Preparation of polyfunctional tertiary amines via the electrophilic amination of arylmagnesium compounds using N-chloroamines

Article abstract of DOI:10.1055/s-2006-951560

Functionalized arylmagnesium compounds prepared via a halogen-magnesium exchange reaction using aryl iodides or bromides and i-PrMgCl·LiCl, react rapidly with benzyl-N-chloroamines at -45 °C providing polyfunctional tertiary amines in good yields. The methodology is also successfully applied to the preparation of chiral N-chloroamines with retention of chirality. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-2006-951560

3304
LETTER
Preparation of Polyfunctional Tertiary Amines via the Electrophilic
Amination of Arylmagnesium Compounds Using N-Chloroamines
Preparation of
r
P
olyfun
a
ctional
T
er
d
A
minesipta Sinha, Paul Knochel*
Department Chemie und Biochemie, Ludwig-Maximilians-Universität München, Butenandtstraße 5–13, 81377 München, Germany
Fax +49(89)218077680; E-mail: Paul.Knochel@cup.uni-muenchen.de
Received 31 August 2006
good yields with the formation of biphenyl as byproduct
Abstract: Functionalized arylmagnesium compounds prepared via
(Table 1). We initiated our study by the reaction of N-ben-
zyl-N-chloromethylamine (1a) with phenylmagnesium
chloride lithium chloride (2a) at –45 °C, which produced
a halogen–magnesium exchange reaction using aryl iodides or bro-
mides and i-PrMgCl·LiCl, react rapidly with benzyl-N-chloroam-
ines at –45 °C providing polyfunctional tertiary amines in good
yields. The methodology is also successfully applied to the prepara- N-benzyl-N-methylaniline (3a) within 15 minutes in 57%
tion of chiral N-chloroamines with retention of chirality.
of isolated yield (Table 1, entry 1). Under similar reaction
conditions, the chloroamine 1a reacted with 1-naphthyl-
magnesium chloride lithium chloride complex (2b) to
produce N-benzyl-N-methylnaphthalen-1-amine (3b) in
56% yield (entry 2). Remarkably, electron-deficient aryl-
magnesium reagents containing an ester or a cyano func-
Key words: electrophilic amination, polyfunctional tertiary
amines, arylmagnesium compounds, halogen–magnesium ex-
change, N-chloroamines
The electrophilic amination reaction1 of organometallic tionality react more efficiently with N-chloroamines
species using mono-, di- and trihaloamines has attracted a providing tertiary amines in good yields. Thus, 4-carbo-
lot of attention for the synthesis of amines.2 Only a few methoxyphenylmagnesium chloride lithium chloride
cases have been reported using alkylchloroamines as pre- complex (2c) reacted smoothly with 1a leading to 4-[N-
cursor for the synthesis of tertiary amines.3 Our interest benzyl-N-methylamino]benzoic acid methyl ester (3c) in
toward the synthesis of polyfunctionalized diarylamines 64% yield (entry 3). This methodology has been applied
utilizing an electrophilic amination of functionalized or- successfully to prepare enantiomerically pure tertiary
ganomagnesium reagents with functionalized nitroarenes amines having a chiral center alpha to nitrogen starting
and arylaza tosylate4 led us to re-examine this reaction. from chiral N-chloroamines. Therefore, the reaction of N-
Herein, we wish to report an improved method for the chloro-N-[(1R)-1-phenylethyl]methylamine (1b) with 4-
preparation of polyfunctional tertiary amines of type 3 cyanophenylmagnesium chloride lithium chloride com-
starting from benzyl-N-chloroamines of type 1 and LiCl- plex (2d) led to 4-{N-methyl-N-[(1R)-1-phenylethyl]ami-
complexed functional arylmagnesium reagents of type 2 no}benzonitrile (3d) in 70% yield and 99% ee (entry 4).
