Reaction of 4-methylene-1,3-dioxolan-2-ones with hydrazines

Article abstract of DOI:10.1023/B:COHC.0000003524.65299.4d

The structure of the products of the reaction of 4-methylene-1,3-dioxolan-2-ones with hydrazines is a function of the structure of the starting hydrazine. 1,3,4-Oxadiazin-2-one derivatives are obtained from hydrazine hydrate. 3-Arylaminooxazolidin-2-ones are obtained from monoarylhydrazines, while mixtures of these derivatives are obtained from aliphatic monoalkylhydrazines.

Full text of DOI:10.1023/B:COHC.0000003524.65299.4d

Chemistry of Heterocyclic Compounds, Vol. 39, No. 8, 2003
REACTION OF 4-METHYLENE-
1,3-DIOXOLAN-2-ONES WITH HYDRAZINES
N. B. Chernysheva, A. A. Bogolyubov, and V. V. Semenov
The structure of the products of the reaction of 4-methylene-1,3-dioxolan-2-ones with hydrazines is a
function of the structure of the starting hydrazine. 1,3,4-Oxadiazin-2-one derivatives are obtained from
hydrazine hydrate. 3-Arylaminooxazolidin-2-ones are obtained from monoarylhydrazines, while
mixtures of these derivatives are obtained from aliphatic monoalkylhydrazines.
Keywords: 3-amino-4-hydroxyoxazolidin-2-ones, hydrazines, 5-hydroxy-1,3,4-oxadiazin-2-ones,
4-methylene-1,3-dioxolan-2-ones.
The reaction of readily available dioxolanones 1, obtained from tertiary propargyl alcohols and CO2,
with hydrazines 2 has not been studied extensively [1-3]. Dimroth [1] identified the products of this reaction as
linear carbamates 3. Such carbamates are undoubtedly obtained as intermediates in the first reaction step, but
then, in our opinion, undergo cyclization to give oxadiazinones 4 or oxazolidinones 6. Joumier et al. [2]
synthesized oxadiazinone 4a from dioxolanone 1a and hydrazine hydrate 2a. 1H NMR and IR spectroscopy was
used to confirm the cyclic structure of 4a, which itself was not isolated. These authors reported that
oxadiazinone 4a may undergo thermal dehydration to give oxadiazinone 5a and considered derivatives 5 to be
new compounds although they had already been reported by Rosenblum et al. [4] in 1963. In previous work [3],
we showed that N,N-dimethylhydrazine (NDMH) reacts with dioxolanone 1b as a primary amine,* leading to
the corresponding 3-dimethylaminooxazolidin-2-one.
O
R
R1
R
R1
.
.
NH2
NH
H2N–NH2
+
O
O
O
2a
O
1a–c
O
3
OH
R
N
NH
NH
NH
1
R
O
O
– H2O
O
5a
O
4a–c
1–4 a R = R1 = Me; b R + R1 = (CH2)5; c R = Me, R1 = Me2C=CHCH2CH2
_______
* The reaction with amines was examined in our earlier work [5].
__________________________________________________________________________________________
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow, Russia;
e-mail: vs@cacr.ioc.ac.ru. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1212-1219,
August, 2003. Original article submitted January 19, 2001.
0009-3122/03/3908-1057$25.00©2003 Plenum Publishing Corporation
1057

In the present study, we investigated the reaction of hydrazine hydrate 2a with dioxolanonones 1a-c,
which gives 1,3,5-oxadiazin-2-ones 4a-c. Crystalline 4a was obtained in 66% yield, mp 88-90°C. The other
indices of this compound given in Tables 1 and 2 are in accord with the data of Joumier [2]. Similar results were
obtained for new oxadiazinones 4b and 4c.
The IR spectra of oxadiazinones 4a-c show bands for OH and NH at 3220-3340 cm-1 and for C=O at
1710-1760 cm-1. The mass spectra of these compounds show an M+ peak.
