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A. Serra-Muns, R. Pleixats / Journal of Organometallic Chemistry 695 (2010) 1231–1236
2.2.2.2. N-cinnamyl-4-nitroaniline, 4c [2a,14]. Eluent: hexane–ethyl
acetate 80:20–70:30; 1H NMR (CDCl3) d = 4.04 (dd, J = 5.7 and
1.5 Hz, 2H), 4.68 (br s, 1H), 6.26 (dt, J = 16.0 and 5.7 Hz, 1H), 6.60
(m, 3H), 7.31 (m, 5H), 8.10 (d, J = 9.2 Hz, 2H).
3. Results and discussion
We initially studied the reaction between ethyl cinnamyl car-
bonate, 2, and N-methylaniline, 3a, in the presence of a 5% molar
of Pd-1 (see Scheme 1, Ar = 2, 4, 6-triisopropylphenyl) and several
phosphine ligands (aromatic and aliphatic monodentate phos-
phines; bidentate phosphines) (Table 1). In all cases the reactions
were performed under inert atmosphere, with equimolar amounts
of reagents, in anhydrous and degassed tetrahydrofuran at room
temperature. Treatment of the crude mixtures by column chroma-
tography through silica gel permitted the obtention of moderate to
good yields of N-cinnamyl-N-methylaniline, 4a, and also the recov-
ery of a mixture of palladium(0) complex Pd-1 and the free macro-
cycle 1 in the molar ratios mentioned in Table 1. The recovery of
macrocycle was nearly quantitative in all cases (if we consider
the sum of its free and metal coordinated forms). 1H NMR spectra
distinguish very well free macrocycles from their palladium(0)
complexes since free macrocycles present signals for the olefinic
protons at d ca. 5.50–5.80, whereas in palladium complexes strong
upfield shifts are observed, up to d ca. 2.50–4.40 depending of the
proton considered [2c,5]. When the aliphatic and bulky monoden-
tate tricyclohexylphosphine (Table 1, entry 1) and the bidentate
1,4-bis(diphenylphosphino)butane (Table 1, entry 2) were used,
partial conversion and total decomplexation was observed (ratio
Pd-1:1 of 0:100). Fortunately, using triphenylphosphine, PPh2-
(o-tolyl), 1,2-bis(diphenylphosphino)ethane (dppe) or 1,10-bis-
(diphenylphosphino)ferrocene (dppf) as ligands, full conversions
and good yields of 4a were achieved (Table 1, entries 3–6), mono-
dentate PPh2(o-tolyl) (entry 4) and bidentate dppf (entry 6) provid-
ing almost complete recovery of the metal in the form of Pd-1
(ratio Pd-1:1 of 97:3). Taking into account the best compromise
between isolated product yield and palladium recovery, the condi-
tions of entry 6 were adopted for subsequent experiences with
other nucleophiles (but 1.0 equivalent of bidentate phosphine with
respect to palladium was used instead of 1.3 equivalents in further
experiments). The recovered mixture Pd-1:1 97:3 of entry 6 was
used in a second run under the same conditions to afford complete
conversion of the substrates to 4a in the given time (85% isolated
yield of 4a; a 96:4 mixture of Pd-1:1 was recovered).
To extend the scope of the reaction we first tested other aro-
matic secondary and primary amines such as 4-chloro-N-methy-
laniline (3b) and 4-nitroaniline (3c) (Table 2, entries 1 and 2,
respectively), as well as secondary and primary aliphatic amines
such as di-n-hexylamine (3d) and n-dodecylamine (3e) (Table 2,
entries 3 and 4, respectively). Using the secondary amine 3b, N-
cinnamyl-N-methyl-4-chloroaniline, 4b, was obtained in 70% iso-
lated yield and quite good recovery of palladium was achieved
(Table 2, entry 1). Highly acidic and non-nucleophilic 4-nitroan-
iline (3c) (pKa value in DMSO: 20.9, as compared with methanol:
29.0) [18] reacted at room temperature with the carbonate 2 un-
der palladium catalysis, presumably through its conjugate base
[2], but N-cinnamyl-4-nitroaniline, 4c, was obtained in low yield
due to a low conversion (76% of 3c was recovered) and to
decomposition of allylic carbonate 2 during the reaction (Table
2, entry 2). Minor amounts of secondary products derived from
2 such as cinnamyl alcohol and cinnamaldehyde were also ob-
tained. The yields of 4c were not improved with other phosphine
ligands such as PPh3 and PPh2(o-tolyl). Allylation of aniline
derivatives under palladium catalysis has previously been re-
ported with N-allylpyridinium salts [19], allylic carbonates [2a]
and allylic alcohols [20].
2.2.2.3. N-cinnamyl-N, N-dihexylamine, 4d. Eluent: hexane–ethyl
acetate 96:4; IR (ATR):
m ;
= 2927, 2857, 1465, 1376, 782 cmꢀ1 1H
NMR (CDCl3) d = 0.88 (t, J = 6.6 Hz, 6H), 1.28 (m, 12H), 1.47 (m,
4H), 2.45 (m, 4H), 3.24 (d, J = 6.5 Hz, 2H), 6.28 (dt, J = 15.7 and
6.5 Hz, 1H), 6.50 (d, J = 15.7 Hz, 1H), 7.28 (m, 5H); 13C NMR (CDCl3)
d = 14.2, 22.8, 27.1, 27.4, 32.0, 54.1, 56.8, 126.4, 127.3, 128.2, 128.6,
132.1, 137.4. HRMS (ESI): m/z = 302.2839 (calcd for C21H35N + H:
302.2842).
