Catalytic Annulation of Epoxides with Heterocumulenes by the Indium-Tin System.

In the synthesis of five-membered heterocycles by the annulation of epoxides with heterocumulenes such as carbon dioxide and isocyanates, we developed the indium-tin catalytic system and synthesized various cyclic adducts including novel types products under mild reaction conditions.

1. Introduction

Synthesis of five-membered heterocycles by the annulation of epoxides with n class="Chemical">heterocumulenes such as carbon dioxide and isocyanates has been intensively studied [1,2,3]. For the use of carbon dioxide, its catalytic transformation to useful organic compounds has attracted much attention [4,5,6,7,8]. In particular, fixation of carbon dioxide to cyclic carbonates is one of the most important processes of high atom efficiency [9]. Cyclic carbonates are known to be efficient aprotic polar solvents [10,11,12], electrolytes in lithium ion batteries [13,14] and materials for producing polycarbonates [15]. Instead of the products from carbon dioxide, the cyclic adducts of epoxides with isocyanates such as 2-oxazolidinones [16,17] are important biologically-active compounds [18,19,20,21,22] and synthetic intermediates such as precursors of amino alcohols and chiral auxiliaries [23,24,25,26,27,28,29,30,31]. We present here a simple, easily available catalyst, the indium-tin system, and provide the environmentally-benign process to annulated adducts under mild conditions.

2. Results

2.1. Synthesis of Cyclic Carbonates

Until now, various catalysts such as transition metal compounds, ionic liquid, n class="Chemical">onium salts and alkali metal salts, etc., have been developed for the reaction of epoxides with carbon dioxide [5,32,33]. However, these methods suffer from either the need for co-solvent, the requirement for high temperature, high CO2 pressure or expensive catalyst. Indium reagents and catalysts have been applied in modern organic synthesis by their mildness and easy handling character [34]. By using the indium halide-phosphine complex, we have already developed the reaction of terminal epoxides to give cyclic carbonates under atmospheric CO2 pressure at room temperature [35], which indicated that indium halide-based catalysts have efficient catalytic activities. As shown in Table 1, we screened indium halide catalytic systems in the reaction of epoxide 1a with CO2 (3.9 MPa) at room temperature. The sole use of InCl3 did not have catalytic activity (Entry 1). Interestingly, the combination of Bu2SnI2 with InCl3 increased the yield of carbonate 2a (Entry 2). The sole use of Bu2SnI2 was not effective at all (Entry 3). Thus, the InCl3-Bu2SnI2 system showed a high catalytic activity. Of particular interest is that the reaction proceeded well even at room temperature. The choice of acetonitrile as a solvent is essential because no reaction proceeded when other solvents such as hexane, benzene, CHCl3 and THF were used. In acetonitrile, the reaction proceeded very well, and various cyclic carbonates 2 were obtained from epoxides 1b–1f catalyzed by InCl3-Bu2SnI2. Epoxides having aliphatic and aromatic substituents were reactive to afford the corresponding cyclic carbonates 2b–2c (Entries 4 and 5). High chemoselectivities were observed because of the mild conditions. Functionalized cyclic carbonates 2d–2f were synthesized from epoxides having halogen and oxygen substitutes (Entries 6–8).

Table 1

Synthesis of cyclic carbonates 2 from epoxides 1 with CO2 at rt a.

Entry	R	Cat.	Time (h)	Product		Yield 2 (%) b
1	Me (1a)	InCl3	5		2a	trace
2		InCl3-Bu2SnI2	5			78
3		Bu2SnI2	5			trace
4	Et (1b)	InCl3-Bu2SnI2	8		2b	85
5	Ph (1c)	InCl3-Bu2SnI2	10		2c	69
6	CH2Cl (1d)	InCl3-Bu2SnI2	5		2d	82
7	CH2OPh (1e)	InCl3-Bu2SnI2	5		2e	90
8	CH2OMe (1f)	InCl3-Bu2SnI2	10		2f	68

a InCl3 0.5 mmol, Bu2SnI2 1 mmol, epoxide 1 10 mmol, CO2 3.9 Pa, MeCN 3 mL; b Determined by 1H-NMR.

