One-Pot Reductive Amination of Conjugated Aldehydes and Ketones with Silica Gel and Zinc Borohydride

Full text of DOI:10.1021/jo971117h

370
J . Org. Chem. 1998, 63, 370-373
Sch em e 1
On e-P ot Red u ctive Am in a tion of
Con ju ga ted Ald eh yd es a n d Keton es w ith
Silica Gel a n d Zin c Bor oh yd r id e
Brindaban C. Ranu,* Adinath Majee, and
Arunkanti Sarkar
Department of Organic Chemistry, Indian Association
for the Cultivation of Science, J adavpur,
Calcutta - 700 032, India
Received J une 19, 1997X
procedure.8 Our recent endeavor of selective reduction
of various important functionalities with zinc borohy-
dride11 prompted us to initiate a systematic study on this
useful transformation. We have discovered that reduc-
tive amination of conjugated aldehyde and ketone is
achieved by treatment of the corresponding carbonyl
compound with an appropriate amine in the presence of
silica gel followed by addition of zinc borohydride in a
one-pot operation (Scheme 1). Although imines are, in
general, prepared by the condensation of the carbonyl
compound with an amine in the presence of a Lewis or
protic acid,12 our attempts to obtain the imines of
conjugated carbonyl compounds, particularly ketones
following reported procedures12 using zinc chloride, boron
trifluoride-etherate, p-toluenesulfonic acid, molecular
sieves, failed. However, with our experience in surface-
mediated solid-phase reactions13 we solved this problem
by carrying out the reaction on the surface of silica gel.
Thus, when a mixture of the conjugated carbonyl com-
pound and the amine being adsorbed on silica gel was
stirred for 2-3 h, the corresponding imines are formed
in good yields. So, a one-pot reductive amination proce-
dure is designed as follows: a mixture of carbonyl
compound and amine is adsorbed on the surface of silica
gel, and a solution of zinc borohydride is added to it, after
being stirred for 4 h. The reaction mixture is then stirred
for another 30-60 min as required for completion (TLC).
The product is isolated by simple extraction of the
reaction mixture with ether.
Reductive amination, which allows the conversion of
carbonyl functionality to an amine, is an important
process in organic synthesis. The reaction involves the
initial formation of an imine from the reaction of a
carbonyl compound with an amine and its subsequent
reduction to an alkylated amine. The reductive amina-
tion reaction is termed as direct when a mixture of the
carbonyl compound and the amine is treated with proper
reducing agent in a single operation. A stepwise or
indirect reaction involves the preformation of the inter-
mediate imine followed by reduction in a separate step.
A variety of reducing agents, such as hydrogen in the
presence of metal catalysts,1 sodium cyanoborohydride,2
borane-pyridine,3 borohydride exchange resin,4 zinc-
acetic acid,5 sodium borohydride-magnesium chlorate,6
zinc borohydride-zinc chloride,7 and recently sodium
triacetoxyborohydride,8 have been developed for this
conversion from time to time. Among these, the most
general and commonly used methods include catalytic
hydrogenation, reduction with sodium cyanoborohydride,
and sodium triacetoxyborohydride. But, hydrogenation
is not compatible with compounds containing a double
or triple bond and several other reducible functional
groups such as nitro or cyano. On the other hand, sodium
cyanoborohydride may require up to a 5-fold excess of
amine9 and may result in the contamination of the
product with cyanide.10 Moreover, this reagent is highly
toxic and generates toxic byproducts HCN and NaCN,
upon workup. Sodium triacetoxyborohydride, although
free from these drawbacks, has limitations with aromatic
and unsaturated ketones. In fact, reductive amination
of conjugated carbonyl compounds has not been ad-
dressed in details in any of the reported methods; only
two examples, 1-acetylcyclohexene and cinnamaldehyde,
have been included in sodium triacetoxyborohydride
(11) (a) Sarkar, D. C.; Das, A. R.; Ranu, B. C. J . Org. Chem. 1990,
55, 5799. (b) Ranu, B. C.; Chakraborty, R. Tetrahedron Lett. 1990, 31,
7663. (c) Ranu, B. C.; Das, A. R. J . Chem. Soc., Chem. Commun. 1990,
1334. (d) Ranu, B. C.; Basu, M. K. Tetrahedron Lett. 1991, 32, 3243.
