Halonium ion-assisted deiodination of styrene-based vicinal iodohydrins followed by rearrangement through phenyl migration

Article abstract of DOI:10.1021/jo9013707

(Chemical Equation Presented) Acid activation of bromate/bromide couple at 0-10°C was found to trigger the deiodination of styrene-based vicinal iodohydrins. Violet coloration of the organic layer was ascribed to formation of IBr. Deiodination was followed by phenyl migration and deprotonation leading to formation of phenyl acetone and 2-phenylpropanal in good yields from 1-iodo-2-phenylpropan-2-ol and 2-iodo-1-phenylpropan-1-ol, respectively. Phenyl acetaldehyde-which was obtained in 92% GC yield from styrene iodohydrin-was also presumably formed in analogous manner. NBS and HOCl too were effective for transformation of styrene iodohydrin into phenyl acetaldehyde. 2009 American Chemical Society.

Full text of DOI:10.1021/jo9013707

pubs.acs.org/joc
compounds with oxidizing agents,2 including the formation
Halonium Ion-Assisted Deiodination of
Styrene-Based Vicinal Iodohydrins Followed by
Rearrangement through Phenyl Migration
2a
2b
of R-ICl2 and R-IdO/R-IO2 when RI is treated with
chloronium or bromonium ion. We report here the observa-
tion of deiodination-cum-phenyl group migration when
styrene-based iodohydrins were reacted with reagents bear-
ing bromonium and chloronium ions.
Manoj K. Agrawal and Pushpito K. Ghosh*
When a stoichiometric amount of acid-activated BrO3-/Br-
(1:2 molar ratio) (eq 1) was reacted with 2-bromo-1-phenyl-
ethanol, the solution gradually turned colorless, and bromo-
methylene phenyl ketone was obtained in 98% yield. In
marked contrast, when a similar reaction was attempted with
2-iodo-1-phenylethanol, the solution turned violet in color and
the product obtained was identified as phenyl acetaldehyde
based on GC retention time and mass fragmentation pattern
Central Salt and Marine Chemicals Research Institute
(Council of Scientific & Industrial Research), G. B. Marg,
Bhavnagar 364 002, Gujarat, India
pkghosh@csmcri.org
Received July 10, 2009
ꢀ
vis-a-vis standard sample (Supporting Information, entry 1,
Table S1). Stirring was sufficient but not so vigorous as to mix
up the two phases. The UV-vis absorption spectral profile of
the product mixture matched that of IBr (prepared from I2 and
Br2) (Figure 1),3 and the absorbance data indicated that all of
the iodide from substrate and bromide from reagent were
transformed into IBr at the end of the reaction. When the
reaction was studied using a range of solvents, the maximum
yield of phenyl acetaldehyde was obtained with 3:1 (v/v)
ethylene dichloride (EDC)/water (Supporting Information,
entry 1, Table S1) which was the initial solvent composition
chosen.
NaBrO3þ2NaBrþ3Hþ f 3HOBrþ3Naþ
ð1Þ
Acid activation of bromate/bromide couple at 0-10 °C
was found to trigger the deiodination of styrene-based
vicinal iodohydrins. Violet coloration of the organic layer
was ascribed to formation of IBr. Deiodination was
followed by phenyl migration and deprotonation leading
to formation of phenyl acetone and 2-phenylpropanal
in good yields from 1-iodo-2-phenylpropan-2-ol and
2-iodo-1-phenylpropan-1-ol, respectively. Phenyl acetal-
dehyde-which was obtained in 92% GC yield from
styrene iodohydrin-was also presumably formed in
analogous manner. NBS and HOCl too were effective
for transformation of styrene iodohydrin into phenyl
acetaldehyde.
