The interaction of linear and cyclic olefins of various structure with CH2N 2 under the ... of which is taken as unity) and the unsaturated compound (UC) being ...
REACTION OF DIAZOALKANES WITH UNSATURATED COMPOUNDS. 11.* R E L A T I V E R E A C T I V I T Y CYCLOPROPANATION
OF OLEFINS ON CATALYTIC
WITH DIAZOMETHANE
AND PALLADI-
UM CATALYSTS UDC 542.97:547.512:547,313: 547.235.421
U. M. Dzhemilev, V. A. Dokichev, S. Z. Sultanov, S. L. Khursan, O. M. Nefedov, Yu. V. Tomilov, and A. B. Kostitsyn
The relative reactivity of unsaturated compounds on catalytic cyclopropanation with diazomethane in thepresence of catalysts based on Pd2+ [Pd(OAc) e, Pd(acac) 2, (PPh3)2"PdCIz] has been studied using competing reactions. An interconnection was shown between the relative reactivity of the olefins and the coordinating activity of the C--C bond depending on its strain and spatial environment. Keywords- unsaturated compounds, cyclopropanes, metal-complex catalysis, diazomethane, relative reactivity. The [1 + 2] cycloaddition of methylene generated from diazomethane to olefins in the presence of Cu, Pd, and Rh complexes is one of the efficient methods of synthesizing cyclopropanes of various structures [2-6]. Unlike other catalysts, the Pd catalysts facilitate the cyclopropanation ofmono-, di-, and triolefins, including those containing functional substituents, with high efficiency and regioselectivity [5-7]. However, there are almost no quantitative literature data on the relative reactivity of unsaturated compounds during cyclopropanation. The interaction of linear and cyclic olefins of various structure with CH2N 2 under the action of Pd compounds has been investigated in order to establish the rules linking olefin structure with cyclopropanation rate. Cyclopropanation was carried out at +5°C by adding an ether solution of CH2N 2 to a mixture of olefins containing norbornene (1) (the reactivity of which is taken as unity) and the unsaturated compound (UC) being investigated at molar ratios of (1):UC:CH 2N2:Pd = 3:3:1:0.01. In view of the large difference in the extent of cyclopropanation of some double bonds, assessment of their relative reactivity was also carried out using pairs of UC of the same type. Due to their close reactivity this enabled the conversion of both UC to the corresponding cyclopropanes to be increased without changing significantly the relative concentration of the UC in the reaction mixture. A more precise analysis of the resulting cyclopropane adducts was therefore possible. + >"--< (U 1 :
(z - f,r) 7
EPdJ (tq)
(z, 15-z~)
The norbornene derivatives (2-7), allyl alcohol (8), styrene (9), methyl methacrylate (10), 2,3-dimethylbutadiene (11), 1-n-alkenes of composition C6-C12 (12a-g), and cyclohexene (13) were selected for investigation.
*For previous communication, see [ 1]. Institute of Organic Chemistry, Urals Branch, Russian Academy of Sciences, 450054 Ufa; N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. I0, pp. 2353-2361, October, 1992. Original article submitted September 10, 1991; revision submitted April 10, 1992.
1846
1063-5211/92/4110-1846 $12.50 ©1993 Plenum Publishing Corporation
4~ .,q
He
(z)
(4)
(17)
(16)
(3)
Me
(is)
(2)
(s)
(14)
Reaction product
(1)
compound
Unsaturated
by the MNDO Method [t0]
m
0.88
1.05
2.50
2.25
Pd(OAc) 2
0.87
1.33
1.68
3.00
Pd(acac)2
0.86
1.12
1,86
3.80
(Ph3P)2PdCI 2
krel (UCII)
31.I a
3 4 . 7 [91 35.6 a
64.6 a
52.8 [81
65.4 a
2 3 . 2 [81 2 7 . 2 [91 26.0 a
mole
kcal/
Estr
w
23.4
62.6
66,2
66.0
25.3
aH°
~
1.352
1.358
1.356
1.360
11.357
r r(c-O
-0,101
-0.103
-0.097
-0.104
-0.103
ql
-0.104!
