Investigation of electronic effects of Rh(II)-mediated α-methyl- substituted carbenoid intramolecular C-H insertion

Full text of DOI:10.1021/jo981279t

J . Org. Chem. 1998, 63, 8589-8594
8589
Sch em e 1
In vestiga tion of Electr on ic Effects of
Rh (II)-Med ia ted r-Meth yl-Su bstitu ted
Ca r ben oid In tr a m olecu la r C-H In ser tion
J ianbo Wang,* Fengting Liang, and Bei Chen
Department of Chemistry, Peking University,
Beijing 100871, People’s Republic of China
Received J une 30, 1998
The electronic effects of Rh(II)-mediated carbenoid
intramolecular C-H insertion have been intensively
investigated. The chemo-, regio-, and stereoselectivity
of the reaction have been observed to be affected by the
electrophilicity of the carbene-Rh intermediate, the
substituents on the carbon at which the C-H insertion
occurs, and steric and conformational factors.1 It has
been well documented that the electronic properties of
the ligands of the Rh(II) catalyst have a marked influence
over the electrophilicity of carbene-Rh intermediate.1c,e,2
In addition, the R-substituent on the carbenoid carbon
is expected to exert a similar effect on the reactivity of
carbene-Rh complex.2c,3 According to the reaction mech-
anism proposed by Doyle, an electron-donating R-sub-
stituent decreases the electrophilicity of the carbene-
Rh complex and causes the C-H insertion to occur with
a later transition state, while an electron-withdrawing
R-substituent operates in the opposite way.1c However,
this prediction lacks solid support by experimental data.
The R-substituent effect, although important, is generally
subtle and may be readily overridden by other effects,
such as steric and conformational effects.3b Most of the
studies on the electronic effects have so far been concen-
trated on electron-withdrawing R-substituents, such as
ester or acetyl groups. We have recently reported a linear
free energy correlation study of the carbenoid C-H
insertion.4 In the study, the electronic effects are evalu-
ated under the condition where possible steric and
conformational interference is minimized through the
measurement of the relative reactivity of the carbenoid
insertion into a series of para-substituted benzylic C-H
bonds. We envisaged that the same approach could be
employed to address the problem of R-substituent effects.
We report in this paper the study on the Hammett
correlation of the R-methyl-substituted carbenoid C-H
insertion.
in this study (Scheme 1). By assuming that kA is
constant through the series of insertion reactions, the
relative reactivity of the para-substituted benzylic C-H
to nonsubstituted benzylic C-H, kX/ kA, is obtained by
the ratio 4/3.
kX/kA [4/3]X
kX/kH
)
)
kH/kA
[4/3]H
The syntheses of diazo compounds 1a -e is outlined in
Scheme 2. Acid 54 was converted into the corresponding
acyl chloride, followed by treatment with diazoethane to
give 1a . To synthesize 1b,d ,e, acid 5 was first converted
to its corresponding methyl ester, which was further
subjected to reduction to give the corresponding amino
compound 6. To prepare 1b, 6 was subjected to a
Sandmeyer reaction5 to yield the 4-chloro compound 7,
followed by hydrolysis, acylation, and diazoethane treat-
ment to give 1b. 1d was prepared by phenylation6 of 6
to give the 4-phenyl compound 8, followed by the same
procedure as that used for the preparation of 1a . To
prepare 1e, 6 was first hydroxylated,7 followed by me-
thylation to yield 9. Further hydrolysis and diazo
transfer gave 1e. 1c was synthesized in a different way.
Diethyl propylmalonate 10 was alkylated with 2-phenyl-
ethyl bromide, followed by hydrolysis, acidification, and
decarboxylation to give acid 11. Acylation and diazo
transfer gave 1c (Scheme 3).
Rh(II)-mediated C-H insertion reactions were con-
ducted at room temperature under standard conditions
as previously reported.4 The remaining catalyst was
removed by a short column of silica gel, and the crude
reaction mixture was carefully analyzed by 1H NMR (400
MHz) and GC-MS.
It was intended that the Hammett approach be applied
to the model compounds 1a -e with three typical Rh(II)
catalysts, rhodium(II) acetate, rhodium(II) trifluoro-
acetate, and rhodium(II) acetamide. However, we found
the diazo decomposition of 1a with Rh2(OAc)4 or Rh2-
(acam)4 did not give the expected C-H insertion products
3a and 4a ; an unstable yellow compound was instead
isolated as the main product (Scheme 4). The structure
Diazo compounds 1a -e, in which the R-substituent is
a methyl group rather than an ester group, are employed
(1) (a) Taber, D. F.; Ruckle, R. E., J r. J . Am. Chem. Soc. 1986, 108,
7686. (b) Stork, G.; Nakatani, K.Tetrahedron Lett. 1988, 29, 2283. (c)
Doyle, M. P.; Westrum, L. J .; Wolthuis, W. N. E.; See, M. M.; Boone,
W. P.; Bagheri, V.; Pearson, M. M. J . Am. Chem. Soc. 1993, 115, 958.
(d) Wang, P.; Adams, J . J . Am. Chem. Soc. 1994, 116, 3296. (e) Pirrung,
M. C.; Morehead, A. T., J r. J . Am. Chem. Soc. 1994, 116, 8991.
(2) (a) Padwa, A.; Austin, D. J .; Hornbuckle, S. F.; Semones, M. A.;
Doyle, M. P.; Protopopova, M. N. J . Am. Chem. Soc. 1992, 114, 1874.
(b) Padwa, A.; Austin, D. J .; Price, A. T.; Semones, M. A.; Doyle, M.
P.; Protopopova, M. N.; Winchester, W. R.; Tran, A. J . Am. Chem. Soc.
1993, 115, 8669. (c) Wee, A. G. H.; Yu, Q. J . Org. Chem. 1997, 62,
3324. (d) Padwa, A.; Austin, D. J .; Hornbuckle, S. F. J . Org. Chem.
1996, 61, 63. (e) Doyle, M. P.; Dyatkin, A. B. J . Org. Chem. 1995, 60,
3035.
(5) Marvel, C. S.; McElvain, S. M. Organic Syntheses; Wiley: New
York, 1941; Vol. I, p 170.
(6) Cadogan, L. I. G. J . Chem. Soc. 1962, 4257.
(7) Icke, R. N.; Redemann, C. E.; Wisegarver, B. B.; Alles, G. A.
Organic Syntheses; Wiley: New York, 1955; Vol. III, p 564.
(3) (a) Doyle, M. P.; Bagheri, V.; Pearson, M. M.; Edwards, J . D.