Keeping the solvent composition fixed, and maintaining
the temperature between 0 and 10 °C,4 the reaction with
2-iodo-1-phenylethanol was studied employing several dif-
ferent bromonium ion-generating reagents (Supporting In-
formation, Table S2). The highest yield (92.1%) of phenyl
acetaldehyde was obtained with 4:1 NaBrO3/NaBr (entry 1,
Table 1).5 HOCl also yielded the same product, albeit in
lower (74.8%) yield, whereas the reaction failed with 1:2
IO3-/I- and I2 (Supporting Information, entries 5 and 6,
Table S2). The reaction with 4:1 BrO3-/Br- was extended to
iodohydrins of other styrene derivatives (Table 1). Iodohy-
drins of the aromatic substituted styrene derivatives studied
gave the corresponding phenyl acetaldehydes in 59-85%
yields (entries 2-6, Table 1). The low yield in case of entry 3
was on account of appreciable formation of side products,
while the low yield in the reaction of entry 4 was due to low
conversion (see the GC-MS in the Supporting Information).
Since phenyl acetaldehyde gave complex NMR spectra
in CDCl3, the above products were converted into their
2,4-DNP derivatives for characterization confirmation. The
crystal structure was also obtained of the derivative of entry 2
(Supporting Information, Figure S1). Iodohydrins of styrene
derivatives with side-chain substitution were also investigated
Oxidizing agents such as m-CPBA are known to convert
alkyl iodides into the corresponding alcohols in nonpolar
solvent and even to olefins through syn elimination when
strongly electron-attracting groups such as carbomethoxy or
sulfonyl are present at R position.1 There are also several
reports in the literature on formation of hypervalent iodo
*To whom correspondence should be addressed. Fax: (þ) 91-278-
2567562.
(1) Reich, H. J.; Peake, S. L. J. Am. Chem. Soc. 1978, 100, 4888.
(2) (a) Willgerodt, C. J. Prakt. Chem. 1886, 33, 154. (b) Boeckman, R. K.;
Shao, P.; Mullins, J. J. Organic Syntheses; Wiley: New York, 2004; Collect. Vol.
X, p 696; 2000, 77, 141. (c) Zhdankin, V. J.; Stang, P. J. Chem. Rev. 2008, 108,
5299. (d) Richardson, R. D.; Wirth, T. Angew. Chem., Int. Ed. 2006, 45, 4402.
(e) Zhdankin, V. J.; Stang, P. J. Chem. Rev. 2002, 102, 2523. (f ) Wirth, T. Angew.
Chem., Int. Ed. 2005, 44, 3656. (g) Page, T. K.; Wirth, T. Synthesis 2006, 18,
3153.
(3) (a) Jolles, Z. E. Bromine and Its Compounds; Ernest Benn Ltd.: London,
1966; p 188. (b) Seery, D. J.; Britton, D. J. Phys. Chem. 1964, 68, 2263.
(4) At room temperature, 2-3% of acetophenone was formed along with
the phenyl acetaldehyde.
(5) Given that there is only 0.43 mol total of Br in this reagent per mole of
iodine in substrate taken, all of the I from the substrate cannot be in the form
of IBr in this case.
DOI: 10.1021/jo9013707
r
Published on Web 09/18/2009
J. Org. Chem. 2009, 74, 7947–7950 7947
2009 American Chemical Society

Agrawal and Ghosh
JOCNote
TABLE 1. Reactions of Styrene-Based Iodohydrins with 4:1
BrO3-/Br-a
FIGURE 1. UV-vis spectra of 5.54 ꢀ 10-4 M I2, Br2, and IBr
(prepared from I2 and Br2) in EDC and of diluted product mixture
obtained from the reaction (in 25 mL of EDC) of 2-iodo-1-phenyl-
ethanol (5.54 ꢀ 10-3 mol) with acid-activated 1:2 BrO3-/Br-
(containing 5.54 ꢀ 10-3 mol of total Br). The organic layer was
diluted 500 times with EDC prior to recording the spectrum.
(entries 7-10, Table 1). Cinnamic acid iodohydrin gave
phenyl acetaldehyde in 74.7% yield under the optimized
reaction conditions, while at room temperature, both phenyl
acetaldehyde and acetophenone were formed in ca. 55% and
45% GC yields, respectively (Supporting Information). When
the reaction was carried out with the iodohydrin of methyl
cinnamate, methyl 3-oxo-3-phenylpropanoate was obtained
as the sole product in 61.9% yield. 1-Iodo-2-phenylpropan-
2-ol and 2-iodo-1-phenylpropan-1-ol gave phenylacetone and
2-phenylpropanal in 64% and 69% yields, respectively
(entries 9 and 10, Table 1). Identities of both products were
cross-checked by solving the crystal structures of their
2,4-DNP derivatives (Supporting Information, Figures S2
and S3). 2-Iodocyclohexanol was also subjected to reaction
under the same conditions. The ring-contracted product,
cyclopentanecarbaldehyde, was obtained in 21.7% yield.