(e) Ranu, B. C.; Chakraborty, R. Tetrahedron Lett. 1991, 32, 3579. (f)
Ranu, B. C.; Das, A. R. J . Org. Chem. 1991, 56, 4796. (g) Ranu, B. C.;
Das, A. R. Tetrahedron Lett. 1992, 33, 2361. (h) Ranu, B. C.;
Chakraborty, R. Tetrahedron 1992, 48, 5317. (i) Ranu, B. C.; Das, A.
R. J . Chem. Soc., Perkin Trans. 1 1992, 1561. (j) Ranu, B. C.; Das, A.
R. J . Chem. Soc., Perkin Trans. 1 1992, 1881. (k) Ranu, B. C.;
Chakraborty, R.; Saha, M. Tetrahedron Lett 1993, 34, 4659. (l) Ranu,
B. C.; Sarkar, A.; Chakraborty, R J . Org. Chem. 1994, 59, 4114. (m)
Ranu, B. C.; Sarkar, A.; Majee, A. J . Org. Chem. 1997, 62, 1841.
(12) (a) Spring, M. M. Chem. Rev. 1940, 26, 297. (b) Layer, R. W.
Chem. Rev. 1963, 63, 489. (c) Bolton, R.; Danks, T. N.; Paul, J . M.
Tetrahedron Lett. 1994, 35, 3411. (d) Niel, J . C. G. V.; Pandit, U.K.
Tetrahederon 1985, 41, 6005. (e) Bonnett, R.; Emerson, T. R. J . Chem.
Soc. 1965, 4508. (f) Yaozhong, J .; Guilan, L.; J inchu, L.; Changyou, Z.
Synth. Commun. 1987, 17, 1545.
(13) (a) Ranu, B. C.; Bhar, S.; Sarkar, D. C. Tetrahedron Lett. 1991,
32, 2811. (b) Ranu, B. C.; Bhar, S.; Chakraborti, R. J . Org. Chem. 1992,
57, 7349. (c) Ranu, B. C.; Bhar, S. J . Chem. Soc., Perkin Trans. 1 1992,
365. (d) Ranu, B. C.; Saha, M.; Bhar, S. Tetrahedron Lett. 1993, 34,
1989. (e) Ranu, B. C.; Saha, M.; Bhar, S. J . Chem. Soc., Perkin Trans.
1 1994, 2197. (f) Ranu, B. C.; Saha, M. J . Org. Chem. 1994, 59, 8269.
(g) Ranu, B. C.; Majee, A.; Das, A. R Synth. Commun. 1995, 25, 363.
(h) Ranu, B. C.; Sarkar, A.; Saha, M.; Bhar, S. Pure Appl. Chem. 1996,
68, 775. (i) Ranu, B. C.; Ghosh, K.; J ana, U. J . Org. Chem. 1996, 61,
9546.
(1) (a) Emerson, W. S. Org. React. 1948, 4, 174. (b) J ohnson, H. E.;
Crosby, D. G. J . Org. Chem. 1962, 27, 2205. (c) Klyuev, M. V.; Khidekel,
M. L. Russ. Chem. Rev. 1980, 49, 14.
(2) (a) Hutchins, R. O.; Natale, N. R. Org. Prep. Proced. Int. 1979,
11, 201. (b) Lane, C. F. Synthesis 1975, 135.
(3) Pelter, A.; Rosser, R. M.; Mills, S. J . Chem. Soc., Perkin Trans.
1 1984, 717.
(4) Yoon, N. M.; Kim, E. G.; Son, H. S.; Choi, J . Synth. Commun.
1993, 23, 1595.
(5) Micovic, I. V.; Ivanovic, M. D.; Piatak, D. M.; Bojic, V. Dj.
