Lewis base-catalyzed addition of trialkylaluminum compounds to epoxides

Article abstract of DOI:10.1002/1099-0690(200112)2001:23<4445::aid-ejoc4445>3.0.co;2-u

A novel concept for catalytic epoxide alkylation has been developed. Lewis bases like phosphanes, arsanes, stibanes, and sulfides were found to catalyze the alkylation of symmetrical epoxides with trialkylaluminum compounds very effectively at a 5 mol % level. Cyclic as well as acyclic epoxides were readily alkylated in good yields. In reactions with terminal epoxides a significant enhancement of rate and/or regioselectivity was noted in the Lewis base-catalyzed process. Coordination of the Lewis base to the Lewis acidic aluminum reagent was proved by ²⁷Al and ³¹p NMR spectroscopy and is proposed to form a more nucleophilic alkylating agent.

Full text of DOI:10.1002/1099-0690(200112)2001:23<4445::aid-ejoc4445>3.0.co;2-u

FULL PAPER
Lewis Base-Catalyzed Addition of Trialkylaluminum Compounds to Epoxides
Christoph Schneider*[a] and Jörg Brauner[a]
Keywords: Catalysis / Epoxides / Lewis bases / Aluminum
A novel concept for catalytic epoxide alkylation has been de- epoxides a significant enhancement of rate and/or regio-
veloped. Lewis bases like phosphanes, arsanes, stibanes, and
sulfides were found to catalyze the alkylation of symmetrical
epoxides with trialkylaluminum compounds very effectively
at a 5 mol % level. Cyclic as well as acyclic epoxides were
readily alkylated in good yields. In reactions with terminal
selectivity was noted in the Lewis base-catalyzed process.
Coordination of the Lewis base to the Lewis acidic aluminum
reagent was proved by 27Al and 31P NMR spectroscopy and
is proposed to form a more nucleophilic alkylating agent.
Results and Discussion
Introduction
We selected the reaction of cyclohexene oxide (1) with
Epoxides are valuable fine chemicals and synthetic inter- Et3Al as our model reaction and screened a broad range of
mediates. As such, a great deal of attention has been paid Lewis bases to evaluate their catalytic activity (Table 1).[17]
to their chemo-, diastereo- and enantioselective preparation Toluene was chosen as a noncoordinating solvent to avoid
by epoxidation of the corresponding alkenes.[1] The syn- interactions with the aluminum reagent.
thetic importance of epoxides stems in large part from their
Phosphanes, arsanes, stibanes, and sulfides were identi-
facile and trans-stereospecific nucleophilic ring opening fied as suitable catalysts at a 5 mol % level in toluene at
with all kinds of nucleophiles to furnish valuable amino al- room temperature to give the ring-opened product, trans-2-
cohols,[2] azido alcohols,[3] halohydrins,[4] diols,[5] and thi- ethyl-1-cyclohexanol (2), in typically excellent yields. Ethers
ols[6] to name the most frequently prepared addition prod- and amines turned out to be totally ineffective as catalysts.
ucts.
Stoichiometric amounts of the aluminum reagent were suf-
Among the carbon nucleophiles that successfully alkylate ficient for a complete reaction but the reaction rate was
epoxides are organolithium compounds in concert with greatly enhanced employing two equivalents of Et3Al.
various activating agents,[7] such as organomagnesium,[8] Without the Lewis base present the reaction did not pro-
organocopper,[9] organozinc[10] and organolanthanide re- ceed at all. The exclusive formation of the trans-addition
agents.[11] A conceptually different approach uses TiIII re- product was indicative of a stereospecific reaction path via
agents, which upon single-electron transfer generate radical a concerted nucleophilic displacement mechanism.
anions from the epoxides which may be trapped with olefins
The alkylation of cyclohexene oxide (1) could be ex-
to accomplish the CϪC bond forming process.[12] Trialkyl- tended to the reaction with Me3Al. Some differences in the
aluminum compounds usually do not alkylate epoxides[13] catalytic activity exist, however. Here sulfides no longer cat-
unless they are either coordinated to the substrate prior to alyze the alkyl transfer efficiently and triphenylstibane was
the reaction[14] or specially activated by organolithium com-
pounds, metal alkoxides, or water which presumably form
Table 1. Lewis base-catalyzed reaction of cyclohexene oxide (1)
with Et3Al (1 equiv.)
