Cathodic reduction of benzoyl cyanides

Full text of DOI:10.1021/jo960282e

J . Org. Chem. 1996, 61, 4835-4837
4835
Ta ble 1. Electr olytic Red u ction of Ben zoyl Cya n id es
1a -h a
Ca th od ic Red u ction of Ben zoyl Cya n id es
% yield of productsb
Mitsuhiro Okimoto, Toshiaki Itoh, and Toshiro Chiba*
maldelonitrile
Department of Applied Chemistry, Kitami Institute of
Technology, Kitami, J apan 090
benzoyl
cyanide 1
benzil 2c
benzoate 3d
Ar
C6H5
2-MeC6H4
4-MeC6H4
2-MeOC6H4
4-MeOC6H4
2-ClC6H4
1a
1b
1c
1d
1e
1f
2a
2b
2c
2d
2e
2f
67 (75)
63
63 (68)
56
63 (70)
64
62
3a
3b
3c
3d
3e
3f
63 (74)
53
Received February 12, 1996
65 (76)
0e
In tr od u ction
43 (57)
65
The chemical reduction of acyl cyanides has been
studied extensively. The products of such reactions are
highly dependent on the reaction conditions and particu-
larly on the reducing agents used. For example, reduc-
tion with Zn/HCl or hydrogen in the presence of a Ni
catalyst yields cyanohydrins, whereas reduction with
LiAlH4 or hydrogen in the presence of a Pd catalyst in
acetic acid yields R-amino alcohols.1 Selective reduction
leading to R-amino ketones is accomplished using the
Stephen reaction.2 Recently, it has been reported that
the action of titanous chloride on benzoyl cyanides
produces hydrodimerization to give benzil dicyanohy-
drins.3 Furthermore, the photoreduction of benzoyl
cyanides to benzil dicyanohydrins has also been inves-
tigated.4
However, the electrochemical reduction of acyl cya-
nides has not been studied thoroughly. We report here
the macroscale cathodic reduction of benzoyl cyanides 1
in acetonitrile at a platinum cathode. We found that the
electrochemical reduction of 1 provides different products
depending upon whether water is present in the electro-
lyte system. When the electrolysis is conducted in
aqueous acetonitrile, the corresponding benzil 2 is formed
as the final product via the benzyl dicyanohydrin,
whereas, only mandelonitrile benzoate (3) is produced in
absolute acetonitrile. In each case, reduction most likely
proceeds via a one-electron process.
1g
1h
4-ClC6H4
4-t-BuC6H4
2g
2h
3g
3h
61
65 (69)
59 (64)
a
Benzoyl cyanide 1 (25 mmol) and Et4NOTs (10 mmol) were
used. Strength of constant current: 0.4 A. Current passed: 1.2
b
F/mol. Isolated yield by distillation or recrystallization. Values
d
in parentheses are GLC yield. c In MeCN-H2O (70-10 mL). In
80 mL of MeCN. e 2d was formed in a yield of 55%.
convenient for preparing symmetrical benzils, such as
2,2′- or 4,4′-dichlorobenzils, or methyl-substituted benzils,
which are not readily obtained by the usual route through
benzoin condensation.5 Replacement of acetonitrile with
another polar aprotic solvent, such as acetone, dioxane,
or DMF, gave lower yields of 2. The use of alkaline metal
salts, like NaClO4, as the supporting electrolyte drasti-
cally decreased the yields. Moreover, electrolysis in a
divided cell caused the hydrolysis of 1 to benzoic acids,
probably via electrogenerated base catalysis.
On the other hand, the electrolysis of 1 in absolute
acetonitrile gave the corresponding mandelonitrile ben-
zoates 3 instead of benzils 2, except for 2-methoxybenzoyl
cyanide (1d ). The same products are produced when 1
is treated with NaBH4 in a two-phase system consisting
of CH2Cl2 and water in the presence of Bu4NBr, where
it is postulated that the benzaldehyde cyanohydrin anion
which is formed as the primary reduction product is
acylated with an unreacted molecule of benzoyl cyanide.6
Indeed, benzoyl cyanides react very readily with alde-
hydes in the presence of cyanide ion to give 3.7 However,
such intermediates were not detected during the present
electrolyses. Instead, benzil 2 was observed during the
initial stage, and was then transformed into mandeloni-
trile benzoate 3 as the electrolysis proceeded.
