Chelation-Assisted Intermolecular Hydroacylation: Direct Synthesis of Ketone from Aldehyde and 1-Alkene

Full text of DOI:10.1021/jo961887d

1
200
J . Org. Chem. 1997, 62, 1200-1201
Ta ble 1. Liga n d -Assisted In ter m olecu la r
Hyd r oa cyla tion of 1-Alk en e w ith Ald eh yd e
Ch ela tion -Assisted In ter m olecu la r
Hyd r oa cyla tion : Dir ect Syn th esis of
Keton e fr om Ald eh yd e a n d 1-Alk en e
a
Chul-Ho J un,* Hyuk Lee, and J un-Bae Hong
Department of Chemistry, Yonsei University,
Seoul 120-749, Korea
Received October 8, 1996
Activation of the aldehydic carbon-hydrogen bond by
transition-metal complexes has especially received inter-
est because of its relevance to organic synthesis through
conversion of aldehyde into ketone (i.e., hydroacylation).1
A negative consequence in the synthesis of ketone from
aldehyde is decarbonylation in the acylmetal intermedi-
ate, formed by cleavage of the aldehydic carbon-
hydrogen bond.2 There are limitations to attempts to
solve decarbonylation for direct intermolecular hydroa-
cylation by cyclometalation with a specially designed
3
model compound or by stabilization of the complex by
pressurization with carbon monoxide gas.4 An indirect
method consisting of a few steps to make ketone from
aldehyde has also been developed with carboxaldimine,
which can be converted by catalytic reaction with 1-alk-
ene into carboxketimines.5 This reaction is followed by
hydrolysis under acid conditions to produce ketone. Until
now, no practical direct intermolecular hydroacylation
has been reported. Herein, we describe a one-step
synthesis of ketone from aldehyde with the cocatalyst
system of the transition-metal complex and 2-amino-3-
picoline.
a
Aldehyde (0.44 mmol), 1-alkene (1.30 mmol), (PPh3)3RhCl
0.022 mmol), and 2-amino-3-picoline (0.086 mmol) in toluene (0.1
In our experiment, 1-alkene 1 reacted with aldehyde
(
2
in toluene at 150 °C for 24 h under a mixture of 5 mol
b
g) at 150 °C for 24 h. Isolated yield after chromatographic
%
of chlorotris(triphenylphosphine)rhodium (I) (3) and
c
isolation (hexane:ethylacetate ) 5:2). Benzene was used as a
solvent. d [R]D + 3.62 from 4-vinylcyclohexene of [R]D + 1.08.
2
0 mol % of 2-amino-3-picoline (4) as a cocatalyst based
6
upon 2 (eq 1).
Ta ble 2. Effect of 2-Am in o-3-p icolin e (4) on
Hyd r oa cyla tion of 1b w ith 2ba
entry mol % of 4 product ratio 5i:anisole isolated yield (%) of 5i
1
2
3
4
5
6
0
10
20
50
70
0b:100
58:42
85:15
85:15
90:10
93:7
0
14
57
70
80
83
Following the reaction, the corresponding hydroacy-
lated product, ketone, was isolated by column chroma-
tography. The reactions between various aldehydes and
100
a
Anisaldehyde (0.22 mmol), 1-pentene (1.08 mmol), (Ph3P)3RhCl
1
-alkenes were examined, and the results are shown in
(0.022 mmol) in THF (2 mL) at 100 °C for 60 h under different
mol % of 2-amino-3-picoline based upon anisaldehyde. 46% yield
of anisole was obtained, determined by GC.
7
b
Table 1.
The resulting hydroacylated ketones were linear in
shape, not branched alkyl ketones. The reaction of a
chiral olefin such as 4-vinylcyclohexene (1g) with ben-
zaldehyde (run 7) affords the corresponding ketone 5g,
which retains an asymmetric center in a 3-cyclohexenyl
group. Aliphatic aldehyde still showed comparable re-
activity with the aromatic aldehyde (runs 10-12). The
reaction of a sterically hindered aliphatic aldehyde such
as tert-butyl aldehyde 2f afforded a lower yield of ketone
compared with those of primary and secondary aliphatic
(
1) (a) Schwartz, J .; Cannon, J . B. J . Am. Chem. Soc. 1974, 96, 4721.
b) Lochow, C. F.; Miller, R. G. J . Am. Chem. Soc. 1976, 98, 1281. (c)
Vora, K. P.; Lochow, C. F.; Miller, R. G. J . Organomet. Chem. 1980,
92, 257. (d) Isnard, P.; Denise, B.; Sneeden, R. P. A.; Cognion, J . M.;
(
1
Durual, P. J . Organomet. Chem. 1982, 240, 285. (e) Marder, T. B.; Roe,
D. C.; Milstein, D. Organometallics 1988, 7, 1451.
(4) (a) Kondo, T.; Akazome, M.; Tsuji, Y.; Watanabe, Y. J . Org. Chem.