Iodohydrins of linear olefins (1-hexene; 1-octene) yielded only
complex mixtures of products.
aBR-O = 4:1 NaBrO3/NaBr; 0.43 mol total of Br taken per mole of
substrate; 0.5 mol of H2SO4 taken per mole of substrate for all reactions;
all reactions were carried out between 0 and 10 °C under gentle stirring.
bSubstrate amount varied from 3 to 14 mmol. cProduct identity was
initially assessed through analyses of mass fragmentation pattern in the
GC-MS of the crude product mixture and later on through preparation
of 2,4-DNP derivatives of all the compounds except those in entries 5, 7,
and 8. dYield refers to GC area % recorded for crude product mixture
after workup. Note that GC-MS of entries 4 and 8 showed only peaks
due to starting material and product (Supporting Information), which is
why the conversion and yield are identical in these cases.
The results of entries 9 and 10 of Table 1 can be rationa-
lized on the basis of bromonium ion-induced deiodination
and accompanying phenyl group migration. With regard to
the reactions of entries 1-6, these too may be explained
through phenyl migration. Formation of phenyl acetalde-
hyde via epoxide formation and O-migration is, of course,
the well-known pathway of the Meinwald rearrangement,
which is less likely with the present methodology.6-8 The
reaction of entry 7 must have also occurred through phenyl
group migration since O-migration would have yielded
phenylpyruvic acid instead. Deiodination and phenyl group
SCHEME 1. Probable Reaction Pathway of the Bromonium
Ion-Assisted Styrene-Based Iodohydrin Rearrangement
migration in the above cases may occur synchronously as
shown in Scheme 1. Abstraction of I- by Brþ would yield
IBr,9 formation of which is evident from Figure 1. (Note,
however, that IBr can also form from I2 and Br2.) The
(6) GC-MS of the product mixtures of the reactions in Table 1 indicated
traces of epoxide which may have formed as an impurity, presumably via a
competing pathway.
(7) Meinwald, J.; Labana, S. S.; Chadha, M. S. J. Am. Chem. Soc. 1963,
85, 582.
(8) (a) Sudha, R.; Narasimhan, K. M.; Saraswathy, V. G.; Sankararaman, S.
J. Org. Chem. 1996, 61, 1877. (b) Kulasegaram, S.; Kulawiec, R. J.
J. Org. Chem. 1997, 62, 6547. (c) Ranu, B. C.; Jana, U. J. Org. Chem.
1998, 63, 8212. (d) Robinson, M. W. C.; Pillinger, K. S.; Graham, A. E.
Tetrahedron Lett. 2006, 47, 5919. (e) Miyamoto, K.; Okuro, K.; Ohta, H.
Tetrahedron Lett. 2007, 48, 3255. (f) Tiffeneau, M. Bull. Soc. Chim. Fr. 1908,
1, 1205 and references cited therein.
(9) Under the reaction conditions prevailing with 1:2 BrO3-/Br- reagent,
the reactive species is likely to be H2OBrþ resulting in a strongly electrophilic
bromonium ion: Gilow, H. M.; Ridd, J. H. J. Chem. Soc., Perkin Trans. 2
1973, 1321. Rao, T. S.; Mali, S. I.; Damgat, V. T. Tetrahedron 1978, 34, 205.