Tetrahedron Lett. 1989, 30, 7001. (b) Wee, A. G. H.; Liu, B.; Zhang, L.
J . Org. Chem. 1992, 57, 4404.
(4) Wang, J .; Chen, B.; Bao, J . J . Org. Chem. 1998, 63, 1853.
10.1021/jo981279t CCC: $15.00 © 1998 American Chemical Society
Published on Web 10/27/1998

8590 J . Org. Chem., Vol. 63, No. 23, 1998
Notes
Sch em e 2
Sch em e 4
Ta ble 1. Rh 2(O2CCF 3)4-Ca ta lyzed Rea ction of Dia zo
Com p ou n d s 1a -ea
yield
(%, 3 + 4)
X
4/3b
kX/kH
1a
1b
1c
1d
1e
NO2
Cl
H
Ph
OMe
83
73
84
82
59
<5:95
23.2:76.8
35.6:64.4
38.9:61.1
54.3:45.7
0.55
1.00
1.15
2.13
a
b
All reactions were run at room temperature in CH2Cl2. The
relative yields for 4b-e and 3b-e were determined by GC-MS
analysis, and an average was taken from two runs in each case.
Average standard deviation is 0.5%.
1H NMR of the crude reaction mixture indicates that the
3a /4a ratio is greater than 95:5. Diazo decomposition of
1b-e with Rh2(O2CCF3)4 gave C-H insertion products
3b-e and 4b-e as main products.
In contrast to the intramolecular C-H insertions by
metal carbenes with R-carboxylate ester substituents in
which the reactions show high stereoselectivity,1a,4 3a -e
and 4b-e in this study were obtained as a mixture of
distereoisomers. Since the insertion products were not
separable by column chromatography, structure identi-
fication was first provided by inspection of the1H NMR
(400 MHz) spectra of the reaction mixture. For benzylic
secondary C-H insertion products, the chemical shift of
the 3-H in the five-membered ring of 4b-e is character-
istically located in the range between 3.40 and 3.60 ppm,
while for the corresponding 3-H of aliphatic secondary
insertion products 3a -e, the chemical shifts are below
3.0 ppm.9 The structure for each isomer was further
established by GC-MS analysis. The mixtures of 3a -e
and 4b-e were separable by gas chromatography, and
the mass spectrum for each isomer was thus obtained
by GC-MS. The characteristic McLafferty rearrange-
ment10 gave different fragment ions for 3a -e and 4b-e,
thus unambiguously establishing the structure for each
insertion product. The product ratio was determined by
GC-MS.11 The 3/4 ratios and the relative rate constants,
kX/ kH, are collected in Table 1.
Sch em e 3
The relative rates are then fitted to the Hammett
equation with both σ and σ+.12 Better linear correlation
is found with σ than with σ+, giving reaction constants
of -1.18 (with σ, r ) 0.99) and -0.58 (with σ+, r ) 0.93),
of this compound was assigned as azine 12 by inspection
of the spectra data. Similar results have been obtained
with other diazo compounds 1b-e. The formation of
azine in the Rh(II)-mediated decomposition of R-methyl-
substituted diazocarbonyl compounds has been previ-
ously reported by Taber.8 On the other hand, when the
reaction was catalyzed by Rh2(O2CCF3)4, the expected
C-H insertion products were isolated as major products.
(9) Similarly, we found in our previous study that, in the diazo
decomposition of R-ester diazo compounds, the chemical shift for the
corresponding 3-H in the benzylic secondary C-H insertion products
locates considerably downfield in the range between 3.60 and 3.90 ppm,
while for the corresponding 3-H in the aliphatic secondary C-H
insertion products, the chemical shifts are below 3.0 ppm; see ref 4.
(10) (a) He, X.; Chen, B.; Wang, J .; He, M. Rapid. Commun. Mass
Spectrom. 1997, 11, 1818. (b) Chen, B.; Liang, F.; Chen, H.; Wang, J .
J . Chem. Res., Synop. 1998, 410.
(11) The product ratio was also analyzed by 1H NMR (400 MHz) of
the reaction mixture in each case, and the results obtained were
comparable to those from GC-MS.
(8) Taber, D. F.; Hennessy, M. J .; Louey, J . P. J . Org. Chem. 1992,
57, 436.
(12) Hansch, C.; Leo, A.; Taft, R. W. Chem. Rev. 1991, 91, 165.

Notes
J . Org. Chem., Vol. 63, No. 23, 1998 8591
compared to the Rh2(O2CCF3)4-catalyzed reaction with
diazo â-ketoester.
In conclusion, the R-substituent effects of the intra-
molecular C-H insertion by Rh(II)-mediated carbenoids
have been investigated through linear free energy cor-
relation analysis. The study has confirmed that electron
donation from the R-methyl group decreases the electro-
philicity of the carbene-Rh complex and leads to the
increase of its selectivity.
Exp er im en ta l Section
Gen er a l. For the details of the general procedure, see our
previous report.4 1H NMR (200 MHz) and 13C NMR (50 MHz)
spectra were recorded with a Varian Mercury 200 spectrometer.
Diazoethane was prepared from N-ethyl-N-nitrosourea according
to a literature procedure.15 GC-MS analysis was performed
with an HP 5971A-5890II GC-MSD. Elemental analyses were
performed at the Institute of Chemistry, Chinese Academy of
Sciences.
F igu r e 1. Plot of log kX/ kH against σ for the C-H insertions
2-Dia zo-6-(4-n itr op h en yl)-4-p r op yl-3-h exa n on e (1a ). To
a solution of 4-(4-nitrophenyl)-2-propylbutanoic acid 5 (200 mg,
0.8 mmol) in anhydrous hexane was added oxalyl chloride (0.7
mL, 8.0 mmol), and the solution was heated under gentle reflux
for 1.5 h. The solvent and excess oxalyl chloride were removed
by distillation, and the residue was kept in vacuo for 1 h. The
acyl chloride was then dissolved in anhydrous hexane (5 mL)
and was added dropwise to a solution of diazoethane (8.0 mmol)
in Et2O (50 mL) at -10 °C. The solution was stirred at 0 °C for
1 h and at room temperature overnight. The solvent and excess
diazoethane were removed under reduced pressure. The residue
was subjected to column chromatography with 15:1 petroleum
ether/EtOAc to give a yellow oil, 1a (120 mg, 52%): Rf ) 0.41
(petroleum ether/EtOAc ) 4:1); 1H NMR (400 Hz) δ 0.80 (t, J )
7.0 Hz, 3H), 1.15-1.40 (m, 4H), 1.50-1.78 (m, 2H), 1.86-2.10
(m, 1H), 1.90 (s, 3H), 2.50-2.72 (m, 2H), 7.24 (d, J ) 8.7 Hz,
2H), 8.06 (d, J ) 8.7 Hz, 2H); 13C NMR (50 MHz) δ 7.89, 13.70,
20.04, 33.02, 33.18, 34.95, 45.18, 62.79, 123.29, 128.73, 146.07,
149.25, 197.01; IR 2905, 2050, 1610, 1505, 1330, 1275 cm-1; MS
(m/z, relative intensity) 261 [(M - N2)+, 18], 218 (58), 144 (20),
122 (22), 111 (64); HRMS (M - N2)+ calcd for C15H19NO3
261.1365, found 261.1370.
