Dimethylzinc-promoted vinylation of nitrones with vinylboronic esters of pinacol: A new route to N-allylic hydroxylamines

Article abstract of DOI:10.1002/ejoc.200300265

Activation of vinylboronic esters of pinacol (alkenyl-4,4,5,5-tetramethyl-1,3,2-dioxaborolanes) with dimethylzinc allows nucleophilic addition of the vinyl group onto nitrones, producing N-allylic hydroxylamines in excellent yields. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003).

Full text of DOI:10.1002/ejoc.200300265

FULL PAPER
Dimethylzinc-Promoted Vinylation of Nitrones with Vinylboronic Esters of
Pinacol: A New Route to N-Allylic Hydroxylamines
[a]
[b]
[b]
[b]
´
Shashi U. Pandya, Sandra Pinet, Pierre Y. Chavant,* and Yannick Vallee*
Keywords: Alkenylation / Boron / Nucleophilic addition / Transmetallation / Zinc
Activation of vinylboronic esters of pinacol (alkenyl-4,4,5,5-
tetramethyl-1,3,2-dioxaborolanes) with dimethylzinc allows
nucleophilic addition of the vinyl group onto nitrones, produ-
cing N-allylic hydroxylamines in excellent yields.
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2003)
Introduction
tively] to nitrones were disappointing, producing complex
mixtures of products. We therefore considered the use of
the vinylboronic ester 1, derived from pinacol (Scheme 1).
Such compounds are easily available from boronic ester
2.[21Ϫ23] This latter compound readily hydroborates 1-
alkynes, and the reaction is compatible with the presence of
various functional groups.[21] Its major advantage, however,
is that the vinylboronate can be handled in air and purified
by silica chromatography, avoiding the difficulties inherent
in the use of a mixture of borane products present in solu-
tion after a hydroboration (unchanged starting materials,
differently substituted boron atoms).
In the course of the preparation of some allylic amines,
we recently showed[1] that the vinylic organometallic species
obtained by the hydrozirconation of a terminal alkyne, fol-
lowed by its transmetallation with dialkylzinc, readily adds
onto nitrones to produce allylic hydroxylamines. Neverthe-
less, we thought that an analogous sequence in which the
hydrozirconation was replaced by hydroboration would be
advantageous.
The question of the addition of a vinylborane onto a car-
bonyl group was first addressed by Brown et al,[2] who pro-
posed direct reactions between 9-BBN derivatives and alde-
hydes. Trialkylboranes react directly with nitrones, with me-
dium efficiency.[3,4] Srebnik[5,6] and Oppolzer[7] found that
vinylboranes can be transmetallated to vinylzinc species by
the action of diethylzinc, addition onto aldehydes then be-
ing achievable in the presence of various amino alcohol
catalysts.[8] This result could be related to the aryl transfer
from a ‘‘Ph3BEt2Zn’’ entity proposed by Tamaru,[9] while
the important studies on the transmetallation of alkylbor-
anes by Knochel’s group[10Ϫ12] should also be mentioned.
Another important breakthrough was initiated by Petasis,
who proposed[13] a three-component reaction between an
amine, formaldehyde and a vinylboronic acid, to produce
an allylic amine. This reaction could be extended to other
aldehydes, provided that they present a vicinal OH or NH
group.[14Ϫ18] The activation of esters of vinylboronic acids
by KOH[19] or MeLi[20] also allows the transfer of vinyl
groups in Rh- (or Ni-) catalysed reactions.
Scheme 1. Preparation of the vinylboronic esters
Results and Discussion
Six vinylboronic esters 1 were prepared by a modified[24]
procedure and chromatographed, in yields from 2 ranging
in our hands from 42 to 57% (Scheme 1).
Transmetallation of these reagents with dialkylzinc had
not, to the best of our knowledge, previously been de-
scribed, although positive results had been obtained from
alkylcatecholboranes.[25]
Another important point is that nitrones react very slug-
gishly with diethylzinc[1] (and trialkylboranes[3,4]). The vi-
nylboronate can therefore be treated with dialkylzinc in the
presence of the nitrone electrophile (Barbier-like con-
Our attempts to adapt Oppolzer’s and Srebnik’s methods
[from dicyclohexyl(vinyl)borane and trivinylborane, respec-
[a]
Department of Chemistry, Sardar Patel University,
Vallabh Vidyanagar 388120, Anand, Gujarat, India
[b]
´
LEDSS, UMR 5616, Universite J. Fourier,
B. P. 53, 38041 Grenoble Cedex 9, France
Fax: (internat.) ϩ 33-4/76635983
E-mail: Pierre-Yves.Chavant@ujf-grenoble.fr
Eur. J. Org. Chem. 2003, 3621Ϫ3627
DOI: 10.1002/ejoc.200300265
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3621

´
S. U. Pandya, S. Pinet, P. Y. Chavant, Y. Vallee
FULL PAPER
ditions). This trapping in situ avoids problems arising from with the simultaneous appearance of a new signal (δ ϭ
1
possible instability of the new species.
33.5 ppm, 61 Hz wide). In the H NMR spectra, the disap-
pearance of the signals of dimethylzinc (δ ϭ Ϫ0.71 ppm)
and vinylboronic ester was synchronous with the appear-
ance of two new lines (δ ϭ 0.22 ppm, broad singlet for
BϪMe, and δ ϭ 0.95 ppm, singlet for pinacol). These new
lines are consistent with literature[27] data for the methylbo-
ronic ester (2,4,4,5,5-pentamethyl-1,3,2-dioxaborolane).
The nitrone disappeared at the same rate. Unfortunately,
the signals of the adduct in its form of a zinc salt were
broad and unreadable.
Dialkylzinc-Promoted Reaction between the Vinylboronate
and a Nitrone
The model reaction between the benzyl benzylidene
nitrone (3a) (easily available from oxidation of dibenzyl-
amine), the vinylboronic ester 1a (1.2 equiv.) and diethyl- or
dimethylzinc was examined in various solvents (Table 1).
From these observations, the simplest hypothesis is that
the rate-limiting step would be a methyl/vinyl exchange pro-
ducing MeZn(vinyl), followed by a nucleophilic addition
onto the nitrone. Alternatively, there could be a methyl
transfer from zinc to boron to produce an ‘‘MeZn؉/
(vinyl)Me(OR)2B؊’’ complex that would be the reactive in-
termediate. We are currently investigating this matter. Obvi-
ously, a globally radical process cannot be ruled out. If this
were the case, a good initiation step could be the reaction
between dimethylzinc and small amounts of oxygen. Never-
theless, we observed that opening of the reaction vessel to
room atmosphere after the reagents had been mixed under
nitrogen did not change the rate of the global process.