With 4:1 BrO3-/Br-, still more reactive intermediates such as asymmetric
Br2O2 are possible: Taube, H.; Dodgen, H. J. Am. Chem. Soc. 1949, 71, 3330
apart from the participation of IBr in the reaction.5
7948 J. Org. Chem. Vol. 74, No. 20, 2009

Agrawal and Ghosh
JOCNote
influence of substituents at the 2-position would be dictated
by electronic effects such as inductive, π-donation (toward
formation of nonclassical carbonium ion), and hyperconju-
gative stabilization effects.10 The effective π-donating ability
of the phenyl substituent toward the stabilization of
the carbocation intermediate may be responsible for the
observed phenyl group migration in these cases. B3LYP/
LACVP* energy calculation on the substrate of entry 1,
Table 1, further suggests that the ground-state energy is
lowest when the phenyl group is antiperiplanar to the leaving
iodo group. This too would facilitate phenyl group migra-
tion.11 H-Migration occurred to a small extent (2-3%) with
styrene iodohydrin when the reaction temperature was raised
from 10 °C to room temperature,4 whereas in the case of
entry 7 the two pathways were equally facile at room
temperature given the similar proportions of phenyl acet-
aldehyde and acetophenone formed. The reaction of entry 8
provided the sole example in which the migratory aptitude of
hydrogen was higher than that of the phenyl group.12
In conclusion, we have chanced upon an interesting reac-
tion involving halonium ion-assisted electrophilic deiodina-
tion of styrene-based iodohydrins with accompanying
phenyl group transfer at 0-10 °C, the reaction with the
iodohydrin of methyl cinnamate being the only case where
H-migration was preferred over phenyl migration. Although
several reagents were effective, the best yields were obtained
with acid-activated bromate/bromide (4:1 mol ratio) which is
a source of reactive bromonium ion.
0.5 equiv of (2, 4-dinitrophenyl)hydrazine and dry THF until
a clear solution was obtained. The reaction mixture was refluxed
for 4 h employing a CaCl2 guard tube. The reaction mixture
was allowed to cool to room temperature, and methanol was
added until turbidity was seen. This solution was allowed
to chill at -15 °C and the precipitate filtered. The derivatives
of the products of entries 2, 4, and 6 were recrystallized from
CHCl3/petroleum ether at room temperature, while those for
entries 9 and 10 were recrystallized from THF/CCl4. The dried
solid was characterized using 1H, 13C, IR, MS, DSC, and
microanalysis (C, H, N) techniques. C, H, and N values indicate
percent (w/w). Data for characterized compounds are provided
below. Products of entries 5, 7, and 8 were identified on the basis
of GC-MS of the crude product mixtures.
1-(2,4-Dinitrophenyl)-2-(2-phenylethylidene)hydrazine (Entry
1, Table 1). 1H NMR (CDCl3, 500 MHz) δ: 3.76 (d, J(H,H) =
5.0 Hz, 2H), 7.26-7.37 (m, 5H), 7.62 (d, J(H,H) = 5.5 Hz, 1H),
7.97 (d, J(H,H) = 9.5 Hz, 1H), 8.31 (d, J(H,H) = 9.5 Hz, 1H),
9.09 (s, 1H), 11.04 (s, 1H). 13C NMR (CDCl3, 125 MHz) δ:
39.07, 116.6, 123.4, 127.2, 129.0, 130.0, 135.4 (quat-C), 137.9
(quat-C), 145.1 (quat-C), 148.7 (quat-C), 150.4 ppm. IR (KBr)
ν
max: 3293, 3101, 1618, 1592, 1332, 1306, 1262, 1215, 1139, 1075,
917, 841, 742, 700, 594 cm-1. GCMS (70 eV) m/z: 300.10 [Mþ],
obsd 323.61 [Mþ þ Na]. Anal. Calcd for C14H12N4O4: C, 56.00,
H, 4.03; N, 18.67. Found: C, 57.04, H, 4.07; N, 17.16. Mp:
112-113 °C.
1-(2,4-Dinitrophenyl)-2-(2-p-tolylethylidene)hydrazine (Entry
2, Table 1). 1H NMR (CDCl3, 500 MHz) δ: 2.34 (s, 3H), 3.70 (s,
2H), 7.13-7.17 (m, 4H), 7.57 (t, J(H,H) = 5.5 Hz, 1H), 7.96
(d, J(H,H) = 9.5 Hz, 1H), 8.30 (dd, J1(H,H) = 10.0 and J2(H,
H) = 2.5 Hz, 1H), 9.09 (d, J(H,H) = 1.0 Hz, 1H), 11.03 (s, 1H).