of an Rh2(O2CCF3)4-catalyzed reaction.
respectively (Figure 1).13 The relatively small and nega-
tive value of the reaction constant suggests that the C-H
insertion proceeds through a transition state with a small
positive charge buildup at the carbon where the insertion
occurs. In our previous study, Rh2(O2CCF3)4-catalyzed
C-H insertion with diazo â-ketoester gives a reaction
constant of -0.66 with σ.4 The numerical difference of
the F values is marked, and the larger value of the
reaction constant obtained in the C-H insertion with
R-methyl-substituted substrates 1b-e suggests that the
carbene-Rh intermediate in this case is less reactive
toward the C-H bond, thus giving higher sensitivity to
the substituent effect. In other words, the partial positive
charge at the benzylic carbon is more developed, and the
C-H insertion occurs at a relatively later transition state
compared to the Rh2(O2CCF3)4-catalyzed C-H insertion
with diazo â-ketoester (Hammond postulate). This is
consistent with the prediction based on Doyle’s model.1c
The formation of azine as a major product in the Rh2-
(OAc)4- or Rh2(acam)4-catalyzed reaction might be related
to the decrease of electrophilicity of the carbene-Rh
complex. Since both the electron-donating R-substituent
and the electron-releasing ligand from Rh can decrease
the electrophilicity of the carbene-Rh complex, the
reactivity of the carbene-Rh complex formed from 1a -e
and Rh2(OAc)4 or Rh2(acam)4, whose ligands are rela-
tively less electron withdrawing compared to Rh2(O2-
CCF3)4, is so decreased that C-H insertion cannot
compete with the other reaction pathway.14 In contrast,
for the Rh2(O2CCF3)4-catalyzed reaction, the decease of
the Rh(II)-carbene reactivity due to R-methyl substitu-
tion is counterbalanced by the strong electron-withdraw-
ing ligand. As a result, the C-H insertion in this case
can occur, but as shown by the reaction constant, the
reaction proceeds with a relatively later transition state
2-Dia zo-6-(4-ch lor op h en yl)-4-p r op yl-3-h exa n on e (1b ).
Acid 5 was first converted to its corresponding methyl ester by
treatment with an ethereal solution of diazomethane. Methyl
4-(4-nitrophenyl)-2-propylbutanoate: Rf ) 0.47 (petroleum ether/
EtOAc ) 7:1); 1H NMR (200 MHz) δ 0.89 (t, J ) 7.2 Hz, 3H),
1.21-2.10 (m, 6H), 2.36-2.48 (m, 1H), 2.62-2.76 (m, 2H), 3.70
(s, 3H), 7.33 (d, J ) 8.5 Hz, 2H), 8.14 (d, J ) 8.5 Hz, 2H); 13C
NMR (50 MHz) δ 14.43, 21.00, 33.94, 34.15, 35.15, 45.29, 52.03,
124.10, 129.64, 147.00, 150.10, 176.74; IR 2925, 1720, 1590,
1505, 1330 cm-1
.
The methyl ester (8.83 g, 33 mmol) was dissolved in 80%
EtOH/H2O (120 mL), followed by addition of 20 drops of
concentrated aqueous HCl and ion powder (18.6 g, 330 mmol).
The mixture was heated under reflux for 1 h while being stirred
with a mechanical stirrer. After completion of the reduction,
the black powder in the reaction mixture was removed by
filtration. EtOH was then removed in vacuo. The residue was
extracted with Et2O (3 × 50 mL), and the combined ethereal
solution was washed with H2O and dried over anhydrous MgSO4.
Removal of the solvent gave an oil of methyl 4-(4-aminophenyl)-
2-propylbutanoate, 6 (6.53 g, 83%). 6 was used in the next step
without further purification: Rf ) 0.43 (petroleum ether/EtOAc
) 2:1); 1H NMR (200 MHz) δ 0.87 (t, J ) 7.2 Hz, 3H), 1.20-
2.00 (m, 6H), 2.30-2.52 (m, 3H), 3.50 (s, br. 1H), 3.66 (s, 3H),
6.60 (d, J ) 8.4 Hz, 2H), 6.94 (d, J ) 8.4 Hz, 2H); 13C NMR (50
MHz) δ 14.50, 21.09, 33.35, 34.97, 35.15, 45.41, 51.85, 115.75,
129.67, 132.18, 144.90, 177.33; IR 3450, 3380, 2940, 1720, 1625,
1515, 1275, 1160 cm-1; MS (m/z, relative intensity) 235 (M+, 19),
204 (3), 119 (42), 106 (100); HRMS calcd for C14H21O2N 235.1572,
found 235.1576.
(13) The nitro group was not included in the Hammett analysis,
since the accurate value of the product ratio could not be obtained. If
we introduce in the Hammett plot the roughly estimated 4/3 ratio of
2.2:97.8 from 1H NMR analysis of the reaction mixture, we can get a
F value of -1.66 with σ (r ) 0.99).
(14) The mechanism for the azine formation in this case is not clear.
Eguchi has also reported an example in which Rh2(acam)4 more
effectively promotes azine formation compared with Rh2(O2CCF3)4 in
Rh(II)-catalyzed diazo decomposition; see: Ohno, M.; Itoh, M.; Umeda,
M.; Furuta, R.; Kondo, K.; Eguchi, S. J . Am. Chem. Soc. 1996, 118,
7075.
(15) Wilds, A. L.; Meader, A. L., J r. J . Org. Chem. 1948, 13, 763.