Scheme 2. Model reaction
We found that the expected reaction does take place, al-
though slowly, at room temperature in diethyl ether and
DMF as solvents. The use of diethylzinc gave a mixture of
vinyl and ethyl adducts, but the side-product was sup-
pressed by replacement with dimethylzinc. This reagent did
not give a detectable adduct, even when present in excess,
traces of methyl adduct being observed only in a control
run in the absence of vinylboronate (Entry 16, Table 1). A
rather large excess (see Entries 11Ϫ13, Table 1) of dimeth-
ylzinc is necessary for complete conversion. As standard
conditions for further study, we selected 2.5 equiv. of di-
Reactions with Other Carbonyl Compounds
The above conditions did not afford any product when
methylzinc in DMF at 60 °C. Note that vinyl addition was applied to simple imines (DMF, 60 °C, 24 h). As far as alde-
not observed in the absence of dimethylzinc (Entry 15, hydes are concerned, the reaction between 1a, dimethylzinc
Table 1). The replacement of dialkylzinc with 2 equiv. of and benzaldehyde was more sluggish than with nitrones
ZnCl2 (NMP, 60 °C, 4 h) did not produce any vinyl adduct. (DMF, 60 °C, 7Ϫ20 h) and afforded the expected allylic al-
No 1,3-dipolar cycloaddition[26] was ever observed.
cohol 6. The addition of methyl residues (product 7,
The model reaction was repeated in deuterated DMF at Scheme 3) competed with the desired process, and we had
50 °C, and its progress was monitored by 11B and 1H NMR to use a larger excess of 1a (2 equiv.) to suppress this methyl
spectroscopy. The 11B signal of the initial vinylboronic ester adduct. Even so, no complete conversion of the aldehyde
(δ ϭ 29.6 ppm, 140 Hz wide) slowly disappeared over 3.5 h, into pure vinyl adduct could be achieved.
Table 1. Reaction between vinylboronate 1, nitrone 3a and dialkylzinc under various conditions
Entry
Solvent
Temp.
Time [h]
Dialkylzinc (amount [mol/mol nitrone])
Vinyl adduct
Alkyl adduct
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
CH2Cl2
Toluene
Et2O
THF
THF
Et2O
Et2O
DMF
DMF
DMF[a]
DMF
DMF
DMF
DMF
DMF
DMF
room temp.
room temp.
room temp.
room temp.
60 °C
24
24
24
48
24
48
96
48
Et2Zn (1)
Et2Zn (1)
Et2Zn (1)
Et2Zn (1)
Me2Zn (2.5)
Me2Zn (1)
Me2Zn (1)
Me2Zn (1.2)
Me2Zn (3)
Me2Zn (3)
Me2Zn (1.5)
Me2Zn (2)
Me2Zn (3)
Et2Zn (3)
none
0
0
7
12
29
0
0
0
0
0
0
0
0
0
40
0
4
traces
11
29
66
29
60
40
80
86
56
88
Ͼ 95
60
room temp.
room temp.
room temp.
room temp.
room temp.
60 °C
48
24
3.5
3.5
3.5
3.5
3.5
3.5
60 °C
60 °C
60 °C
60 °C
0
60 °C
Me2Zn (1.2)[b]
0[b]
[a]
[b]
Commercial, undried DMF. Run in the absence of vinylboronate.
3622
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Eur. J. Org. Chem. 2003, 3621Ϫ3627

Dimethylzinc-Promoted Vinylation of Nitrones
FULL PAPER
and mass spectroscopy). Analogous structures have already
been isolated in transmetallation reactions with ce-
rium.[29,30] We tentatively explain their formation in terms
of Scheme 4: after transmetallation, the first vinylzinc spec-
ies, unreactive towards a ketone, would carbometallate a
second vinylborane to give 10. The allylic species 10 could
add onto a ketone with allylic transposition to give 11. This
is also an allylic organometallic compound, and is therefore
also able to add onto a second molecule of ketone, produc-
ing 9 on hydrolysis.
These results raise an observation. In studies directed
towards new preparations of mildly reactive organometallic
species, such as dialkylzinc compounds, one generally needs
a simple transformation to verify the presence of the ex-
Scheme 3. Competition between aldehyde and nitrone
Scheme 5. Examples of additions to nitrones (R2,R3: see Table 2)
Other aldehydes gave poor isolated yields of vinyl ad-
ducts [6b from cinnamaldehyde: 29%; 6c from 2-phenylpro-
panal: 28% (30% de)]. Note that the results did not change
in the presence of 5% of Chirald, a catalyst for the ad-
dition of diethylzinc to aldehydes.[28]
Table 2. Addition of vinylboronates onto nitrones in the presence
of Me2Zn
In an attempt to compare the reactivities of the nitrone
and the aldehyde electrophiles, we designed the competition
experiment described in Scheme 3. All four possible adducts
were recovered, together with unchanged electrophiles.
Clearly, the nitrone reacted more rapidly with the vinylic
organometallic compound than the aldehyde. In this run,
with the vinylboronic ester in deficit, methyl addition onto
the nitrone (product 5) was evident in small proportions. It
is likely that the formation of 5 took place after all the
vinylic species had been consumed.
The same reaction was repeated with benzophenone and
propiophenone as trapping reagents. In each case, none of
the expected allyl alcohol was present in the crude product.
Instead, we recovered (chromatography in 50 and 77%
yields from ketones, respectively) two products of the gen-
eral formula 9 in Scheme 4 (as mixtures of isomers; the
structure of 9 was ascertained by extensive NMR studies
[a] Fast reaction, product decomposes. [b] Me adduct is present: 40%
yield. 2 mol-equiv. of 1e, 1h.
[c]
Scheme 4. Reaction with ketones
Eur. J. Org. Chem. 2003, 3621Ϫ3627
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´
S. U. Pandya, S. Pinet, P. Y. Chavant, Y. Vallee
FULL PAPER
spectrometer by chemical ionisation (ammonia/isobutane ϭ 63:37).
HRMS and elemental analyses were performed at the Service Cen-
tral d’Analyse du CNRS, Vernaison, France.
pected species. This has to be a robust, simple and efficient
reaction, and, preferably, one that results in a new CϪC
bond. In dialkylzinc chemistry, uncatalysed additions to
carbonyl groups do not fulfil these conditions.[31] The com-
parison of nitrones with aldehydes in the current work
prompts us to suggest that the addition to nitrones may be
a useful tool for such purposes.