13C NMR (CDCl3, 125 MHz) δ: 20.5, 38.1, 116.0, 122.9, 128.3,
129.1, 129.4, 131.7 (quat-C), 136.4 (quat-C), 137.4 (quat-C),
144.6 (quat-C), 148.5 (quat-C), 150.1. IR (KBr) νmax: 3278,
3055, 2919, 2358, 1614, 1513, 1425, 1327, 1129, 1066, 1043,
915, 811, 740, 561, 515 cm-1. MS (70 eV) m/z: calcd 314.30 [Mþ],
obsd 345.57 [Mþ þ Na]. Anal. Calcd for C15H14N4O4: C, 57.32;
H, 4.49; N, 17.83. Found: C, 57.70; H, 4.46; N, 17.74. Mp:
148-149 °C.
1-(4-tert-Butylstyryl)-2-(2,4-dinitrophenyl)hydrazine (Entry 3,
Table 1). 1H NMR (CDCl3, 500 MHz) δ: 1.37 (s, 9H), 2.22-2.58
(m, 1H), 3.73-3.75 (t, J(H,H) = 6.5 Hz), 7.57(d, J(H,H) = 8.5
Hz, 2H), 8.05 (d, J(H,H) = 8.5 Hz, 2H), 8.11 (s, 1H), 8.28 (d,
J(H,H) = 9.5 Hz, 2H), 9.16 (d, J(H,H) = 2.5 Hz, 1H), 15.61 (s,
1H). 13C NMR (CDCl3, 125 MHz) δ: 30.5, 30.7 (quat-C), 116.7,
122.4 (quat-C), 125.7 125.8, 125.9, 128.3, 129.2, 130.3, 133.1
(quat-C), 143.9 (quat-C), 158.1 (quat-C). IR (KBr) νmax: 3291,
3106, 3026, 2924, 1614, 1591, 1508, 1413,1333, 1270, 1217, 1136,
1069, 1045, 790, 602, 470 cm-1. MS (70 eV) m/z: calcd 356.32
[Mþ], obsd 356.63 [Mþ]. Anal. Calcd for C18H20N4O4: C, 60.66;
H, 5.66; N, 15.72. Found: C, 57.57; H, 4.22; N, 14.72 (halogen-
containing impurities in the product may have depressed the C,
H, N values). Mp: 200-202 °C.
Experimental Section
General Procedure for Reaction of Iodohydrins with 4:1
BrO3-/Br- (Entry 1, Table 1). 2-Iodo-1-phenylethanol (744
mg, 3.0 mmol)13 and EDC (12 mL) were taken in a 50 mL round
bottomed flask and stirred in water bath at 0-10 °C. To the
above solution was added 177 mg of 4:1 NaBrO3/NaBr [1.0 mmol
NaBrO3 þ 0.25 mmol NaBr] in 2.0 mL of water followed by
H2SO4 (1.5 mmol in 1 mL water) in one portion under gentle
magnetic stirring, ensuring that the two phases were maintained
separate (Schotten-Baumann condition). Stirring was continued
for 3.0 h under the same conditions. The reaction mixture was
diluted with water and extracted with CH2Cl2 (25 mL ꢀ 3). The
combined organic layers were washed with aqueous Na2S2O3.
Finally, the layers were dried over anhydrous Na2SO4 and
concentrated under reduced pressure to get crude product
(92.1% yield by GCMS area %).
General Procedure for Preparation of the (2,4-Dinitrophenyl)-
hydrazine Derivatives of Carbonyl Compounds Obtained from the
Reactions of Iodohydrins with 4:1 BrO3-/Br- (Entry 1, Table 1).