Figure 1 shows the product distributions of the elec-
trolysis of 1a based on GLC analysis of the electrolyte
as a function of the applied charge. The total yields of
2a and 3a increased almost linearly with an increase in
the applied charge. Using the slope of the line, we can
estimate that the 1 F is consumed per mole of 1a for the
formation of 2a and 3a . This suggests that the trans-
formation of 2a into 3a does not involve electron transfer
between the cathode and 2a .
A simple mechanism for the present reaction is shown
in Scheme 1. Benzoyl cyanides undergo one-electron
reduction to form radical anions, followed by dimerization
to give benzil dicyanohydrin dianions A. In aqueous
acetonitrile, the resulting dianion is immediately proto-
nated to give benzil dicyanohydrin, which slowly decom-
poses to benzil 2. On the other hand, in absolute
acetonitrile, a proton is not readily available, and dian-
ions A eject a cyanide ion to form epoxide, which
undergoes displacement and subsequent protonation to
give the corresponding mandelonitrile benzoate 3.8
Resu lts a n d Discu ssion
Preparative electrolyses were performed in an undi-
vided cell by passing a constant current at rt. Tetra-
ethylammonium p-toluenesulfonate (Et4NOTs) was used
as the supporting electrolyte. The results are sum-
marized in Table 1. In most cases, the starting benzoyl
cyanides 1 were almost totally consumed by the time
approximately 1.2 F/mol had passed through the elec-
trolyte.
In aqueous acetonitrile, a precipitate of benzyl dicy-
anohydrins was often observed during electrolysis. How-
ever, during the final stage, a considerable amount of the
benzyl dicyanohydrins was converted into benzils 2, thus
liberating hydrogen cyanide, due to their instability.4
Consequently, the product yields were determined such
that the remaining dicyanohydrins were completely
converted into 2 by heating the mixture of products,
although the actual electrolysis products were the benzyl
dicyanohydrins.
As shown in Table 1, the yields of 2 were not signifi-
cantly influenced by the nature or position of the sub-
stituent on the benzene ring. This method may be
(1) (a) Thesing, J .; Witzel, D.; Brehm, A. Angew. Chem. 1956, 68,
425. (b) Ho¨nig, S.; Schaller, R. Angew. Chem. 1982, 94, 1.
(2) Stuckwisch, C. G. J . Org. Chem. 1972, 37, 318.
(3) (a) Clerici, A.; Porta, O. J . Org. Chem. 1993, 58, 2889. (b) Clerici,
A.; Porta, O.; Riva, M. Tetrahedron Lett. 1981, 22, 1043.
(4) Raaen, V. F. J . Org. Chem. 1966, 31, 3310.
(5) Ide, W. S.; Buck, J . S. Org. React. 1948, 4, 269.
(6) Photis, J . M. J . Org. Chem. 1981, 46, 182.
(7) Marvel, C. S.; Brace, N. O.; Miller, F. A.; J ohnson, A. R. J . Am.
Chem. Soc. 1949, 71, 34.
S0022-3263(96)00282-4 CCC: $12.00 © 1996 American Chemical Society

4836 J . Org. Chem., Vol. 61, No. 14, 1996
Notes
given in ppm downfield (δ) from Me4Si as an internal standard.
GC/MS analyses were performed using a 30-m capillary column
(0.25 mm diameter; liquid phase, SPB-1) with an ionization
potential of 70 eV. Gas-liquid chromatography (GLC) was
performed using a 2.0-m glass column packed with FFAP on
Chromosorb W AW and a 1-m stainless steel column packed with
Silicone SE-30 on Uniport B. The carrier gas for each column
was N2 and the detector was FID. Elemental analyses were
performed by the Instrumental Analyses Laboratories at Hok-
kaido University.
Benzoyl cyanides 1a -h were prepared from the correspond-
ing benzoyl chlorides and CuCN as reported elsewhere.10
Et4NOTs was prepared by refluxing an ethanol solution of
triethylamine and ethyl p-toluenesulfonate according to the
method in the literature.11 Anhydrous acetonitrile was obtained
by refluxing with P2O5, followed by distillation under dry
nitrogen.
P r ep a r a tive-Sca le Electr olyses. Electrolyses were per-
formed in a 100-mL beaker. A platinum gauze cylinder (33 mm
diameter, 40 mm high) served as the cathode, and a cylindrical
platinum gauze anode (25 mm diameter, 40 mm high) was
concentrically placed inside the cathode.
