Synthesis of secondary amines via N-(benzoyloxy)amines and organoboranes

Article abstract of DOI:10.1021/jo981613l

A variety of primary amines (R-NH₂) were converted to their corresponding N-(benzoyloxy)amines (i.e., R-NHOCOPh) under biphasic conditions in excellent yields (63-90%). The intermediate N- (benzoyloxy)amines were converted to their N-ethylamine derivatives upon reaction with triethylborane in THF in good yield (54-89%). These experiments demonstrated the similar chemistry of N-chloro- and N-(benzoyloxy)amines with organoboranes.

Full text of DOI:10.1021/jo981613l

J . Org. Chem. 1999, 64, 803-806
803
Syn th esis of Secon d a r y Am in es via N-(Ben zoyloxy)a m in es a n d
Or ga n obor a n es
O. Phanstiel, IV,* Q. X. Wang, D. H. Powell,† M. P. Ospina,† and B. A. Leeson
Center for Diagnostics and Drug Development, Department of Chemistry, University of Central Florida,
Orlando, Florida 32816, and Department of Chemistry, University of Florida, Gainesville, Florida 32611
Received August 7, 1998
A variety of primary amines (R-NH2) were converted to their corresponding N-(benzoyloxy)amines
(i.e., R-NHOCOPh) under biphasic conditions in excellent yields (63-90%). The intermediate
N-(benzoyloxy)amines were converted to their N-ethylamine derivatives upon reaction with
triethylborane in THF in good yield (54-89%). These experiments demonstrated the similar
chemistry of N-chloro- and N-(benzoyloxy)amines with organoboranes.
In tr od u ction
which perform the same transformation, would clearly
augment the existing methods of amine synthesis.
The synthesis of amines has long been of interest as a
result of their unique biological activities and their
potential as organic intermediates.1 Organoborane tech-
nology allows access to substituted amines and protected
amines by a variety of routes. For example, primary
amines can be generated by the reaction of trialkylbo-
ranes with chloramine,2-4 hydroxylamine-O-sulfonic acid,5
or other N-activated reagents6,7 (eq 1). Alternative meth-
Because both the azide and N-chloro groups represent
leaving groups appended to nitrogen, it seemed likely
that N-(benzoyloxy)amines (R-NH-OCOPh), which con-
tain a comparable motif, would also undergo similar
chemistry with organoboranes. Having developed an
improved entry to these systems,14 our goal was to
evaluate the N-(benzoyloxy)amines15,16 as potential N-
chloro replacements. Indeed, this paper introduces a new
methodology for the synthesis of secondary amines via
the reaction of organoboranes and N-(benzoyloxy)amine
derivatives (eq 3).
ods allow for the generation of protected amine deriva-
tives (e.g., sulfonamides) directly from trialkylboranes.8
Borane-mediated amination reactions usually involve the
regiospecific replacement of the boron atom by the amino
group via an anionotropic rearrangement of an organobo-
rate complex.9,10 In addition, secondary amines can be
accessed via N-chloro derivatives of primary amines10 or
organic azides11,12 (eq 2). Many of these nitrogen-based
Resu lts a n d Discu ssion
When amine derivatives react with organoboranes,
several factors have been shown to influence the reaction
rate and product distribution. Previous work by Brown
demonstrated that the degree of substitution on the
carbon flanking the nitrogen (i.e., R in eq 2) influenced
the yield of secondary amines (when generated from
organic azides and trialkylboranes).12 Later work dem-
onstrated that the steric demands of both the reacting
amine functionality and the alkylborane unit (R′) influ-
enced the rate of the N-alkylation process.9,10 In general,
hindered motifs gave low yields of secondary amines.
Therefore, the amine systems chosen for study included
an adjacent 1°, 2°, and 3° substituted carbon center to
observe the scope and limitations of the respective
N-(benzoyloxy)amine reagents.
reagents are unstable or corrosive and are typically
generated just prior to use or in situ.10,13 New reagents,
† University of Florida.
(1) (a) Bergeron, R. J .; Feng, Y.; Weimar, W. R.; McManis, J . S.;
Dimova, H.; Porter, C.; Raisler, B.; Phanstiel, O. J . Med. Chem. 1997,
40, 1475-1494. (b) Carboni, B.; Vaultier, M. Bull. Soc. Chim. Fr. 1995,
132, 1003-1008.
(2) Rathke, M. W.; Inoue, N.; Varma, K. R.; Brown, H. C. J . Am.
Chem. Soc. 1966, 88, 2870.