more reactive aluminum ‘‘ate’’ complexes.[15]
We report here a novel approach to catalyze the addition
of trialkylaluminum compounds to epoxides. Stimulated by
the powerful amine catalysis in diethylzinc additions to al-
dehydes[16] we envisioned the activation of trialkylaluminum
compounds with catalytic quantities of Lewis bases to effect
the epoxide opening. Principally, coordination of a Lewis Entry
base to the Lewis acid R3Al should result in the formation
of a tetracoordinate aluminum complex which resembles
Lewis base
Yield (%)[a]
1
2
3
4
5
6
7
8
9
Ϫ
NEt3
Et2O
PBu3
PPh3
P(NMe2)3
AsPh3
SbPh3
Me2S
0
0
0
89
99
97
100
89
100
the above mentioned ‘‘ate’’ complexes and which should ex-
hibit a comparable reactivity towards the epoxides.
[a]
Institut für Organische Chemie,
Georg-August-Universität Göttingen
Tammannstraße 2, 37077 Göttingen, Germany
Fax: (internat.) ϩ 49-(0)551-399660
E-mail: cschnei1@gwdg.de
[a]
Determined by GC.
Eur. J. Org. Chem. 2001, 4445Ϫ4450
WILEY-VCH Verlag GmbH, 69451 Weinheim, 2001
1434Ϫ193X/01/1223Ϫ4445 $ 17.50ϩ.50/0
4445

C. Schneider, J. Brauner
FULL PAPER
shown to be the most active catalyst along with triphenylar- good product yield within 24 h. The diastereomeric cis- and
sane and tris(dimethylamino)phosphane, furnishing the ad- trans-2-butene oxides (5) and (6), respectively, were al-
dition product trans-2-methyl-1-cyclohexanol (3), again in kylated with Et3Al to yield the anti-product 11 from 5 and
very good yields (Table 2). Triphenylarsane was selected as the syn-product 12 from 6, exclusively, proving a strictly
our standard Lewis base catalyst for the subsequent studies stereospecific reaction course. The rather moderate yields
on disubstituted epoxides as it has the broadest scope and observed in these reactions are presumably due to the volat-
applicability.
Cyclic and acyclic epoxides were readily alkylated with reaction with Me3Al was not attempted here.
either Me3Al or Et3Al according to the general protocol The uncatalyzed addition of Et3Al to cis-stilbene oxide
ility of the products during their isolation. Accordingly, the
giving rise to the alkylated products in typically good isol- (7) gave rise to a product mixture consisting mainly of the
ated yields (Table 3). The alkylation of the more unreactive rearranged product 16 and none of the desired product 13
cyclopentene oxide (4) was conducted at 50 °C to achieve a (Figure 1). The AsPh3-catalyzed nucleophilic addition of
either trialkylaluminum reagent to 7, however, cleanly fur-
nished the ring-opened products 13 and 14, respectively, in
Table 2. Lewis base-catalyzed reaction of cyclohexene oxide (1)
good yields. On the other hand. however, the reaction of
trans-stilbene oxide (8) with Et3Al even under Lewis base
catalysis yielded a mixture of the two diastereomeric 1,2-
diphenyl-1-butanols (13) and (15) along with the rearranged
product 16 in roughly equal amounts. Two conclusions may
be drawn from this observation. Apparently, the phenyl ring
adjacent to the epoxide provides sufficient resonance stabil-
ization for the formation of a putative carbenium ion, shift-
ing the mechanism of the epoxide alkylation towards a two-
step process. Secondly, the substrate configuration plays a
critical role in determining whether this change in mechan-
ism actually occurs.
with Me3Al (1 equiv.)
Entry
Lewis base
Yield (%)[a]
1
2
3
4
5
6
Ϫ
PPh3
P(NMe2)3
AsPh3
SbPh3
Me2S
2
81
90
87
99
3
[a]
Determined by GC.