(Scheme 1, Table 1). The required N-benzyl-N-chloro- Similarly, 1b reacted with 2-carbethoxyphenylmagne-
amines 1a–f were prepared from the corresponding N- sium chloride lithium chloride complex (2e) producing
benzylamines using the reaction of N-chlorosuccinimide the tertiary amine 3e in 67% yield and 99% ee (entry 5). It
in hexane.5 The arylmagnesium reagents 2a–h were is interesting to note that the presence of an electron-with-
prepared by a bromine–magnesium or iodine–magnesium drawing group attached to the phenyl ring of the N-chlo-
exchange6 by the reaction of aryl bromides or iodides with roamine also exhibits a good reactivity in the amination
i-PrMgCl·LiCl (Scheme 1). The amination reaction oc- reaction. Thus, N-(4-bromobenzyl)-N-chloromethyl-
curred very rapidly within 15 minutes in tetrahydrofuran amine (1c) reacted rapidly with 3-cyanophenylmagne-
at –45 °C producing tertiary amines 3a–l in moderate to sium chloride lithium chloride complex (2f) giving rise to
Ar2-X (X = Br, I)
i-PrMgCl⋅LiCl
R1
R1
R1
Ar2MgCl⋅LiCl
2
N-chlorosuccinimide
n-hexane, r.t.
R2
R2
R2
Ar1
N
Ar1
N
Ar1
N
THF, –45 °C
H
Ar2
Cl
1
3
R
R
1 = H, Me
2 = Me, Et, n-Hex
Scheme 1
SYNLETT 2006, No. 19, pp 3304–3308
0
1
.1
2
.2
0
0
6
Advanced online publication: 23.11.2006
DOI: 10.1055/s-2006-951560; Art ID: G24706ST
© Georg Thieme Verlag Stuttgart · New York

LETTER
Preparation of Polyfunctional Tertiary Amines
3305
3-[N-(4-bromobenzyl)-N-methylamino]benzonitrile (3f) presence of the less reactive heteroarylmagnesium reagent
in 70% yield (entry 6). The presence of an ester function- 2h yielding N-benzyl-N-ethylpyridin-3-amine (3j) in 27%
ality in the organomagnesium reagent 2c provided the cor- yield (entry 10). We also examined the reactivity of N-
responding tertiary amine 3g in 73% yield by reacting chloro-N-(1-napthalen-2-ylethyl)methylamine (1e) which
with the chloroamine 1c (entry 7). Interestingly, 4-io- reacted with 2f to produce tertiary amine 3k in 65% yield
dophenylmagnesium chloride lithium chloride (2g) react- (entry 11). The chiral N-chloroamine 1f reacted with the
ed with N-chloroamine 1d producing N-benzyl-N-ethyl-4- Grignard reagent 2c leading to the chiral tertiary amine 3l
iodoaniline (3h) in 33% yield (entry 8). Furthermore, the in 34% yield and 98% ee (entry 12).
chloroamine 1d reacted with electron-deficient arylmag-
nesium reagent 2e to give the tertiary amine 3i in 67%
yield (entry 9). The amination reaction takes place even in
Table 1 Preparation of Tertiary Amines of Type 3 from Benzyl-N-chloroamines of Type 1 and Arylmagnesium Reagents of Type 2a
Entry
1
N-Chloroamine of type 1
Arylmagnesium reagent of type 2 Product of type 3
Yield (%)b,c
Me
MgCl⋅LiCl
N
Me
N
57
Cl
1a
2a
3a
Me
MgCl⋅LiCl
N
Me
N
2
3
56
64
Cl
1a
2b
3b
Me
MgCl⋅LiCl
N
Me
N
Cl
1a
CO2Me
CO2Me
2c
3c
Me
MgCl⋅LiCl
Me
Me
N
Me
N
4
70d
Cl
CN
1b
CN
N
2d
3d
3e
Me
MgCl⋅LiCl
Me
Me
CO2Et
CO2Et
Me
N
5
6
67e
Cl
1b
2e
2f
Me
MgCl⋅LiCl
N
Me
N
70
Br
Cl
Br
CN
CN
1c
3f
Synlett 2006, No. 19, 3304–3308 © Thieme Stuttgart · New York

3306
P. Sinha, P. Knochel
LETTER
Table 1 Preparation of Tertiary Amines of Type 3 from Benzyl-N-chloroamines of Type 1 and Arylmagnesium Reagents of Type 2a
(continued)
Entry
N-Chloroamine of type 1
Arylmagnesium reagent of type 2 Product of type 3
Yield (%)b,c
Me
MgCl⋅LiCl
N
Me
N
Br
7
73
Cl
Br
CO2Me
1c
CO2Me
Me
2c
3g
MgCl⋅LiCl
N
N
Me
8
33
Cl
1d
I
I
2g
2e
2h
3h
3i
MgCl⋅LiCl
N
Me
N
Me
Me
CO2Et
CO2Et
9
67
27
Cl
1d
1d
MgCl⋅LiCl
N
Me
N
10
Cl
N
N
3j
Me
MgCl⋅LiCl
Me
Me
N
Me
N
11
12
65
Cl
CN
CN
1e
2f
3k
Me
MgCl⋅LiCl
Me
N
Me
34f
N
Me
Cl
CO2Me
1f
CO2Me
2c
3l
a All reactions were carried out using the N-chloroamines (1 mmol) and the arylmagnesium reagents (1.02 mmol).
