620
R. Salas-Coronado et al. / Journal of Organometallic Chemistry 694 (2009) 616–622
Its solid state structure is the first example of a diphenylboron in a
seven membered ring coordinated by a carbonyl group determined
by X-ray diffraction analysis. Although no crystals were obtained
for the tin compounds derived from the
NMR experiments at low temperature showed the presence of
by crystallization from DMSO (1.3 g, 11.4%). [
a]D = +75.58 (CH2Cl2,
c = 0.01). M.p. 103 °C. IR (KBr): (
m
, cmꢂ1) 3532–3297, 3060, 2929,
1633, 1538, 1051. NMR (CD2Cl2, 25 °C): 13C d = 17.5 (CH3-2), 21.9
(CH3-5), 36.7 (C-3), 38.0 (C-2), 48.8 (C-5), 60.0 (C-4), 126.0
(2Cm), 127.1 (Cp), 128.5 (2Co), 144.0 (Ci), 175.9 (C-1). 1H d = 1.12
(d, J = 7.0, 3H, [CH3-2]), 1.41 (d, J = 7.0, 3H, [CH3-5]), 1.58 (m, 1H,
H-3B), 1.72 (m, 1H, H-3A), 2.45 (dq, J = 6.8 and 8.35, 1H, H2),
3.12 (br s, 1H, OH), 3.49 (t, J = 6.3, 1H, H-4), 5.00 (quint, J = 7.0,
1H, H-5), 6.49 (d, J = 7.0, 1H, NH), 7.18–7.31 (m, 5H, Ar). MS m/z
(%): M+ 221(28), 190(20), 177(37), 105(100), 73(24), 55(23). Anal.
Calc. for C13H19NO2: C, 70.56; H, 8.65; N, 6.33. Found: C, 70.05;
H, 8.66; N, 6.33%.
c
-hydroxyamides, 119Sn
C@O ? Sn seven membered chelates.
4. Experimental
4.1. Physical methods
All solvents were freshly distilled. 1H (400 MHz), 13C
(67.9 MHz), 15N (30.42 MHz), 11B (86.68 MHz) and 119Sn
(100.72 MHz) NMR spectra were recorded. d 1H and 13C were refer-
enced to TMS, 15N to CH3NO2, 11B to BF3–OEt2 and d 119Sn to Me4Sn.
15N spectra were obtained by the INEPT pulse sequence with and
without decoupling using 1J(15N–1H) = 90 Hz. 1H and 13C NMR data
of compounds 1–9 were assigned by 2D NMR experiments, HET-
COR and COSY. Melting points were measured on a Gallenkamp
apparatus and are uncorrected. Elemental analyses were per-
formed in a Flash 1112 Thermo Finnigan analyzer. MS spectra were
obtained to 20 eV in a HP 5989. High resolution mass spectra were
obtained by LC/MSD TOF on an Agilent Technologies instrument
with APCI as ionization source.
Isomer 3b(2S,5R) was identified by 1H and 13C NMR (CDCl3,
25 °C) from the mother liquors: 13C d = 17.8 (CH3-2), 21.8 (CH3-
5), 36.6 (C-3), 38.1 (C-2), 48.7 (C-5), 60.3 (C-4), 126.2 (2Co),
127.4 (Cp), 128.7 (2Cm), 143.4 (Ci), 176.0 (C-1). 1H d = 1.12 (d,
J = 7.0, 3H, CH3-2), 1.48 (d, J = 7.0, 3H, CH3-5), 1.57 (m, 1H, H-3B),
1.75 (m, 1H, H-3A), 2.46 (m, 1H, H2), 2.84 (br s, 1H, OH), 3.64
(dd, J = 11.2, 5.4, 2H, H-4), 5.05 (q, J = 7.0, 1H, H-5), 6.32 (br s, 1H,
NH), 7.18–7.31 (m, 5H, Ar).