Table 3. AsPh3-catalyzed (5 mol %) addition of Et3Al and Me3Al
(1 equiv.) to symmetrical epoxides (toluene, room temp., 24 h)
Figure 1. Unwanted side product from the reaction of trans-stilbene
oxide and Et3Al
We noted, however, some limitations in this newly de-
veloped process. Cyclooctene oxide, a notoriously unreact-
ive epoxide, could not be alkylated using this method. Not
unexpectedly, reactions with higher trialkylaluminum com-
pounds, such as triisobutylaluminum, with the epoxides re-
sulted in β-hydride transfer furnishing the corresponding al-
cohols.
We also investigated the alkylation of terminal epoxides
with trialkylaluminum compounds, which proceeds even in
the absence of a Lewis base. The regioselectivity, however,
was significantly affected in the presence of catalytic quant-
ities of a Lewis base. Thus, styrene oxide (17) was alkylated
with Et3Al and Me3Al with high regioselectivity at the in-
ternal position to furnish 18a and 19a, respectively, in excel-
lent yields in the presence of 5 mol % of PPh3. On the other
hand, the uncatalyzed reaction furnished substantial
amounts of the regioisomers 18b and 19b, which were pre-
sumably formed through an epoxide opening-hydride mi-
gration-alkylation sequence (Table 4). The opposite regiose-
lectivity is reported in reactions of styrene oxide with
higher-order cyanocuprates, which are the most popular or-
ganometallics employed in epoxide alkylations,[9c] whereas
one has to resort to diorganomagnesium reagents to find
the same regioselectivity as in our study.[9f] Thus, our results
[a] Isolated yields of chromatographed product. Ϫ [b] Reaction con-
ducted at 50°C. Ϫ 1:1:1 Mixture of 15, 13 and 16.
[c]
4446
Eur. J. Org. Chem. 2001, 4445Ϫ4450

Addition of Trialkylaluminum Compounds to Epoxides
FULL PAPER
obtained with trialkylaluminum/Lewis base combinations
constitute a useful addition to current synthetic methodo-
logy.
Table 4. PPh3-catalyzed (5 mol %) addition of Et3Al and Me3Al to
styrene oxide (17)
Entry R3Al Lewis base Ratio a/b Major Product Yield [%][a]
1
2
3
4
Et3Al --
Et3Al PPh3
Me3Al --
2/1
50/1
3/1
18a
18a
19a
19a
75
95
90
92
Scheme 2
Me3Al PPh3
24/1
[a] Combined yield of both isomers after chromatographic purifica-
tion.
As long as R3Al is employed in excess (2 equiv.) the com-
petition between the epoxide and the catalytic Lewis base
poses no problem and the trialkylaluminum-Lewis base
complex 24 should form easily (Scheme 2). If the trialkylal-
uminum reagent is employed only stoichiometrically, how-
ever, 24 will form in significantly lower concentrations be-
cause the epoxide, as a hard Lewis base, coordinates to the
hard Lewis acidic aluminum center more effectively. These
two complexes 23 and 24 are presumed to effect the al-
kylation of the epoxide, with one equivalent of the trialkyla-
luminum reagent serving as a Lewis acid to activate the ep-
oxide and the second equivalent of the trialkylaluminum
reagent coordinated by the catalytic Lewis base delivering
the alkyl group in a nucleophilic sense. Such a transition
structure with two trialkylaluminum compounds participat-
ing in the transition structure has already been suggested
for the reaction of trimethylaluminum and benzo-
phenone.[20]
A significant rate enhancement was noted in the reaction
of triethylaluminum with 1-hexene oxide (20) under Lewis
base catalysis (Scheme 1). Without the Lewis base present
the addition products 21 and 22 were obtained in 58% com-
bined yield with a regioselectivity of 15:1 in favor of the
internal addition product 21. In the presence of 5 mol % of
PPh3, however, the reaction proceeded almost to comple-
tion within 24 h at room temp. giving rise to a 95% yield of
the same regioisomeric composition.