The characteristic singlets for 5-OH (4.20-5.83 ppm) and 5-Me (3.92-1.34 ppm) disappear in the
1H NMR spectrum in going from 4 to 5, while the intensity of the NH peak at 3.92-4.12 ppm is reduced in half
and a singlet appears for the 5-Me group at the ring C=N bond at about 1.9 ppm.
In contrast to the case of hydrazine hydrate 2a, six-membered oxadiazinones A are not obtained from
aromatic hydrazines 2b and 2c and dioxolanones 1a-d, but rather five-membered oxazolidinones 6a-f. The
assignment of structure 6 was made on the basis of an X-ray diffraction structural determination of 6a [6, 7].
The 1H NMR spectra of 6a-f show signals for 4-OH at 6.16-6.39 ppm (1H, s or br. s), for 4-Me at 1.26-1.41 ppm
(3H, s or 2s), and for 3-NHAr at 7.42-7.67 ppm (1H, s). The IR spectra of these compounds have bands for OH
and NH at 3305-3390 cm-1 and for C=O at 1730-1765 cm-1. Their mass spectra show M+ peaks.
OH
R
R1
.
.
N
Ar
B
NH2–NH2–Ar
1a–d
+
O
NH
2b,c
O
A
O
O
N
R
R1
R
R1
R
R1
OH
+
+ HB
_
H
N
.
+
_
O
O
O
N
.
B
– HB
H
N
NH
Ar
NH–Ar
.
B
Ar
O
3
O
O
.
6a–f
1 d R = Me, R1 = Et; 2 b Ar = Ph, c Ar = 4-MeC6H4; 6 a R = R1 = Me, Ar = Ph;
b R+R1 = (CH2)5, Ar = Ph; c R = Me, R1 = Et, Ar = Ph, d R = Me, R1 = Et, Ar = 4-MeC6H4, e R = R1 = Me,
Ar = 4-MeC6H4, f R = Me, R1 = Me2C=CHCH2CH2, Ar = Ph
We attribute this change in the reaction course to the bond of the α-NH group in the arylhydrazines to
an aromatic ring. Thus, this group is not only less basic but also more sterically hindered than the β-NH2 group
so that the attack on the carbonyl group of dioxolanone 1 is achieved through the β-NH2 group.
The formation of oxazolidinone 6 instead of oxadiazinone A may also be attributed to the greater acidity
of the CONH proton in comparison with the NHAr proton. Thus, the CONH proton is more readily lost to base
:B (another arylhydrazine molecule or specially added base). The anion thereby obtained then attacks the
Me–C=O carbonyl group. Evidence for this scheme is seen in the increase in the yields of products 6 and in the
reaction rate in the presence of NEt3, which is a stronger base. In case of hydrazine hydrate 2a, the Me–C=O
group is attacked by the sterically less hindered primary NH2 group, which is more nucleophilic than the NHAr
group of the arylhydrazine.