1990, 55, 1286. (b) Tsuji, Y.; Yoshii, S.; Ohsumi, T.; Kondo, T.;
Watanabe, Y. J . Organomet. Chem. 1987, 331, 379.
(5) (a) Suggs, J . W. J . Am. Chem. Soc. 1979, 101, 489. (b) J un, C.-
H.; Han, J .-S.; Kang, J .-B.; Kim, S.-I. J . Organomet. Chem. 1994, 474,
183. (c) J un, C.-H.; Kang, J .-B.; Kim, J .-Y. J . Organomet. Chem. 1993,
458, 193. (d) J un, C.-H.; Kang, J .-B.; Kim, J .-Y. Tetrahedron Lett. 1993,
34, 6431.
(6) A mixture of 46.6 mg (0.44 mmol) of 2a , 9.3 mg (0.086 mmol) of
4, and 20 mg (0.022 mmol) of 3 was dissolved in toluene (0.1 g) in a 1
mL screw-capped vial. After the mixture was stirred for several
minutes, 109.0 mg (1.30 mmol) of 1a was added. The mixture was
magnetically stirred for 24 h at 150 °C. The solution was concentrated
to give a residue that was purified by column chromatography (hexane:
(2) (a) McQuillin, F. J .; Parker, D. G.; Stephenson, G. R. Transition
metal organometallics for organic synthesis; Cambridge University
Press: Cambridge, 1991; p 306. (b) Kondo, T.; Tantayanon, S.; Tsuji,
Y.; Watanabe, Y. Tetrahedron Lett. 1989, 30, 4137. (c) Ohno, K.; Tsuji,
J . J . Am. Chem. Soc. 1968, 90, 99. (d) Ohno, K.; Tsuji, J . J . Am. Chem.
Soc. 1968, 90, 94. (e) Doughty, D. H.; Pignolet, L. H. J . Am. Chem.
Soc. 1978, 100, 7083. (f) Walborsky, H. M.; Allen, L. E. J . Am. Chem.
Soc. 1971, 93, 5465. (g) O’connor, J . M.; Ma, J . J . Org. Chem. 1992,
5
7, 5075.
3) (a) J un, C.-H. Organometallics 1996, 15, 895. (b) J un, C.-H.; Lim,
(
Y.-G. Tetrahedron Lett. 1995, 36, 3357. (c) Lee, H.; J un, C.-H. Bull.
Korean Chem. Soc. 1995, 16, 66. (d) J un, C.-H. J . Organomet. Chem.
1
990, 390, 361. (e) Suggs, J . W.; Wovkulich, M. J .; Cox, S. D.
Organometallics 1985, 4, 1101. (f) Suggs, J . W. J . Am. Chem. Soc. 1978,
00, 640.
EtOAc ) 5:2, SiO
2
) to give 60.1 mg of 5a (72% isolated yield), which
was characterized by spectroscopic analysis.
1
S0022-3263(96)01887-7 CCC: $14.00 © 1997 American Chemical Society

Communications
J . Org. Chem., Vol. 62, No. 5, 1997 1201
Sch em e 1. P r op osed Ca ta lytic Cycle for Liga n d -Assisted Hyd r oa cyla tion (L ) P P h
3
)
Ta ble 3. Ca ta lytic Activities of Som e Tr a n sition Meta l
To identify the effect of 4, different molar ratios of 4
were applied for hydroacylation of 1-pentene with 4-anis-
aldehyde (2b) under mild conditions (10 mol % of 3, THF,
a
Com p lexes
isolated yield (%)
entry
catalyst
P) RhCl
additiveb
hexanophenonec
00 °C, 60 h) (Table 2).9
1
1
2
3
4
5
6
7
8
9
(Ph
3
3
72
68
16
(10)e
(9)
0
Without the addition of 4, the decarbonylation product,
RhCl ‚xH
Rh(CO)(PPh
Ru (CO)12
Ru(PPh
Ir(CO)(PPh
(Ph P) IrCl
[(C RhCl]
3
2
O
PPh
(CH
3
anisole, was obtained exclusively in 46% yield (Table 2,
run 1). With 10 mol % of 4, 4′-methoxyhexanophenone
(5i) was isolated in 14% yield along with a 10% yield of
anisole. By increasing the concentration of 4 to 20 mol
3
2
) Cl
NOd
3 3
)
3
3
)
3
Cl
) Cl
3 2
2
NaBH
4
, PPh
3
3
3
3
0
%, 50 mol %, 70 mol %, and 100 mol %, the ratio of 5i to
8
H
14
)
2
2
PPh
(p-CH
(p-(CH
Cy
(CH
3
48
61
56
38
0
3
C
6
H
4
)
P
anisole was increased to 85:15, 85:15, 90:10, and 93:7.
This result indicates that hydroacylation competes with
the decarbonylation of aldehyde. The above results show
that increasing the concentration of 2-amino-3-picoline
also increases the probability of carbon-hydrogen cleav-
age of carboxaldimine.