Synthesis 1991, 1043.
(6) Brussee, J .; van Benthem, R. A. T. M.; Kruse, C. G.; van der
Gen, A. Tetrahedron: Asymmetry 1990, 1, 163.
(7) Bhattacharyya, S.; Chatterjee, A.; Duttachowdhury, S. K. J .
Chem. Soc., Perkin Trans. 1 1994, 1.
(8) Abdel-Magid, A. F.; Carson, K. G.; Harris, B. D.; Maryanoff, C.
A.; Shah, R. D. J . Org. Chem. 1996, 61, 3849.
(9) Borch, R. F.; Bernstein, M. D.; Durst, H. D. J . Am. Chem. Soc.
1971, 93, 2897.
(10) Moormann, A. E. Synth. Commun. 1993, 23, 789.
S0022-3263(97)01117-1 CCC: $15.00 © 1998 American Chemical Society
Published on Web 01/07/1998

Notes
J . Org. Chem., Vol. 63, No. 2, 1998 371
Ta ble 1. Red u ctive Am in a tion of Con ju ga ted Ald eh yd es a n d Keton es

372 J . Org. Chem., Vol. 63, No. 2, 1998
Notes
column chromatography over silica gel to provide the pure
A variety of R,â-unsaturated aldehydes and ketones
were subjected to reductive aminations by this procedure.
The results are reported in Table 1. The acyclic, cyclic,
and aromatic conjugated carbonyl compounds underwent
successful reductive aminations with cyclohexylamine,
aniline, and benzylamine to produce the corresponding
amines in very good yields. In all the cases the reduc-
tions were very fast being complete within 60 min,
although prior to addition of zinc borohydride the reaction
was run for 4 h to ensure complete imine formation. The
direct process using carbonyl compound, amine, and zinc
borohydride all together also leads to reductive amina-
tion, but is always accompanied with reduction of car-
bonyl compounds to a varying degree. However, the
stepwise process is free from any side reaction. The
present procedure does not affect nitro (entry 16) and
cyano18 groups. The double bonds in conjugation do not
undergo any isomerization or reduction during the
process as well as in isolation. Moreover, zinc borohy-
dride is neutral in nature and, in general, is compatible
with many sensitive functionalities11 like acetal11d and
silyl ether.14a
When a secondary amine such as pyrrolidine was
treated with cyclohexanone on the surface of silica gel
followed by stirring with a solution of zinc borohydride
in a similar way, the corresponding amine from the
reduction of enamine was obtained without any difficulty.
In conclusion, the present procedure using silica gel
and zinc borohydride provides a first general and efficient
methodology for reductive amination of conjugated alde-
hydes and ketones. The notable advantages of this
procedure are (a) operational simplicity, (b) use of no
costly or toxic chemicals, (c) no environmental pollution
from waste, (d) mild condition, (e) fast reaction, and (f)
high yield.
product,8 N-cinnamylbenzylamine (950 mg, 85%) as an oil:
IR(neat) 1340, 1515, 1670, 3020 cm-1 1H NMR (300 MHz,
;
CDCl3) δ 3.53 (2H, d, J ) 6.9 Hz), 4.02 (2H, s), 6.38 (1H, dt, J
) 15.9, 6.9 Hz), 6.58 (1H, d, J ) 15.9 Hz), 7.22-7.56 (10H, m).
This procedure is followed for reductive amination of all
conjugated aldehydes and ketones listed in Table 1. Although
the results reported in Table 1 were based on mmol scale
reactions, a few gram scale reactions were carried out to afford
the corresponding products in analogously high yields. All the
1
products have been characterized by their spectral (IR, H and
13C NMR) and analytical data. These data are presented below
in order of the entries in Table 1.