The electrodes were connected to an adjustable DC power
supply. The power source was a Torio Model PR-653 regulated
DC supply (35 V, 3 A). For electrolysis in anhydrous acetonitrile,
a calcium chloride tube was connected to the equipment. The
cell was cooled with running water and the electrolyte was
magnetically stirred. The progress of the reaction was monitored
by either GLC or TLC.
F igu r e 1. Relationships between the product yields and
consumed current in the electrolysis of benzoyl cyanide 1a (25
mmol) in 0.125 M Et4NOTs-MeCN (80 mL). 2, benzil 2a ; b,
mandelonitrile benzoate 3a ; O, total yield.
Sch em e 1
Ca th od ic Red u ction of Ben zoyl Cya n id es (1a -h ). Gen -
er a l P r oced u r e in a qu eou s MeCN. A mixture of benzoyl
cyanide 1 (25 mmol), Et4NOTs (10 mmol), MeCN (70 mL), and
H2O (10 mL) was electrolyzed at a constant current of 0.4 A.
The terminal voltage ranged from 5 to 7 V. After 1.2 F/mol of
charge had been passed, the catholyte was evaporated in vacuo
at rt. The residue was treated with brine (70 mL), and the
liberated oily layer was extracted with Et2O (50 mL × 3). The
ether extracts were washed with brine (30 mL), dried (MgSO4),
and concentrated. The crude products that were obtained from
three such electrolyses were combined and slowly heated in an
oil bath. At about 150 °C, the evolution of hydrogen cyanide
was observed. The oil bath temperature was then maintained
at 210 °C for 40 min, and the hot reaction mixture was distilled
in vacuo. The isolated yields of 2 are given in Table 1.
Analytical samples were obtained by recrystallization from
EtOH.
Ben zil (2a ): mp 96-97 °C, yellowish rodlike crystals from
EtOH (lit.12 mp 95 °C); bp 154-156 °C/3 Torr (lit.12 bp 188 °C/
12 Torr); IR (KBr) 1661 cm-1; 1H NMR δ 7.4-7.8 (m, 6H), 7.9-
8.2 (m, 4H); 13C NMR δ 129.0 (CH), 129.9 (CH), 133.1 (C), 134.9
(CH), 194.5 (CO); MS m/ z (rel intensity) 210 (M+, 6), 105 (100),
77 (37).
2,2′-Dim eth ylben zil (2b): mp 92-95 °C, yellow needles from
EtOH (lit.12 mp 92-94 °C); bp 164-167 °C/3 Torr; IR (KBr) 1672
cm-1; 1H NMR δ 2.70 (s, 6H), 7.1-7.8 (m, 8H); 13C NMR δ 21.8
(CH3), 126.0 (CH), 131.9 (C), 132.6 (CH), 133.0 (CH), 133.6 (CH),
141.5 (C), 196.9 (CO); MS m/ z (rel intensity) 238 (M+, 1), 119
(100), 91 (31).
4,4′-Dim eth ylben zil (2c): mp 104-105 °C, yellow plates
from EtOH, (lit.12 mp 104-105 °C); bp 209-211 °C/7 Torr; IR
(KBr) 1661 cm-1; 1H NMR δ 2.41 (s, 6H), 7.28 (d, J ) 8 Hz, 4H),
7.86 (d, J ) 8 Hz, 4H); 13C NMR δ 21.9 (CH3), 129.7 (CH), 130.0
(CH), 130.8 (C), 146.0 (C), 194.4 (CO); MS m/ z (rel intensity)
238 (M+, 4), 119 (100), 91 (27).
2,2′-Dim eth oxyben zil (2d): mp 131-132 °C, colorless needles
from EtOH (lit.13 mp 128-129 °C); bp 201-204 °C/3 Torr; IR
(KBr) 1655 cm-1; 1H NMR δ 3.55 (s, 6H), 6.8-7.3 (m, 4H), 7.4-
7.7 (m, 2H), 8.0-8.3 (m, 2H); 13C NMR δ 55.8 (CH3), 112.6 (CH),
121.4 (CH), 123.5 (C), 130.4 (CH), 135.6 (CH), 160.4 (C), 192.5
(CO); MS m/ z (rel intensity) 270 (M+, 5), 135 (100).