Vinylboronic Ester 1f:[24] Colourless oil. TLC: Rf ϭ 0.85 (cyclohex-
ane/ethyl acetate, 85:15). 11B NMR (96.3 MHz, CDCl3/BF3·Et2O):
δ ϭ 29.5 (288 Hz width at half heights) ppm. 1H NMR (300 MHz,
CDCl3/TMS): δ ϭ 1.13 (s, 9 H), 1.16 (s, 12 H), 3.91 (dd, J ϭ 1.8,
3.5 Hz, 2 H), 5.64 (dt, J ϭ 1.8, 8.0 Hz, 1 H), 6.60 (dt, J ϭ 3.5,
6.6 Hz, 1 H) ppm. 13C NMR (75 MHz, CDCl3/TMS): δ ϭ 24.75,
27.53, 63.73, 73.23, 83.12, 118.3 (br.), 150.97 ppm. IR (KBr disc):
Other Nitrones and Vinylboronic Esters
We thus studied the extension of the reaction to different
nitrones and vinylboronates (Table 2). The reaction pro-
ceeds readily with N-aryl- and N-alkyl-substituted nitrones,
and several functional groups, both on the nitrone and on
the vinylic reagents, are tolerated. Poor yields in hy-
droxylamine in Entries 20Ϫ22 (Table 2) are due to sub-
sequent side-reactions already observed by us.[1] The very
reactive cyclic nitrone of Entry 23 (Table 2) gave a mixture
of methyl (40% yield) and vinyl (37%) adducts. The most
disappointing results are summarized in Entry 30 (Table 2):
All attempts to obtain adducts from vinylboronic esters de-
rived from propargylic alcohol derivatives gave very poor
yields. When Entry 31 (Table 2) was repeated in a 1H NMR
tube in [D7]DMF, we observed the rapid formation of a new
vinylic species that does not react further with the nitrones.
ν˜ ϭ 2976, 2931, 2873, 1644, 1388, 1345, 1321, 973, 849 cmϪ1
.
LRMS (CI): m/z (%) ϭ 259 (16), 258 (100), 257 (44). HRMS (CI):
calcd. for C13H29BNO3 258.2240; found 258.22300.
General Procedure A. Reaction of Nitrones in DMF: Dimethylzinc
(2  solution in toluene, 0.625 mL, 1.25 mmol, 2.5 equiv.) was ad-
ded under nitrogen to a mixture of nitrone (0.5 mmol) and vinyl-
borane (0.6 mmol) in anhydrous DMF (0.50 mL). The mixture was
stirred at 60 °C for 3.5 h. Hydrolysis was performed at 20 °C by
addition of a saturated solution of NaHCO3 (2 mL) and the mix-
ture was extracted with DCM (3 ϫ 5 mL). The collected organic
phases were filtered through a pad of silica gel, dried with sodium
sulfate and concentrated under reduced pressure. The crude mate-
rial was chromatographed on silica gel (pentane/DCM, 90:10) to
yield the hydroxylamine as a colourless oil. The reaction of the
N,N-dialkylhydroxylamine with triphenyltetrazolium chloride on
the TLC plate[32] provided an efficient diagnosis (strong red colour
on gentle heating).
General Procedure B. Reaction of Nitrones in NMP: Dimethylzinc
(2  solution in toluene, 0.625 mL, 1.25 mmol, 2.5 equiv.) was ad-
ded under nitrogen to a mixture of nitrone (0.5 mmol) and vinyl-
borane (0.6 mmol) in anhydrous NMP (0.25 mL). The mixture was
stirred at 60 °C for 2 h. Hydrolysis was performed at 20 °C by
addition of a saturated solution of NaHCO3 (2 mL) and the mix-
ture was extracted with DCM (3 ϫ 5 mL). The combined organic
phases were dried with sodium sulfate and concentrated under re-
duced pressure. The crude material was purified by double chroma-
tography on silica gel. The first (cyclohexane/ethyl acetate, 50:50)
eliminated the NMP. The second (cyclohexane/ethyl acetate, 90:10)
yielded the pure hydroxylamine (colourless oil).
Conclusion
We have thus found that the reaction between a vinylbo-
ronic ester of pinacol and a nitrone in the presence of di-
methylzinc efficiently provides various N-allylic hy-
droxylamines in good yields. The boronic esters of pinacol,
easily available from the corresponding borane, are interest-
ing derivatives because of their stability to air and moist-
ure.[21] This work is the first example of successful transmet-
allation of members of this family with dialkylzinc.
General Procedure C. Reaction of Aldehydes or Ketones in DMF:
Dimethylzinc (2  solution in toluene, 0.750 mL; 1.5 mmol; 3
equiv.) was added under nitrogen to a mixture of aldehyde
(0.5 mmol) and vinylborane (1 mmol) in anhydrous DMF (0.5 mL).
The mixture was stirred at 60 °C for 7Ϫ20 h. Hydrolysis was per-
formed at 20 °C by addition of a saturated solution of NaHCO3
(2 mL) and the mixture was extracted with DCM (3 ϫ 5 mL). The
combined organic phases were dried with sodium sulfate and con-
centrated under reduced pressure. Chromatography (cyclohexane/
ethyl acetate, 90:10) furnished the pure allylic alcohol.
Experimental Section
General: All reactions were performed by use of conventional
Schlenk techniques, under dry nitrogen in oven-dried glassware,
with magnetic stirring. All reagents were purchased from Aldrich,
Acros or Fluka and were used as received. Dichloromethane
(DCM) was distilled from CaH2. Diethyl ether and THF were dis-
tilled from sodium/benzophenone. Toluene was distilled from so-
dium. Dimethylformamide (DMF) and N-methylpyrrolidin-2-one
˚
(NMP) were distilled and stored over 4 A molecular sieves. The
reactions were monitored by thin layer chromatography (TLC) on
commercial aluminium-backed silica gel plates (Merck, Kieselgel
60 F254). Forced-flow column chromatography was performed on
MachereyϪNagel Silica Gel 60, 230Ϫ400 mesh. Infrared (IR) spec-
N-Benzyl-N-(1-phenylhept-2-enyl)hydroxylamine (4a):[1] This com-
pound was prepared by General Procedure A from benzyl(benzyl-
idene)azane oxide (3a, 0.5 mmol, 105 mg) and dioxaborolane 1a
(0.6 mmol, 126 mg), in 90% yield (133 mg). Colourless oil. TLC:
1
tra were obtained either from neat films or sintered KBr discs. All Rf ϭ 0.52 (cyclohexane/ethyl acetate, 50:50). H NMR (200 MHz,
IR spectra were recorded with a Nicolet Impact-400 FTIR appar-
CDCl3/TMS): δ ϭ 0.87 (t, J ϭ 6.8 Hz, 3 H), 1.20Ϫ1.45 (m, 4 H),
2.05 (q, J ϭ 6.7 Hz, 2 H), 3.68 (d, J ϭ 13.7 Hz, 1 H), 3.83 (d, J ϭ
13.4 Hz, 1 H), 4.17 (d, J ϭ 7.9 Hz, 1 H), 5.19 (s, 1 H), 5.64 (dd,
J ϭ 6.2, 15.4 Hz, 1 H), 5.80 (dd, J ϭ 7.5, 15.8 Hz, 1 H), 7.15Ϫ7.40
1
atus. H NMR (200 or 300 MHz), and 13C NMR (50 or 75 MHz)
spectra were recorded either with a Bruker AC 200 or with an Ad-
vance 300 spectrometer. All chemical shifts for 1H spectra (refer-
ence tetramethylsilane) are listed according to: chemical shift (m, 10 H) ppm. 13C NMR (75 MHz, CDCl3/TMS): δ ϭ 14.36,
(ppm), multiplicity, integration, and coupling constants (Hz). Mass 22.71, 29.32, 31.76, 61.50, 75.05, 127.52, 127.60, 128.44, 128.64,
spectra were recorded with a ThermoFinnigan PolarisQ ion-trap
128.91, 129.47 (br.), 129.82, 135.23, 138.68, 142.36 ppm. IR (KBr
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 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Eur. J. Org. Chem. 2003, 3621Ϫ3627

Dimethylzinc-Promoted Vinylation of Nitrones
FULL PAPER
disc): ν˜ ϭ 3553, 3240, 3086, 3061, 2955, 2922, 1591, 1502, 1380, acetate, 75:25) furnished solely the rearranged O-alkylated product
971, 702 cmϪ1. LRMS (EI, 70 eV): m/z (%) ϭ 295 (2) [Mϩ], 213 in 18% yield (21 mg), colourless oil. TLC: Rf ϭ 0.46 (cyclohexane/
1
(7), 212 (9), 173 (30), 91 (100). C20H25NO (295.4): calcd. C 81.31,
H 8.53, N 4.74; found C 81.60, H 8.53, N 4.74.