2.2.2.4. N, N-dicinnamyl-N-dodecylamine, 4e. Eluent: hexane–ethyl
acetate 90:10; IR (ATR):
m
= 3025, 2923, 2852, 1599, 1494, 1449,
1362, 1317, 1150, 965, 742, 692, 659, 629 cmꢀ1
;
1H NMR (CDCl3)
d = 0.88 (t, J = 6.6 Hz, 3H), 1.25 (m, 18H), 1.52 (m, 2H), 2.50 (m,
2H), 3.30 (d, J = 6.5 Hz, 4H), 6.30 (dt, J = 15.7 and 6.7 Hz, 2H), 6.52
(d, J = 15.7 Hz, 2H), 7.27 (m, 10H); MS-ESI: m/z = 418 [M+H]+;
HRMS (ESI): m/z = 418.3462 (calcd for C30H44N: 418.3468).
2.2.2.5. 1-Cinnamylbenzotriazole, 4f and 2-cinnamylbenzotriazole, 40
f. Eluent: hexane–ethyl acetate 100:0–95:5; 4f [3f]: 1H NMR
(CDCl3) d = 5.36 (d, J = 6.2 Hz, 2H), 6.36 (dt, J = 15.7 and 6.2 Hz,
1H), 6.65 (d, J = 15.7 Hz, 1H), 7.35 (m, 7H), 7.54 (dt, J = 8.4 and
1.1 Hz, 1H), 8.05 (dt, J = 8.4 and 1.1 Hz, 1H); 40f [3f]: 1H NMR
(CDCl3) d = 5.50 (dd, J = 6.7 and 1.2 Hz, 2H), 6.55 (dt, 15.8 and
6.6 Hz, 2H), 6.79 (d, J = 15.8 Hz, 1H), 7.34 (m, 7H), 7.88 (m, 2H).
2.2.2.6. N, N, N’, N’-tetracinnamylsulfamide, 4g [2b]. Eluent: hex-
ane–ethyl acetate 100:0–90:10; IR (ATR):
m
= 3026, 2924, 2852,
1495, 1448, 1322, 1145, 966, 902, 746, 692 cmꢀ1
;
1H NMR (CDCl3)
d = 4.03 (d = 6.5 Hz, 8H), 6.23 (dt, J = 15.8 and 6.7 Hz, 4H), 6.55 (d,
J = 15.8 Hz, 4H), 7.29 (m, 20H).
2.2.2.7. (Cinnamyloxy)benzene, 4h [15]. Eluent: hexane–ethyl ace-
tate 100:0–98:2; 1H NMR (CDCl3) d = 4.69 (d, J = 5.7 Hz, 2H), 6.41
(dt, J = 16.0 and 5.7 Hz, 1H), 6.73 (d, J = 16.0 Hz, 1H), 6.96 (m,
3H), 7.32 (m, 7H).
2.2.2.8. 1-Cinnamyloxy-2-nitrobenzene, 4i [16]. Eluent: hexane–
ethyl acetate 98:2–90:10; 1H NMR (CDCl3) d = 4.86 (d, J = 5.5 Hz,
2H), 6.39 (dt, J = 16.0 and 5.5 Hz, 1H), 6.79 (d, J = 16.0 Hz, 1H),
7.1–7.6 (m, 8H), 7.85 (dd, J = 8.0 and 1.5 Hz, 1H); MS: m/z = 255
[M+].
2.2.2.9. 1-Cinnamyloxy-4-nitrobenzene, 4j [17]. Eluent: hexane–
ethyl acetate 100:0–90:10; IR (ATR):
m
= 2927, 1590, 1515, 1495,
1339, 1255, 1108, 996, 970, 854, 789, 750 cmꢀ1
;
1H NMR (CDCl3)
d = 4.80 (d, J = 6.0 Hz, 2H), 6.38 (dt, J = 16.0 and 6.0 Hz, 1H), 6.76
(d, J = 16.0 Hz, 1H), 7.01 (d, J = 9.2 Hz, 2H), 7.32 (m, 5H), 8.21 (d,
J = 9.5 Hz, 2H); 13C NMR (CDCl3) d = 69.2, 114.7, 122.8, 125.8,
126.5, 128.2, 128.6, 134.1, 135.9, 163.5. HRMS (ESI): m/
z = 278.0782 (calcd for C15H13NO3 + Na: 278.0788).
2.2.2.10. 1-Cinnamyloxy-4-tert-butylbenzene, 4k. Eluent: hexane–
ethyl acetate 100:0–97:3; IR (ATR):
m = 2960, 2926, 1513, 1260,
1016, 799, 744, 692 cmꢀ1 1H NMR (CDCl3) d = 1.34 (s, 9H), 4.72
;
(d, J = 5.8 Hz, 2H), 6.46 (dt, J = 15.9 and 5.7 Hz, 1H), 6.63 (d,
J = 15.9 Hz, 1H), 6.94 (d, J = 8.6 Hz, 2H), 7.2-7.4 (m, 5H), 7.45 (d,
J = 7.2 Hz, 2H); 13C NMR (CDCl3) d = 31.7, 34.2, 68.8, 114.3, 124.9,
126.4, 126.7, 127.9, 128.7, 132.9, 136.6, 143.7, 156.5; HRMS
(ESI): m/z = 289.1552 (calcd for C19H22O + Na: 289.1563).
A more nucleophilic secondary aliphatic amine 3d afforded 4d
in good yield in a room temperature reaction (Table 2, entry 3)
and the primary amine 3e gave the diallylation product 4e under
similar conditions when equimolar amounts of reagents were used