(3) Kabalka, G. W.; Sastry, K. A. R.; McCollum, G. W.; Yoshioka,
H. J . Org. Chem. 1981, 46, 4296.
(4) Chloroamine: Brown, H. C.; Heydkamp, W. R.; Breuer, E.;
Murphy, W. S. J . Am. Chem. Soc. 1964, 86, 3565.
Several N-(benzoyloxy)amines (1-7) were prepared
and isolated by a modification of our published method
using benzoyl peroxide (BPO, see Scheme 1).14 Prior
(5) Brown, H. C.; Malhotra, S. V.; Ramachandan, P. V. Tetrahedron:
Asymmetry 1996, 7, 3527-3534.
(6) Primary amines via hydrazoic acid: Kabalka, G. W.; Henderson,
D. A.; Varma, R. S. Organometallics 1987, 6, 1369-1370.
(7) Primary amines via O-mesitylenesulfonylhydroxylamine: Tamu-
ra, Y.; Minamikawa, J .; Fujii, S.; Ikeda, M. Synthesis 1974, 196.
(8) Protected amines via organoborane technology: (a) Yang, R.; Dai,
L. Synthesis 1993, 481-482. (b) J igajinni, V. B.; Pelter, A.; Smith, K.
Tetrahedron Lett. 1978, 181-182. (c) Genet, J .-P.; Hajicek, J .; Bischoff,
L.; Greck, C. Tetrahedron Lett. 1992, 33, 2677.
(11) Organic azides: Suzuki, A.; Sono, S.; Itoh, M.; Brown, H. C.;
Midland, M. J . Am. Chem. Soc. 1971, 93, 4329.
(12) Secondary amines via organic azides: Brown, H. C.; Midland,
M. M., Levy, A. B. J . Am. Chem. Soc. 1972, 94, 2114-2115.
(13) N-chloroamine in situ: Kabalka, G. W.; McCollum, G. W.;
Kunda, S. A. J . Org. Chem. 1984, 49, 1656-1657.
(14) Wang, Q. X.; King, J .; Phanstiel IV, O. J . Org. Chem., 1997,
62, 8104-8108.
(15) Biloski, A. J .; Ganem, B. Synthesis 1983, 537-538.
(16) Milewska, M. J .; Chimiak, A. Synthesis 1990, 233-234.
(9) Negisihi, E.; Idecavage, M. K. Org. React. NY 1985, 33, 1.
(10) Dialkylamine synthesis: Kabalka, G. W.; Wang, Z. Organome-
tallics 1989, 8, 1093-1095 and references therein.
10.1021/jo981613l CCC: $18.00 © 1999 American Chemical Society
Published on Web 01/12/1999

804 J . Org. Chem., Vol. 64, No. 3, 1999
Phanstiel et al.
Sch em e 1
increase was obtained by a minor modification of the
excellent procedure described by Kabalka.6 Preacidifica-
tion of the reaction mixture to pH 1 prior to removal of
the THF and water mixture (under reduced pressure)
limited significant losses of the low molecular weight,
volatile amines 8 and 13.
The N-ethylation reaction is analogous to the reaction
of N-chloroalkylamines with organoboranes and presum-
ably occurs via migration of an alkyl group from boron
to nitrogen (see Scheme 2).9,10 As the benzoyloxylation
procedure is highly versatile,14,17 this discovery opens up
a promising new route to a diverse number of secondary
amines with reagents that are stable to chromatography
and completely soluble in THF and that tolerate ap-
preciable steric bulk near the amine center.
In summary, this technology provides another source
of “activated” amine (RNH-OCOPh), which is comple-
mentary to the published N-chloroamine and organic
azide methods and utilizes classic organoborane chem-
istry to yield secondary amines in good yield.
experiments had indicated that 2 equiv of BPO provided
high yields during the in situ oxidation of amine sub-
strates.14 However, we later found that using 1 equiv of
BPO facilitated the chromatographic isolation of the
intermediate N-(benzoyloxy)amines, which often had Rf
values close to that of BPO. This modified procedure gave
excellent yields of the desired N-(benzoyloxy)amines (63-
90%, see Table 1).
As these materials (1-7) represent new “activated
amine” sources, we evaluated their general storage
properties. At room temperature, an uncapped vial
containing the purified benzoyloxyamine 4 slowly de-
composed (over several days) as evidenced by new spots
on the TLC plate. This phenomenon was slowed upon
storing the sample in a capped vial at 0 °C. Samples,
which were stored under argon at 0 °C, remained in their
pure state for several weeks. On the basis of these
observations, these reactive intermediates are routinely
stored under oxygen-free environments (i.e., Ar atmo-
sphere) in the freezer.