4.2.4. Diphenylborinic acid 3-benzylcarbamoyl-propyl ester (4)
Compound 4 was prepared by reaction of hydroxyamide 1
(200 mg, 1.03 mmol) and diphenylborinic anhydride (180 mg,
0.51 mmol) in 50 mL of toluene by refluxing for 4 h in a Dean-Stark
trap, and the solvent was evaporated. Compound 4 crystallized
4.2. Synthetic methods
from CH2Cl2 (320 mg, 88%). M.p. 95 °C. IR (KBr): (m
, cmꢂ1) 3042,
2923, 2876, 1624, 1580, 1429, 1153, 743,704. NMR (CD2Cl2,
25 °C): 13C d = 27.7 (C-3), 32.8 (C-2), 43.4 (C-6), 67.1 (C-4), 127.3
(Cp), 128.6 (2Cm), 127.6 (4Cm-B, 2Cp-B), 130.1 (2Co), 134.1 (4Co-
B), 135.0 (2Ci-B), 138.8 (Ci), 172.4 (C-1). 1H d = 2.02 (m, 2H, H-3),
2.36 (t, J = 7.4, 2H, H-2), 4.16 (t, J = 6.0, 2H, H-4), 4.36 (d, J = 6.0,
1H, H-5), 6.19 (br s, 1H, NH), 7.26–7.69 (m, 15H, Ar). Anal. Calc.
for C23H24BNO2: C, 77.33; N, 3.92; H, 6.77. Found: C, 77.35; N,
3.89; H, 6.79%.
4.2.1. N-Benzyl-4-hydroxy-butyramide (1)
BnNH2 (2.8 mL, 26.0 mmol) and
c-butyrolactone (2.0 mL,
26.0 mmol) were dissolved in benzene (30 mL) and refluxed for
12 h. The reaction mixture was cooled at rt and a solid was sepa-
rated by filtration and washed with benzene. Compound 1 is a col-
orless solid (4.9 g, 98%). M.p. 73–74 °C (M.p. lit. 70–72 °C [25,26]).
IR (KBr): (m
, cmꢂ1) 3270, 1635, 1015. NMR (CD2Cl2, 25 °C): 13C
d = 28.3 (C-3), 33.7 (C-2), 43.4 (C-5), 62.1 (C-4), 127.3 (Cp), 127.5
(2Cm), 128.6 (2Co), 138.7 (Ci), 173.5 (C-1). 1H d = 1.78 (m, 2H, H-
3), 2.30 (t, J = 7.0, 2H, H-2), 3.56 (t, J = 5.9, 2H, H-4), 3.47 (br s,
1H, OH), 4.33 (d, J = 5.7, 2H, H-5), 7.20–7.32 (m, 5H, Ar), 6.56 (br
s, 1H, NH). MS m/z (%): [M+] 193(57), 162(23), 149(79), 106(100),
91(97), 79(16). Anal. Calc. for C11H15NO2: C, 68.37; N, 7.25; H,
7.82. Found: C, 68.04; N, 7.19; H, 7.70%.
4.2.5. Diphenylborinic acid 3-[(R)-1-phenyl-ethylcarbamoyl]-propyl
ester (5)
Following the general procedure described above, compound 2
(200 mg, 0.97 mmol), and diphenylborinic anhydride (170 mg,
0.48 mmol) formed compound 5, which is a yellow oil (320 mg,
90%). [a]D = +44.1 (CH2Cl2, c = 0.03). IR (CHCl3): (m
, cmꢂ1) 3399,
3248, 2923, 1624, 1578, 1429, 1153, 734, 703. NMR (CD2Cl2,
25 °C): 13C d = 21.9 (CH3-Bn), 27.9 (C-3), 33.0 (C-2), 48.9 (C-5),
67.9 (C-4), 126.3 (2Cm), 127.4 (Cp), 128.5 (4Cm-B), 128.7 (2Co),
130.2 (2Cp-B), 134.2 (4Co-B), 137.6 (2Ci-B), 143.5 (Ci), 171.9 (C-
1). 1H d = 1.53 (d, J = 7.0, 3H, CH3-Bn), 2.11 (m, 2H, H-3), 2.44
(ddt, J = 6.9, 7.5, 14.6, 2H, H-2), 4.26 (t, J = 5.9, 2H, H-4), 5.23 (q,
J = 7.0, 1H, H-5), 6.52 (br s, 1H, NH), 7.35-7.76 (m, 15H, Ar). Anal.