8592 J . Org. Chem., Vol. 63, No. 23, 1998
Notes
To 6 (2.7 g, 11.5 mmol) were added H2O (20 mL) and
concentrated HCl (2.7 mL, 33 mmol). The mixture was warmed
for 10 min until it became a homogeneous solution. A TLC check
of the mixture indicated that all free amine had been changed
to its salt. The solution was then cooled to 0 °C with an ice
bath, and a solution of NaNO2 (1.18 g, 17.2 mmol) was added
dropwise with stirring. The solution was further stirred between
0 and 5 °C for 1 h, and then urea (0.34 g, 5.7 mmol) was added
to remove excess NaNO2. The mixture was added dropwise to
CuCl [freshly prepared from CuSO4‚5H2O (8.56 g, 34.5 mmol)]
at 0 °C with stirring. The mixture was allowed to warm to room
temperature. After being stirred at room temperature for 1 h,
the mixture was heated between 50 and 60 °C for 45 min. After
cooling, the mixture was extracted with Et2O (3 × 150 mL). The
combined ethereal solution was washed with 5% aqueous NaOH,
H2O, concentrated H2SO4, and H2O and finally dried over
anhydrous MgSO4. Removal of the solvent gave a crude product
(2.2 g), which was subjected to column chromatography, eluting
with 25:1 petroleum ether/EtOAc to give methyl 2-(4-chlorophe-
nyl)-2-propylbutanoate, 7 (1.7 g, 58%): Rf ) 0.54 (petroleum
ether/EtOAc ) 10:1); 1H NMR (200 MHz) δ 0.88 (t, J ) 7.1 Hz,
3H), 1.20-2.05 (m, 6H), 2.34-2.65 (m, 3H), 3.68 (s, 3H), 7.09
(d, J ) 8.2 Hz, 2H), 7.24 (d, J ) 8.2 Hz, 2H); 13C NMR (50 MHz)
δ 13.61, 20.18, 32.73, 33.59, 34.29, 44.47, 51.07, 128.08, 129.39,
131.27, 139.74, 176.15; IR 2955, 1725, 1485, 1450, 1200, 1160
cm-1; MS (m/z, relative intensity) 254 (M+, 6), 138 (11), 125 (30),
116 (81), 87 (100); HRMS calcd for C14H19ClO2 254.1074, found
254.1066.
Methyl ester 7 (1.96 g, 7.7 mmol) was dissolved in MeOH (40
mL), to which was added aqueous NaOH (770 mg, 19 mmol).
The mixture was refluxed for 6 h. MeOH was removed, and
the usual workup gave 4-(4-chlorophenyl)-2-propylbutanoic acid
as an oily product (1.24, 67%): 1H NMR (200 MHz) δ 0.90 (t, J
) 7.0 Hz, 3H), 1.24-2.08 (m, 6H), 2.32-2.79 (m, 3 H), 7.01 (d,
J ) 8.4 Hz, 2H), 7.23 (d, J ) 8.4, 2H); 13C NMR (50 MHz) δ
14.56, 21.05, 33.56, 34.22, 34.92, 45.29, 129.08, 130.39, 132.00,
140.56, 183.38; IR 3000 (br), 1700, 1450, 1240 cm-1. The acid
was used in the next step without further purification.
The same procedure was followed as for the preparation of
1a , and the acid (1.22 g, 5.08 mmol) was converted to diazo
compound 1b (440 mg, 31%): Rf ) 0.50 (petroleum ether/EtOAc
) 6:1); 1H NMR (400 MHz) δ 0.86 (t, J ) 7.2 Hz, 3H), 1.22-
1.34 (m, 2H), 1.38-1.42 (m, 1H), 1.62-1.73 (m, 2H), 1.95 (s, 3H),
1.93-2.06 (m, 1H), 2.44-2.51 (m, 1H), 2.54-2.67 (m, 2H), 7.07
(d, J ) 8.4 Hz, 2H), 7.23 (d, J ) 8.4 Hz, 2H); 13C NMR (100
MHz) δ 8.29, 14.07, 20.45, 32.95, 33.87, 35.30, 45.51, 63.06,
128.45, 129.60, 131.65, 140.07, 197.85; IR 2920, 2060, 1620,
1450, 1280 cm-1; MS (m/z, relative intensity) 250 [(M - N2)+,
8], 235 (3), 207 (12), 152 (11), 140 (20), 125 (100); HRMS (M -
N2)+ calcd for C15H19OCl 250.1124, found 250.1119.
(d, J ) 8.2 Hz, 2H), 7.30-7.37 (m, 1H), 7.40-7.47 (m, 2H), 7.51
(d, J ) 8.2 Hz, 2H), 7.58-7.61 (m, 2H); 13C NMR (100 MHz) δ
8.28, 14.13, 20.51, 33.23, 34.08, 35.31, 45.60, 63.16, 126.98,
127.04, 127.12, 128.72, 128.72, 138.90, 140.74, 141.03, 198.05;
IR 2915, 2055, 1620, 1445, 1280, 1040 cm-1; MS (m/z, relative
intensity) 292 [(M - N2)+, 35], 235 (11), 180 (89), 167 (100);
HRMS (M - N2)+ calcd for C21H24O 296.1776, found 296.1766.
2-Dia zo-6-(4-m eth oxyp h en yl)-4-p r op yl-3-h exa n on e (1e).
To amino compound 6 (1.24 g, 5.27 mmol) in H2O (20 mL) was
added aqueous H2SO4 (0.5 M, 36 mL), and the mixture was
warmed until it became homogeneous. A TLC check of the
mixture indicated that all of the free amine had been changed
to its salt. After the mixture cooled to 0 °C, a solution of NaNO2
(545 mg, 7.9 mmol) was added dropwise while the temperature
was maintained between 0 and 5 °C. The resulting solution was
stirred at 5 °C for another 1.5 h after the addition. Urea (158
mg, 2.6 mmol) was added to remove excess NaNO2. Aqueous
H2SO4 (0.5 M, 20 mL) was added dropwise, and the solution was
refluxed for 30 min. The mixture was cooled to room temper-
ature, and the usual workup gave methyl 4-(4-hydroxyphenyl)-
2-propylbutanoate as an oily product: Rf ) 0.34 (petroleum
1
ether/EtOAc ) 4:1); H NMR (200 MHz) δ 0.87 (t, J ) 7.1 Hz,
3H), 1.20-2.02 (m, 6H), 2.37-2.48 (m, 1H), 2.49 (t, J ) 7.4 Hz,
2H), 3.68 (s, 3H), 5.73 (s, 1H), 6.75 (d, J ) 8.2 Hz, 2H), 7.00 (d,
J ) 8.2 Hz, 2H); 13C NMR (50 MHz) 13.90, 20.51, 32.78, 34.27,
34.60, 44.93, 51.53, 115.18, 129.39, 133.47, 153.92, 177.33. IR
3400 (br), 2960, 1700, 1600, 1520, 1440, 1380, 1220 cm-1. The
hydroxyl compound was used in the next step without further
purification.