To the crude product obtained in the above step was added
1-(2-(4-Bromophenyl)ethylidene)-2-(2,4-dinitrophenyl)hydrazine
(Entry 4, Table 1). 1H NMR (CDCl3, 500 MHz) δ: 3.71 (d, J(H,-
H) = 3.5 Hz, 2H), 7.14 (d, J(H,H) = 7.0 Hz, 2H), 7.47 (d, J(H,-
H) = 7.0 Hz, 2H), 7.58 (s, 1H), 7.93 (d, J(H,H) = 9.0 Hz, 1H), 8.31
(d, J(H,H) = 8.5 Hz, 1H), 9.09 (s, 1H), 11.07 (s, 1H). 13C NMR
(CDCl3, 125 MHz) δ: 38.4, 116.5, 121.2 (quat-C), 123.4, 129.1
(quat-C), 130.0, 130.7, 132.0, 134.4 (quat-C), 138.1 (quat-C),145.0
(quat-C), 149.3 ppm. IR (KBr) νmax: 3291, 3106, 3026, 2924, 1614,
1591, 1508, 1413,1333, 1270, 1217, 1136, 1069, 1045, 790, 602, 470
cm-1. (MS (70 eV) m/z: 377.99 [Mþ]/379.99 [Mþ þ 2], obsd 401.46
[Mþ þ Na]/403.46 [Mþ þ 2 þ Na]. Anal. Calcd for C14H11BrN4-
O4: C, 44.52; H, 2.92; N, 14.78. Found: C, 44.18; H, 2.57; N, 14.44.
Mp: 153-154 °C.
(10) (a) Alem, K. V.; Lodder, G.; Zuilhof, H. J. Phys. Chem. A 2002, 106,
10681. (b) Smith, M. B.; March, J. March’s Advanced Organic Chemistry:
Reactions, Mechanisms and Structure; Wiley: New York, 2007; Vol. 6, p 446.
(11) All geometries were fully optimized with the Becke3 Lee-
Yang-Parr (B3LYP) method: Becke, A. D. J. Chem. Phys. 1993, 98, 5648.
Lee, C.; Yang, W.; Parr, R. G. Phys. Rev. B 1988, 37, 785. The reactions used
the pseudopotential basis set LACVP*: Hay, P. J.; Wadt, W. R. J. Chem.
Phys. 1985, 82, 270. Vibrational analyses were also performed to confirm
the local minima. All calculations were performed using Spartan’06
(Wavefunction, Inc.: Irvine, CA) quantum chemical program (Ganguly,
B.; Kesharwani, M. K.; Agrawal, M. K.; Ghosh, P. K. Unpublished results).
(12) For the substrate of entry 8, Table 1, the ground-state energies of the
two conformers, i.e., phenyl antiperiplanar to I and H antiperiplanar to I,
were nearly equal, the former being lower by only 0.3 kcal/mol at the same
level of theory.11
(13) All the iodohydrins employed in the present work were synthesized
and isolated following the literature procedure: Agrawal, M. K.; Adimurthy,
S.; Ganguly, B.; Ghosh, P. K. Tetrahedron 2009, 65, 2791.
1-(2-(4-(Chloromethyl)phenyl)ethylidene)-2-(2,4-dinitrophenyl)-
hydrazine (Entry 6, Table 1). 1H NMR (CDCl3, 500 MHz) δ: 3.76
J. Org. Chem. Vol. 74, No. 20, 2009 7949

Agrawal and Ghosh
JOCNote
(d, J(H,H) = 5.5 Hz, 2H), 4.58 (s, 2H), 7.26-7.40 (m, 4H), 7.59 (t,
J(H,H) = 5.5 Hz, 1H), 7.95 (d, J(H,H) = 9.5 Hz, 1H), 8.31 (dd,
J1(H,H) = 2.5and J2(H,H) = 9.5 Hz, 1H), 9.08 (d, J(H,H) = 2.5
Hz, 1H), 11.05 (s, 1H). 13C NMR (CDCl3, 125 MHz) δ: 38.2, 45.3,
116.0, 122.9 (quat-C), 127.8 (quat-C), 128.5, 128.7, 128.8, 128.9,
129.5, 135.2 (quat-C), 144.5 (quat-C), 149.3. IR (KBr) νmax: 3299,
3095, 2925, 2856, 1618, 1592, 1423, 1332, 1311, 1266, 1133, 1076,
832, 741, 720, 679, 593, 508 cm-1. MS (70 eV) m/z: calcd 348.06
[Mþ]/350.08 [Mþ þ 2], obsd 347.62 [Mþ]/349.60 [Mþ þ 2]. Anal.