Scheme 1
Although we have not undertaken a systematic kinetic
investigation we observed a significant rate increase in the
PPh3-catalyzed (5 mol %) reaction of Et3Al and cyclohex-
Mechanistic Considerations
Trimethylaluminum and triethylaluminum are known to ene oxide (1) when using two equivalents as opposed to one
form dimers in hydrocarbon solution that are in equilibrium equivalent of the aluminum reagent. When we monitored
with small quantities of the monomeric species.[18] When the conversion as a function of time we noted that half of
the epoxide is added to the solution of the aluminum re- the substrate was consumed within only 80 min at room
agent in toluene it will certainly Ϫ as a Lewis base itself Ϫ temperature when using two equivalents Et3Al whereas the
coordinate to the Lewis acidic aluminum reagent to form a half-time was 5 h in the reaction with only 1 equivalent of
monomeric
trialkylaluminum-epoxide
complex
23 Et3Al under otherwise identical reaction conditions.
(Scheme 2). Once the catalytic Lewis base is added to the
The origin of rate enhancement in the Lewis base-cata-
reaction mixture it competes with the epoxide for coordina- lyzed reaction may be electronic and/or steric. The bonds
tion to the aluminum reagent. to the attached carbon ligands are likely to be weakened
We were able to show by NMR spectroscopy that coor- due to electron donation from the Lewis base to the elec-
dination of a phosphane to triethylaluminum actually oc- tron-deficient aluminum atom. This same effect has previ-
curs. Mixing equimolar quantities of triethylaluminum and ously been observed in other Lewis base-catalyzed organo-
tris(dimethylamino)phosphane results in a downfield shift metallic reactions, most notably in the amine-catalyzed ad-
in the 27Al NMR spectrum from δ ϭ 155 (for Et3Al alone) dition of dialkylzinc compounds to aldehydes,[16] the N,N-
to δ ϭ 165 (for a 1:1 mixture of Et3Al and the phosphane), dimethylformamide-catalyzed addition of allyltrichlorosil-
suggesting the formation of a monomeric tetracoordinate anes to aldehydes,[21] the phosphoramide-catalyzed aldol re-
aluminum species.[19] An even more significant upfield shift action of trichlorosilyl enolates,[22] the amine- and phos-
from δ ϭ 123 to δ ϭ 97 was observed in the 31P NMR spec- phane-catalyzed addition of trimethylsilyl cyanide to alde-
trum.
hydes,[23] and the phosphane-catalyzed aldol reaction of ke-
Eur. J. Org. Chem. 2001, 4445Ϫ4450
4447

C. Schneider, J. Brauner
FULL PAPER
(CϪO). EI-MS (70 eV): m/z ϭ 128 (5) [Mϩ], 110 (72) [Mϩ Ϫ H2O],
tene silyl acetals.[24] A weakening of the AlϪC bonds may
also, however, be caused by compression of the binding
angle around the aluminum atom upon coordination of the
bulky Lewis base.
57 (100) [C4H9ϩ].
trans-2-Methyl-1-cyclohexanol (3):[25] Yield: 280 mg (82%). tR
ϭ
4.98 min (100 °C, 10 min, 20 °C/min). 1H NMR (300 MHz,
CDCl3): δ ϭ 1.02 (d, J ϭ 6.5 Hz, 3 H, CH3), 1.12Ϫ1.40 (m, 5 H),
1.55Ϫ2.02 (m, 5 H), 3.12 (dt, J ϭ 4.5, 9.5 Hz, 1 H, 1-H). 13C NMR
(50 MHz, CDCl3): δ ϭ 18.6, 25.2, 25.7, 33.6, 35.5, 40.3, 76.5. IR
Conclusion
Ϫ1
˜
(film): ν ϭ 3419 cm (OϪH), 2930, 2858 (CϪH), 1090 (CϪO).
EI-MS (70 eV): m/z ϭ 114 (20) [Mϩ], 96 (60) [Mϩ Ϫ H2O], 81 (62),
We have devised a novel strategy to catalyze the addition
of trialkylaluminum compounds to epoxides. Only 5 mol %
68 (69), 57 (100) [C4H9ϩ].
of a soft Lewis base was employed to effect the methylation trans-2-Ethyl-1-cyclopentanol (9):[26] Yield: 257 mg (75%). tR
ϭ
4.94 min (50 °C, 2.5 °C/min). 1H NMR (300 MHz, CDCl3): δ ϭ
0.95 (t, J ϭ 7.0 Hz, 3 H, CH3), 1.10Ϫ1.28 (m, 2 H), 1.45Ϫ2.00 (m,
8 H), 3.83 (q, J ϭ 6.0 Hz, 1 H, 1-H). 13C NMR (50 MHz, CDCl3):
and ethylation of cyclic and acyclic epoxides. The epoxide-
opening reaction was shown to proceed stereospecifically
in all but one cases to furnish the trans-addition products
exclusively. Aside from the rate enhancement, which was
also observed in reactions with other electrophiles,[17] a sig-
nificant increase of rate and/or regioselectivity was noted in
the alkylation of styrene oxide and 1-hexene oxide. Spectro-
scopic evidence suggests a coordination of the Lewis base
to the aluminum atom which apparently results in the
formation of a more nucleophilic alkylating agent.