b Isolated yield of analytically pure product.
c To determine the enantiomeric excess of the product, HPLC Chiralcel OD-H (0.46 cm × 25 cm) column was used.
d HPLC eluent: heptane–i-PrOH = 95:5, 0.4 mL/min, tR (major) = 41.67 min, tR (minor) = 38.21 min; ee 99%.
e HPLC eluent: heptane–i-PrOH = 99:1, 0.4 mL/min, tR (major) = 34.27 min, tR (minor) = 20.01 min; ee 99%.
f HPLC eluent: heptane–i-PrOH = 98:2, 0.5 mL/min, tR (major) = 26.80 min, tR (minor) = 22.46 min; ee 98%.
In summary, we have shown that N-chloroamines react sions of this method are currently underway in our
rapidly with functionalized arylmagnesium reagents com- laboratory.
plexed with LiCl at low temperature yielding polyfunc-
tional tertiary amines.7 This electrophilic amination
Acknowledgment
reaction can also be applied to chiral N-chloroamines
We thank the Fonds der Chemischen Industrie and Merck Research
laboratories (MSD) for financial support. P.S. thanks the Alexander
von Humboldt Foundation for financial support. We also thank
Chemetall GmbH (Frankfurt) and BASF AG (Ludwigshafen) for
the generous gift of chemicals.
leading to the corresponding chiral tertiary amines. How-
ever, the amination process is limited to benzyl-N-chloro-
amines only. This methodology offers a possible
alternative strategy to transition-metal-catalyzed amina-
tion reactions which usually require a strong base. Exten-
Synlett 2006, No. 19, 3304–3308 © Thieme Stuttgart · New York

LETTER
Preparation of Polyfunctional Tertiary Amines
3307
7.35 (d, J = 9.1 Hz, 2 H), 7.14–7.29 (m, 5 H), 6.67 (d, J = 9.1
Hz, 2 H), 5.09 (q, 1 H), 2.67 (s, 3 H), 1.50 (d, J = 7.1 Hz, 3
H). 13C NMR (75 MHz, CDCl3): d = 152.3, 141.2, 133.5,
128.6, 127.3, 126.5, 120.5, 111.8, 97.6, 55.9, 31.9, 16.9. MS
(EI, 70 eV): m/z (%) = 236 (48), 221 (53), 205 (9), 132 (23),
105(100), 103 (7). HRMS: m/z calcd for C16H16N2:
236.1313; found: 236.1326. IR (film): 3029, 2977, 2213,
1605, 1519, 1449, 1385, 1180, 817, 701 cm–1.
2-{N-Methyl-N-[(1R)-1-phenylethyl]amino}benzoicAcid
Ethyl Ester (3e): 1H NMR (300 MHz, CDCl3): d = 7.49 (m,
1 H), 7.09–7.23 (m, 6 H), 6.81–6.89 (m, 2 H), 4.51 (q, 1 H),
4.16–4.32 (m, 2 H), 2.47 (s, 3 H), 1.36 (d, J = 7.1 Hz, 3 H),
1.25 (t, J = 7.1 Hz, 3 H). 13C NMR (75 MHz, CDCl3): d =
168.9, 151.4, 142.2, 131.4, 130.4, 128.1, 127.1, 126.8,
125.3, 120.5, 120.3, 61.8, 60.8, 36.0, 17.7, 14.2. MS (EI, 70
eV): m/z (%) = 283 (10), 268 (100), 254 (36), 222 (16), 178
(25), 132 (29), 105(87), 77 (21). HRMS: m/z calcd for
C18H21NO2: 283.1572; found: 283.1554. IR (film): 3028,
2979, 1716, 1596, 1448, 1366, 1121, 701 cm–1.