1:15 N-Cin n a m ylcycloh exyla m in e: mp 122 °C; IR(KBr)
1200, 1670, 3020, 3320 cm-1; 1H NMR (300 MHz, CDCl3) δ 0.85-
1.74 (6H, m), 1.62-1.92 (4H, m), 2.86-2.89 (1H, m), 3.2 (1H,
broad), 3.53-3.64 (2H, m), 6.39 (1H, dt, J ) 15, 6 Hz), 6.60 (1H,
d, J )15 Hz), 7.3-7.42 (5H, m).
2:15 N-Cin n a m yla n ilin e: IR(neat) 1340, 1515, 1670, 3020
1
cm-1; H NMR (300 MHz, CDCl3) δ 3.74 (1H, broad), 3.85 (2H,
d, J ) 6 Hz), 6.27 (1H, dt, J ) 12,6 Hz), 6.54-6.73 (4H, m),
7.13-7.34 (7H, m).
4: N-(3,7-Dim eth yl-2,6-octa d ien yl)cycloh exyla m in e: IR-
1
(neat) 1200, 1640, 1670, 3020, 3400 cm-1; H NMR (300 MHz,
CDCl3) δ 0.8-1.34 (6H, m), 1.59 (3H, s), 1.66 (6H, s), 1.76-1.83
(4H, m), 2.03-2.07 (4H, m), 2.74-2.82 (1H, m), 3.12 (1H, broad),
3.34-3.41 (2H, m), 5.04-5.06 (1H, m), 5.28-5.37 (1H, m); 13C
NMR (75 MHz, CDCl3) δ 16.4 (CH3), 17.6 (CH3), 23.4 (CH3), 25.4
(CH2), 25.4 (CH2), 25.7 (CH2), 26.1 (CH2), 27.3 (CH2), 29.9 (CH2),
32.1 (CH2), 49.8 (CH), 60.4 (CH2), 118.1 (CH), 119.0 (CH), 131.9
(C), 132.8 (C). Anal. Calcd for C16H29N: C, 81.63; H, 12.42; N,
5.95. Found: C, 81.70; H, 12.20; N, 5.72.
5: N-(3,7-Dim eth yl-2,6-octa d ien yl)a n ilin e IR(neat) 1340,
1515, 1670, 3020, 3400 cm-1; 1H NMR (300 MHz, CDCl3) δ 1.62
(3H, s), 1.69 (3H, s), 1.71 (3H, s), 2.04-2.12 (4H, m), 3.59-3.71
(2H, m), 5.07-5.11 (1H, m), 5.31-5.35 (1H, m), 6.60-6.72 (3H,
m), 7.15-7.24 (2H, m); 13C NMR (75 MHz, CDCl3) δ 16.3 (CH3),
17.6 (CH3), 25.7 (CH3), 26.4 (CH2), 39.4(CH2), 41.9 (CH2), 112.8
(2 CH), 117.2 (CH), 121.5 (CH), 122.2 (C), 123.9 (CH), 129.1 (2
CH), 138.9 (C), 148.9 (C). Anal. Calcd for C16H23N: C, 83.79;
H, 10.11; N, 6.11. Found: C, 83.91; H, 10.21; N, 6.13.
6: N-(3,7-Dim eth yl-2,6-octa d ien yl)ben zyla m in e IR(neat)
1500, 1670, 3020, 3400 cm-1; 1H NMR (300 MHz, CDCl3) δ 1.56
(6H, s), 1.61 (3H, s), 1.91-2.06 (4H, m), 3.15-3.20 (2H, m), 3.17
(2H, s), 5.04-5.06 (1H, m), 5.25-5.27 (1H, m), 7.16-7.28 (5H,
m); 13C NMR (75 MHz, CDCl3) δ 16.2 (CH3), 17.6 (CH3), 25.7
(CH3), 26.5 (CH2), 39.6 (CH2), 46.3 (CH2), 53.4 (CH2), 122.6 (CH),
123.5 (CH), 123.9 (CH), 124.1 (CH), 126.9 (CH), 128.1 (CH), 128.3
(CH), 128.3 (C), 137.9 (C), 140.2 (C). Anal. Calcd for C17H25N:
C, 83.89; H, 10.35; N, 5.75. Found: C, 84.1; H, 10.40; N, 5.47.