˜
δ ϭ 12.6, 21.9, 26.6, 29.6, 34.7, 50.0, 78.9. IR (film): ν ϭ 3346
cmϪ1 (OϪH), 2958, 2874 (CϪH), 1092 (CϪO). EI-MS (70 eV):
m/z ϭ 114 (18) [Mϩ], 96 (52) [Mϩ Ϫ H2O], 81 (57), 68 (62), 57
(100) [C4H9ϩ].
trans-2-Methyl-1-cyclopentanol (10):[26] Yield: 210 mg (70%). tR
ϭ
3.65 min (50 °C, 2.5 °C/min). 1H NMR (300 MHz, CDCl3): δ ϭ
0.96 (t, J ϭ 7.0 Hz, 3 H, CH3), 1.16 (mc, 1 H), 1.42Ϫ1.80 (m, 5
H), 1.90 (mc, 2 H), 3.74 (q, J ϭ 6.0 Hz, 1 H, 1-H). 13C NMR
(50 MHz, CDCl3): δ ϭ 18.2, 21.5, 31.6, 34.1, 42.7, 80.6. IR (film):
Ϫ1
˜
ν ϭ 3348 cm (OϪH), 2956, 2872 (CϪH), 1080 (CϪO). EI-MS
(70 eV): m/z ϭ 100 (10) [Mϩ], 82 (39) [Mϩ Ϫ H2O], 81 (57), 57
Experimental Section
(100) [C4H9ϩ].
General: All reactions were carried out under N2 using flame-dried
glassware. Solvents were distilled from the appropriate drying
agents immediately prior to use. All reactions were monitored by
gas chromatography using a Varian Star 3400 CX instrument, a
BP1 column of SGE (50m ϫ 0.25 mm) and hydrogen (22 psi) as
carrier gas. 1H and 13C NMR: Varian VXR 200 (200 MHz), Bruker
AMX 300 (300 MHz) and Varian VXR 500 (500 MHz) with tetra-
methylsilane as internal standard. 27Al NMR: Bruker AM 250
(65.2 MHz) with AlCl3 as external standard. 31P NMR: Bruker Av-
ance 500 (162 MHz) with H3PO4 as external standard. IR: Bruker
IFS 25 FT-IR. MS: Finnigan MAT 95A. Column chromatography
was performed on silica gel (0.063Ϫ0.200 mm) from
MachereyϪNagel & Co.
anti-2-Hydroxy-3-methylpentane (11):[27] Yield: 190 mg (62%). tR ϭ
6.32 min (50 °C, 4 min, 10 °C/min). H NMR (300 MHz, CDCl3):
1
δ ϭ 0.85 (d, J ϭ 6.0 Hz, 3 H, CH3), 0.90 (t, J ϭ 6.5 Hz, 3 H, CH3),
1.12 (d, J ϭ 6.0 Hz, 3 H, CH3), 1.35Ϫ1.58 (m, 4 H), 3.67 (quint,
J ϭ 6.0 Hz, 1 H, 2-H). 13C NMR (50 MHz, CDCl3): δ ϭ 11.6,
14.1, 19.4, 25.2, 41.8, 71.5. IR (film): ν˜ ϭ 3362 cmϪ1 (OϪH), 2966,
2933, 2878 (CϪH), 1100 (CϪO). DCI-MS (70 eV): m/z ϭ 120 (100)
[M ϩ NH4ϩ].