ethyl acetate, 50:50). H NMR (300 MHz, CDCl3/TMS): δ ϭ 0.81
(t, J ϭ 6.8 Hz, 3 H), 0.95 (d, J ϭ 6.3 Hz, 3 H), 1.07 (d, J ϭ 6.3 Hz,
3 H), 1.15Ϫ1.30 (m, 4 H ϩ OH), 1.40Ϫ1.55 (m, 1 H), 1.70Ϫ1.85
(m, 1 H), 3.02 (sept, J ϭ 6.3 Hz, 1 H), 3.26 (dt, J ϭ 4.5, 9.0 Hz, 1
H), 6.10 (dd, J ϭ 9.1, 16.0 Hz, 1 H), 6.07 (d, J ϭ 3.3 Hz, 1 H),
6.22 (d, J ϭ 16.0 Hz, 1 H), 6.29 (dd, J ϭ 1.9, 3.3 Hz, 1 H), 7.26
(d, J ϭ 1.8 Hz, 1 H) ppm. 13C NMR (75 MHz, CDCl3/TMS): δ ϭ
13.84, 20.33, 20.38, 22.65, 28.41, 32.57, 53.78, 66.15, 107.19,
111.16, 120.74, 127.56, 141.69, 152.57 ppm. LRMS (CI): m/z (%) ϭ
236 (100), 220 (30), 177 (29), 163 (80), 124 (14), 110 (8).
N-Benzyl-N-(1-phenylethyl)hydroxylamine (5):[33] This compound
was identified as a side product. Colourless oil. TLC: Rf ϭ 0.64
(cyclohexane/ethyl acetate, 85:15). 1H NMR (300 MHz, CDCl3/
TMS): δ ϭ 1.44 (d, J ϭ 6.5 Hz, 3 H), 3.69 (br. d, J ϭ 13.4 Hz, 1
H), 3.72 (d, J ϭ 13.4 Hz, 1 H), 3.80 (q, J ϭ 6.6 Hz, 1 H), 4.56 (s,
OH), 7.15Ϫ7.35 (m, 10 H) ppm.
N-Benzyl-N-(1-phenylpropyl)hydroxylamine (5Ј):[1] This compound
was identified as a side product. 1H NMR (300 MHz, CDCl3/
TMS): δ ϭ 0.65 (t, J ϭ 7.4 Hz, 3 H), 1.64 (ddt, J ϭ 13.5, 9.5,
7.5 Hz, 1 H), 2.05 (ddt, J ϭ 13.5, 9.5, 5.0 Hz, 1 H), 3.45 (dd, J ϭ
5.0, 9.5 Hz, 1 H), 3.45 (d, 13.1 Hz, 1 H), 3.60 (d, J ϭ 13.1 Hz, 1
H), 3.64 (d, J ϭ 13.4 Hz, 1 H), 3.77 (br. d, J ϭ 13.4 Hz,1 H),
7.15Ϫ7.30 (m, 10 H) ppm.
1-Hex-1-enyl-3,4-dihydro-1H-isoquinolin-2-ol (4e):[34] This com-
pound was prepared by General Procedure B from 3,4-dihydroiso-
quinoline N-oxide (74 mg, 0.5 mmol) and dioxaborolane 1a
(0.6 mmol, 126 mg) for only 1 h at 60 °C. On TLC (cyclohexane/
ethyl acetate, 50:50) the reaction was complete in 30 min. Chroma-
tography produced allylic hydroxylamine (28 mg, 37% yield) and
methyl adduct (33 mg, 40% yield). Colourless oils. TLC: Rf ϭ 0.57
and 0.26, respectively (cyclohexane/ethyl acetate, 50:50),
N-Benzyl-N-[1-(4-trifluoromethylphenyl)hept-2-enyl]hydroxylamine
(4b): This compound was prepared by General Procedure B from
benzyl(4-trifluoromethylbenzylidene)azane
oxide
(138 mg,
1
Vinyl Adduct 4e: H NMR (300 MHz, CDCl3/TMS): δ ϭ 0.92 (t,
0.5 mmol) and dioxaborolane 1a (0.6 mmol, 126 mg) in 92% yield
(166 mg).Colourless oil. TLC: Rf ϭ 0.63 ( cyclohexane/ethyl acet-
ate, 50:50). 1H NMR (300 MHz, CDCl3/TMS): δ ϭ 0.88 (t, J ϭ
7.0 Hz, 3 H), 1.20Ϫ1.45 (m, 4 H), 2.12 (td, J ϭ 7.6, 6.4 Hz, 2 H),
3.70 (d, J ϭ 13.4 Hz, 1 H), 3.99 (d, J ϭ 13.4 Hz, 1 H), 4.27 (d, J ϭ
7.7 Hz, 1 H), 4.66 (br. s, OH), 5.65Ϫ5.80 (m, 2 H), 7.2Ϫ7.4 (m, 5
H), 7.5Ϫ7.7 (m, 4 H) ppm. 13C NMR (75.5 MHz, CDCl3/TMS):
δ ϭ 13.85 (CH3), 22.24 (CH2), 31.21 (CH2), 32.17 (CH2), 61.37
(CH2), 74.37 (CH), 125.39 (CH), 127.26 (CH), 127.82 (CF3), 128.12
(CH), 128.18 (CH), 128.30 (CH), 129.09 (CH), 129.26 (CH), 135.74
(CH), 138.05 (C), 146.19 (C) ppm. IR (film): ν˜ ϭ 3543, 3445, 3071,
3035, 2964, 2932, 2878, 2857, 1621, 1453, 1421, 1325, 1168, 1129,
J ϭ 7.03 Hz, 3 H), 1.2Ϫ1.5 (m, 4 H ϩ OH), 2.15 (q, J ϭ 6.5 Hz,
2 H), 2.81Ϫ2.95 (m, 1 H), 2.95Ϫ3.15 (m, 2 H), 3.40Ϫ3.55 (m, 1
H), 4.28 (br. d, J ϭ 8.2 Hz, 1 H), 5.51 (dd, J ϭ 8.2, 15.1 Hz, 1 H),
5.78 (dt, J ϭ 15.3, 6.7 Hz), 7.05Ϫ7.20 (m, 4 H) ppm. 13C NMR
(75.5 MHz, CDCl3/TMS): δ ϭ 13.92, 22.31, 28.28, 31.42, 32.14,
53.45(br., CH2ϪN), 71.40 (br., CHϪN), 125.87, 126.55,
127.94.128.12, 129.73 (br., NϪCHϪCHϭ), 133.26, 135.85, 136.98
(ϭCHϪBu) ppm. IR (film): ν˜ ϭ 3219, 3068, 3026, 2956, 2929,
2863, 1629, 1464, 752 cmϪ1. LRMS (CI): m/z (%) ϭ 232 (6), 231
(19), 214 (12), 172 (25), 148 (80), 129 (100).