-0.103
-0.097
-0.104
-0.103
q2
9.65
9.47 9.81
9.60
9.64
9.65
IPcalc MO type
1141
8.69 9.55 [131
835 1151
8.90
8.97 [131
MO type
IPexp
TABLE 1. Relative Rate (Constants (kre0 for the Cyclopropanation of Unsaturated Compounds (UC) with Diazomethane in the Presence of Pd Compounds (norbornene: UDC:CH2N2:Pd = 3:3:1:0.01, 5°C), Heats of formation (AH °, kcal.mole), Bond Lengths (r, A), Charge Distribution on the sp 2 Hybridized Carbon Atoms (q, electron units), and Ionization Potentials (IP, eV) of the UC Calculated
(2o)
(Zl)
(8)
(9)
(10)
(19)
(7)
(22)
[ ~ °x.~
(18)
Reaction product
(6)
Jnsaturated compound
TABLE 1 (continued)
3.18 c
D,18
D.20b
0.22 c
0.24
0,21
0.10
).26c 0.26
0.24
0.82
0.73
3.55
~.08 b
[Ph3P)2PdCI 2
?d(acac)2
Pd(OAc)2
~rel (UC/1)
L6 a
10.48
.0.76 (rtc =c)
8.84 (rt) 9.42 (/t)
}.61
~8.6 a
mole
IPcalc ~0 type
kcal /
Estr
IPexp
~o.28 [16]
10.55 ( ~ c = c )
8.50 (~) 9.30 (~) [16]
8.80
MO type
4~
OO
(26)
~0.001
~0.001
0.0120.015
(2$a-g)
0.010.012
0.08
0.02
(PhsP)2PdCI2
Estr kcal/
C3-Methoxycarbonyl-3-methyl-l-pyrazoline (23) was formed in addition to the cyclopropane adduct (22). The ratio (,f (22):(23) in the presence of Pd(acac)2. dCalculated for l-hexene.
"t=3-9
(24)
Pd(acae)~
Pd(OAc)2
krel (uc/l)
[191.
(13)
(lla-g)
Reaction product
aCalculated from tile formula E = AH ° - - E, where E is the heat of formation calculated by adding thermochemical increments bCatalyst was (PhCN)2PdC12.
n=3-9
(11)
Unsaturated compound
TABLE 1 (continued)
As was to be expected, the greatest reactivity was possessed by the polycyclic hydrocarbons containing a bicyclo[2.2.1 lheptene residue (see Table 1). An increase in the strain energy of the polycyclic structure containing a double bond leads to an increase of reactivity (hydrocarbons 2-4). On the other hand, the introduction of substituents, particularly laterally to the double bond (hydrocarbons 5-7"), leads to reduction of reactivity compared to 1. However, unlike other UC [5, 6], even the trisubstituted double bond in 7 is fairly successfully cycloprotonated by diazomethane under the action of Pd catalysts. Further, the reaction of CH2N2 with a mixture of the isomeric tetracyclic olefins 7 and 27 in the presence of Pd(acac)2 leads mainly to cyclopropanation of the trisubstituted norbornene bond in 7 and not of the disubstituted double bond in 27. Pd(acac)2 ~
+ ~
+ CH2N z
Me
(z) 2
(~g/,~ez %
(ez] :
!