In the case of alkylhydrazines, the α-NH group attached to an electron-donor substituent is more basic
than the β-NH2 group but more sterically hindered. Thus, the attack on the carbonyl site of dioxolanone 1a
proceeds by means of either amino group. Benzylhydrazine 2d reacts with dioxolanone 1a to give a mixture of
1058

TABLE 1. Physical Characteristics of Oxadiazinones 4 and 5 and Oxazolidinones 6*
IR spectrum,
Com-
mp*2, °C
Rf (system)
Mass-spectrum, m/z (I, %)
Yield, %
ν, cm-1
pound
88-90
0.4 (B)
1760 (CO)
160 (M+ 28.0), 142 (58.2), 117 (24.8), 101 (21.7), 99 (30.7), 85 (60.7), 84 (100.0)
66
4a
4b
4c
5b
5c
6a
6b
6c
6d
6e
6f
(92-95 [1])
108-110
3220, 3320 (NH, OH)*3
(91 [1])
1730 (CO)
200 (M+ 7.0), 198 (8.0), 182 (13.0), 149 (6.0), 126 (10.5), 125 (100.0), 112 (30.7),
108 (12.5), 99 (24.3), 96 (14.7), 91 (16.7)
81
0.82 (B)
(64-65 [1])
74-81
3340 (NH, OH)
(89 [1])
1710, 1740 (CO)
(M+ absent), 211 (3.3), 129 (67.9), 109 (17.6), 98 (11.8), 96 (15.6), 92 (41.6)
68*4
27
0.66 (B)
0.7 (C, twice)
0.43 (B, twice)
0.5 (D)
3340 (NH, OH)
1705 (C=N)
232 (M+ 19.1), 200 (4.0), 191 (25.7), 150 (16.1), 133 (30.8), 128 (35.5), 105 (13.7),
91 (100.0)
108-110
108-110
1675 (C=N)
3385 (OH)*5
186 (M+ 39.5), 169 (9.0), 156 (31.8), 155 (42.2), 143 (69.6), 111 (59.6), 97 (32.5)
36
1733 (CO)
236 (M+ 55.3), 218 (7.9), 174 (9.7), 153 (95.9), 150 (16.4), 135 (33.4), 134 (100.0),
108 (66.6), 107 (82.9), 93 (56.4), 92 (83.5)
67
134-136
(177-183 [1])
3340 (NH, OH)
(96 [1])
1730, 1750 (CO)
276 (M+ 7.2), 259 (5.5), 258 (0.2), 214 (4.9), 215 (11.3), 153 (10.3), 151 (100.0),
134 (43.6), 126 (52.7), 108 (43.9), 107 (14.2), 106 (12.7), 93 (21.9), 92 (40.6)
57
73
37
34
75
48
182-184
0.58 (E)
3330, 3340 (NH, OH)
1740 (CO)
250 (M+ 14.5), 232 (10.4), 188 (5.9), 173 (11.0), 151 (100.0), 134 (60.0), 107 (28.4),
93 (24.3), 92 (30.6)
92-94
0.55 (D)
3380 (NH, OH)*3
1740 (CO)
264 (M+ 2.9), 246 (8.3), 202 (4.1), 187 (9.5), 166 (69.6), 147 (74.0), 106 (100.0),
91 (73.0)
127-129
135-138
115-117
101-104
0.6 (D)
3390 (NH, OH)*3
1735, 1755 (CO)
250 (M+ 13.0), 232 (11.5), 188 (9.3), 187 (8.5), 166 (68.6), 147 (100.0), 121 (47.4),
106 (84.7), 91 (64.2)
0.51 (D)
3350 (NH, OH)
1765 (CO)
304 (M+ 2.1), 242 (0.5), 174 (15.3), 152 (47.3), 136 (11.2), 135 (32.2), 161 (11.0),
108 (35.7), 107 (17.4), 106 (14.5), 105 (13.9), 95 (14.6), 93 (40.7)
0.66 (E)
3310, 3370 (NH, OH)
1735 (CO)
250 (M+ 5.0), 206 (0.2), 166 (16.2), 148 (19.0), 146 (12.4), 128 (13.5), 127 (10.4),
122 (21.0), 112 (12.2), 107 (20.2), 106 (80.3), 105 (32.0), 104 (20.3), 97 (14.5),
91 (100.0)
0.24 (C, twice)
6g
3305, 3360 (NH, OH)
_______
* Products 4c, 6c, 6d, and 6f are epimers.
*2 In a sealed capillary.
*3 Spectrum taken on a UR-20 spectrometer.
*4 Without additional purification.
5
β
* Hydroxyl group of the -hydroxyethyl substituent.