As shown in Table 1, the N-(benzoyloxy)amines 1-7
were each reacted with 1 M triethylborane in THF to give
their respective N-ethylamine derivatives. It should be
noted that the reaction time during the ethylation step
was dependent on the steric bulk of the R group (see
Scheme 1). Although the reaction could be carried out at
room temperature for many of the amines studied, the
conversion rate became quite slow with the more hin-
dered benzoyloxyamines (5-7). Refluxing THF (67 °C)
was often required to achieve a convenient rate of
reaction for these systems with triethylborane.
In general, reactions involving sterically demanding
amine derivatives (or, for that matter, bulky trialkylbo-
rane substrates) often fail completely.10,13 For example,
a reaction involving the in situ generation of a N-
chloroamine derivative (i.e., 1-methyloctylamine + so-
dium hypochlorite) and trihexylborane gave a 0% yield
of the desired secondary amine.10 Amines with adjacent
3° carbon centers are often precluded from such reactions.
Not surprisingly, the reaction of hindered benzoy-
loxyamine 7 with triethylborane gave none of the antici-
pated N-ethylamine derivative 14. Similar observations
were found with the related N-chloro systems involving
hindered substrates10,13 and have been shown to involve
a radical pathway.10
Exp er im en ta l Section
Ma ter ia ls a n d Meth od s. Reagents were purchased from
either the ACROS Chemical Company or the Aldrich Chemical
Co. All commercially available amines were distilled prior to
use. An authentic sample of N-ethylcyclohexylamine (13) was
purchased from the Aldrich Chemical Co. 1H NMR spectra
were recorded at 200 MHz on a Varian Gemini 200 spectro-
meter. The pH 10.5 buffer solution was prepared by combining
222 mL of 0.75 N aqueous NaHCO3 and 78 mL of 1.5 N
aqueous NaOH. The TLC and column chromatography sol-
vents are expressed in volume %. Ca u tion : although we did
not observe the N-benzoyloxyamines to be shock sensitive,
proper safety procedures should be followed when handling
these compounds.
Gen er a l P r oced u r e for Am in e Oxid a tion . A solution of
benzoyl peroxide (BPO, 1 equiv) in CH2Cl2 (5 mL/mmol BPO)
was added quickly to a mixture of the amine (1 equiv) and a
pH 10.5 buffer solution (5 mL/mmol amine) at room temper-
ature. [Note: using 1 equiv of BPO facilitated the isolation of
the intermediate benzoyloxyamines, which often had Rf values
close to that of BPO.] TLC was used to monitor the consump-
tion of starting material, and the plates were typically stained
(after solvent elution) with iodine vapor to visualize the amine
starting materials. After the reaction was complete, the
aqueous layer was extracted twice with CH2Cl2. The organic
layers were combined, dried over anhydrous Na2SO4, filtered,
and concentrated to give the crude product, which was
subjected to flash column chromatography.
Gen er a l P r oced u r e for Eth yla tion . Triethylborane (1
molar equiv) in THF (1 mL/mmol triethylborane) and an
equivalent volume of a 0.4 M aqueous sodium carbonate
solution were cooled to 0 °C while maintaining a nitrogen
atmosphere. One molar equivalent of the N-(benzoyloxy)amine
in THF (1 M solution) was then added dropwise. After the
addition was complete, the solution was allowed to warm to
room temperature. The disappearance of starting material was
monitored by TLC. [Note: sluggish reactions were refluxed to
facilitate conversion.]
Wor k u p Meth od A. (Best for high molecular weight
adducts) After the reaction was complete, the THF was
removed under reduced pressure. The semisolid residue was
dissolved in a minimum amount of water and extracted three
times with diethyl ether. The organic layers were combined,
dried over anhydrous Na2SO4, filtered, and concentrated to
give the crude product. The crude mixture was subjected to
flash column chromatography to give the corresponding N-
ethylamine.
Systems containing 1° and 2° carbons adjacent to the
amine center (1-6) gave good-to-excellent yields in the
N-ethylation step (see Table 1). The adjacent secondary
carbon present in 5 and 6 did not preclude the formation
of the desired secondary amines 12 (54%) and 13 (86%).
