Notes
J . Org. Chem., Vol. 62, No. 19, 1997 6683
NMR (200 MHz, C
.21 (12H, m), 2.03 (3H, d, J ) 5.8 Hz, HNCH
NH), 4.51 (1H, br s, NH), 5.91 (1H, d), 6.49 (1H, d), 6.94 (1H, t),
.01 (1H, d), 7.33 (1H, t), 7.49 (1H, d). Anal. Calcd for
: C 78.09, H 8.62, N 9.58; found: C 77.62, H 8.55, N
6
D
6
) δ 0.58 (1H, br s), 0.78 (1H, br s), 1.23-
2
3
), 4.14 (1H, br s,
7
19 2
C H25BN
9
.02.
2
-Et was prepared as above by reacting 1 with ethyl iodide
1
in ca. 95% yield. H NMR (200 MHz, C
Hz), 0.56 (1H, br s), 0.90 (1H, br s), 1.57-2.13 (12H, m), 2.55
1H, m), 2.80 (1H, m), 4.13 (1H, br s, NH), 4.31 (1H, br s, NH),
6 6
D ) δ 0.33 (3H, t, J ) 7
(
6
7
9
.05 (1H, d), 6.48 (1H, d), 6.90 (1H, t), 6.94 (1H, d), 7.31 (1H, t),
.50 (1H, d). Anal. Calcd for C20 : C 78.44, H 8.89, N
.15; found: C 78.17, H 9.01, N 8.98.
-Bn was prepared as above by reacting 1 with benzyl chloride
H
27BN
2
2
1
in ca. 90% yield. H NMR (200 MHz, C
.12 (1H, br s), 1.81-2.26 (12H, m), 2.8-2.95 (2H, m), 3.70 (1H,
m), 4.20 (1H, m), 4.30 (1H, br s, NH), 4.86 (1H, br s, NH), 5.51
6 6
D ) δ 0.66 (1H, br s),
1
F igu r e 1. Molecular view of 2-Me as obtained from a
preliminary X-ray structure (H atoms of 9-BBN and naphtha-
lene units are omitted for clarity).
(
(
1H, d), 6.37 (2H, d), 6.56 (1H, d), 6.60 (1H, t), 6.86 (2H, t), 6.92
1H, t), 7.03 (1H, d), 7.36 (1H, t), 7.42 (1H, d). Anal. Calcd for
25 2
C H29BN : C 81.52, H 7.94, N 7.61; found: C 81.18, H 7.93, N
7
.26.
3
Sch em e 2a
-Me,Me was prepared as above by reacting 2-Me with
1
methyl iodide in ca. 95% yield. H NMR (200 MHz, C
1H, br s), 0.97 (1H, br s), 1.23-2.43 (12H, m), 1.89 (3H, d, J )
.8 Hz, HNCH ), 3.18 (3H, s, NCH ), 4.50 (1H, br s, NH), 5.90
1H, d), 6.72 (1H, d), 6.96 (1H, t), 7.08 (1H, d), 7.47 (1H, t), 7.53
1H, d). Anal. Calcd for C20 : C 78.44, H 8.89, N 9.15;
6 6
D ) δ 0.48
(
5
(
(
3
3
H
27BN
2
found: C 78.15, H 8.85, N 9.18.
3
-Et,Et was prepared as above by reacting 2-Et with ethyl
1
iodide in ca. 90% yield. H NMR (200 MHz, C
J ) 7 Hz), 0.50 (1H, br s), 1.08 (1H, br s), 1.31 (3H, t, J ) 7 Hz),
.40-2.40 (13H, m), 2.75 (1H, m), 3.66 (2H, m), 4.35 (1H, m,
NH), 6.02 (1H, d), 6.84 (1H, d), 6.93 (1H, t), 7.08 (1H, d), 7.43
1H, t), 7.53 (1H, d). Anal. Calcd for C22 : C 79.04, H
9.35, N 8.38; found: C 78.78, H 9.36, N 8.36.
6 6
D ) δ 0.39 (3H, t,
a
Key: R ) Me, Et, Bn; r ) H, Me, Et. (i) 1 N HCl, rt, 2 d. (ii)
1
N NaOH, rt, 2 d.
1
derivatives 4 is hydrolysis of the bridging 9-BBN group.
This is performed by either mild acidic conditions or mild
basic conditions at room temperature (Scheme 2).
An even milder hydrolysis procedure, which works
efficiently, however, only for the N-monoalkyl naphtha-
lene diamines, is reacting 2-R with a slight excess of
ethanolamine in ether at rt for 30 min and filtering off
the precipitated ethanolamine-9-BBN adduct.6
Compared to the published synthesis, the method we
present here is carried out under mild conditions, and
we hope it will enable the preparation of hydrolysis-
sensitive symmetrical and nonsymmetrical derivatives
of 1,8-diaminonaphthalene. In this synthesis, 9-BBN
serves in the unorthodox roles of enhancing the acidity
of the NH protons and directing of the incoming alkyl
groups. We are currently investigating the stereoelec-
tronic effects in the boron-bridged system and their
applications.