The hydroxyl compound was dissolved in DMF (20 mL). To
the solution was added NaH (15.8 mmol), and the mixture was
stirred at room temperature for 1 h. MeI (0.98 mL, 15.8 mmol)
was then added, and the solution was stirred overnight. Et2O
(150 mL) was added to the solution, and then H2O (150 mL)
and 5% aqueous HCl (4 mL) were added. The ethereal layer
was separated, washed with H2O twice, and then dried over
anhydrous MgSO4. Removal of the drying agent and solvent
gave a crude oil, which was purified with column chromatogra-
phy, eluting with 20:1 petroleum ether/EtOAc to give methyl
4-(4-methoxyphenyl)-2-propylbutanoate, 9, as oily product (998
1
mg, 76% from 6): Rf ) 0.56 (petroleum ether/EtOAc ) 8:1); H
NMR (200 Hz) δ 0.88 (t, J ) 7.0 Hz, 3H), 1.22-2.00 (m, 6H),
2.33-2.70 (m, 3H), 3.68 (s, 3H), 3.78 (s, 3H), 6.81 (d, J ) 8.4
Hz, 2H), 7.08 (d, J ) 8.4 Hz, 2H); 13C NMR (50 MHz) δ 13.63,
20.21, 32.46, 34.01, 34.30, 44.54, 51.01, 54.88, 113.41, 128.94,
133.41, 157.46, 176.37; MS (m/z, relative intensity) 250 (26), 219
(8), 134 (81), 121 (100); HRMS calcd for C15H22O3 250.1569, found
250.1586.
The methyl ester 9 (785 mg, 3.14 mmol) was hydrolyzed in
aqueous MeOH with NaOH to give 4-(4-methoxyphenyl)-2-
propylbutanoic acid (586 mg, 79%), which was converted to diazo
compound 1e (209 mg, 33%) by the same procedure as that used
for the preparation of 1a . 1e: Rf ) 0.43 (petroleum ether/EtOAc
) 6:1); 1H NMR (400 MHz) δ 0.86 (t, J ) 7.2 Hz, 3H), 1.22-
1.33 (m, 2H), 1.38-1.49 (m, 1H), 1.60-1.72 (m, 2H), 1.95 (s, 3H),
1.93-2.05 (m, 1H), 2.40-2.47 (m, 1H), 2.52-2.70 (m, 2H), 3.77
(s, 3H), 6.81 (d, J ) 8.4 Hz, 2H), 7.05 (d, J ) 8.4 Hz, 2H); 13C
NMR (100 MHz) δ 8.28, 14.12, 20.52, 32.66, 34.38, 35.25, 45.54,
55.26, 63.14, 113.79, 129.18, 133.67, 157.80, 198.19; IR 2920,
2055, 1620, 1500, 1445, 1240 cm-1; HRMS (m/z, relative
intensity) 246 (M+, 14), 134 (7), 121 (100); HRMS (M - N2)+
calcd for C16H22O2 246.1586, found 246.1603.
2-Dia zo-6-p h en yl-4-p r op yl-3-h exa n on e (1c). To absolute
EtOH (60 mL) was added sodium (3.4 g, 148 mmol). When the
formation of sodium ethoxide was complete, diethyl propyl-
malonate 10 (20 mL, 99 mmol) was added dropwise over 1.5 h.
A solution of (2-bromoethyl)benzene (37 g, 200 mmol) in 20 mL
of absolute EtOH was added dropwise. The mixture was stirred
for 20 h under reflux. EtOH was removed by distillation, and
ice water was added to the residue. The mixture was extracted
with Et2O (3 × 200 mL). The combined ethereal solution was
washed with H2O and dried over anhydrous MgSO4. Removal
of the drying agent and solvent gave a crude product, which was
distilled under vacuum to yield diethyl 2-propyl-(2-phenylethyl)-
malonate (6.3 g, 21%): bp 134-136 °C, 0.17 mmHg; 1H NMR
(200 MHz) 0.94 (t, J ) 7.0 Hz, 3H), 1.26 (t, J ) 7.2 Hz, 6H),
1.90-2.00 (m, 2H), 2.15-2.22 (m, 2H), 2.42-2.58 (m, 2H), 4.19
2-Dia zo-6-(4-p h en ylp h en yl)-4-p r op yl-3-h exa n on e (1d ). A
solution of amino compound 6 (2.23, 9.5 mmol) and n-pentyl-
nitrite (1.75 g, 15 mmol) in benzene (40 mL) was stirred for 20
min, until gas evolution had stopped. The solution was then
refluxed for 1.5 h. The solvent was removed in vacuo, and the
residue was subjected to column chromatography, eluting with
5:1 petroleum ether/EtOAc to give methyl 4-(4-phenylphenyl)-
2-propylbutanoate, 8, as a light-yellow oil (1.60 g, 57%): Rf )
0.52 (petroleum ether/EtOAc ) 10:1); 1H NMR (200 MHz) δ 0.89
(d, J ) 7.1 Hz, 3H), 1.20-2.10 (m, 6H), 2.33-2.71 (m, 3H), 3.68
(s, 3H), 7.15-7.64 (m, 9H); 13C NMR (50 MHz) δ 13.95, 20.54,
33.35, 34.04, 34.64, 44.97, 51.40, 126.96, 127.06, 128.37, 128.68,
128.79, 138.86, 140.80, 141.03, 176.63; IR 2960, 1730, 1460,
1200, 1161 cm-1
. The methyl ester (1.38 g, 4.66 mmol) was
hydrolyzed in aqueous MeOH with NaOH to give 4-(4-phen-
ylphenyl)-2-propylbutanoic acid (1.2 g, 91%): 1H NMR (200
MHz) δ 0.92 (t, J ) 7.0 Hz, 3H), 1.24-2.15 (m, 6H), 2.38-2.57
(m, 1H), 2.59-2.82 (m, 2H), 7.20-7.67 (m, 9H); 13C NMR (50
MHz) δ 13.98, 20.46, 33.23, 33.79, 34.34, 44.61, 125.95, 127.00,
127.12, 128.38, 128.70, 128.84, 140.67, 141.00, 181.34; IR 3000
(br), 1700, 1460, 1245 cm-1
.