In comparison, N-chloro-2-octylamine and triethylborane
generated amine 12 in a reported 85% yield.13 Although
the yield of 12 is lower than that reported via the
N-chloro route, we found the yields for these reactions
to be highly dependent on the workup procedure (espe-
cially for low molecular weight amine products). For
example, by altering the workup method (see Experi-
mental Section, Method A versus Method B), the yield
of 13 was increased from 26% to 86%. This dramatic
(17) Wang, Q. X.; Phanstiel, O., IV. J . Org. Chem. 1998, 63, 1491-
1495.

Synthesis of Secondary Amines
J . Org. Chem., Vol. 64, No. 3, 1999 805
Ta ble 1. P r im a r y Am in es Con ver ted to N-Eth yla m in es
then extracted three times with diethyl ether. These ether
layers were combined, dried over anhydrous Na2SO4, filtered,
and concentrated to give the pure N-ethylamine. One spot was
observed by TLC (2% concentrated NH4OH/MeOH). The yield
and the product were confirmed by 1H NMR using a known
amount of a diphenylmethane (DPM) standard. In general,
comparison of the integration value determined for the DPM
singlet at 3.95 ppm and the H-C-N multiplet (typically near
2.6 ppm) provided the yields listed in Table 1. Although
Sch em e 2
1
structure-dependent, the H NMR N-ethyl group pattern was
usually observed as a quartet near 2.6 ppm and a triplet at
1.1 ppm.
N-Ben zoyloxy-h exyla m in e (1). Hexylamine (1.62 g, 16
mmol) was reacted with benzoyl peroxide using the general
procedure. TLC (2% concentrated NH4OH/MeOH, Rf ) 0.41)
was used to monitor the consumption of hexylamine. The crude
product was subjected to flash column chromatography (CHCl3,
Rf ) 0.45) to give N-benzoyloxy-hexylamine 1 (2.62 g, 74%):
1H NMR (CDCl3) δ 8.03 (d, 2H), 7.50 (m, 3H), 3.13 (t, 2H),
1.61 (m, 2H,), 1.35 (m, 6H), 0.88 (t, 3H). Anal. Calcd for
Wor k u p Meth od B. (Best for low molecular weight ad-
ducts) After the reaction was complete, the reaction mixture
was acidified with 10% (by volume) HCl to pH < 2. The
volatiles were removed under reduced pressure. The resultant
residue was suspended in water and washed with diethyl
ether. [Note: TLC and 1H NMR analysis of this ether layer
confirmed the presence of benzoic acid, the expected byproduct.
This ether layer was then discarded.] Next, 2 N NaOH was
added to the water layer until pH >12. The water phase was
C
13H19N1O2: C, 70.56; H, 8.65; N, 6.33. Found: C, 70.45; H,
8.72; N, 6.32.

806 J . Org. Chem., Vol. 64, No. 3, 1999
Phanstiel et al.
N3-Ben zoyloxy-3-(ter t-b u t oxyca r b on yla m in o)p r op y-
la m in e (2). 3-(tert-Butoxycarbonylamino)propylamine17 (5.22
g, 30 mmol) was reacted with benzoyl peroxide using the
general procedure. TLC (4% concentrated NH4OH/MeOH) was
used to monitor the consumption of N1-BOC-propane diamine.
The crude product was subjected to flash column chromatog-
raphy (40% ethyl acetate/hexane, Rf ) 0.43) to give the known
amine 2 (6.35 g, 72%):17 1H NMR (CDCl3) δ 8.03 (d, 2H), 7.52
(m, 3H), 4.81 (broad m, 1H), 3.22 (m, 4H), 1.82 (m, 2H), 1.41
(s, 9H); HRMS-FAB calcd for C15H23N2O4 (M + 1) 295.1658,
found 295.1645.
1.75 (broad s, 1H), 1.49 (m, 2H), 1.20 (m, 9H), 0.85 (t, 3H);
consistent with literature spectrum.18
N1-Eth yl-3-(ter t-bu toxycar bon ylam in o)pr opylam in e (9).
N1-Benzoyloxy-3-(tert-butoxycarbonylamino)propylamine
2
(0.735 g, 2.5 mmol) was reacted with triethylborane using the
general procedure for ethylation. TLC (Rf ) 0.42, 40% ethyl
acetate/hexane) was used to monitor the disappearance of 2.
The crude mixture was subjected to flash column chromatog-
raphy (2% NH4OH/MeOH, Rf ) 0.28) to give 9 (0.31 g, 61%):
1H NMR (CDCl3) δ 5.35 (br s, 1H), 3.19 (virtual q, 2H), 2.63
(m, 4H), 1.75-1.50 (m, 3H), 1.43 (s, 9H), 1.1 (t, 3H); HRMS-
FAB calcd for C10H22N2O2 (M + 1) 203.1760, found 203.1759.