A similar displacement has been found to take place
in the reaction of 2a with sodium cyanide in aprotic
solvents, such as DMSO or DMF, in which the carbanion
of 3a is formed as an intermediate, although 3a itself
has not been isolated.9 The failure of 1d to provide the
corresponding 3d may be due to the electrometric effect
of the methoxy group at the ortho position, which hinders
the intramolecular nucleophilic attack of the cyanohydrin
carbon center by the oxyanion to give the epoxide.
Exp er im en ta l Section
Melting and boiling points are uncorrected. The 1H NMR and
13C NMR spectra were measured at 90 and 22.4 MHz, respec-
tively, in CDCl3, unless otherwise noted. Chemical shifts are
(8) In the cathodic reduction of aroyl chlorides, it has been reported
that aroyl free radicals are formed through the ejection of chloride ion
from the radical anions that initially form, and that these free radicals
then couple. The resulting diaroyl intermediate is immediately reduced
to an ene diol because it has a lower reduction potential than the aroyl
chloride. See: Guirado, A.; Manzanera, C.; Velasco, M. D. J . Org. Chem.
1982, 42, 142.
(9) (a) Trisler, J . C.; Frye, J . L. J . Org. Chem. 1965, 30, 306. (b)
Kuebrich, J . P.; Schowen, R. L. J . Am. Chem. Soc. 1971, 93, 1220. see
also, (c) Kwart, H.; Baevsky, M. M. J . Am. Chem. Soc. 1958, 80. 580.
(10) Oakwood, T. S.; Weisberger, C. A. Org. Synth. 1955, 3, 112.
(11) Baizer, M. M. J . Electrochem. Soc. 1964, 111, 215.
(12) Pollack, J . R. A.; Stevens, R. Dictionary of Organic Compounds;
Eyre and Spottiswoode Ltd: Great Britain, 1965.
(13) Leonard, N. J .; Rapala, R. T.; Rapala, H. L.; Blout, E. R. J .
Am. Chem. Soc. 1949, 71, 2997.

Notes
J . Org. Chem., Vol. 61, No. 14, 1996 4837
4,4′-Dim eth oxyben zil (2e): mp 133-134 °C, golden yellow
(CH), 128.2 (C), 128.6 (CH), 129.3 (CH), 130.1 (CH), 130.4 (CH),
132.0 (C), 134.1 (CH), 164.6 (CO); MS m/ z (rel intensity) 237
(M+, 36), 116 (69), 105 (100), 77 (41).
needles from EtOH (lit.12 mp 133 °C); bp 215-219 °C/3 Torr; IR
(KBr) 1655 cm-1; 1H NMR δ 3.86 (s, 6H), 6.95 (d, J ) 9 Hz, 4H),
7.94 (d, J ) 9 Hz, 4H); 13C NMR δ 55.6 (CH3), 114.3 (CH), 126.4
(C), 132.3 (CH), 164.9 (C), 193.5 (CO); MS m/ z (rel intensity)
270 (M+, 2), 135 (100).
r-Cya n o-2-m eth ylben zyl o-m eth ylben zoa te (3b): mp 50-
52 °C, prisms from EtOH; IR (KBr) 2243 (vw), 1734, 1238 cm-1
;
1H NMR δ 2.49 (s, 3H), 2,61 (S, 3H), 6.74 (S, 1H), 7.1-8.1 (m,
8H); 13C NMR δ 19.0 (CH3), 21.8 (CH3), 61.3 (CH), 116.2 (CN),
126.0 (CH), 126.8 (CH), 127.2 (C), 128.6 (CH), 130.2 (C), 130.5
(CH), 131.0 (CH), 131.4 (CH), 132.1 (CH), 133.2 (CH), 136.7 (C),
141.5 (C), 165.0 (CO); MS m/ z (rel intensity) 265 (M+, 28), 135
(42), 130 (78), 119 (100). Anal. Calcd for C17H15NO2: C, 76.96;
H, 5.70; N, 5.28. Found: C, 77.08; H, 5.85; N, 5.26.
2,2′-Dich lor oben zil (2f): mp 134-135 °C, golden yellow
needles from EtOH (lit.12 mp 133 °C); bp 186-188 °C/3 Torr; IR
1
(KBr) 1684 cm-1; H NMR δ 7.2-7.8 (m, 6H), 7.9-8.2 (m, 6H);
13C NMR δ 127.3 (CH), 130.9 (CH), 132.2 (C), 132.7 (CH), 134.8
(CH), 135.0 (C), 191.0 (CO); MS m/ z (rel intensity) 278 (M+,
trace), 139 (100), 111 (24).