The same procedure was followed as for the preparation of
1a , and the acid (1.1 g, 3.9 mmol) was converted to diazo
compound 1d (450 mg, 36%): Rf ) 0.42 (petroleum ether/EtOAc
) 6:1); 1H NMR (400 MHz) δ 0.87 (t, J ) 7.2 Hz, 3H), 1.23-
1.36 (m, 2H), 1.40-1.48 (m, 1H), 1.60-1.79 (m, 2H), 1.95 (s, 3H),
2.02-2.11 (m, 1H), 2.50-2.60 (m, 1H), 2.61-2.71 (m, 1H), 7.22

Notes
J . Org. Chem., Vol. 63, No. 23, 1998 8593
(q, J ) 7.2 Hz, 4H), 7.12-7.34 (m, 5H); 13C NMR (50 MHz) 14.69,
14.99, 18.03, 31.24, 34.97, 35.41, 58.13, 61.61, 126.55, 128.89,
128.95, 142.13, 172.22; IR 2995, 1725, 1460, 1370, 1200 (br),
1040 cm-1. The diester was then subjected to hydroxylation and
decarboxylation by the conventional method, as previously
reported, to provide 4-phenyl-2-propylbutanoic acid, 11 (3.2 g,
46%): 1H NMR (200 MHz) δ 0.90 (t, J ) 7.2 Hz, 3H), 0.79-1.10
(m, 1H), 1.20-2.19 (m, 6H), 2.28-2.80 (m, 2H), 7.02-7.56 (m,
5H); 13C NMR (50 MHz) δ 13.59, 20.43, 33.59, 33.76, 34.29, 44.79,
125.92, 128.35, 128.40, 141.52, 183.20; MS (m/z, relative inten-
sity) 206 (M+, 14), 105 (82), 91 (53), 73 (100); HRMS calcd for
C13H18O2 206.1307, found 206, 1307.
(d, J ) 8.4 Hz), 7.11 (d, J ) 8.4 Hz), 7.22 (d, J ) 8.4 Hz), 7.30
(d, J ) 8.4 Hz); IR 2960, 1730, 1490, 1460, 1160, 1090 cm-1
.
Anal. Calcd for C15H19ClO: C, 71.85; H, 7.64. Found: C, 72.18;
H, 7.62. GC-MS analysis of the mixture gave five peaks, which
were labeled as 3b-1, 3b-2, 3b-3, 4b-1, and 4b-2. The following
product ratios were obtained from GC-MS: 3b-1/3b-2/3b-3 )
62:11:27; 4b-1/4b-2 ) 65:35; (4b-1 + 4b-2)/(3b-1 + 3b-2 + 3b-
3) ) 23.2:76.8. MS (m/z, relative intensity) 3b-1: 250 (M+, 9),
127 (5), 112 [(M - p-ClC6H4CHdCH2)+, 100], 97 (15). 3b-2: 250
(M+, 12), 127 (6), 112 [(M - p-ClC6H4CHdCH2)+, 100], 97 (10).
3b-3: 250 (M+, 11), 127 (6), 112 [(M - p-ClC6H4CHdCH2)+, 100],
97 (17). 4b-1: 250 (M+, 14), 208 [(M - CH3CHdCH2)+, 100],
193 (6), 179 (8), 152 (16), 139 (8), 117 (20). 4b-2: 250 (M+, 20),
221 (5), 208 [(M - CH3CHdCH2)+, 100], 193 (4), 179 (8), 165
(3), 151 (20), 115 (20).
Rh (II)-Ca ta lyzed Din itr ogen Extr u sion of 2-Dia zo-6-
p h en yl-4-p r op yl-3-h exa n on e (1c). The diazo decomposition
of 1c with Rh2(O2CCF3)4 as a catalyst gave C-H insertion
products in 84% isolated yield. An 1H NMR spectrum of the
product indicated that it was a mixture of diastereomeric isomers
of aliphatic C-H insertion products 3c and benzylic C-H
insertion products 4c. The mixture was not separable by TLC
or column chromatography. The mixture gave the following
analytical data: 1H NMR (400 MHz): δ 0.68 (d, J ) 7.8 Hz),
0.85 (d, J ) 7.2 Hz), 0.92 (d, J ) 7.5 Hz), 0.96 (t, J ) 7.0 Hz),
1.00 (d, J ) 7.1 Hz), 1.01 (d, J ) 6.4 Hz), 1.06 (d, J ) 6.5 Hz),
1.13 (d, J ) 6.1 Hz), 1.14 (d, J ) 6 Hz), 1.22-1.75 (m), 1.82-
2.46 (m), 2.60-2.78 (m), 3.42-3.58 (m, 0.32 H, 4c), 7.15-7.35
(m, 5H); IR 2960, 1730, 1600, 1495, 1455, 1375, 1160 cm-1. Anal.
Calcd for C15H20O: C, 83.28; H, 9.32. Found: C, 82.99; H, 9.36.
GC-MS analysis of the mixture gave six peaks, which were
labeled as 3c-1, 3c-2, 3c-3, 4c-1, 4c-2 and 4c-3. The following
product ratios were obtained from GC-MS: 3c-1/3c-2/3c-3 )
53:11:36; 4c-1/4c-2/4c-3 ) 35:6:59; (4c-1 + 4c-2 + 4c-3)/(3c-1
+ 3c-2 + 3c-3) ) 35.6:64.4. MS (m/z, relative intensity) 3c-1:
216 (M+, 18), 112 [(M-C6H4CHdCH2)+, 100], 97 (18), 91 (26).
3c-2: 216 (M+, 20), 112 [(M - C6H4CHdCH2)+, 100], 97 (21),
91 (35). 3c-3: 216 (M+, 22), 112 [(M - C6H4CHdCH2)+, 100],
97 (22), 91 (32). 4c-1: 216 (M+, 11), 174 [(M - CH3CHdCH2)+,
100], 159 (12), 145 (17), 131 (8), 117 (45), 91 (26). 4c-2: 216
(M+, 15), 174 [(M - CH3CHdCH2)+, 100], 145 (14), 117 (53), 91
(30). 4c-3: 216 (M+, 17), 174 [(M - CH3CHdCH2)+, 100], 145
(20), 117 (69), 91 (36).
The acid 11 (400 mg, 1.94 mmol) was converted to diazo
compound 1c (250 mg, 53%): Rf ) 0.57 (petroleum ether/EtOAc
) 6:1); 1H NMR (200 MHz) δ 0.79 (t, J ) 7.2 Hz, 3H), 1.08-
1.39 (m, 3H), 1.44-1.76 (m, 3H), 1.88 (s, 3H), 2.38-2.62 (m, 3H),
6.95-7.22 (m, 5H); 13C NMR (50 MHz) δ 8.23, 14.05, 20.44,
33.50, 34.02, 35.20, 45.46, 63.25, 125.85, 128.23, 128.32, 141.55,
198.10; MS (m/z, relative intensity) 216 [(M - N2)+, 12], 173 (17),
111 (21), 104 (24), 91 (100); HRMS (M - N2)+ calcd for C15H22
216.1514, found 216.1528.