Methyl Adduct: 1H NMR (300 MHz, CDCl3/TMS): δ ϭ 1.50 (d,
1069, 1019, 973, 834, 808, 745, 698 cmϪ1. LRMS (CI): m/z (%) ϭ J ϭ 6.7 Hz,3 H), 2.75Ϫ3.10(m, 3 H), 3.30Ϫ3.45 (m, 1 H), 3.90 (br.,
364 (82), 346 (34), 241 (48), 185 (17), 177 (18), 136 (28), 124 (20),
122 (23), 91 (64), 81, 60 (100). C21H24F3NO (363.42): calcd. C TMS): δ ϭ 19.88 (br.), 27.79 (br.), 53.47 (br.), 63.17 (br.), 126.13,
1 H), 6.95Ϫ7.10 (m, 4 H) ppm. 13C NMR (75.5 MHz, CDCl3/
69.40, H 6.66, N 3.85; found C 69.66, H 6.65, N 3.86.
126.27, 126.50, 128.20, 133.01, 138.10 ppm. IR (film): ν˜ ϭ 3259,
3075, 2966, 2937, 2849, 1650, 1455, 737 cmϪ1. LRMS (CI): m/z
(%) ϭ 165 (7), 164 (57), 163 (12), 162 (100), 159 (17), 160 (22), 148
(19), 146 (26), 144 (12).
Methyl 4-{1-[Hydroxy(methyl)amino]hept-2-enyl}benzoate (4c): This
compound was prepared by General Procedure B from 4-{(Z)-
[methyl(oxido)imino]methyl}benzoate (97 mg, 0.5 mmol) and diox-
aborolane 1a (0.6 mmol, 126 mg) in 85% yield (118 mg). Colourless
oil. TLC: Rf ϭ 0.46 (cyclohexane/ethyl acetate, 50:50). 1H NMR
N-Benzyl-N-(1-phenyltridec-2-enyl)hydroxylamine (4f): This com-
pound was prepared by General Procedure A from benzyl(benzyl-
(300 MHz, CDCl3/TMS): δ ϭ 0.86 (t, J ϭ 7.0 Hz, 3 H), 1.15Ϫ1.40 idene)azane oxide (211 mg, 1 mmol) and dioxaborolane 1b
(m, 5 H), 2.12 (td, J ϭ 6.9, 6.3 Hz, 2 H), 2.58 (s, 3 H), 3.90 (s, 3 (1.2 mmol, 319 mg), in 91% isolated yield (346 mg). Colourless oil.
H), 4.03 (d, J ϭ 7.9 Hz, 1 H), 5.55Ϫ5.80 (m, 2 H), 7.41 (d, J ϭ TLC: Rf
0.33 (diethyl ether/pentane, 90:10). 1H NMR
8.2 Hz), 7.99 (d, J ϭ 8.2 Hz, 2 H) ppm. 13C NMR (75.5 MHz,
(300 MHz, CDCl3/TMS): δ ϭ 0.79 (t, J ϭ 6.5 Hz, 3 H), 1.05Ϫ1.35
ϭ
CDCl3/TMS): δ ϭ 13.82 (CH3), 22.15 (CH2), 31.11 (CH2), 32.08 (m, 16 H), 1.97 (q, J ϭ 6.9 Hz, 2 H), 3.61(d, J ϭ 13.4 Hz, 1 H),
(CH2), 45.85 (CH3), 52.01 (CH3), 77.28 (CH), 127.80 (CH), 128.71 3.77 (br. d, J ϭ 13.3 Hz, 1 H), 4.10(d, J ϭ 8.2 Hz, 1 H), 4.93 (br.
(C), 129.03 (C), 128.85 (CH), 135.25 (CH), 147.15 (C), 166.92 (C) s, 1 H), 5.58(dt, J ϭ 6.3, 15.5 Hz, 1 H), 5.67 (dd, J ϭ 8.1, 15.8 Hz,
ppm. IR (film): ν˜ ϭ 3465, 3189, 3039, 2999, 2960, 2931, 2876, 2861, 1 H), 7.10Ϫ7.35 (m, 10 H) ppm. 13C NMR (75 MHz, CDCl3/
1721, 1669, 1615, 1460, 1434, 1417, 1284, 1185, 1116, 1022, 976,
TMS): δ ϭ 14.27, 22.85, 29.32, 29.37, 29.51, 29.62, 29.78(2 C),
772, 714 cmϪ1. LRMS (CI): m/z (%) ϭ 278 (38) [MHϩ], 360 (24), 32.08, 32.68, 61.24, 74.76, 127.22, 127.29, 128.17, 128.34, 128.62,
231 (100). C16H23NO3 (277.36): calcd. C 69.29, H 8.36, N 5.05;
found C 69.38, H 8.34, N 5.04.
129.23, 129.52, 134.95, 138.52, 142.11 ppm. IR (KBr disc): ν˜ ϭ
3543, 3249, 3025, 2917, 2840, 1461, 1069, 1037, 960, 914, 743 cmϪ1
.