Calcd for C15H13ClN4O4: C, 51.66; H, 3.76; N, 16.07. Found: C,
51.73; H, 3.79; N, 15.98. Mp: 116-130 °C.
1-(2,4-Dinitrophenyl)-2-(1-phenylpropan-2-ylidene)hydrazine
(Entry 9, Table 1). 1H NMR (CDCl3, 500 MHz) δ: 2.00 (s, 3H),
2.73 (s, 2H), 7.25-7.36 (m, 5H), 8.00 (d, J(H,H) = 9.5 Hz, 1H),
8.31 (dd, J1(H,H) = 2.5 and J2(H,H) = 9.5 Hz, 1H), 9.12 (d,
J(H,H) = 2.5 Hz, 1H), 11.05 (s, 1H). 13C NMR (CDCl3, 125
MHz) δ: 14.9, 44.9, 116.0, 122.9 (quat-C), 126.6, 128.3, 128.5,
129.5, 135.6 (quat-C), 137.3 (quat-C), 144.7 (quat-C), 156.1
(quat-C). IR (KBr) νmax: 3299, 3095, 2925, 2856, 1618, 1592,
1423, 1332, 1311, 1266, 1133, 1076, 832, 741, 720, 679, 593, 508
cm-1. MS (70 eV) m/z calcd 314.10 [Mþ], obsd 315.55 [Mþ þ
Hþ]. Anal. Calcd for C15H14N4O4: C, 57.32; H, 4.49; N, 17.83.
Found: C, 56.77; H, 4.50; N, 17.44. Mp: 144-145 °C.
18.0, 42.5, 116.1, 122.9 (quat-C), 126.8, 127.0, 128.5, 129.5, 140.7
(quat-C), 144.7 (quat-C), 153.8. IR (KBr) νmax: 3291, 3069, 2931,
2887, 1615, 1515, 1451, 1424, 1326, 1220, 1129, 1090, 1018, 914,
836, 763, 699, 545, 516 cm-1. (MS (70 eV) m/z calcd 314.10 [Mþ],
obsd 337.57 [Mþ þ Na]. Anal. Calcd for C15H14N4O4: C, 57.32;
H, 4.49; N, 17.83. Found: C, 57.26; H, 4.21; N, 17.73. Mp:
116-118 °C.
Acknowledgment. We are grateful to Dr. B. Ganguly for
preliminary computational results, Dr. E. Suresh for single-
crystal X-ray data, Miss D. Kuvadia for GC-MS data,
Mr. V. Vakhani for microanalysis, Mr. H. Bhatt for NMR,
and Dr. P. Paul for all-round analytical support. We are
indebted to Dr. P. Harvey for pointing out errors in ele-
mental analyses which have since been corrected. We thank
the reviewers for their valuable comments. M.K.A. thanks
UGC, New Delhi, for the award of a UGC-NET fellowship,
and P.K.G. thanks CSIR, India, for support of this program.
Supporting Information Available: Solvent and reagent
1
optimization; GC-MS of crude products; H and 13C NMR
1-(2,4-Dinitrophenyl)-2-(2-phenylpropylidene)hydrazine (Entry
10, Table 1). 1H NMR (CDCl3, 500 MHz) δ: 1.58 (d, J(H,H) =
7.0 Hz, 3H), 3.85 (q, J(H,H) = 5.5 Hz, 1H), 7.26-7.60 (m, 6H),
7.97 (d, J(H,H) = 9.5 Hz, 1H) 8.31 (d, J(H,H) = 7.5 Hz, 1H),
9.10 (s, 1H), 11.02 (s, 1H). 13C NMR (CDCl3, 125 MHz) δ:
spectra; and combined crystallographic information files in CIF
format for 2,4-DNP derivatives of compounds of entries 2, 9,
and 10, Table 1, with CCDC nos. CCDC-739028, CCDC-
738835, and CCDC-738836, respectively. This material is avail-
able free of charge via the Internet at http://pubs.acs.org.
7950 J. Org. Chem. Vol. 74, No. 20, 2009