O
Gen er a l P r oced u r e for Rh (II)-Ca ta lyzed Din itr ogen
Extr u sion fr om Dia zo Com p ou n d s 1a -e. 1a -e (2.0 mmol)
in CH2Cl2 (20 mL) was added to a stirring solution of CH2Cl2
(20 mL) containing 1.0 mol % Rh(II) at room temperature under
a nitrogen atmosphere. The homogeneous solution was stirred
for 10-14 h until complete disappearance of the diazo compound
was observed. The catalyst was removed by a short column of
silica gel, and the crude C-H insertion products were analyzed
with 1H NMR (400 MHz) and GC-MS for the product ratio
determination and structure characterization.
Rh (II)-Ca ta lyzed Din itr ogen Extr u sion of 2-Dia zo-6-(4-
n itr op h en yl)-4-p r op yl-3-h exa n on e (1a ). The diazo decom-
position of 1a with Rh2(OAc)4 gave an unstable yellow oil of azine
12 (74%) as the major product. 12: Rf ) 0.64 (petroleum ether/
1
EtOAc ) 10:1); H NMR (200 MHz) δ 0.88 (t, J ) 7.2 Hz, 6H),
1.19-2.12 (m, 12H), 2.33 (s, 6H), 2.63 (t, J ) 8.0 Hz, 4H), 3.32-
3.47 (m, 2H), 7.30 (d, J ) 8.7 Hz, 4H), 8.13 (d, J ) 8.7 Hz, 4H);
13C NMR (50 MHz) δ 13.68 (CH3), 20.11(CH2), 23.69(CH3), 31.40-
(CH2), 33.06(CH2), 33.25(CH2), 42.73(CH), 123.35(CH), 128.80-
(CH), 146.16(C), 148.96(C), 197.49(CdO or CdN), 201.71(CdO
or CdN); IR 2920, 1705, 1600, 1515, 1340 cm-1; MS (m/z, relative
intensity) 234 (33), 206 (26), 160 (31), 150 (22), 131 (26), 57 (100).
The diazo decomposition of 1a with Rh2(O2CCF3)4 as a catalyst
Rh (II)-Ca ta lyzed Din itr ogen Extr u sion of 2-Dia zo-6-(4-
p h en ylp h en yl)-4-p r op yl-3-h exa n on e (1d ). The diazo decom-
position of 1d with Rh2(O2CCF3)4 as a catalyst gave C-H
insertion products in 82% isolated yield. An 1H NMR spectrum
of the product indicated that it was a mixture of diastereomeric
isomers of aliphatic C-H insertion products 3d and benzylic
C-H insertion products 4d . The mixture was not separable by
TLC or column chromatography. The mixture gave the following
analytical data: 1H NMR (400 MHz): δ 0.72 (d, J ) 7.8 Hz),
0.85 (d, J ) 7.1 Hz), 0.93 (t, J ) 7.5 Hz), 0.97 (d, J ) 7.0 Hz),
1.00 (d, J ) 6.3 Hz), 1.05 (d, J ) 6.4 Hz), 1.06 (d, J ) 6.3 Hz),
1.13 (d, J ) 5.8 Hz), 1.14 (d, J ) 6.0 Hz), 1.22-1.52 (m), 1.58-
1.80 (m), 1.82-2.08 (m), 2.10-2.48 (m), 2.59-2.80 (m), 3.49-
3.58 (m, 0.38 H, 4d ), 7.23-7.27 (m, 2H), 7.28-7.36 (m, 1H),
7.38-7.46 (m, 2H), 7.48-7.53 (m, 1H), 7.54-7.61 (m, 3H); IR
1
gave C-H insertion products in 83% isolated yield. An H NMR
spectrum of the crude product indicated that it was a mixture
of diastereomeric isomers of aliphatic C-H insertion products
3a and a tiny amount of benzylic C-H insertion product 4a was
detected (δ 0.68, d, J ) 7.5 Hz). 3a to 4a ratio was estimated to
be greater than 95:5. The mixture of 3a was not separable by
TLC or column chromatography. The mixture gave the following
analytical data: 1H NMR (400 MHz): δ 0.87 (d, J ) 7.2 Hz),
0.94 (d, J ) 7.4 Hz), 1.11 (d, J ) 6.4 Hz), 1.06 (d, J ) 6.9 Hz),
1.08 (d, J ) 6.5 Hz), 1.15 (d, J ) 5.7 Hz), 1.24-1.45 (m, 1H),
1.57-1.66 (m, 2H), 2.02-2.40 (m, 4H), 2.76-2.84 (m, 2H), 7.35
(d, J ) 8.6 Hz, 2H), 8.14 (d, J ) 8.6 Hz, 2H); IR 2960, 1730,
1600, 1515, 1455, 1340 cm-1
. Anal. Calcd for C15H19NO3: C,
68.94; H, 7.33; N, 5.36. Found: C, 69.10; H, 7.17; N, 5.39. GC-
MS analysis of the mixture gave three peaks, which were labeled
as 3a -1, 3a -2, and 3a -3. The ratio of 3a -1/3a -2/3a -3 is 71:
10:19. MS (m/z, relative intensity) 3a -1: 261 (M+, 2), 112 [(M
- p-NO2C6H4CHdCH2)+, 100], 97 (12). 3a -2: 261 (M+, 2), 112
[(M - p-NO2C6H4CHdCH2)+, 100], 97 (13). 3a -3: 261 (M+, 2),
112 [(M - p-NO2C6H4CHdCH2)+, 100], 97 (13).