3-[N-(4-Bromobenzyl)-N-methylamino]benzonitrile (3f):
1H NMR (300 MHz, CDCl3): d = 7.36 (d, J = 8.8 Hz, 2 H),
7.18 (m, 1 H), 6.97 (d, J = 8.8 Hz, 2 H), 6.88 (m, 1 H), 6.82
(m, 2 H), 4.42 (s, 2 H), 2.98 (s, 3 H). 13C NMR (75 MHz,
CDCl3): d = 149.3, 136.6, 131.9, 129.9, 128.1, 121.0, 120.0,
119.6, 116.3, 114.8, 113.0, 55.8, 38.7. MS (EI, 70 eV): m/z
(%) = 302 (34), 300(35), 171 (98), 169 (100), 145 (10), 102
(9), 90 (18). HRMS: m/z calcd for C15H13BrN2: 300.0262;
found (C15H1379BrN2): 300.0238. HRMS: m/z calcd for
C15H13BrN2: 300.0262; found (C15H1381BrN2): 302.0220. IR
(film): 3042, 2922, 2225, 1599, 1486, 1382, 1071, 1010, 774
cm–1.
4-[N-(4-Bromobenzyl)-N-methylamino]benzoic Acid
Methyl Ester (3g): 1H NMR (300 MHz, CDCl3): d = 7.85 (d,
J = 9.1 Hz, 2 H), 7.40 (d, J = 8.4 Hz, 2 H), 7.02 (d, J = 8.4
Hz, 2 H), 6.63 (d, J = 9.1 Hz, 2 H), 4.53 (s, 2 H), 3.83 (s, 3
H), 3.07 (s, 3 H). 13C NMR (75 MHz, CDCl3): d = 167.2,
152.5, 136.8, 131.8, 131.4, 128.2, 120.9, 117.8, 110.9, 55.5,
51.5, 38.6. MS (EI, 70 eV): m/z (%) = 335 (36), 333 (38), 304
(6), 302 (8), 178 (31), 171 (99), 169 (100), 132 (17), 90 (30),
89 (24), 77 (10). HRMS: m/z calcd for C16H16BrNO2:
333.0364; found (C16H1679BrNO2): 333.0353. HRMS: m/z
calcd for C16H16BrNO2: 333.0364; found (C16H1681BrNO2):
335.0321. IR (film): 2952, 1698, 1607, 1434, 1386, 1287,
1191, 770 cm–1.
References and Notes
(1) For reviews, see: (a) Erdik, E.; Ay, M. Chem. Rev. 1989, 89,
1947. (b) Boche, G. In Houben-Weyl, Methods of Organic
Chemistry; Helmchen, G.; Hoffmann, R. W.; Mulzer, J.;
Schaumann, E., Eds.; Thieme: Stuttgart, 1995. (c) Mulzer,
J.; Altenbach, H. J.; Braun, M.; Krohn, K.; Reissig, H. U. In
Organic Synthesis Highlights; VCH: Weinheim, 1991, 45–
53. (d) Narasaka, K.; Kitamura, M. Eur. J. Org. Chem. 2005,
4505.
(2) For reaction of organomagnesium reagent with N-
haloamines, see: (a) Coleman, G. H.; Hauser, C. R. J. Am.
Chem. Soc. 1928, 50, 1193. (b) Coleman, G. H.; Yager, C.
B. J. Am. Chem. Soc. 1929, 51, 567. (c) Coleman, G. H.;
Forrester, R. A. J. Am. Chem. Soc. 1936, 58, 27.
(d) Coleman, G. H.; Blomquist, R. F. J. Am. Chem. Soc.
1941, 63, 1692. (e) Coleman, G. H.; Saroos, H.; Yager, C. B.
J. Am. Chem. Soc. 1933, 55, 2075. (f) Coleman, G. H.;
Buchanan, M. A.; Paxson, W. L. J. Am. Chem. Soc. 1933, 55,
3669. (g) Coleman, G. H.; Yager, C. B.; Saroos, H. J. Am.
Chem. Soc. 1934, 56, 965. (h) For the reaction of
organolithium reagents with N-haloamines, see: Coleman,
G. H.; Hermanson, J. L.; Johnson, H. L. J. Am. Chem. Soc.
1937, 59, 1896. (i) Wolf, V.; Kowitz, F. Justus Liebigs Ann.
Chem. 1960, 638, 33. (j) Yamada, S.; Oguri, T.; Shioiri, T.
J. Chem. Soc., Chem. Commun. 1972, 623. (k) Oguri, T.;
Shioiri, T.; Yamada, S. Chem. Pharm. Bull. 1975, 23, 167.