LRMS (CI): m/z (%) ϭ 380 (100) [MHϩ], 362 [M Ϫ OH]ϩ (18), 257
O-(1-Butyl-3-furan-2-ylallyl)-N-isopropylhydroxylamine (from 4d):
This compound was prepared by General Procedure B from (2-
(51). HRMS (CI) calcd. for C26H38NO: 380.2953; found 380.2975.
furylmethylene)isopropylazane oxide (77 mg, 0.5 mmol) and diox- N-Benzyl-N-(6-chloro-1-phenylhex-2-enyl)hydroxylamine (4g): This
aborolane 1a (0.6 mmol, 126 mg). Conventional workup produced
a crude material that, by H NMR, was a mixture of N-(1-furan-
2-ylhept-2-enyl)-N-(isopropyl)hydroxylamine (4d) and its re-
arrangement product O-[1-butyl-3-(furan-2-yl)allyl]-N-isopropylhy-
droxylamine. Silica gel column chromatography (cyclohexane/ethyl
compound was prepared by General Procedure A from benzyl-
(benzylidene)azane oxide (211 mg, 1 mmol) and dioxaborolane 1d
(1.2 mmol, 242 mg) in 90% isolated yield (284 mg). Colourless oil.
TLC: Rf ϭ 0.75 (cyclohexane/ethyl acetate, 50:50). 1H NMR
(300 MHz, CDCl3/TMS): δ ϭ 1.73 (quint, J ϭ 6.9 Hz, 2 H), 2.11
1
Eur. J. Org. Chem. 2003, 3621Ϫ3627
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 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3625

´
S. U. Pandya, S. Pinet, P. Y. Chavant, Y. Vallee
FULL PAPER
(q, 7.1 Hz, 2 H), 3.36 (t, J ϭ 6.6 Hz, 2 H), 3.59 (d, J ϭ 13.3 Hz, 1
δ ϭ 13.79, 19.43, 22.15, 31.48, 32.22, 41.48, 45.70, 76.84, 124.85,
H), 3.68 (br. d, J ϭ 13.3 Hz, 1 H), 4.08 (d, J ϭ 8.6 Hz, 1 H), 5.11 125.94, 127.72, 128.11, 136.83, 145.68 ppm.
(s, OH), 5.51 (dt, J ϭ 6.4, 15.4 Hz, 1 H), 5.77 (dd, J ϭ 8.6, 15.4 Hz,
(1-Isobutylhept-2-enyl)[1-(naphthalen-1-yl)ethyl]amine (4k): This
1 H), 7.10Ϫ7.30 (m, 10 H) ppm. 13C NMR (75 MHz, CDCl3/
TMS): δ ϭ 29.65Ϫ31.91, 44.38, 61.19, 74.42, 127.24, 127.40,
128.13, 128.33, 128.62, 129.44, 130.89, 132.32, 138.23, 141.62 ppm.
IR (KBr disc): ν˜ ϭ 3535, 3453, 3232, 3060, 3030, 2930, 1950, 1595,
1495, 1455, 1305, 970 cmϪ1. LRMS (CI): m/z (%) ϭ 319 (8), 318
(30), 317 (24), 316 (88), 196 (4), 195 (32), 194 (14), 193 (100).
C19H22ClNO (315.8): calcd. C 72.25, H 7.02, N 4.43; found C
72.51, H 7.03, N 4.45.
compound was obtained by General Procedure A from nitrone
(255 mg, 1.0 mmol) and dioxaborolane 1a (250 mg, 1.2 mmol) in
56% yield (188 mg). Colourless oil. TLC: Rf ϭ 0.50 (cyclohexane/
ethyl acetate, 50:50).The product was dissolved in a 4:1 acetic acid/
water mixture and stirred with zinc dust (721 mg) overnight at
room temp. The suspension was filtered, concentrated, taken up in
ethyl acetate, and washed with 2 ϫ 1 mL of a saturated NaHCO3
solution. Measurement of the de was accomplished by HPLC: col-
umn Kromasil C18, 250 ϫ 4.6 mm, UV detection 218 nm, eluent
acetonitrile/water (95:5), 2 mL/min, major peak 11.7 min, minor
peak 13.7min. NMR of major isomer: 1H NMR (300 MHz,
CDCl3/TMS): δ ϭ 0.72 (J ϭ 6.5 Hz, 3 H), 0.77 (d, J ϭ 6.6 Hz, 3
H), 0.98 (m, 3 H), 1.2Ϫ1.4 (m, 4 H), 1.49 (d, J ϭ 6.8 Hz, 3 H),
1.9Ϫ2.0 (m, 2 H), 2.8Ϫ2.95 (m, 1 H),; 4.84 (q, J ϭ 6.6 Hz, 1 H),
5.03 (dt, J ϭ 15.4, 6.6 Hz, 1 H), 5.22 (br. dd, J ϭ 15.2, 8.8 Hz, 1
H), 7.4Ϫ8.85 (m, 7 H) ppm. 13C NMR (75 MHz, CDCl3/TMS):
δ ϭ 14.07, 22.35, 22.39, 23.13, 24.26, 24.74, 32.10, 32.16, 45.32,
49.94, 56.68, 122.91, 122.79, 125.68, 125.30, 127.21, 128.88, 131.40,
131.21, 132.63, 132.51, 133.92, 140.23 ppm. LRMS (CI): m/z (%) ϭ
338 (14), 325 (21), 324 (100), 323 (8), 322 (21), 266 (12), 186 (22),
155 (27) (3) [MHϩ], 302 (7) [M Ϫ OH]ϩ, 214 (8), 197 (100). HRMS
(CI) calcd. for C23H34N 324.2691; found 324.256.
N-Benzyl-N-[3-(cyclohex-1-enyl)-1-phenylallyl]hydroxylamine (4h):
This compound was prepared by General Procedure A from
benzyl(benzylidene)azane oxide (211 mg, 1 mmol) and dioxaborol-
ane 1c (282 mg, 1.2 mmol) in 66% yield (209 mg). Colourless oil.
TLC: Rf ϭ 0.60 (cyclohexane/ethyl acetate, 50:50). 1H NMR
(300 MHz, CDCl3/TMS): δ ϭ 1.45Ϫ1.55 (m, 4 H), 1.95Ϫ2.15 (m,
4 H), 3.6 (d, J ϭ 13.8 Hz, 1 H), 3.86 (d, J ϭ 13.8 Hz, 1 H), 4.22
(d, J ϭ 8.7 Hz, 1 H), 4.49 (s, OH), 5.65Ϫ5.80 (m, 2 H), 6.17 (d,
J ϭ 15.8 Hz, 1 H), 7.10Ϫ7.40 (m, 10 H) ppm. 13C NMR (75 MHz,
CDCl3/TMS): δ ϭ 22.53, 22.60, 24.74, 26.01, 61.46, 75.64, 125.17,
127.19, 127.37, 128.01, 128.35, 128.74, 129.32, 130.16, 135.42,
136.66, 138.70, 142.16 ppm. IR (KBr disc): ν˜ ϭ 3518, 3437, 3216,
3055, 3025, 2922, 2863, 2238, 1957, 1498, 1453, 1022, 971, 905
cmϪ1. LRMS (CI): m/z (%) ϭ 320 (3) [MHϩ], 302 [M Ϫ OH]ϩ (7),
214 (8), 197 (100). HRMS (CI) calcd. for C22H26NO: 320.2014;
found 320.2070.