4,4′-Dich lor oben zil (2g): mp 197-199 °C yellow needles
from EtOH, (lit.12 mp 199 °C); bp 216-220 °C/3 Torr; IR (KBr)
1659 cm-1; 1H NMR δ 7.43 (d, J ) 9 Hz, 4H), 7.92 (d, J ) 9 Hz,
4H); 13C NMR δ 129.5 (CH), 131.3 (CH), 141.8 (C), 159.7 (C),
192.4 (CO); MS m/ z (rel intensity) 278 (M+, 1), 139 (100), 111
(27).
4,4′-Di-ter t-Bu tylben zil (2h ): mp 103-104 °C, fine powder
crystals from EtOH (lit.9a mp 104-104.5 °C); bp 235-240 °C/6
Torr; IR (KBr) 1682 cm-1; 1H NMR δ 1.33 (s, 18H), 7.51 (d, J )
9 Hz, 4H), 7.92 (d, J ) 9 Hz, 4H); 13C NMR δ 31.0 (CH3), 35.2
(C), 126.0 (CH), 129.9 (CH), 130.7 (C), 158.8 (C), 194.5 (CO);
MS m/ z (rel intensity) 322 (M+, 1), 161 (100). Anal. Calcd for
r-Cya n o-4-m eth ylben zyl p-m eth ylben zoa te (3c): mp 50-
52 °C, fine powder cryatals from EtOH; IR (KBr) 2253 (vw),
1722, 1088 cm-1 1H NMR δ 2.38 (s, 3H), 2.40 (s, 3H), 6.62 (s,
;
1H), 7.2-8.1 (m, 8H); 13C NMR δ 21.3 (CH3), 21.7 (CH3), 63.1
(CH), 116.4 (CN), 125.5 (C), 127.9 (CH), 129.2 (C), 129.3 (CH),
129.9 (CH), 130.1 (CH), 140.6 (C), 145.0 (C), 164.7 (CO); MS m/ z
(rel intensity) 265 (M+, 22), 130 (53), 119 (100), 91 (30). Anal.
Calcd for C17H15NO2: C, 76.96; H, 5.70; N, 5.28. Found: C,
76.97; H, 5.76; N, 5.24.
r-Cya n o-4-m eth oxyben zyl p-m eth oxyben zoa te (3e): mp
64-66 °C, leaflets from EtOH (lit.14 mp 69-70 °C); IR (KBr)
2268 (vw), 1711, 1255 cm-1; 1H NMR δ 3.81 (s, 3H), 3.84 (s, 3H),
6.59 (s, 1H), 6.8-7.1 (m, 4H), 7.4-8.2 (m, 4H); 13C NMR δ 55.4
(CH3), 55.5 (CH3), 62.8 (CH), 113.9 (CH), 114.6 (CH), 116.6 (CN),
120.6 (C), 124.3 (C), 129.6 (CH), 132.2 (CH), 161.1 (C), 164.2
(C), 164.3 (CO); MS m/ z (rel intensity) 297 (M+ ,18), 146 (100),
135 (44). Anal. Calcd for C17H15NO4: C, 68.67; H, 5.08; N, 4.71.
Found: C, 68.72; H, 5.16; N, 4.67.
C
22H26O2: C, 81.95; H, 8.13. Found: C, 82.08; H, 8.34.
Isola tion of Ben zil Dicya n oh yd r in . The electrolysis of 1a
(25 mmol) was repeated by passing a current of 30 mF. After
the usual workup, the residue of the ether extracts was
suspended in benzene (15 mL), and insoluble materials were
collected by filtration and washed with small amounts of
benzene. The crude product was recrystallized from acetone-
hexane (1:2) to which a few drops of acetic acid had been added
(0.73 g, 22%). Ben zil d icya n oh yd r in : mp 177-180 °C dec
white powder crystals (lit.3b mp 175-176 °C dec). The IR and
1H NMR spectra were in agreement with those reported.3b IR
(KBr) 3368, 2255(vw) cm-1; 1H NMR (acetone-d6) δ 7.05 (s, 2H),
7.24-7.74 (m, 10H); 13C NMR (acetone-d6) δ 79.8 (C), 119.4 (CN),
128.3 (CH), 128.4 (CH), 130.5 (CH), 136.0 (C). It has been
reported that dicyanohydrins are unstable, even at rt, and
therefore the results of elementary analyses do not always agree
with the calculated values.4
Gen er a l P r oced u r e in An h yd r ou s MeCN. Using a pro-
cedure similar to that in aqueous MeCN, benzoyl cyanide 1 (25
mmol) was electrolyzed without the addition of water. The
termimal voltage ranged from 7 to 12 V. After the usual workup,
the residue of the ether extracts was passed through a short
column (25 mm diameter, 15 cm high) of silica gel by eluting
with ether. The eluate was evaporated to dryness, and the
residue was recrystallized from EtOH. The yields of the purified
products are given in Table 1.