syn-2-Hydroxy-3-methylpentane (12):[27] Yield: 180 mg (59%). tR
ϭ
1
6.19 min (50 °C, 4 min, 10 °C/min). H NMR (300 MHz, CDCl3):
δ ϭ 0.90 (d, J ϭ 6.0 Hz, 3 H, CH3), 0.91 (t, J ϭ 6.5 Hz, 3 H, CH3),
1.15 (d, J ϭ 6.0 Hz, 3 H, CH3), 1.27Ϫ1.58 (m, 4 H), 3.70 (mc, 1
H, 2-H). 13C NMR (50 MHz, CDCl3): δ ϭ 11.8, 13.8, 20.3, 25.3,
General Protocol for the Addition of Trialkylaluminum Compounds
to Epoxides: 0.15 mmol of the Lewis base was added to a solution
of 3.00 mmol epoxide in 6 mL dry toluene and subsequently
3.00 mmol of the respective trialkylaluminum compound was ad-
ded as a solution in either hexane or toluene. The mixture was
stirred for 24 h at room temp. or 50 °C under a nitrogen atmo-
sphere, cooled to Ϫ78 °C and then quenched with 5 mL of a 1 
HCl solution. The phases were separated and the aqueous layer
was extracted twice with ether. The combined organic extracts were
dried over MgSO4 and the solvents evaporated in vacuo. The crude
products were purified by flash chromatography over silica gel with
ether/pentane mixtures. The yields given in Table 1 and 2 were de-
termined by GC on the crude products with n-decane as internal
standard and with use of a calibrated curve. The yields given in
Table 3 and 4 and in the Exp. Sect. are isolated yields of chromato-
graphed and analytically pure material.
Ϫ1
˜
41.6, 71.2. IR (film): ν ϭ 3356 cm (OϪH), 2964, 2878 (CϪH),
1078 (CϪO). DCI-MS (70 eV): m/z ϭ 120 (100) [M ϩ NH4ϩ].
anti-1,2-Diphenyl-1-butanol (13):[28] Yield: 535 mg (79%). tR
ϭ
15.68 min (100 °C, 6 min, 20 °C/min). 1H NMR (300 MHz,
CDCl3): δ ϭ 0.75 (t, J ϭ 7.0 Hz, 3 H, CH3), 1.57 (br. s, 1 H, OH),
1.75 (mc, 1 H, CH2), 1.98 (mc, 1 H, CH2), 2.84 (ddd, J ϭ 10.5,
6.0, 4.0 Hz, 1 H, 2-H), 4.80 (d, J ϭ 6.0 Hz, 1 H, 1-H), 7.00Ϫ7.25
(m, 10 H, phenyl-H). 13C NMR (50 MHz, CDCl3): δ ϭ 12.1, 22.7,
55.5, 78.4, 126.3, 126.5, 127.1, 127.9, 128.0, 128.9, 141.3, 143.0. IR
Ϫ1
˜
(film): ν ϭ 3403 cm (OϪH), 2963, 2930, 2874 (CϪH), 1025
(CϪO). EI-MS (70 eV): m/z ϭ 226 (2) [Mϩ], 120 (100) [Mϩ
PhCHOH], 107 (96) [PhCHOHϩ ϩ1].
Ϫ
anti-1,2-Diphenyl-1-propanol (14):[29] Yield: 450 mg (71%). tR
ϭ
15.24 min (100 °C, 6 min, 20 °C/min). 1H NMR (500 MHz,
CDCl3): δ ϭ 1.32 (d, J ϭ 6.0 Hz, 3 H, CH3), 1.84 (br. s, 1 H, OH),
3.11 (quint, J ϭ 6.0 Hz, 1 H, 2-H), 4.82 (d, J ϭ 6.0 Hz, 1 H, 1-H),
trans-2-Ethyl-1-cyclohexanol (2):[25] Yield: 360 mg (94%). tR
ϭ
7.57 min (100 °C, 10 min, 20 °C/min). 1H NMR (300 MHz, 7.10Ϫ7.25 (m, 10 H, phenyl-H). 13C NMR (50 MHz, CDCl3): δ ϭ
CDCl3): δ ϭ 0.90 (t, J ϭ 7.5 Hz, 3 H, CH3), 1.04Ϫ1.42 (m, 6 H), 14.9, 47.2, 78.7, 126.3, 126.4, 127.1, 127.9, 128.0, 128.2, 142.8,
Ϫ1
1.61Ϫ2.02 (m, 6 H), 3.23 (dt, J ϭ 4.5, 9.5 Hz, 1 H, 1-H). 13C NMR
˜
143.5. IR (film): ν ϭ 3395 cm (OϪH), 2960, 2928, 2871 (CϪH),
(126 MHz, CDCl3): δ ϭ 10.8, 24.6, 25.0, 25.6, 29.5, 35.7, 46.5, 74.4. 1015 (CϪO). EI-MS (70 eV): m/z ϭ 212 (6) [Mϩ], 106 (100) [Mϩ
IR (film): ν ϭ 3345 cm (OϪH), 2961, 2929, 2858 (CϪH), 1045 Ϫ PhCHOH], 107 (96) [PhCHOHϩ ϩ 1].