Reactions with Aldehydes
1-Phenylethanol: This compound was isolated as a side product.
TLC: Rf ϭ 0.19 (cyclohexane/ethyl acetate, 50:50). 1H NMR
(200 MHz, CDCl3/TMS): δ ϭ 1.42 (d, J ϭ 6.5 Hz, 3 H), 1.7 (OH),
4.83 (q, J ϭ 6.5 Hz, 1 H), 7.1Ϫ7.3 (m, 5 H) ppm.
5-(Benzylhydroxyamino)-5-phenylpent-3-enyl 2,2-Dimethylpropio-
nate (4i): This compound was prepared by General Procedure B
from benzyl(benzylidene)azane oxide (42 mg, 0.2 mmol) and diox-
aborolane 1e (0.4 mmol, 68 mg) in 90% yield (66 mg). Colourless
oil. TLC: Rf ϭ 0.61 (cyclohexane/ethyl acetate, 50:50). 1H NMR
(300 MHz, CDCl3/TMS): δ ϭ 1.11 (s, 9 H), 2.38 (q, J ϭ 6.6 Hz, 2
H), 3.71 (d, J ϭ 13.6 Hz, 1 H), 3.87 (d, J ϭ 13.6 Hz, 2 H), 4.09 (t,
J ϭ 6.4 Hz, 1 H), 4.22 (d, J ϭ 8.4 Hz, 1 H), 4.93 (s, OH), 5.65 (dt,
J ϭ 6.7, 15.6 Hz, 1 H), 5.87 (dd, J ϭ 8.3.15.6 Hz, 1 H), 7.20Ϫ7.40
(m, 10 H) ppm. 13C NMR (75.5 MHz, CDCl3/TMS): δ ϭ 27.06,
31.89, 38.60, 61.14, 63.30, 74.54, 127.04, 127.91, 128.15, 128.49,
129.19, 129.44, 132.12, 138.20, 141.43, 178.43 ppm. IR (film): ν˜ ϭ
3469, 3108, 3088, 3064, 3030, 2974, 2935, 2906, 2873, 1950, 1884,
1805, 1726, 1601, 1495, 1481, 1456, 1398, 1368, 1286, 1158, 1029,
968, 739, 698 cmϪ1. LRMS (CI): m/z (%) ϭ 368 (26), 350 (22), 302
(2), 262 (3), 248 (5), 143 (100).
1-Phenylhept-2-en-1-ol (6a):[2,35] This compound was prepared by
General Procedure C from dioxaborolane 1a (420 mg, 2 mmol), di-
methylzinc in toluene (3 mmol, 1.5 mL) and benzaldehyde (106 mg,
1 mmol) in 89% yield. Colourless oil. TLC: Rf ϭ 0.55 (pentane/
CH2Cl2, 90:10). 1H NMR (200 MHz, CDCl3/TMS): δ ϭ 0.88 (t,
J ϭ 7.1 Hz, 3 H), 1.2Ϫ1.45 (m, 4 H), 1.95Ϫ2.15 (m, 2 H), 5.15 (d,
J ϭ 6.0 Hz, 1 H), 5.66 (dd, J ϭ 5.5, 14.4 Hz, 1 H), 5.73 (dd, J ϭ
5.7, 14.3 Hz, 1 H), 7.2Ϫ7.4 (m, 5 H) ppm.
1-Phenylpentadeca-1,4-dien-3-ol (6b): This compound was prepared
by General Procedure C from dioxaborolane 1b (294 mg, 1 mmol),
dimethylzinc in toluene (1.6 mmol, 0.8 mL) and cinnamaldehyde
(70 mg, 0.5 mmol) in 29% yield. Colourless oil. TLC: Rf ϭ 0.6
1
(pentane/CH2Cl2, 90:10). H NMR (300 MHz, CDCl3/TMS): δ ϭ
N-Methyl-N-[1-(1-phenylethyl)hept-2-enyl]hydroxylamine (4j): This
compound was prepared by General Procedure A from methyl(2-
phenylpropylidene)azane oxide (163 mg, 1 mmol) and dioxaborol-
ane 1a (250 mg, 1.2 mmol) in 50% isolated yield (120 mg). Colour-
less oil. TLC: Rf ϭ 0.78 (cyclohexane/ethyl acetate, 50:50 ; dia-
stereoisomers unresolved). The diastereoisomeric excess (43%) was
measured by NMR spectroscopy. Major Isomer: 1H NMR
(300 MHz, CDCl3/TMS): δ ϭ 0.80 (t, J ϭ 7.2 Hz, 3 H), 1.05Ϫ1.40
(m, 4 H), 1.33 (d, 7.1 Hz, 3 H), 1.85Ϫ1.95 (m, 2 H), 2.58 (s, 3 H),
2.98 (t, J ϭ 8.4 Hz, 1 H), 3.14 (quint, J ϭ 6.0 Hz, 1 H), 5.16 (dd,
J ϭ 9.0, 15.4 Hz, 1 H), 5.30 (dt, J ϭ 15.6, 6.7 Hz), 7.0Ϫ7.3 (m, 5
H) ppm. 13C NMR (75 MHz, CDCl3/TMS): δ ϭ 13.79, 19.43,
21.82, 31.29, 32.00, 41.71, 45.70, 76.57, 124.97, 125.94, 127.93,
128.32, 136.57, 144.55 ppm. Minor Isomer: 1H NMR (300 MHz,
0.88 (t, J ϭ 6.5 Hz, 3 H), 1.10Ϫ1.50 (m, 16 H), 1.47 (br. s, OH),
2.05 (q, J ϭ 6.9 Hz, 2 H), 4.75 (t, J ϭ 6.4 Hz, 1 H), 5.56 (ddt, J ϭ
6.5, 15.4, 1.3 Hz, 1 H), 5.64 (br. dt, J ϭ 15.5, 6.6 Hz, 1 H), 6.25
(dd, J ϭ 6.2, 15.9 Hz, 1 H), 6.58 (d, J ϭ 15.7 Hz, 1 H)7.20Ϫ7.40
(m, 5 H) ppm. 13C NMR (75 MHz, CDCl3/TMS): δ ϭ 14.27, 22.85,
29.25, 29.39, 29.51, 29.66, 29.78 (ϩ unresolved lines), 32.08, 32.44,
73.83, 139.02, 124.71, 136.73, 133.04, 131.15, 130.96, 130.11,
128.49, 127.58, 126.48 ppm. IR (KBr disc): ν˜ ϭ 3354, 3028, 2920,
2849, 1592, 1469 cmϪ1. LRMS (CI): m/z (%) ϭ 299 (5), 285 (21),
283 (100), 282 (12), 257 (5), 143 (9). C21H32O (300.5): C 83.94, H
10.73; found C 84.04, H 11.11.