Rh (II)-Ca ta lyzed Din itr ogen Extr u sion of 2-Dia zo-6-(4-
ch lor op h en yl)-4-p r op yl-3-h exa n on e (1b). The diazo decom-
position of 1b with Rh2(O2CCF3)4 as a catalyst gave C-H
insertion products in 73% isolated yield. An 1H NMR spectrum
of the product indicated that it was a mixture of diastereomeric
isomers of aliphatic C-H insertion products 3b and benzylic
C-H insertion products 4b. The mixture was not separable by
TLC or column chromatography. The mixture gave the following
analytical data: 1H NMR (400 MHz) δ 0.67 (d, J ) 7.8 Hz), 0.85
(d, J ) 7.2 Hz), 0.92 (d, J ) 7.5 Hz), 0.95 (t, J ) 7.0 Hz), 0.99 (d,
J ) 7.1 Hz), 1.00 (d, J ) 6.5 Hz), 1.06 (d, J ) 6.6 Hz), 1.14 (d,
J ) 6.0 Hz) 1.15 (d, J ) 6.0 Hz), 1.28-1.79 (m), 1.85-2.00 (m),
2.02-2.48 (m), 2.58-2.76 (m), 3.48-3.58 (m, 0.23 H, 4b), 7.12
2950, 1720, 1480, 1440, 1140 cm-1
. Anal. Calcd for C21H24O:
C, 86.26; H, 8.27. Found: C, 85.88; H, 8.37. GC-MS analysis
of the mixture gave six peaks, which were labeled as 3d -1, 3d -
2, 3d -3, 3d -4, 4d -1, and 4d -2. The following product ratios were
obtained from GC-MS: 3d -1/3d -2/3d -3/3d -4 ) 45:26:9:20; 4d -
1/4d -2 ) 13:87; (4d -1 + 4d -2)/(3d -1 + 3d -2 + 3d -3 + 3d -4) )
38.9:61.1. MS (m/z, relative intensity) 3d -1: 292 (M+, 8), 180
[(p-C6H5C6H4CHCH2)+, 100], 167 (13), 152 (3), 112 [(M-p-
PhC6H4CHdCH2)+, 2.5]. 3d -2: 292 (M+, 8), 180 [(p-PhC6H4CHd
CH2)+, 100], 167 (13), 152 (3), 112 [(M - p-PhC6H4CHdCH2)+,
3.2]. 3d -3: 292 (M+, 9), 180 [(p-PhC6H4CHdCH2)+, 100], 167
(13), 152 (3), 112 [(M - p-PhC6H4CHdCH2)+, 4.2]. 3d -4: 292
(M+, 9), 180 [(p-PhC6H4CHdCH2)+, 100], 167 (100), 151 (2), 112
[(M - p-PhC6H4CHdCH2)+, 2.5]. 4d -1: 292 (M+, 100), 250 [(M
- CH3CHdCH2)+, 94], 193 (47), 178 (40), 167 (33), 152 (11). 4d -
2: 292 (M+, 100), 250 [(M - CH3CHdCH2)+, 97], 221 (18), 193
(68), 178 (45), 167 (38).
Rh (II)-Ca ta lyzed Din itr ogen Extr u sion of 2-Dia zo-6-(4-
m eth oxyp h en yl)-4-p r op yl-3-h exa n on e (1e). The diazo de-

8594 J . Org. Chem., Vol. 63, No. 23, 1998
Notes
composition of 1e with Rh2(O2CCF3)4 as a catalyst gave C-H
insertion products in 59% isolated yield. An 1H NMR spectrum
of the product indicated that it was a mixture of diastereomeric
isomers of aliphatic C-H insertion products 3e and benzylic
C-H insertion products 4e. The mixture was found to be not
separable by TLC or column chromatography. The mixture gave
following analytical data: 1H NMR (400 MHz): δ 0.67 (d, J )
7.8 Hz), 0.85 (d, J ) 7.2 Hz), 0.94 (t, J ) 7.3 Hz), 0.96 (d, J )
7.0 Hz), 1.00 (d, J ) 7.2 Hz), 1.01 (d, J ) 6.4 Hz), 1.04 (d, J )
7.1 Hz), 1.06 (d, J ) 6.4 Hz), 1.14 (d, J ) 6.0 Hz), 1.15 (d, J )
6.0 Hz), 1.22-1.70 (m), 1.80-1.96 (m), 2.02-2.42 (m), 2.52-2.70
(m), 3.40-3.54 (m, 0.55 H, 4e), 3.78 (s, 1.60 H), 3.80 (s, 1.40 H),
6.82 (d, J ) 8.6 Hz), 6.88 (d, J ) 8.6 Hz), 6.96 (d, J ) 8.6 Hz),
7.10 (d, J ) 8.6 Hz), 7.11 (d, J ) 8.6 Hz), 7.17 (d, J ) 8.6 Hz);
[(M-p-MeOC6H4CHdCH2)+, 2.2], 121 (21). 3e-4: 246 (M+, 9),
134 [(p-MeOC6H4CHdCH2)+, 100], 112 [(M - p-MeOC6H4CHd
CH2)+, 2.0]. 121 (22). 4e-1: 246 (M+, 100), 204 [(M - CH3CHd
CH2)+, 77], 189 (18), 175 (14), 162 (18), 147 (60), 135 (42), 121
(56). 4e-2: 246 (M+, 100), 204 [(M - CH3CHdCH2), 68), 203
(74), 189 (24), 175 (17), 162 (19), 147 (64), 135 (38), 121 (57).
Ack n ow led gm en t. Financial support by the State
Education Commission of China (Excellent Young Teach-
er’s Foundation to J.W.) and NSFC (Grant No. 29702002)
is gratefullly acknowledged. We thank the Bioorganic
Molecular Engineering Laboratory of Peking University
and Ms. Yufang Sun for GC-MS measurement.
IR 2960, 1730, 1605, 1505, 1465, 1240 cm-1
16H22O2: C, 78.01; H, 9.00. Found: C, 78.28; H, 8.95. GC-
. Anal. Calcd for
C
Su p p or tin g In for m a tion Ava ila ble: Hammett plot (with
σ+), copies of 1H and 13C NMR spectra for all title compounds,
and the GC-MS data for insertion products (34 pages). This
material is contained in libraries on microfiche, immediately
follows this article in the microfilm version of the journal, and
can be ordered from the ACS; see any current masthead page
for ordering information.
MS analysis of the mixture gave six peaks, which were labeled
as 3e-1, 3e-2, 3e-3, 3e-4, 4e-1, and 4e-2. The following product
ratios were obtained from GC-MS: 3e-1/3e-2/3e-3/3e-4 ) 34:
24:9:33; 4e-1/4e-2 ) 56:44; (4e-1 + 4e-2)/(3e-1 + 3e-2 + 3e-3 +
3e-4) ) 54.3:45.7. MS (m/z, relative intensity) 3e-1: 246 (M+,
8), 134 [(p-MeOC6H4CHdCH2)+, 100], 112 [(M - p-MeOC6H4-
CHdCH2)+, 2.4], 121 (21). 3e-2: 246 (M+, 13), 134 [(p-MeOC6H4-
CHdCH2)+, 100], 112 [(M - p-MeOC6H4CHdCH2)+, 2.1], 121
(23). 3e-3: 246 (M+, 9), 134 [(p-MeOC6H4CHdCH2)+, 100], 112
J O981279T