Ϫ1
˜
4448
Eur. J. Org. Chem. 2001, 4445Ϫ4450

Addition of Trialkylaluminum Compounds to Epoxides
FULL PAPER
See for example: [3a] H. B. Mereyala, B. Frei, Helv. Chim. Acta
[3]
syn-1,2-Diphenyl-1-butanol (15):[28] Yield: 515 mg (76%) of a 1:1:1-
mixture of 13, 15, and 16 were obtained in the reaction of trans-
stilbene oxide (8) with Et3Al and 5 mol % of AsPh3 according to
the general procedure. Data for 15: tR ϭ 15.45 min (100 °C, 6 min,
20 °C/min). 1H NMR (300 MHz, CDCl3): δ ϭ 0.63 (t, J ϭ 7.0 Hz,
3 H, CH3), 1.42Ϫ1.64 (m, 2 H, CH2), 1.67 (br. s, 1 H, OH), 2.75
(ddd, J ϭ 12.0, 8.0, 4.0 Hz, 1 H, 2-H), 4.72 (d, J ϭ 8.0 Hz, 1 H,
1-H), 7.00Ϫ7.25 (m, 10 H, phenyl-H). 13C NMR (50 MHz,
CDCl3): δ ϭ 11.9, 24.9, 56.1, 78.3, 126.4, 126.7, 127.1, 127.8, 128.1,
128.9, 141.1, 143.0.
1986, 69, 415Ϫ418. [3b] W. A. Nugent, J. Am. Chem. Soc. 1992,
[3c]
114, 2768Ϫ2769.
M. Meguro, N. Asao, Y. Yamamoto, J.
Chem. Soc., Chem. Commun. 1995, 1021Ϫ1022. [3d] L. E. Mart-
inez, J. L. Leighton, D. H. Carsten, E. N. Jacobsen, J. Am.
Chem. Soc. 1995, 117, 5897Ϫ5898.
[4]
[4a]
See for example:
G. C. Andrews, T. C. Crawford, L. G.
[4b]
Contillo, Tetrahedron Lett. 1981, 22, 3803Ϫ3806.
S. E.
Denmark, P. A. Barsanti, K. T. Wong, R. A. Stavenger, J. Org.
Chem. 1998, 63, 2428Ϫ2429.
[5]
[6]
See for example: M. Tokunaga, J. F. Larrow, F. Kakiuchi, E.
N. Jacobsen, Science 1997, 277, 936Ϫ938.
1,1-Diphenyl-2-butanol (16):[30] tR ϭ 15.78 min (100 °C, 6 min, 20
See for example: [6a] A. E. Vougioukas, H. B. Kagan, Tetrahed-
1
°C/min). H NMR (300 MHz, CDCl3): δ ϭ 0.99 (t, J ϭ 7.0 Hz, 3
[6b]
ron Lett. 1987, 28, 6065Ϫ6068.
T. Iida, N. Yamamoto, H.
H, CH3), 1.30Ϫ1.48 (m, 2 H, CH2), 1.67 (br. s, 1 H, OH), 3.90 (d,
J ϭ 7.5 Hz, 1 H, 1-H), 4.29 (dt, J ϭ 3.0, 7.5 Hz, 1 H, 2-H),
7.00Ϫ7.25 (m, 10 H, phenyl-H). 13C NMR (50 MHz, CDCl3): δ ϭ
10.1, 27.8, 58.3, 75.0, 126.3, 126.5, 127.1, 127.9, 128.0, 128.9,
141.3, 143.0.
Sasai, M. Shibasaki, J. Am. Chem. Soc. 1997, 119, 4783Ϫ4784.
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[7b]
106, 3693Ϫ3694.
M. Mizuno, M. Kanai, A. Iida, K. To-
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N.