2-Phenylnon-4-en-3-ol (6c):[36,37] This compound was prepared by
General Procedure C from dioxaborolane 1a (210 mg, 1 mmol), di-
CDCl3/TMS): δ ϭ 0.88 (t, J ϭ 7.0 Hz, 3 H), 1.05Ϫ1.40 (m, 4 H), methylzinc in toluene (1.6 mmol, 0.8 mL) and rac-2-phenylpro-
1.20 (d, J ϭ 7.0 Hz, 3 H), 2.0Ϫ2.10 (m, 2 H), 2.51 (s, 3 H), 3.04 panal (67 mg, 0.5 mmol) in 28% yield (diastereoisomers not sepa-
(t, J ϭ 8.0 Hz, 1 H), 3.14 (quint, J ϭ 6.0 Hz, 1 H), 5.38Ϫ5.45 (m,
rated). Colourless oil. Major Isomer (erythro):[38] TLC: Rf ϭ 0.52
2 H), 7.0Ϫ7.3 (m, 5 H) ppm. 13C NMR (75 MHz, CDCl3/TMS):
(cyclohexane/ethyl acetate, 50:50 ). 1H NMR (300 MHz, CDCl3/
3626
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2003, 3621Ϫ3627

Dimethylzinc-Promoted Vinylation of Nitrones
FULL PAPER
W. Oppolzer, R. N. Radinov, J. Am. Chem. Soc. 1993, 115,
1593Ϫ1594.
[7]
[8]
TMS): δ ϭ 0.84 (t, J ϭ 7.3 Hz, 3 H), 1.31 (d, J ϭ 7.0 Hz, 3 H),
1.15Ϫ1.40 (m, 4 H), 1.53 (br. s, OH), 1.97 (br. q, J ϭ 6.9 Hz, 2 H),
2.87 (quint, J ϭ 6.8 Hz, 1 H), 4.15 (br. t, J ϭ 6.2 Hz, 1 H), 5.37
(ddt, J ϭ 6.8, 14.1, 2.7 Hz, 1 H), 5.52 (ddt, J ϭ 0.9, 15.4, 6.8 Hz),
7.15Ϫ7.40 (m, 5 H) ppm. Minor Isomer: TLC: Rf ϭ 0.58 (cyclohex-
W. Oppolzer, R. N. Radinov, E. El-Sayed, J. Org. Chem. 2001,
66, 4766Ϫ4770.
[9]
K. Shibata, M. Kimura, K. Kojima, S. Tanaka, Y. Tamaru, J.
Organomet. Chem. 2001, 624, 348Ϫ353.
E. Hupe, P. Knochel, K. J. Szabo, Organometallics 2002, 21,
2203Ϫ2207.
E. Hupe, P. Knochel, Org. Lett. 2001, 3, 127Ϫ130.
F. Langer, L. Schwink, A. Devasagayaraj, P.-Y. Chavant, P.
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583Ϫ586.
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1
ane/ethyl acetate, 50:50). H NMR (300 MHz, CDCl3/TMS): δ ϭ
[10]
0.89 (t, J ϭ 7.5 Hz, 3 H), 1.22 (d, J ϭ 7.5 Hz, 3 H), 1.15Ϫ1.40 (m,
4 H), 1.45 (br. s, OH), 2.10 (br. q, J ϭ 6.7 Hz, 2 H), 2.66 (quint,
J ϭ 7.3 Hz, 1 H), 4.08 (br. t, J ϭ 7.7 Hz, 1 H), 5.46 (ddt, J ϭ 7.6,
15.4, 1.4 Hz), 5.69 (ddt, J ϭ 0.8, 6.8, 15.4 Hz), 7.15Ϫ7.40 (m, 5
H) ppm.
[11]
[12]
[13]
[14]
Reactions with Ketones
2,5-Dibutyl-1,1,6,6-tetraphenylhex-3-ene-1,6-diol (9):[30] This com-
pound was prepared by General Procedure C from dioxaborolane
1a (210 mg, 1 mmol), dimethylzinc in toluene (1 mmol, 0.5 mL)
and benzophenone (91 mg, 0.5 mmol). Chromatography yielded
88 mg of a compound that was identified on the basis of its mass
spectrum and NMR experiments. Colourless oil. Yield for
C38H44O2 (532): 66%. 1H NMR (300 MHz, CDCl3/TMS): δ ϭ 0.82
(t, 6 H), 0.8Ϫ0.95 (m, 2 H, d), 1.05Ϫ1.45 (m, 4 H, e,f), 1.60Ϫ1.75
(m, 2 H, dЈ), 3.58 (br. quint, Jab ഠ 9.0 Hz; JaЈb ഠ Ϫ1.0 Hz, 2 H,
b), 4.14 (s, OH), 6.02 (m, JaaЈ ഠ 15 Hz, 2 H, a), 7.1Ϫ7.4 (m, 20 H)
ppm. 13C NMR (75.5 MHz, CDCl3/TMS): δ ϭ 14.29 (g), 23.31 (f),
31.12 (e), 33.01 (d), 46.16 (b), 81.22 (c), 127.09, 127.32, 127.69,
128.21, 128.58, 129.09, 133.91 (a), 143.47, 146.65 ppm (structure
and assignments are in agreement with COSY and H-to-C-corre-
lations). IR (KBr disc): ν˜ ϭ 3358, 3076, 3031, 2960, 2935, 2864,
1494, 1463, 969, 758, 702 cmϪ1. LRMS (CI): m/z (%) ϭ 533 (1),
498 (30), 497 (100) [C38H41ϩ], 391 (5), 279 (7), 249 (13). MS2 of
ion 497: m/z (%) ϭ 419 (86), 349(80), 249 (100).
[15]
[16]
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[17]
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Q. Wang, M. G. Finn, Org. Lett. 2000, 2, 4063Ϫ4065.
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[19]
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[21]
[22]
Y. Kobayashi, R. Mizojiri, E. Ikeda, J. Org. Chem. 1996, 61,
5391Ϫ5399.
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Received May 2, 2003
Eur. J. Org. Chem. 2003, 3621Ϫ3627
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