2.2. Synthesis of 2-Oxazolidinones

Instead of using carbon dioxide, the cyclic adducts of n class="Chemical">epoxides with isocyanates are highly in demand [18,19,20,21,22,23,24,25,26,27,28,29,30,31]. To effect the reaction, various catalysts have been used such as lithium halides [36,37,38,39,40,41,42], quaternary ammonium salts [43,44], phosphonium salt [45], AlCl3 [46], magnesium halides [47], tetraphenylantimony iodide [48,49,50] and the chromium(Salphen) complex [51]. These catalysts promoting reactions require relatively severe conditions (over 100 °C). The Pd-catalyzed reaction enabled mild conditions and accomplished an asymmetric reaction; however, in the reaction, only vinyl-substituted epoxides could be applicable where π-allyl palladium intermediates should be generated [52]. We have already reported that the Bu3SnI-Ph3PO or Ph4SbI catalyzes the annulation of epoxides with aromatic isocyanates to give 3,5-disubstututed-2-oxazolidinones [53,54,55,56], which indicated that tin halide-based catalysts would afford efficient catalytic activity. In view of these backgrounds, we tested the catalytic activity of the Bu2SnI2-InCl3 system as shown in Table 2. In the reaction of epoxybutane 1b with tert-BuN=C=O (3a), a quantitative yield of 2-oxazolidinone 4a was obtained (Entry 1). Interestingly, steric hindrance of isocyanates was not a problem to give 2-oxazolidinones 4. The use of either Bu2SnI2 or InCl3 was not effective (Entries 2 and 3). Thus, it was clear that the InCl3-Bu2SnI2 catalytic system showed a high activity even for the synthesis of 2-oxazolidinones 4. Other epoxides such as epichlorohydrin 1d and glycidylic ethers 1e, 1f also reacted well (Entries 4–6). Of course, primary aliphatic isocyanate 3b and phenyl isocyanate 3c also gave the desired products 4e and 4f, although the yields were moderate owing to the trimerization of an isocyanate as a side reaction (Entries 7 and 8) [51,57]. Thus, higher yields of 4a–d in the reaction of tert-BuN=C=O (3a) were achieved because the trimerization would be depressed by steric hindrance of 3a. In all cases, regioselective ring opening of epoxides took place at the less substituted site to give 3,5-disubstituted-2-oxazolidinones 4.

Table 2

Synthesis of 2-oxazolidinones 4 from epoxides 1b–f with isocyanates 3 a.

Entry	R1	R2	Conditions	Product		Yield 3 (%) b
1	Et (1b)	t-Bu (3a)	rt, 10 h		4a	79
2						7 c
3						trace d
4	CH2Cl (1d)		60 °C, 3 h		4b	79
5	CH2OPh (1e)		60 °C, 3 h		4c	90
6	CH2OMe (1f)		60 °C, 3 h		4d	99
7	Et (1b)	n-Bu (3b)	60 °C, 7 h		4e	49
8	Et (1b)	Ph (3c)	rt, 20 h		4f	64

a InCl3 0.25 mmol, Bu2SnI2 0.5 mmol, epoxide 1 5 mmol, isocyanate 3 5.5 mmol, MeCN 1.5 mL, under nitrogen; b Determined by 1H-NMR; c Only Bu2SnI2 was used; d Only InCl3 was used.

In the reaction with diphenyl carbodiimide, an analogue of n class="Chemical">isocyanates, the oxazolidin-2-imine 5, was obtained in good yield (Scheme 1).

Scheme 1

Catalytic synthesis of oxazolidin-2-imine 5.

3. Discussion

As shown in Figure 1, the structure of the Bu2SnI2-n class="Chemical">InCl3 system could be supposed by the measurement of 119Sn-NMR spectra in acetonitrile. The addition of equimolar InCl3 to Bu2SnI2 in acetonitrile clearly changed the 119Sn peak from a strong one at −38 ppm to a broad one at 3 ppm. This downfield shift indicates that tin species had a positive character by the combination with InCl3 [58,59].

Figure 1

119Sn NMR of the tin-indium system.

The catalytic cycle is explained as shown in Scheme 2. By the interaction of tin and n class="Chemical">indium species, Lewis acidic tin species like Bu2SnI+[InCl3I]− would be generated, which activate the epoxide ring [60,61,62,63]. This active bimetallic species is plausible because transmetallation between tin and indium reagents easily takes place [64,65,66,67,68]. The ring opening of an epoxide to A proceeds regioselectively at the less substituted carbon. Next, the tin-oxygen bond in A is added to heterocumulene to give an adduct B. In the case of isocyanates, the addition occurs at the C=N group selectively to give a stannylcarbamate B [69,70,71]. At the last stage, the Sn-X (X=O, NR) bond in the intermediate B attacks the terminal alkyl iodide [72,73] to afford cyclic carbonates 2 and 2-oxazolidinones 4 and regenerate the catalyst. The 1H-NMR of products 4 showed single regio isomers because of the regioselective ring opening of epoxides. For example, 5-H and 4-H peaks for 4f were found at 4.59 (1H), 4.08–3.66 (2H) ppm, respectively. On the other hand, it has been reported by us that 1H-NMR for another regio isomer showed its 5-H and 4-H peaks at 4.65–4.30 (2H), 4.22–4.04 (1H) ppm, respectively [49].