TABLE 2. 1H NMR Spectra of 4, 5 and 6
Proton chemical shifts, δ, ppm (SSCC, J, Hz)*
Com-
4/5-OH*2
(1H, s)
4/5-CH3*2
(3H, s)
R1
NR2
pound
NH
R
4.20, 4.30
(2s)
5.23
3.92 (2H, s)
1.34
1.28
[1.45 (3H, s), 1.42 (3H, s)] two CH3
4a
4b
4c
—
—
4.08 (1H, s),
4.12 (1H, s)
4.11 (2H, s)
[1.10-1.80 (9H, m), 1.90-2.00 (1H, m)] (CH2)5
—
5.83
1.25,
1.33, 1.49
(3H, 2s, CH3)
[1.47-1.76 (2H, m), 1.90-2.20 (2H, m)] CH2CH2,
1.29 (2s)
5.05-5.17 (1H, m, CH=C(CH3)2),
[1.60 (3H, s), 1.66 (3H, s)] CH=C(CH3)2
1.97
1.98
1.42 (6H, s, two CH3)
1.42 (6H, s, two CH3)
4.79 (2H, s, PhCH2); 7.22-7.40 (5H, m, 2'-6'-HPh)
5a
5b
—
—
—
—
3.58 (2H, q, CH2CH2OH); 3.55 (2H, t, CH2CH2OH);
4.60 (1H, t, CH2CH2OH)
6.22
6.16
7.64 (1H, s)
7.53 (1H, s)
1.41
1.26
[1.30 (3H, s), 1.38 (3H, s)] two CH3
[1.46-1.76 (8H, m), 1.77-1.80 (1H, m), 1.89-2.11 (1H, m)] (CH2)5
6.15-7.00 (3H, m); 7.05-7.22 (2H, m, 2'-6'-HPh)
6a
6b
6.84 (1H, d, J = 7.1, 2'-, 6'-HPh); 7.14 (2H, t,
3'-, 5'-HPh); 6.75 (1H, t, 4'-HPh)
6.26
7.63 (1H, s)
7.42 (1H, s)
7.50 (1H, s)
7.67 (1H, s)
1.40
1.31
1.60-1.95 (2H, m, CH2CH3),
0.94 (3H, t, CH2CH3)
[6.15-7.0 (3H, m); 7.05-7.22 (2H, m)] 2'-6'-HPh
6c
6d
6e
6f
(br. s)
(3H, s, CH3)
6.22
6.25
6.39
1.37,
1.30, 1.32
1.52-1.94 (2H, m, CH2CH3),
[6.72 (2H, d, J = 8.5), 6.98 (2H, d, J = 8.5)]
1.40 (2s)
(3H, 2s, CH3)
0.93-1.08 (3H, m, CH2CH3)
2'-, 3'-, 5'-, 6'-HPh); 2.20 (3H, s, 4'-CH3(Ph))
1.40
[1.30 (3H, s), 1.38 (3H, s)] two CH3
[6.72 (2H, d, J = 8.5); 6.98 (2H, d, J = 8.5)]
2-', 3'-, 5'-, 6'-HPh; 2.18 (3H, s, 4'-CH3(Ph)
)
1.45
1.35
1.55-1.89 (2H, m), 2.00-2.21 (2H, m), CH2CH2,
5.17 (1H, t, CH=C(CH3)2); [1.63 (3H, s),
1.67 (3H, s)] CH=C(CH3)2
6.85 (1H, d, J = 8.63, 2'-, 6'-HPh);
(3H, s, CH3)
7.16 (2H, t, 3'-, 5'-HPh); 6.75 (1H, t, 4'-HPh)
4.93
5.79 (1H, s)
1.26
[0.94 (3H, s), 1.14 (3H, s)] two CH3
[3.98 (1H, d, J = 1.0); 4.02 (1H, d, J = 1.0)] PhCH2;
6g
7.20-7.40 (5H, m, 2'-, 6'-HPh)
_______
* 1H NMR spectra taken in CDCl3 (4a) and DMSO-d6 (other compounds).
*2 Position 4 in oxazolidinones 6 and position 5 in oxadiazinones 4 and 5.