7:16 N-(1-P h en yleth yl)cycloh exyla m in e: IR(neat) 1200,
Exp er im en ta l Section
Gen er a l Meth od s. General information regarding instru-
ments and techniques used are the same as mentioned in our
previous paper.11m
The conjugated carbonyl compounds and the amines are all
commercial materials and were distilled before use. Silica gel
(HF 254) was from SRL, India, and was activated by heating in
a oven at 150 °C for 12 h before use. Zinc borohydride in DME
was prepared from zinc chloride and sodium borohydride ac-
cording to a reported procedure,14b and the crude solution was
used without any purification.
Gen er a l P r oced u r e for Red u ctive Am in a tion . Rep r e-
sen ta tive P r oced u r e. A mixture of cinnamaldehyde (660 mg,
5 mmol) and benzylamine (535 mg, 5 mmol) was uniformly
adsorbed on the surface of activated silica gel (5 g) by dropwise
addition under stirring, and the mixture was then stirred at
room temperature (30 °C) under nitrogen for 4 h to allow
complete formation of the corresponding imine. A solution of
zinc borohydride (5 mmol) in DME (5 mL) was added, and
stirring was continued for 60 min to complete the reaction (TLC).
The reaction mixture was then decomposed by careful dropwise
addition of water (2 mL) and extracted with ether (3 × 20 mL).
The extract was washed with brine, dried (Na2SO4), and
evaporated to leave the crude product which was purified by
1640 cm-1 1H NMR (200 MHz, CDCl3) δ 0.96-1.67 (10H, m),
;
1.32 (3H, d, J ) 6.6 Hz), 1.97 (1H, broad), 2.27-2.50 (1H, m),
3.94 (1H, q, J ) 6.6 Hz), 7.20-7.34 (5H, m).
8:8 N-(1-P h en yleth yl)a n ilin e: IR(neat) 1500, 1670, 3020,
3420 cm-1 1H NMR (300 MHz, CDCl3) δ 1.42 (3H, d, J ) 6.6
;
Hz), 1.69 (1H, broad), 4.00 (1H, q, J ) 6.6 Hz), 7.06-7.36 (10H,
m).
9:17 N-(1-P h en yleth yl)ben zyla m in e: IR(neat) 1300, 1640
cm-1 1H NMR (200 MHz, CDCl3) δ 1.40 (3H, d, J ) 6.6 Hz),
;
1.82 (1H, broad), 3.64 (2H, d, J ) 5.5 Hz), 3.82 (1H, q, J ) 6.6
Hz), 7.06-7.36 (10H, m).
10: N-[1-Meth yl-3-(2,6,6-tr im eth ylcycloh ex-1-en yl)p r op -
2-en yl]cycloh exyla m in e: IR(neat) 1200, 1640, 1670 cm-1; 1H
NMR (300 MHz, CDCl3) δ 0.98 (6H, s), 1.02-1.24 (4H, m), 1.38
(3H, d, J ) 6 Hz), 1.40-1.47 (2H, m), 1.62 (3H, s), 1.58-1.97
(10H, m), 2.91 (1H, broad), 3.03 (1H, m), 3.56-3.61 (1H, m), 5.38
(1H, dd, J ) 15,9 Hz), 6.07 (1H, d, J ) 15 Hz); 13C NMR (75
MHz, CDCl3) δ 19.1 (CH3), 19.2 (CH3), 19.8 (CH2), 25.4 (2 CH2),
25.6 (CH2), 28.6 (CH3), 28.8 (CH3), 31.1 (CH2), 32.5 (C), 39.1 (2
CH2), 39.2 (CH2), 59.9 (CH), 60.6 (CH), 129.4 (C), 131.4 (CH),
133.6 (CH), 136.2 (C). Anal. Calcd for C19H33N: C, 82.84; H,
12.07; N, 5.08. Found: C, 82.71; H, 12.10; N, 5.21.