Scheme 2

A plausible catalytic cycle.

4. Materials and Methods

4.1. Analysis

FTIR spectra were recorded as a thin film on a Nicolet IS5 spectrometer (Thermo Electron Scientific Instruments LLC, Madison, WI, USA). All 1H and n class="Chemical">13C-NMR spectra were recorded with a JEOL JMTC-400/54/SS (400 and 100 MHz, respectively) in deuteriochloroform (CDCl3) containing 0.03% (w/v) of tetramethylsilane as an internal standard. Temperatures shown in schemes or tables were controlled by a constant-temperature oil bath. Yields were determined by 1H-NMR using 1,1,1,2-tetrachloroethane or 1,1,2,2-tetrachloroethane as an internal standard. Mass spectra were recorded on a JEOL JMS-DS-303 spectrometer (JEOL Ltd., Tokyo, Japan). Flash column chromatography was performed by Yamazen YFLC-AI-580 using Hi-Flash Silica gel 2L Hi-Flash Column 20 mL/min eluted by hexane/EtOAc with the gradation mode changing from 9/1–3/7 depending on Rf values of each compound. Bulb-to-bulb distillation (Kugelrohr) was accomplished at the oven temperature and pressure indicated.

Dehydrated n class="Chemical">acetonitrile (MeCN) was purchased from commercial sources and used as obtained. Deuterated acetonitrile was also purchased and stored drying over 4 Å molecular sieves. All epoxides, isocyanates, carbodiimide and InCl3 were also purchased and used as obtained. Bu2SnI2 was prepared according to the previous report [74].

4.2. General Procedure for Synthesis of Cyclic Carbonates – from Epoxides with CO2

To a 50-mL autoclave, InCl3 (0.5 mmol), n class="Chemical">Bu2SnI2 (1.0 mmol) and epoxide 1 (10 mmol) were added in MeCN (3 mL). The autoclave was flushed with CO2 (3.9 MPa) and stirred at room temperature for 5–10 h. After release of the CO2 gas, the reaction mixture was quenched with H2O (20 mL) and extracted with Et2O (3 × 20 mL). The collected organic layer was dried over MgSO4. After filtration, the mixture was concentrated in vacuo. The residue was purified by column chromatography. Further purification was performed by Kugelrohr distillation to give a pure product 2.

4-Methyl-1.3-dioxolan-2-one (2a). Colorless liquid. The NMR data of n class="Chemical">1H and 13C agreed with the previous report. [75]. 1H-NMR: (270 MHz, CDCl3) δ 4.70 (ddd, J = 6.4, 7.3, 7.8 Hz, 1H, 4-H), 4.38 (dd, J = 7.8, 8.3 Hz, 1H, 5HH), 3.84 (dd, J = 7.3, 8.3 Hz, 1H, 5HH), 1.29 (d, J = 6.34 Hz, 3H, 4-CH3). 13C-NMR: (67.5 MHz, CDCl3) δ 155.00 (C-2), 73.55 (C-4), 70.58 (C-5), 19.18 (4-CH3).

4-Ethyl-1.3-dioxolan-2-one (2b). Colorless liquid. The NMR data of n class="Chemical">1H and 13C agreed with the previous report [76]. 1H-NMR: (270 MHz, CDCl3) δ 4.70–4.65 (m, 1H, 4-H), 4.56 (dd, J = 8.3, 8.3 Hz, 1H, 5HH), 4.12 (dd, J = 7.8, 7.8 Hz, 1H, 5HH) 1.88–1.68 (m, 2H, 4-CH2CH3), 1.03 (t, J = 7.3 Hz, 3H, 4-CH2CH3). 13C NMR: (67.5 MHz, CDCl3) δ 154.91 (C-2), 77.88 (C-4), 68.83 (C-5), 26.59 (4-CH2CH3), 8.20 (4-CH2CH3).

4-Phenyl-1.3-dioxolan-2-one (2c). Colorless liquid. The NMR data of n class="Chemical">1H and 13C agreed with the previous report [75]. 1H-NMR: (270 MHz, CDCl3) δ 7.44–7.18 (m, 5H, Ph), 5.66 (t, J = 8.1 Hz, 1H, 4-H) 4.78 (dd, J = 8.3, 8.3 Hz, 1H, 5HH), 4.33 (dd, J = 7.8, 7.8 Hz, 1H, 5HH). 13C-NMR: (67.5 MHz, CDCl3) δ 154.71 (C-2), 135.67 (i), 129.62 (m), 129.12 (p), 125.77 (o), 77.92 (C-4), 71.10 (C-5).

