na 237.1461; found 237.1461. C12H22O3
(214.16): calcd. C 67.26, H 10.35; found C 67.11, H 10.39.
1168 cm–1. 1H NMR (400 MHz, CDCl3): δ = 2.25 (s, 3 H, 3-H),
5.14 (s, 1 H, 1-H), 7.2–7.4 (m, 10 H, Ph) ppm. 13C NMR
(100 MHz, CDCl3): δ = 30.0 (CH3), 65.0 (CH), 127.2 (2 CH), 128.7
(4 CH), 128.9 (4 CH), 138.2 (2 C), 206.5 (C) ppm. MS (EI): m/z
(%) = 210 (1) [M+], 167 (100), 152 (20), 139 (3), 128 (2), 115 (3),
102 (1), 82 (4), 63 (6), 43 (12). HRMS (ESI): calcd. for C15H14ONa
233.0942; found 233.0948. Data for 32: IR: ν = 3363, 2910, 1449,
˜
1121 cm–1. 1H NMR (400 MHz, CDCl3): δ = 1.92 (s, 3 H, Me),
4.18 (s, 2 H, 1-H), 7.1–7.3 (m, 10 H, Ph) ppm. 13C NMR
(100 MHz, CDCl3): δ = 18.0 (CH3), 64.9 (CH2), 126.6 (CH), 126.8
Reaction of (3-Hexyloxiran-2-yl)methyl Formate (8) with Cp2TiCl: (CH), 127.9 (2 CH), 128.0 (2 CH), 129.5 (2 CH), 129.5 (2 CH),
According to GP1, reaction of 8 (170 mg, 0.91 mmol) with Cp2TiCl
followed by flash chromatography (hexane/diethyl ether, 9:1) fur-
133.4 (C), 140.5 (C), 141.9 (C), 142.3 (C) ppm. MS (EI): m/z (%)
= 224 (10) [M+ – 16], 206 (8), 191 (12), 178 (4), 167 (100), 152 (3),
139 (1), 103 (15), 91 (18), 77 (11), 51 (13). HRMS (ESI): calcd. for
nished 9 (67 mg, 44%) and 10 (40 mg, 30%). Data for 10: IR: ν =
˜
3334, 1010 cm–1. 1H NMR (200 MHz, CDCl3): δ = 0.81 (t, J = C16H16O2Na 263.1043; found 263.1045. C16H16O2 (240.11): calcd.
6.2 Hz, 3 H, 9-H), 1.21 (m, 10 H), 3.98 (q, J = 6 Hz, 1 H, 3-H),
5.01 (d, J = 10.4 Hz, 1 H, 1-H), 5.14 (d, J = 17.2 Hz, 1 H, 1-H),
5.78 (ddd, J = 6, 10.4, 17.2 Hz, 1 H, 2-H) ppm. 13C NMR
C 79.97, H 6.71; found C 79.88, H 6.72. Data for 33: IR: ν = 3401,
˜
1
2929, 1462, 1046 cm–1. H NMR (400 MHz, CDCl3): δ = 1.25 (s,
3 H, Me), 3.39 (d, J = 10.0 Hz, 1 H, 1-H), 3.53 (d, J = 10.0 Hz, 1
(50 MHz, CDCl3): δ = 13.8 (CH3), 22.4 (CH2), 25.1 (CH2), 29.0 H, 1-H), 3.98 (s, 1 H, 3-H), 7.2–7.3 (m, 6 H, Ph), 7.5–7.6 (m, 4 H,
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Titanocene-Promoted Eliminations on Epoxy Alcohols and Epoxy Esters
Ph) ppm. 13C NMR (100 MHz, CDCl3): δ = 24.1 (CH3), 58.6 (CH),
69.3 (CH2), 75.0 (C), 126.6 (CH), 126.7 (CH), 128.3 (2 CH), 128.5
(2 CH), 129.6 (2 CH), 129.7 (2 CH), 140.9 (C), 141.2 (C) ppm. MS
(EI): m/z (%) = 211 (3) [M+ – 31], 168 (100), 152 (8), 133 (6), 115
(5), 105 (18), 91 (11), 75 (63), 57 (58). HRMS (ESI): calcd. for
C16H18O2Na 265.1199; found 265.1207. C16H18O2 (242.13): calcd.
C 79.31, H 7.49; found C 79.46, H 7.47.
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Supporting Information (see footnote on the first page of this arti-
cle): Experimental procedures, spectroscopic data, and copies of
1
selected H and 13C NMR spectra.
Acknowledgments
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Financial support for this work from the Ministerio de Ciencia y
Tecnología of Spain (CTQ2005-05026/BQU) and the Junta de Cas-
tilla y León (SA079A06) is gratefully acknowledged. We also thank
the Ministerio de Educación and the Universidad de Salamanca
for fellowships to S. E. M. and P. H. T.
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III
Related radicals have been produced from aldehydes and Ti
,
see for example: A. Gansäuer, M. Moschioni, D. Bauer, Eur. J.
Org. Chem. 1998, 9, 1923–1927.
Received: October 27, 2009
Published Online: January 4, 2010
Eur. J. Org. Chem. 2010, 856–861
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
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