products 5b and 6g.* Ethanolhydrazine 2e also gives a complex mixture of products, from which oxadiazinone
5c could be isolated. The five-membered product 6g is formed instead of six-membered B apparently due to
steric hindrance to attack of the PhCH2NH moiety at the ketonic carbonyl group in the corresponding linear
intermediate oxourethane 3.
OH
O
NH
N
+ NH2NHCH2R
H
N
+
1a–c
O
O
CH2R
NHCH2R
O
3
O
2d,e
4
–H2O
OH
OH
NBn
NH
N
N
O
N
O
O
NHCH2R
CH2R
O
O
B
O
6g
5b,c
2d, 5b, 6g R = Ph; 2e, 5c R = CH2OH
The dehydrated product, cyclic hydrazone 5b is formed from the corresponding 5-hydroxyoxadiazinone
4 but the latter could not be isolated. The question of the structure of 6g was elucidated by X-ray diffraction
structural analysis [6, 7]. The 1H NMR spectrum of oxazolidinone 6g shows signals for 4-OH at 4.93 ppm (1H,
s) and 3-NHCH2Ph at 5.79 ppm (1H, s), which are shifted downfield relative to the signals of the analogous
protons in oxazolidinones 6a-f. The expected bands for C=O and NH are found in the IR spectrum of 6g, while
the mass spectrum of this compound shows a molecular peak. Products 4c and 6f, which have two asymmetric
sites, appear upon thin-layer chromatography as two spots belonging to two epimers. The 1H NMR spectra of 5a
and 5b lack NH and OH peaks, while the hydroxyl group in the 3-CH2CH2OH substituent in 5c appears as a
triplet at 4.6 ppm. The 5-Me group in oxadiazinones 5b and 5c appears at 1.97-1.98 ppm since it is located at
the C=N bond. The IR spectra of these compounds show a band for the C=N bond at 1675-1705 cm-1 but lack a
band for NH (the hydroxyl group of the 3-CH2CH2OH substituent in 5c appears at 3385 cm-1). The structure of
5c was also supported by its 13C NMR spectrum in DMSO-d6, δ, ppm: 17.43 (q, CH3-6,6), 23.39 (q, CH3-5),
52.30 (t, H2-α), 59.37 (t, CH2-β), 79.12 (s, C-6), 149.61 (s, C-5), 152.98 (s, C-2).
Thus, we have found that the structure and composition of the products of the reaction of dioxolanones
1 with hydrazines depend on the structure of the hydrazine.
In acid media, 4c and 6f undergo an extremely interesting intramolecular amidoalkylation, leading in
both cases to derivatives of the same new tricyclic system, namely, 4,4,6a,6b-tetramethylhexahydro-3H-1-oxa-
2a,3-diazacyclopenta[cd]pentalen-2-ones [8]. This question will be treated in a future publication.
_______
* Thin-layer chromatography indicated that several minor components are present in the reaction medium but
these products could not be isolated.
1061

EXPERIMENTAL
1
The H NMR spectra were taken on a Bruker WM-250 spectrometer at 250 MHz with TMS as the
internal standard. The IR spectra were taken on a Perkin–Elmer spectrometer for KBr pellets or neat samples.
The mass spectra were taken on a Kratos MS-30 mass spectrometer with direct sample inlet and 70 eV ionizing
voltage. The temperature of the ionization chamber was 250°C. Thin-layer chromatography was carried out on
Silufol UV-254 plates with the following eluents: 2:1 benzene–ethyl acetate (A), 2:1 acetonitrile–benzene (B),
4:1 benzene–ethyl acetate (C), 1:1 benzene–ethyl acetate (D), and 2:1 benzene–acetonitrile (E).
Chromatographic separation was obtained by flash chromatography on a dry column packed with Silufol 5/40
[10] with gradient elution with benzene–ethyl acetate.
Dioxolanones 1a-d were obtained according to Dimroth [9].