r-Cya n o-2-ch lor oben zyl o-ch lor oben zoa te (3f): mp 49-
51 °C fine powder crystals from EtOH; IR (KBr) 2257 (vw), 1742,
1234 cm-1; 1H NMR δ 6.94 (s, 1H), 7.1-8.0 (m, 8H); 13C NMR δ
61.2 (CH), 115.1 (CN), 126.8 (CH), 127.5 (C), 127.7 (CH), 129.2
(C), 129.7 (CH), 130.3 (CH), 131.4 (CH), 131.9 (CH), 132.0 (CH),
133.5 (C), 133.8 (CH), 134.6 (C), 163.1 (CO); MS m/ z (rel
intensity) 305 (M+, 15), 150 (53), 139 (100). Anal. Calcd for
C
15H9NO2Cl2: C, 58.85; H, 2.96; N, 4.58; Cl, 23.16. Found: C,
58.89; H, 3.08; N, 4.52; Cl, 22.91.
r-Cya n o-4-ch lor oben zyl p-ch lor oben zoa te (3g): mp 77-
78 °C, fine powder crystals from EtOH; IR (KBr) 2262 (vw), 1728,
1094 cm-1 1H NMR δ 6.63 (s, 1H), 7.3-7.7 (m, 6H), 7.9-8.1
;
(m, 2H); 13C NMR δ 62.9 (CH), 115.7 (CN), 126.4 (C), 129.1 (CH),
129.3 (CH), 129.7 (CH), 130.3 (C), 131.4 (CH), 136.9 (C), 140.9
(C), 163.7 (CO); MS m/ z (rel intensity) 305 (M+,17), 150 (59),
139 (100). Anal. Calcd for C15H9NO2Cl2: C, 58.85; H, 2.96; N,
4.58; Cl, 23.16. Found: C, 58.91; H, 3.09; N, 4.53; Cl, 23.12.
r-Cya n o-4-ter t-bu tylben zyl p-ter t-bu tylben zoa te (3h ):
mp 107-109 °C fine powder crystals from EtOH; IR (KBr) 2245
r-Cya n oben zyl ben zoa te (3a ): mp 60-62 °C, leaflets from
EtOH (lit.14 mp 63-64 °C); bp 176-177 °C/3 Torr. The IR and
NMR spectra were in agreement with those reported:15 IR (KBr)
2249 (vw), 1732, 1248 cm-1; 1H NMR δ 6.67 (s, 1H), 7.3-7.8 (m,
8H), 8.0-8.2 (m, 2H); 13C NMR δ 63.4 (CH), 116.2 (CN), 127.8
(vw), 1720, 1263 cm-1 1H NMR δ 1.32 (s, 18H), 6.67 (s, 1H),
;
7.4-7.6 (m, 6H), 7.9-8.1 (m, 2H); 13C NMR δ 31.0 (CH3), 31.2
(CH3), 34.8 (C), 35.2 (C), 63.0 (CH), 116.4 (CN), 125.6 (CH), 126.2
(CH), 127.7 (CH), 129.2 (C), 130.0 (CH), 153.6 (C), 157.9 (C),
159.6 (C), 164.6 (CO); MS m/ z (rel intensity) 349 (M+ ,14), 334
(15), 172 (14), 161 (100). Anal. Calcd for C23H27NO2: C, 79.05;
H, 7.79; N, 4.01. Found: C, 78.88; H, 7.93; N, 3.90.
(14) Francis, F.; Davis, O. C. M. J . Chem. Soc. 1909, 95, 1403.
(15) Hoffmann, H. M. R.; Ismail, Z. M.; Hollweg, R.; Zein, A. R. Bull.
Chem. Soc. J pn. 1990, 63, 1807.
J O960282E