Oguni, Y. Miyagi, K. Itoh, Tetrahedron Lett. 1998, 39,
9023Ϫ9026. [7d] A. Alexakis, E. Vrancken, P. Mangeney, Synlett
2-Phenyl-1-butanol (18a):[31] Yield: 400 mg (89%) of a 50:1 re-
gioisomeric mixture. tR ϭ 11.93 min (100 °C, 6 min, 10 °C/min),
regioisomer: tR ϭ 11.47 min. 1H NMR (300 MHz, CDCl3): δ ϭ
0.82 (t, J ϭ 7.0 Hz, 3 H, CH3), 1.50 (br. s, 1 H, OH), 1.55Ϫ1.83
(m, 2 H, 3-H), 2.68 (mc, 1 H, 2-H), 3.71 (dd, J ϭ 10.0, 7.5 Hz, 1
H, 1-H), 3.76 (d, J ϭ 10.0, 6.0 Hz, 1 H, 1-H), 7.20Ϫ7.38 (m, 5 H,
phenyl-H). 13C NMR (50 MHz, CDCl3): δ ϭ 12.0, 25.0, 50.5, 67.3,
126.6, 128.1, 128.6, 142.2. IR (film): ν˜ ϭ 3361 cmϪ1 (OϪH), 2962,
2929, 2874 (CϪH), 1453, 1037 (CϪO). DCI-MS (70 eV): m/z ϭ
168 (100) [M ϩ NH4ϩ].
[7e]
1998, 1165Ϫ1167.
T. Ooi, N. Kagoshima, H. Ichikawa, K.
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C. Huynh, F. Derguini-Boumechal, G. Linstrumelle, Tetrahed-
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2-Phenyl-1-propanol (19a):[32] Yield: 330 mg (81%) of a 24:1 re-
gioisomeric mixture. tR ϭ 10.27 min (100 °C, 6 min, 10 °C/min),
regioisomer: tR ϭ 9.33 min. 1H NMR (300 MHz, CDCl3): δ ϭ 1.39
(d, J ϭ 7.0 Hz, 3 H, CH3), 1.58 (br. s, 1 H, OH), 3.05 (sext, J ϭ
7.0 Hz, 1 H, 2-H), 3.80 (d, J ϭ 7.0 Hz, 2 H, 1-H), 7.25Ϫ7.34 (m,
5 H, phenyl-H). 13C NMR (50 MHz, CDCl3): δ ϭ 17.6, 42.4, 68.7,
126.7, 127.5, 128.6, 143.7. IR (film): ν˜ ϭ 3354 cmϪ1 (OϪH), 2962,
2929, 2874 (CϪH), 1583, 1091, 1068 (CϪO). EI-MS (70 eV):
m/z ϭ 136 (9) [Mϩ], 105 (100) [Mϩ Ϫ CH2OH], 77 (16) [Phϩ].
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A. Gansäuer, H. Bluhm, M. Pierobon, J.
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eric mixture. tR ϭ 6.24 min (50 °C, 2 °C/min). 1H NMR (300 MHz,
CDCl3): δ ϭ 0.90 (2 ϫ t, J ϭ 7.0 Hz, 6 H, CH3), 1.20Ϫ1.58 (m,
10 H), 3.50 (dd, J ϭ 11.0, 6.0 Hz, 1 H, 1-H), 3.54 (dd, J ϭ 11.0,
Am. Chem. Soc. 1998, 120, 12849Ϫ12859; for a catalytic en-
[12c]
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A. Gansäuer, T. Lauterbach, H.
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[13]
Ϫ1
˜ ˜
23.2, 23.4, 29.1, 30.2, 42.0, 65.1. IR (film): νγ) ϭ 3346 cm
(OϪH), 2958, 2930, 2872 (CϪH), 1013 (CϪO). DCI-MS (70 eV):
[14] [14a]
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T. Suzuki, H. Saimoto, H. Tomioka, K. Oshima, H. No-
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Acknowledgments
This work was supported by the Deutsche Forschungsgemeinschaft
(Schn 441/3Ϫ1) and the Fonds der Chemischen Industrie. We
would like to thank Timo Weide for additional experiments.
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Received July 14, 2001
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4450
Eur. J. Org. Chem. 2001, 4445Ϫ4450