Calc. for C24H26BNO2: C, 77.64; N, 3.77; H, 7.06. Found: C, 77.50;
N, 3.78; H, 7.05%.
4.2.2. 4-Hydroxy-N-[(R)-1-phenyl-ethyl]-butyramide (2)
A mixture of [R]-(ꢂ)-MeBnNH2 (3.3 mL, 26.0 mmol) and
c-buty-
rolactone (2.0 mL, 26.0 mmol) in benzene (50 mL) was refluxed for
12 h. The solvent was evaporated under vacuum, and the product
purified by distillation at 135 °C (0.25 mmHg). Compound 2 is a
yellow oil (4.8 g, 90%). [
m
a]D = +122.2 (CDCl3, c = 0.02). IR (CHCl3,):
(cmꢂ1) = 3434, 3302, 3066, 1648, 1512, 1450, 1243, 1220, 1056.
NMR (CD2Cl2, 25 °C): 13C d = 22.0 (CH3), 28.6 (C-3), 33.1 (C-2),
48.8 (C-5), 61.4 (C-4), 126.1 (2Cm), 127.0 (Cp), 128.4 (2Co), 143.8
(Ci), 173.2 (C-1). 1H d = 1.39 (d, J = 6.9, 3H, CH3), 1.75 (m, 2H, H-
3), 2.25 (dt, J = 6.9, 6.0, 2H, H-2), 3.53 (t, J = 5.9, 2H, H-4), 4.03 (br
s, 1H, OH), 4.99 (quint, J = 7.0, 1H, H-5), 7.02 (d, J = 7.0, 1H, NH),
7.19–7.33 (m, Ar). MS m/z (%): [M+] 207(27), 192(8), 163(38),
120(62), 106(100), 79(14). Anal. Calc. for C12H17NO2: C, 69.54; N,
6.76; H, 8.27. Found: C, 69.55; N, 6.72; H, 8.27%.
4.2.6. Diphenylborinic acid (R)-3-[(R)-1-phenyl-ethylcarbamoyl]-
butyl ester (6)
Compound 3a (200 mg, 0.9 mmol) and diphenylborinic anhy-
dride (160 mg, 0.45 mmol) produced compound 6 which is a yel-
low oil (34 mg, 99%). [
a]D = +38.8 (CH2Cl2, c = 0.05). IR (CHCl3):
(m
, cmꢂ1) 3295, 3055, 2970, 1644, 1540, 1331. NMR (CDCl3,
25 °C): 13C d = 18.03 (CH3), 22.14 (CH3-Bn), 36.19 (C-3), 37.89 (C-
2), 48.83 (C-5), 65.94 (C-4), 126.2 (2Cp-B), 127.2 (Cp), 127.8 (4Co-
B), 128.7 (2Co), 130.2 (2Cm), 134.3 (2Cm-B), 144.13 (Ci), 175.18
(C-1). 1H d = 1.27 (d, J = 7.0, 3H, CH3), 1.49 (d, J = 6.0, 3H, CH3-Bn),
1.85 (ddt, J = 13.8, 9.3 and 7.0, 1H, H-3B), 2.09 (dq, J = 13.8, and
6.7, 1H, H-3A), 2.68 (qd, J = 6.7 and 7.0, 1H, H-2), 4.14 (ddd,
J = 10.8, 9.3 and 6.7,1H, H-4B), 4.20 (ddd, J = 10.8, 9.3 and 6.0, 1H,
H-4A), 5.16 (qd, J = 7.2 and 6.0, 1H, H-5), 6.55 (d, J = 7.2, 1H, NH),
4.2.3. (R)-4-Hydroxy-2-methyl-N-[(R)-1-phenyl-ethyl]-butyramide
(3a) and (S)-4-hydroxy-2-methyl-N-[(R)-1-phenyl-ethyl]-butyramide
(3b)
The procedure for (2) was followed, using ( )-a-methyl-c-buty-
rolactone (5.0 g, 50 mmol), and [R]-(ꢂ)-MeBnNH2 (6.35 mL,
50 mmol), in 50 mL of toluene. A yellow oil was obtained (7.57 g,
69%). The oil was dissolved in Et2O and the isomer 3a(R,R) purified