(14) (a) Ito, Y.; Yamaguchi, M. Tetrahedron Lett. 1983, 24, 5385.
(b). Crabbe, P.; Garcia, G. A.; Rius, C. J . Chem. Soc., Perkin Trans. 1
1973, 810.
(15) Hurd, C. D.; J enkins, W. W. J . Org. Chem. 1957, 22, 1418.
(16) Kotsuki, H.; Yoshimura, N.; Kadota, I.; Ushio, Y.; Ochi, M.
Synthesis 1990, 401.
(17) Willoughby, C. A.; Buchwald, S. L. J . Am. Chem. Soc. 1992,
114, 7562.
(18) Benzyl cyanide remained unaffected under this procedure.
11: N-[1-Meth yl-3-(2,6,6-tr im eth ylcycloh ex-1-en yl)p r op -
2-en yl]a n ilin e: IR(neat) 1300, 1640, 1670, 3020, 3400 cm-1
;
1H NMR (300 MHz, CDCl3) δ 0.89 (3H, s), 0.94 (3H, s), 1.35 (3H,
d, J ) 6 Hz), 1.39-1.60 (6H, m), 1.60 (3H, s), 3.92-4.10 (1H,

Notes
J . Org. Chem., Vol. 63, No. 2, 1998 373
m), 5.35 (1H, dd, J ) 15,9 Hz), 6.07 (1H, d, J ) 15 Hz), 6.63-
6.66 (3H, m), 7.12-7.17 (2H, m); 13C NMR (75 MHz, CDCl3) δ
19.8 (CH2), 21.3 (CH3), 22.6 (CH3), 28.5 (CH3), 28.6 (CH3), 32.5
(CH2), 32.7 (C), 39.2 (CH2), 51.3 (CH), 113.6 (2 CH), 117.1 (CH),
127.5 (CH), 128.1 (C), 129.0 (2 CH), 129.2 (C), 136.9 (CH), 147.5
(C). Anal. Calcd for C19H27N: C, 84.70; H, 10.10; N, 5.20.
Found: C, 84.70; H, 10.32; N, 5.33.
broad), 5.42 (1H, broad s), 6.67-6.74 (5H, m); 13C NMR (75 MHz,
CDCl3) δ 23.4 (CH3), 26.1 (CH3), 31.0 (C), 31.1 (CH3), 44.0 (CH2),
45.2 (CH2), 66.8 (CH), 115.0 (2 CH), 118.5 (CH), 123.5 (2 CH),
129.2 (CH), 136.0 (C), 147.0 (C). Anal. Calcd for C15H21N: C,
83.67; H, 9.83; N, 6.50. Found: C, 83.63; H, 10.05; N, 6.23.
15: N-(3,5,5-Tr im eth ylcycloh ex-2-en yl)ben zyla m in e: IR-
1
(neat) 1360, 1600, 1670, 3020, 3400 cm-1; H NMR (300 MHz,
12: N-[1-Meth yl-3-(2,6,6-tr im eth ylcycloh ex-1-en yl)p r op -
CDCl3) δ 0.86 (3H, s), 0.98 (3H, s), 1.55-1.86 (4H, m), 1.66 (3H,
s), 3.18-3.28 (1H, broad), 3.81 (2H, d, J ) 12 Hz), 4.17-4.22 (1H,
broad), 5.40-5.43 (1H, m), 7.25-7.36 (5H, m); 13C NMR (75
MHz, CDCl3) δ 23.5 (CH3), 26.1 (CH3), 30.0 (C), 31.8 (CH3), 44.2
(CH2), 45.1 (CH2), 53.0 (CH2), 66.5 (CH), 122.5 (CH), 123.8 (2
CH), 126.9 (CH), 128.3 (2 CH), 134.7 (C), 140.4 (C). Anal. Calcd
for C16H23N: C, 83.79; H, 10.11; N, 6.11. Found: C, 84.01; H,
10.21; N, 6.40.