:
k2. In the other case when the concentration of CH2N 2 in the reaction mixture is comparable to the UC concentration, a significantly higher extent of conversion of CH2N2 into ethylene and consequently a significant reduction in the yield of cyctopropane adducts might be expected. The introduction of electron-accepting substituents at the double bond probably reduces the rate ofdenitrogenation ofCH2N 2 to a large extent when reacting it with the r-olefin complex of palladium. A 1,3-dipolar cycloaddition of CH2N2 to the activated double bond becomes the competing reaction. From the results of the investigations carried out it has been established that the reactivity of unsaturated compounds of various swacture on cyclopropanation with diazomethane in the presence of Pd compounds is determined mainly by the coordination activity of the C ~ C double bond. This is characterized by the bond strain and the accessibility of the 7r orbitats toward complex formation with the central atom of the catalyst. EXPERIMENTAL
Analysis of the reaction mixture was carried out by GLC on a Tsvet-560 chromatograph using the SAA-06 automated analysis system in the integration mode. Columns were 120 x 0.3 cm of 5% SE-30 on Chromaton N-AW-HMDS and 370 x 0.3 cm of 15% PEG-6000 on Chromaton N-AW-HMDS, the carrier gas being helium. PMR spectra were obtained on a Bruker WM-250 (250 MHz) spectrometer for solutions in CDCI3. Quantum chemical calculations were carried out for compounds 1-13 with complete optimization of the geometry by the MNDO method [10]. The ether solution of diazomethane was obtained in - 60% yield (titration) by the hydrolysis of N-nitroso-N-methylurea. Freshly distilled unsaturated compounds of purity -99.7% were used in reactions. The cyclopropanes obtained were identified by comparing their characteristics with literature data [5, 6, 17, 18]. Endo-8-methylpentacycto[4.4.0.02,4.03,7,08, I°]decane (19) was synthesized by the reaction of 8-methyltetracyclo[4.4.0.02,a.03,7]non-8-ene (7) with a threefold molar excess of CH,N, in the presence of Pd(acac)2. It was isolated by vacuum distillation and had bp 103-104°C (80 ram). PMR spectra (CDCI~, 6, ppm): 2.07 n.m (H1), 1.92 t (J - 2 Hz, H7), 1.40 n.m (HS), 1.37 m (H6), 1.23 s (CH3), 1.28 m, 1.19 m, 1.08 m (H 2, H3, H4), 0.77 br.d.d (Jcis = 7.6, Jtrans = 3.3 Hz, Hi0), 0.64 d.d (Jtrans = 3.3, Jgem = 5.4 Hz, Hsyn9), -0.06 d.d (Hamig). ~3C NMR spectrum (CDC13, 6, ppm): 48.0 (CH), 44.2 (CH), 32.7 (CH), 31.3 (CH~), 24.5 (CH), 23.5 (C), 19.8 (CH), 18.3 (cn), 17.2 (CH), 16.8 (CH), 12.3 (CH2). Competing Reactions of Diazomethane with Norbornene and the Unsaturated Compounds. A solution of CHzN 2 (5.3 mmoles) in diethyl ether (12 ml) was added with stirring during t rain to a solution of norbornene (t6 mmoles), the unsaturated compound (t6 mmoles), and Pd catalyst (0.053 mmole) in CH2C12 (10 ml) at 5°C (molar ratio I:UC:CH~N~:Pd = 3:3:t:0.01 ). The end of the reaction was checked by taking three test samples (5-rain intervals) and analyzing by GLC. Experiments were carried out analogously with pairs of UC close in reactivity but in this case 3-6 times more CH2N 2 was added. The relative reactivity of the UC was calculated from the formula kreI = S 1/S°.a.b, where SO is the area of the peak bekmging to the produc~ of norbornene cyclopropanation, viz., exo-tricyclo[3.2.1.02,4]octane (14), S t is the area of the peak of the cyclopropanation product of the UC, a is the number of double bonds in the molecule, and b is a calibration constant. REFERENCES
1. 2. 3,
Yu. V. Tomilov, E. V. Shulishov, and O. M. Nefedov, Izv. A~ad. Nauk SSSR, Set'. Khim., No. 5, 1057 (t991). G. Maas, Top. Curt'. Chem., 137, 75 (1987). O.M. Nefedov, A. I. loffe, and L. G. Menchikov, Carbene Chemistry [in Russian[, Khimiya, Moscow (t990), p. 158.
185I
4. 5. 6. 7. 8. 9. 10. 11. 12. t3. 14. 15. t6. 17. 18. 19.
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