1
1
1
0
1
2
3
6 4 3
OC H ) P
3
P
3
)
3
P
a
Benzaldehyde (0.22 mmol), 1-pentene (1.08 mmol), transition-
metal complexes (0.022 mmol), and 2-amino-3-picoline (0.22 mmol)
b
in THF (2 mL) at 100 °C for 40 h. All phosphines added were
c
0
.11 mmol. Figures in parentheses were GC yield based upon
A variety of organometallic compounds, with or without
additives, were studied in the conversion of 1 into 5 at
d
benzaldehyde. 0.066 mmol was added, and without additive, 3%
e
of hexanophenone was formed. Without additive, 1% of hex-
1
00 °C for 40 h. This reaction requires the catalyst, 10
anophenone was formed.
mol % of metal complex, and 100 mol % of 4 (Table 3).
.
The complexes (PPh
Rh(CO)(PPh Cl, Ru (CO)12 with (CH
Cl with NaBH , and PPh
3 2
It is interesting to note that even Rh(CO)(PPh )
3
)
3
RhCl, RhCl
3
H
2
O with PPh
3
3
,
-
aldehydes (run 13). This hydroacylation process is
believed to proceed as illustrated in Scheme 1.
The first step might be condensation of aldehyde 2 and
-amino-3-picoline (4) to generate aldimine 6 and H O.
2
A carbon-hydrogen bond in 6 is cleaved by rhodium(I)
in 3 to give an (iminoacyl)rhodium(III) hydride 7, which
3
)
2
3
3
)
3
NO, Ru(PPh
3
)
2
4
3
were all catalytically active.
Cl
2
showed catalytic activity since it can be generated from
2
decarbonylation of aldehyde by 3 (Table 3, run 3). This
result explains that although partial decarbonylation
occurred during hydroacylation, the generated Rh(CO)-
was previously found from the reaction of aldimine 6 and
8
3
.
Coordination of 1-alkene 1 to 7 and subsequent
(
PPh
ity. When different types of phosphines were tested
under the [(C RhCl] catalyst, the best result was
3 2
) Cl catalyst still has catalytic hydroacylation activ-
hydride insertion into 1-alkene in 8 leads to an (iminoa-
cyl)rhodium(III) alkyl 9. Reductive elimination in 9
produces carboxketimine 10 with regeneration of catalyst
8
H
14
)
2
2
obtained using tris(p-methylphenyl)phosphine (Table 3,
runs 8-12).
In conclusion, this report shows the general direct
intermolecular hydroacylation of 1-alkene with aldehyde
with the assistance of 2-amino-3-picoline.
3
. Hydrolysis of 10 with H
the condensation of 2 and 4, synthesizes products 5 and
. In this process, 4 and complex 3 act as catalysts.
2
O, previously generated from
4
Linear alkyl ketones were obtained in this reaction
through hydrometalation in 8 following anti-Markowni-
koff’s rule, due to the steric congestion of the (iminoacyl)-
rhodium(III) complex system.
Ack n ow led gm en t. The support of this research by
the Korea Science and Engineering Foundation (Grant
No. 961-0306-054-2) and the Ministry of Education
(Project No. BSRI-96-3422) is gratefully acknowledged.
The authors also acknowledge a Research Grant from
Yonsei University.
(
7) All ketones were the reported compounds except 5h . Spectro-
1
scopic data for 5h : H NMR (300 MHz, CDCl
J ) 8.3 Hz, 2H, 2,6-Hs in phenyl group), 7.4-7.2 (m, 3H, 3,4,5-Hs in
phenyl group), 3.3 (t, J ) 7.2 Hz, 2H, R-CH to CO), 3.1 (t, J ) 7.3 Hz,
to CO); 13C NMR (72.5 MHz, CDCl
, 25 °C, TMS) δ 197.7
CO), 136.2-127.9 (Cs of C and C group), 37.3 (R-C of CO), 17.0
â-C of CO); IR (neat) 2917, 1692 (CO), 1598, 1515, 1450, 1289, 1204,
3
, 25 °C, TMS) δ 8.0 (dd,
2
2
(
(
1
(
3
H, â-CH
2
3
6
H
5
6 5
F
J O961887D
-1
+
171, 1045, 957, 760, 695 cm ; MS (70 eV) m/ z 300 (31) [M ], 181
+
+
5), 105 (100) [PhCO ], 77 (86.2) [C
00.057356, found 300.057686.
8) Intermediates, aldimine 6 (R ) Ph), and complex 7 were already
prepared and characterized in ref 7a.
6
H
5
]; HRMS calcd for C15
H
9
OF
5
(9) Other 2-aminopyridine derivatives have been tested for this
reaction, and 2-amino-3-picoline showed the best result. Toluene and
THF did not show any large difference in results, but we preferred
THF to toluene under mild conditions such as 100 °C.
(