(
H31BN
2
3-Et,Me was prepared as above either by reacting 2-Et with
methyl iodide or by reacting 2-Me with ethyl iodide in ca. 90%
1
yield. H NMR (200 MHz, C
6
D
6
) δ 0.39 (3H, t, J ) 7 Hz), 0.51
(
3
6
1H, br s), 0.87 (1H, br s), 1.59-2.46 (13H, m), 2.75 (1H, m),
.18 (3H, s, NCH
.94 (1H, t), 7.08 (1H, d), 7.47 (1H, t), 7.54 (1H, d). Anal. Calcd.
: C 78.75, H 9.13, N 8.75; found: C 78.46, H 9.10,
3
), 4.36 (1H, m, NH), 6.06 (1H, d), 6.72 (1H, d),
for C21
H29BN
2
N 8.77.
3-Bn ,Me was prepared as above either by reacting 2-Bn with
methyl iodide or by reacting 2-Me with benzyl chloride in ca.
1
9
(
0% yield. H NMR (200 MHz, C
6
D
6
) δ 0.55 (1H, br s), 1.23
), 3.40 (1H,
m), 4.16 (1H, m), 4.86 (1H, m, NH), 5.49 (1H, d), 6.38 (2H, d),
.63 (1H, d), 6.78 (1H, t), 6.83 (2H, t), 6.94 (1H, t), 7.10 (1H, d),
1H, br s), 1.45-2.55 (12H, m), 3.24 (3H, s, NCH
3
6
7.46 (1H, t), 7.49 (1H, d). Anal. Calcd for C26H31BN : C 81.67,
2
H 8.17, N 7.33; found: C 81.47, H 8.24, N 7.31.
Gen er a l Hyd r olysis P r oced u r es. In a typical acidic hy-
drolysis, 15 mL of 1 N aqueous HCl were added to 3-Me,Me (1
g) dissolved in THF, and the reaction mixture was stirred at rt
for two days. Neutralization, extraction with methylene chlo-
ride, and purification by chromatography over alumina with
ethyl acetate/hexane as eluent gave 1,8-bis(methylamino)naph-
thalene as a light yellow crystalline solid in 95% yield. In a
typical basic hydrolysis, 1 N NaOH was added to 3-Me,Me
dissolved in THF, and the reaction mixture was stirred at rt for
two days. After neutralization, 1,8-bis(methylamino)naphtha-
lene was isolated in a similar yield following the same workup.
Exp er im en ta l Section
1
was prepared from 1,8-diaminonaphthalene and 9-BBN as
4
described elsewhere. All the operations leading to the N-alkyl
derivatives 2-R, and N,N′-dialkyl derivatives 3-R,r , were done
under a dry nitrogen atmosphere. THF was distilled from
sodium benzophenone ketyl. Pentane was distilled from sodium
benzophenone ketyl and tetraglyme. All other reagents were
of commercial source and used as received.
P r ep a r a tion of N-Alk yl Der iva tives (2-R) a n d N,N′-
Dia lk yl Der iva tives (3-R,r ) of th e Am in e-Am in obor a n e 1.
Ack n ow led gm en t. We thank the Israel Science
Foundation administered by the Israel Academy of
Sciences and Humanities for financial support. We
thank Prof. I. Goldberg for his help with the x-ray data
collection and structure elucidation.
2
-Me. A 1.1 equiv amount of KOt-Bu was added to a solution
of 1 (2.5 g) in THF under nitrogen, and the mixture was stirred
for 30 min. A 1.1 equiv amount of methyl iodide was added,
and the reaction mixture was stirred for another 30 min.
Filtration, removal of the solvent under reduced pressure, and
1
1
Su p p or tin g In for m a tion Ava ila ble: H NMR spectra and
C NMR peak lists for several compounds of the type 2-4 (10
precipitation with pentane gave pure 2-Me in ca. 95% yield. H
1
3
pages). This material is contained in libraries on microfiche,
immediately follows this article in the microfilm version of the
journal, and can be ordered from the ACS; see any current
masthead page for ordering information.
(
5) A suitable crystal of 2-Me was grown from THF/pentane and
mounted on a CAD4 diffractometer under a stream of nitrogen at ca.
00 K. The data collected afforded unequivocal determination of the
1
X-ray structure of 2-Me. The correctness of the structure was confirmed
by a clean difference Fourier map. However, due to poor quality of the
crystal, the structure could not be refined beyond an R factor of 9.4.
(6) Singaram, B. Heteroat. Chem. 1992, 3, 245.
J O970541F