General Method for the Reaction of Hydrazines 2 with Dioxolanones 1. A solution of corresponding
hydrazine (10-40 mmol) in CH2Cl2 (or pure hydrazine) was added with stirring to a solution of the
corresponding dioxolanone 1 in CH2Cl2 or in 10:3 ether–hexane (10-40 mmoles reagent per 5-30 ml solvent).
Heating was sometimes noted and the mixture was cooled in these cases. The mixture was maintained for the
period indicated for each procedure at room temperature. The solvent was evaporated off and the residue was
maintained for the indicated period at 60°C. Specific work-up followed as indicated for each procedure.
2,3,4,5,6-H-5-Hydroxy-5,6,6-trimethyl-1,3,4-oxadiazin-2-one (4a). A sample of hydrazine hydrate 2a
(1.20 g, 24 mmol) was added with cooling to dioxolanone 1a (3.07 g, 24 mmol) in CH2Cl2 (10 ml) for 10 min.
The mixture was maintained for 48 h at room temperature and for 20 h at 60°C. The crystals obtained were
washed with three 2-ml benzene portions to give 2.15 g of 4a as white crystals.
2,3,4,5,6-H-5-Hydroxy-5-methyl-6,6-pentamethylen-1,3,4-oxadiazin-2-one (4b).
A
sample of
hydrazine hydrate 2a (0.97 g, 30.3 mmol) was added with cooling to dioxolanone 1b (5.88 g, 30 mmol) in
CH2Cl2 (10 ml). The mixture was maintained for 48 h at room temperature. The solvent was evaporated. Then,
hexane (10 ml) was added and the residue was crystallized upon trituration. The crystals were washed with five
5-ml hexane portions to give 5.55 g of 4b as white crystals.
2,3,4,5,6-H-5-Hydroxy-5,6-dimethyl-6-(4-methyl-3-pentenyl)-1,3,4-oxadiazin-2-one (4c). A sample
of hydrazine hydrate 2a (1.14 g, 30.3 mmol) was added with cooling to dioxolanone 1c (5.85 g, 30 mmol) in
CH2Cl2 (5 ml). The mixture was maintained for 48 h at room temperature and 20 h at 60°C. Then, the mixture
was dissolved in CH2Cl2 (5 ml) and 3 ml hexane was added to the solution. The mixture was triturated in an ice
bath. The crystals were washed with three 4-ml hexane portions and filtered to give 2.63 g product. The wash
liquids were combined with the mother liquor and evaporated to 10 ml. This mixture was treated as before to
give an additional 1.23 g product. All the crude crystalline product was combined and recrystallized from
benzene (4 ml) by adding hexane (15 ml) and triturating the precipitated product on an ice bath to give 4.62 g of
white crystalline 4c. (If the product proved insufficiently pure by thin-layer chromatography, it was
recrystallized from 15:4 hexane–benzene (19 ml). This procedure gave 4.31 g final product from 4.62 g of crude
product).
2,3,6-H-3-Benzyl-5,5,6-trimethyl-oxadiazin-2-one (5b), 3-Benzylamino-4-hydroxy-4,5,5-trimethyl-
oxazolidin-2-one (6g). A sample of hydrazine (3.17 g, 20 mmol) hydrochloride 2d was dissolved in water
(10 ml) and, then, solid NaOH (0.8 g, 20 mmol) was added. The mixture was stirred until all the solid dissolved.
Then, dioxolanone 1a (2.56 g) was added. The mixture became turbid, warmed, and separated into two layers. A
white precipitate formed. The mixture was left at room temperature for 48 h. The crystals were removed and
washed with water to give 3.85 g of crystals (1H NMR spectroscopy indicated a ~1:1 mixture of 5b and 6g).
Recrystallization once from 12 ml of benzene and once from 8 ml of benzene gave 2.18 g of white crystalline
6g. The mother liquor was evaporated and 1.67 g residue was subjected to chromatography to give 1.25 g of
white crystalline 5b and an additional 0.2 g of 6g (the total yield of 6g was 2.38 g). The total yield of 5b and 6g
was 75%.