N-Ben zoyloxy-ben zyla m in e (3). Benzylamine (1.71 g, 16
mmol) was reacted with benzoyl peroxide using the general
procedure. TLC (2% concentrated NH4OH/MeOH, Rf ) 0.56)
was used to monitor the consumption of benzylamine. The
crude product was subjected to flash column chromatography
(10% ethyl acetate/hexane, Rf ) 0.33) to give N-benzoyloxy-
benzylamine 3 (2.29 g, 63%): 1H NMR (CDCl3) δ 7.96 (d, 2H),
7.40 (m, 8H), 4.27 (s, 2H). Anal. Calcd for C14H13N1O2: C,
73.99; H, 5.77; N, 6.16. Found: C, 73.91; H, 5.76; N, 6.14.
N-Eth ylben zyla m in e (10). N-Benzoyloxy-benzylamine 3
(0.568 g, 2.5 mmol) was reacted with triethylborane using the
general procedure for ethylation. The reaction solution was
refluxed for 24 h. TLC (Rf ) 0.33, 10% ethyl acetate/hexane)
was used to monitor the disappearance of 3. The crude mixture
was subjected to flash column chromatography (2% NH4OH/
MeOH, Rf ) 0.41) to give 10 (0.21 g, 62%): 1H NMR (CDCl3)
δ 7.35 (m, 5H), 3.79 (s, 2H), 2.67 (q, 2H), 1.65 (br s, 1H), 1.10
(t, 3H), consistent with literature spectrum.18
N-Ben zoyloxy-2-p h en eth yla m in e (4). Phenethylamine
(0.484 g, 4 mmol) was reacted with benzoyl peroxide using the
general procedure. TLC (2% concentrated NH4OH/MeOH, Rf
) 0.53) was used to monitor the consumption of phenethyl-
amine. The crude product was subjected to flash column
chromatography (20% ethyl acetate/hexane, Rf ) 0.47) to give
N-benzoyloxy-2-phenethylamine 4 (0.70 g, 73%): 1H NMR
(CDCl3) δ 8.01 (d, 2H), 7.35 (m, 8H), 3.45 (t, 2H), 2.98 (t, 2H);
HRMS-FAB calcd for C15H15N1O2 (M + 1) 242.1209, found
242.1204. Anal. Calcd: C, 74.67; H, 6.27; N, 5.81. Found: C,
75.04; H, 6.45; N, 5.86.
N-Eth ylp h en eth yla m in e (11). N-Benzoyloxy-phenethyl-
amine 4 (0.60 g, 2.5 mmol) was reacted with triethylborane
using the general procedure for ethylation. The reaction
solution was refluxed for 4 h. TLC (Rf ) 0.34, 10% ethyl
acetate/hexane) was used to monitor the disappearance of 4.
The crude mixture was subjected to flash column chromatog-
raphy (2% NH4OH/MeOH, Rf ) 0.40) to give 11 (0.28 g, 76%):
1H NMR (CDCl3) δ 7.23 (m, 5H), 2.85 (m, 4H), 2.66 (q, 2H),
1.52 (br s, 1H), 1.08 (t, 3H), consistent with literature
spectrum.18
N-Ben zoyloxy-1-m eth yl-h ep tyla m in e (5). 1-Methyl-hep-
tylamine (1.03 g, 8 mmol) was reacted with benzoyl peroxide
using the general procedure. TLC (2% concentrated NH4OH/
MeOH, Rf ) 0.30) was used to monitor the consumption of
1-methyl-heptylamine. The crude product was subjected to
flash column chromatography (10% ethyl acetate/hexane, Rf
) 0.25) to give 5 (1.73 g, 87%): IR (neat) 3234, 3064, 2930,
N-(Eth yl)-1-m eth yl-h ep tyla m in e (12). N-Benzoyloxy-1-
methyl-heptylamine 5 (0.99 g, 4 mmol) was reacted with
triethylborane using the general procedure for ethylation. The
reaction solution was refluxed for 5 h. TLC (Rf ) 0.25, 10%
ethyl acetate/hexane) was used to monitor the disappearance
of 5. The crude mixture was subjected to flash column
chromatography (2% NH4OH/MeOH, Rf ) 0.42) to give 12 (0.34
g, 54%): 1H NMR (CDCl3) δ 2.55 (m, 3H), 1.35 (br m, 1H),
1.30-1.10 (br s, 10H), 1.03 (t, 3H), 0.95 (d, 3H), 0.80 (t, 3H);
HRMS-FAB calcd for (C10H23N1) (M + 1) 158.1869, found
158.1889.