(l) For the reaction of organozinc reagents with N-
haloamines, see ref 2h.
(3) (a) Coleman, G. H. J. Am. Chem. Soc. 1933, 55, 3001.
(b) Klages, F.; Neber, G.; Kircher, F. Liebigs Ann. Chem.
1941, 547, 25.
(4) (a) Sapountzis, I.; Knochel, P. J. Am. Chem. Soc. 2002, 124,
9390. (b) Sapountzis, I.; Knochel, P. Angew. Chem. Int. Ed.
2004, 43, 897.
(5) (a) Cho, B. R.; Namgoong, S. K.; Kim, T. R. J. Chem. Soc.,
Perkin Trans. 2 1987, 853. (b) Bartsch, R. A.; Cho, B. R. J.
Am. Chem. Soc. 1989, 111, 2252. (c) Cho, B. R.; Suh, Y. W.
J. Org. Chem. 1989, 54, 2855. (d) Noack, M.; Goettlich, R.
Eur. J. Org. Chem. 2002, 3171. (e) Noack, M.; Kalsow, S.;
Goettlich, R. Synlett 2004, 1110.
(6) (a) Krasovskiy, A.; Knochel, P. Angew. Chem. Int. Ed. 2004,
43, 3333. (b) Knochel, P.; Dohle, W.; Gommermann, N.;
Kneisel, F. F.; Kopp, F.; Korn, T.; Sapountzis, I.; Vu, V. A.
Angew. Chem. Int. Ed. 2003, 42, 4302. (c) Knochel, P.;
Sapountzis, I.; Gommermann, N. In Metal-Catalyzed Cross-
Coupling Reactions, Vol. 2; De Meijere, A.; Diederich, F.,
Eds.; Wiley-VCH: Weinheim, 2004, 671–698.
N-Benzyl-N-ethyl-4-iodoaniline (3h): 1H NMR (300 MHz,
CDCl3): d = 7.31 (d, J = 9.1 Hz, 2 H), 7.11–7.26 (m, 5 H),
6.37 (d, J = 9.1 Hz, 2 H), 4.41 (s, 2 H), 3.36 (q, 2 H), 1.12 (t,
J = 7.1 Hz, 3 H). 13C NMR (75 MHz, CDCl3): d = 147.9,
138.5, 137.7, 128.6, 126.9, 126.4, 114.4, 76.6, 53.8, 45.3,
11.9. MS (EI, 70 eV): m/z (%) = 337 (100), 322 (42), 260 (9),
230 (5), 195 (7), 91 (56), 77 (2). HRMS: m/z calcd for
C15H16IN: 337.0327; found: 337.0308. IR (film): 2966,
2922, 1589, 1454, 1359, 1268, 1076, 733 cm–1.
(7) Preparation of 4-{N-Methyl-N-[(1R)-1-phenyl-
ethyl]amino}benzonitrile (3d); Typical Procedure:
A flame-dried argon-flushed 25-mL two-necked round-
bottomed flask equipped with a magnetic stirrer and septum
was charged with 4-bromobenzonitrile (186 mg, 1.02 mmol)
dissolved in THF (1 mL) and cooled to –20 °C.
2-(N-Benzyl-N-ethylamino)benzoic Acid EthylEster (3i):
1H NMR (300 MHz, CDCl3): d = 7.51 (m, 1 H), 7.09–7.27
(m, 6 H), 6.95 (m, 1 H), 6.85 (m, 1 H), 4.25 (q, 2 H), 4.21 (s,
2 H), 3.01 (q, 2 H), 1.28 (t, J = 7.1 Hz, 3 H), 0.93 (t, J = 6.9
Hz, 3 H). 13C NMR (75 MHz, CDCl3): d = 168.9, 150.4,
138.8, 131.4, 130.6, 128.2, 128.1, 126.8, 126.3, 121.3,
120.8, 60.8, 56.6, 47.3, 14.2, 11.8. MS (EI, 70 eV): m/z = 283
(2), 255 (13), 254 (76), 208 (100), 192 (16), 146 (39), 91
(49), 77 (9). HRMS: m/z calcd for C18H21NO2: 283.1572;
found: 283.1548. IR (film): 3063, 2977, 2931, 2872, 1720,
1597, 1446, 1366, 1249, 761, 732 cm–1.