1062

2,3,6-H-3-(2-Hydroxyethyl)-5,5,6-trimethyl-1,3,4-oxadiazin-2-one (5c). By analogy to 4a, the
addition of hydrazine 2e (2.28 g, 30 mmol) without cooling to dioxolanone 1a (4.10 g, 32 mmol) in CH2Cl2
(10 ml) followed by standing at room temperature for 20 h gave 2 g of 5c as white crystals. Thin-layer
chromatography indicated that the mother liquor contained not less than five minor products, which were not
isolated.
4-Hydroxy-4,5,5-trimethyl-3-phenylaminooxazolidin-2-one (6a). By analogy to 4a, the addition of
hydrazine 2b (1.62 g, 15 mmol) without cooling to dioxolanone 1a (1.92 g, 15 mmol) in CH2Cl2 (10 ml)
followed by standing for 48 h at room temperature and, after evaporation, for 6 h at 60°C gave 2.38 g of 6a as
white crystals.
4-Hydroxy-4-methyl-5-pentamethylene-3-phenylaminooxazolidin-2-one (6b). The reaction of
hydrazine 2b (3.27 g, 30.3 mmol) and dioxolanone 1b (5.88 g, 30 mmol) in CH2Cl2 (10 ml) after standing for
24 h at room temperature (according to the general method without cooling at the onset and without heating at
60°C after evaporation) gave crude product, from which crystals were separated. The precipitate was washed
with four 10-ml portions of 3:2 hexane–benzene and three 15-ml portions of 4:1 hexane–benzene to give 5.21 g
of 6b as crystals which yellow slightly in the air.
5-Ethyl-4-hydroxy-4,5-dimethyl-3-phenylaminooxazolidin-2-one (6d). By analogy to 4a, the
addition of hydrazine 2b (1.12 g, 11 mmol) without cooling to dioxolanone 1d (1.42 g, 10 mmol) in CH2Cl2
(15 ml) in the presence of two or three drops of NEt3 followed by standing for 48 h at room temperature and,
after evaporation of the solvent, 2 h at 60°C gave 1.83 g of 6c as white crystals.
5-Ethyl-4-hydroxy-4,5-dimethyl-3-(4-methylphenyl)aminooxazolidin-2-one (6d). By analogy to 4a,
the addition of hydrazine 2c (4.88 g, 40 mmol) without cooling to dioxolanone 1d (5.68 g, 40 mmol) in CH2Cl2
(30 ml) followed by standing for 26 h at room temperature and, after evaporation of the solvent, 9 h at 60°C
gave 3.89 g of 6d as white crystals.
4-Hydroxy-3-(4-methylphenyl)amino-4,5,5-trimethyloxazolidin-2-one (6e). By analogy to 4a, the
addition of hydrazine 2c (4.88 g, 40 mmol) without cooling to dioxolanone 1a (5.12 g, 40 mmol) in CH2Cl2
(30 ml) followed by standing for 16 h at room temperature and, after evaporation of the solvent, 9 h at 60°C
gave 3.93 g of 6e as white crystals.
4-Hydroxy-4,5-dimethyl-5-(4-methyl-3-pentenyl)-3-phenylaminooxazolidin-2-one (6f). The reaction
of hydrazine 2b (3.35 g, 31 mmol) and dioxolanone 1c (5.85 g, 30 mmol) in 12:1 hexane–ether (13 ml) with
standing for 144 h at room temperature (according to the general procedure without cooling at the onset and
without maintenance at 60°C at the end) gave a mixture, from which crystalline crude product was separated.
The crude product was washed with two 6-ml portions of hexane–ether to give 2.07 g of product. The wash
liquids and mother liquor were combined and three or four drops of NEt3 was added. The mixture was left for
24 h. The crystalline precipitate was filtered off and washed as previously indicated to give an additional 4.77 g
of product. The total product was 6.84 g of 6f as slightly brownish crystals.
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