1
1720, 1601, 1452, 1270, 1092, 708 cm-1; H NMR (CDCl3) δ
8.07 (t, 2H), 7.54 (m, 3H), 3.20 (m, 1H), 1.30 (m, 13 H), 0.87
(t, 3H); HRMS-FAB calcd for C15H23N1O2 (M + 1) 250.1807,
found 250.1821. Anal. Calcd: C, 72.25; H, 9.30; N, 5.62.
Found: C, 72.58; H, 9.43; N, 5.67.
N-Ben zoyloxy-cycloh exyla m in e (6). Cyclohexylamine
(1.58 g, 16 mmol) was reacted with benzoyl peroxide using the
general procedure. TLC (2% concentrated NH4OH/MeOH, Rf
) 0.41) was used to monitor the consumption of cyclohexyl-
amine. The crude product was subjected to flash column
chromatography (10% ethyl acetate/hexane, Rf ) 0.40) to give
6 (2.90 g, 82%): 1H NMR (CDCl3) δ 8.05 (d, 2H), 7.72 (s, 1H),
7.53 (m, 3H), 3.05 (m, 1H), 1.98 (m, 2H), 1.80 (m, 2H), 1.68
(m, 1H), 1.28 (br s, 5H). Anal. Calcd for C13H17N1O2: C, 71.21;
H, 7.81; N, 6.39. Found: C, 71.15; H, 7.79; N, 6.31.
N-Eth ylcycloh exyla m in e (13). N-Benzoyloxy-cyclohexyl-
amine 6 (0.88 g, 4.02 mmol) was reacted with triethylborane
using the general procedure for ethylation. The reaction
solution was refluxed overnight, and N-ethylcyclohexylamine
13 (0.44 g, 86%) was isolated via Method B: 1H NMR (CDCl3)
δ 2.66 (q, 2H), 2.40 (m, 1H), 1.92-1.49 (m, 6H), 1.40-0.9 (m,
8H); matched the 1H spectrum (CDCl3) of a commercial sample
of 13.
Ack n ow led gm en t. Financial support was gener-
ously provided by the University of Central Florida
Department of Chemistry and the Center for Diagnos-
tics and Drug Development (grant 11-64-879). In addi-
tion, this research was supported by an award from
Research Corporation. We also appreciate the financial
support from the National Science Foundation in the
purchase of our 200 MHz NMR instrument (grant
CHE-8608881).
N-Ben zoyloxy-ter t-octyla m in e (7). tert-Octylamine (1.03
g, 8 mmol) was reacted with benzoyl peroxide using the general
procedure. TLC (2% concentrated NH4OH/MeOH, Rf ) 0.33)
was used to monitor the consumption of tert-octylamine. The
crude product was subjected to flash column chromatography
(10% ethyl acetate/hexane, Rf ) 0.25) to give 7 (1.79 g, 90%):
IR (neat) 3221, 3050, 2954, 1718, 1600, 1451, 1272, 1093, 707
1
cm-1; H NMR (CDCl3) δ 8.04 (t, 2H), 7.47 (m, 3H), 1.59 (s,
2H), 1.25 (s, 6H), 1.07 (s, 6H); HRMS-FAB calcd for C15H23N1O2
(M + 1) 250.1807, found 250.1821. Anal. Calcd: C, 72.25; H,
9.30; N, 5.62. Found: C, 72.30; H, 9.29; N, 5.65.
J O981613L
N-Eth ylh exylam in e (8). N-(Benzoyloxy)hexylamine 1 (0.774
g, 3.5 mmol) was reacted with triethylborane using the general
procedure. After it warmed to room temperature, the reaction
was refluxed to facilitate complete conversion. The reaction
was cooled to room temperature, and the amine 8 (0.40 g, 89%)
was isolated by Method B: 1H NMR (CDCl3) δ 2.60 (m, 4H),
(18) 1H NMR spectral data for N-ethylamine derivatives; for com-
pound 8, see: Pienemann, T.; Schafer, H.-J . Synthesis 1987, 1005-
1007. 10: Pouchert, C. J .; Campbell, J . R. The Aldrich Library of NMR
Spectra 1974, Vol. V, 97. 11: Ishihara, Y.; Kato, K.; Goto, G. Chem.
Pharm. Bull. 1991, 39, 3225-3235.