Isopropylmagnesium chloride lithium chloride (0.71 mL,
1.1 mmol, 1.55 M in THF) was added dropwise to the above
solution and I–Mg exchange was monitored by GC analysis
until completion. The organomagnesium reagent thus
formed was further cooled to –45 °C and a solution of N-
chloro-N-[(1R)-1-phenylethyl]methylamine (1b; 170 mg,
1.0 mmol) in THF (2 mL) was added to it dropwise. The
reaction mixture was stirred at –45 °C for 15 min and was
quenched with a sat. solution of NH4Cl and the residue was
extracted with Et2O (2 × 10 mL), washed with brine (2 × 10
mL), and dried over Na2SO4. Solvent removal under reduced
pressure followed by flash chromatography over silica gel
(eluent: pentane–Et2O, 90:10) afforded 3d (165 mg, 70%) as
a viscous yellow liquid. 1H NMR (300 MHz, CDCl3): d =
N-Benzyl-N-ethylpyridin-3-amine (3j): 1H NMR (300
MHz, CDCl3): d = 8.06 (m, 1 H), 7.85 (m, 1 H), 7.14–7.27
(m, 5 H), 6.97 (m, 1 H), 6.85 (m, 1 H), 4.45 (s, 2 H), 3.42 (q,
Synlett 2006, No. 19, 3304–3308 © Thieme Stuttgart · New York

3308
P. Sinha, P. Knochel
LETTER
2 H), 1.15 (t, J = 7.1 Hz, 3 H). 13C NMR (75 MHz, CDCl3):
d = 144.2, 138.2, 137.5, 134.9, 128.7, 127.0, 126.4, 123.5,
118.4, 53.7, 45.1, 11.9. MS (EI, 70 eV): m/z (%) = 212 (21),
197 (20), 135 (6), 91 (100), 65 (8). HRMS: m/z calcd for
C14H16N2: 212.1313; found: 212.1292. IR (film): 2971,
2926, 1730, 1582, 1494, 1432, 791, 731 cm–1.
3-{N-Methyl-N-[1-(naphthalen-2-yl)ethyl]amino}benzo-
nitrile (3k): 1H NMR (300 MHz, CDCl3): d = 7.83 (m, 3 H),
7.71 (m, 1 H), 7.49 (m, 2 H), 7.25–7.38 (m, 2 H), 6.98–7.07
(m, 3 H), 5.23 (q, 1 H), 2.73 (s, 3 H), 1.66 (d, J = 6.6 Hz, 3
H). 13C NMR (75 MHz, CDCl3): d = 150.0, 139.2, 133.3,
132.6, 129.9, 128.4, 127.9, 127.6, 126.3, 125.9, 125.4,
124.9, 119.8, 119.7, 116.8, 115.4, 113.0, 56.5, 31.9, 16.3.
MS (EI, 70 eV): m/z (%) = 286 (9), 271 (6), 255 (2), 155
(100), 135 (5), 115 (3). HRMS: m/z calcd for C20H18N2:
286.1470; found: 286.1476. IR (film): 3057, 2973, 2882,
2226, 1593, 1496, 1376, 1112, 821, 761 cm–1.
4-{N-Hexyl-N-[(1S)-1-phenylethyl]amino}benzoic Acid
Methyl Ester (3l): 1H NMR (300 MHz, CDCl3): d =7.91 (d,
J = 9.1 Hz, 2 H), 7.26–7.38 (m, 5 H), 6.73 (d, J = 9.1 Hz, 2
H), 5.21 (q, 1 H), 3.88 (s, 3 H), 3.14–3.26 (m, 2 H), 1.66 (d,
J = 6.6 Hz, 3 H), 1.53 (m, 2 H), 1.27 (m, 6 H), 0.90 (t, J = 6.9
Hz, 3 H). 13C NMR (75 MHz, CDCl3): d = 167.3, 151.9,
141.8, 131.3, 128.5, 127.1, 126.9, 116.9, 111.5, 56.2, 51.4,
46.3, 31.3, 28.2, 26.7, 22.5, 17.6, 13.9. MS (EI, 70 eV): m/z
(%) = 339 (14), 324 (17), 268 (13), 164 (41), 105 (100), 77
(5). HRMS: m/z calcd for C22H29NO2: 339.2198; found:
339.2188. IR (film): 2929, 2855, 1709, 1606, 1519, 1278,
1186, 769 cm–1.
Synlett 2006, No. 19, 3304–3308 © Thieme Stuttgart · New York