2-en yl]ben zyla m in e: IR(neat) 1640, 1670, 3020, 3400 cm-1
;
1H NMR (300 MHz, CDCl3) δ 1.00 (3H, s), 1.01 (3H, s), 1.22 (3H,
d, J ) 9 Hz), 1.42-1.99 (6H, m), 1.69 (3H, s), 3.28 (1H, quintet,
J ) 6 Hz), 3.67-3.87 (2H, AB q, J ) 54, 12 Hz), 5.28 (1H, dd, J
) 15, 9 Hz), 5.95 (1H, d, J ) 15 Hz), 7.25-7.32 (5H, m); 13C
NMR (75 MHz, CDCl3) δ 19.2 (CH2), 21.7 (CH3), 22.6 (CH3), 28.9
(CH3), 28.9 (CH3), 32.6 (CH2), 33.8 (C), 39.3 (CH2), 51.5 (CH2),
56.1 (CH), 126.8 (CH), 128.1 (CH), 128.2 (CH), 128.2 (CH), 128.3
(CH), 128.4 (CH), 128.4 (C), 137.0 (C), 137.7 (CH), 140.4 (C).
Anal. Calcd for C20H29N: C, 84.75; H, 10.31; N, 4.94. Found:
C, 84.60; H, 10.40; N, 5.20.
16: N-(3-Nitr oben zyl)cycloh exyla m in e: mp 115-117 °C;
1
IR (KBr) 1670, 3010, 3400 cm-1; H NMR (300 MHz, CDCl3) δ
0.85-2.05 (10H, m), 2.79 (1H, t, J ) 9 Hz), 3.77 (1H, broad, NH),
4.01 (2H, d, J ) 6 Hz), 7.56 (1H, t, J ) 6 Hz), 7.72 (1H, d, J )
6 Hz), 8.20 (1H, s), 8.22 (1H, d, J ) 6 Hz); 13C NMR (75 MHz,
CDCl3) δ 25.1 (CH2), 25.3 (CH2), 25.4 (CH2), 27.7 (CH2), 29.4
(CH2), 55.2 (CH2), 61.9 (CH), 123.7 (CH), 124.4 (CH2), 130.0 (CH),
135.9 (CH), 136.8 (C), 148.4 (C). Anal. Calcd for C13H18N2O2:
C, 66.63; H, 7.75; N, 11.96. Found: C, 66.75; H, 7.86; N, 12.08.
13: N-(3,5,5-Tr im eth ylcycloh ex-2-en yl)cycloh exyla m in e:
IR(neat) 1200, 1670, 3020, 3400 cm-1 1H NMR (300 MHz,
;
CDCl3) δ 0.96 (3H, s), 1.02 (3H, s), 1.02-1.85 (10H, m), 1.85 (3H,
broad s), 1.90-2.33 (4H, m), 3.65-3.75 (1H, m), 3.84-3.90 (1H,
m), 5.34 (1H, broad); 13C NMR (75 MHz, CDCl3) δ 25.0 (CH2),
25.1 (CH3), 25.1 (CH2), 25.3 (CH2), 25.4 (CH2), 28.1 (CH3), 28.4
(CH3), 30.4 (CH2), 32.5 (C), 40.9 (CH), 44.6 (CH2), 45.2 (CH2),
62.5 (CH), 115.7 (CH), 134.0 (C). Anal. Calcd for C15H27N: C,
81.38; H, 12.29; N, 6.33. Found: C, 81.52; H, 12.60; N, 6.53.
14: N-(3,5,5-Tr im eth ylcycloh ex-2-en yl)a n ilin e: IR(neat)
1360, 1670, 3020, 3400 cm-1; 1H NMR (300 MHz, CDCl3) δ 0.88
(3H, s), 0.99 (3H, s), 1.58-1.88 (4H, m), 1.67 (3H, s), 4.1 (1H,
Ack n ow led gm en t. We are pleased to acknowledge
the financial support from CSIR, New Delhi (Grant No.
01(1364)/95) for this investigaton. A.M. and A.S are
thankful to CSIR for their fellowships.
J O971117H