4-(Chloromethyl)-1,3-dioxolan-2-one (2d). Colorless liquid. The NMR data of n class="Chemical">1H and 13C agreed with the previous report [75]. 1H-NMR: (270 MHz, CDCl3) δ 5.10–5.02 (m, 1H, 4-H), 4.63 (dd, J = 8.8, 8.8 Hz, 1H, 5HH), 4.41 (dd, J = 5.8, 8.8 Hz, 1H, 5HH), 3.88 (dd, J = 4.4, 12.2 Hz, 1H, CHHCl), 3.76 (dd, J = 3.4, 12.2 Hz, 1H, CHHCl). 13C-NMR: (67.5 MHz, CDCl3) δ 154.33 (C-2), 74.33 (C-4), 66.70 (C-5), 44.01 (CH2Cl).

4-(Phenoxymethyl)-1,3-dioxolan-2-one (2e). Colorless liquid. The NMR data of n class="Chemical">1H and 13C agreed with the previous report [76]. 1H-NMR: (270 MHz, CDCl3) δ 7.35–6.87 (m, 5H, Ph), 5.08–4.99 (m, 1H, 4-H), 4.62 (dd, J = 8.3, 8.8 Hz, 1H, CHHOPh), 4.54 (dd, J = 6.4, 8.8 Hz, 1H, CHHOPh), 4.25 (dd, J = 3.9, 10.3 Hz, 1H, 5HH), 4.15 (dd, J = 3.9, 10.3 Hz, 1H, 5HH). 13C-NMR: (67.5 MHz, CDCl3) δ 157.72 (o), 154.67 (C-2), 129.55 (p), 121.98 (m), 114.59 (m), 74.10 (CH2OPh), 66.87 (C-4), 66.23 (C-5).

4-(Methoxymethyl)-1,3-dioxolan-2-one (2f). Colorless liquid. The NMR data of n class="Chemical">1H and 13C agreed with the previous report [35]. 1H-NMR: (270 MHz, CDCl3) δ 4.88–4.80 (m, 1H, 4-H), 4.51 (dd, J = 8.3, 8.8 Hz, 1H, 5HH), 4.37 (dd, J = 6.3, 8.3 Hz, 1H, 5HH), 3.67 (dd, J = 3.4, 11.2 Hz, 1H, CHHOCH3), 3.54 (dd, J = 3.9, 11.2 Hz, 1H, CHHOCH3), 3.43 (s, 3H, OCH3). 13C-NMR: (67.5 MHz, CDCl3) δ 154.91 (C-2), 75.01 (C-4), 71.27 (CH2OCH3), 65.97 (C-5), 59.34 (OCH3).

4.3. General Procedure for Synthesis of 2-Oxazolidinones from Epoxides – with Isocyanates and Oxazolidin-2-imine

To a two-neck 10-mL reaction vessel, InCl3 (0.25 mmol), n class="Chemical">Bu2SnI2 (0.50 mmol), epoxide 1 (5 mmol) and isocyanate 3 (5.5 mmol) were added in MeCN (1.5 mL) under N2 atmosphere. The reaction mixture was stirred at room temperature or 60 °C for 3–20 h. After completion of the reaction, the mixture was quenched with H2O (20 mL) and extracted with Et2O (3 × 20 mL). The collected organic layer was dried over MgSO4. After filtration, the mixture was concentrated in vacuo. The residue was purified by column chromatography. For some cases, further purification was performed by distillation to give a pure product 4.

3-(tert-Butyl)-5-ethyloxazolidin-2-one (4a). Colorless liquid. bp: 78 °C/2 mmHg. IR (neat): 1743.33 cm−1. HRMS: (EI+, 70 eV) Calculated (n class="Chemical">C9H17NO2) 171.1259 (M+) Found: 171.1257. 1H-NMR: (270 MHz, CDCl3) δ 4.30 (ddd, J = 6.4, 7.8, 8.8 Hz, 1H, 5-H), 3.64 (dd, J = 8.3, 8.8 Hz, 1H, 4HH), 3.20 (dd, J = 7.8, 8.3 Hz, 1H, 4HH), 1.70 (m, 2H, CH2CH3), 1.38 (s, 9H, NC(CH3)3), 0.99 (t, J = 7.3 Hz, 3H, CH2CH3), 13C-NMR: (67.5 MHz, CDCl3) δ 159.76 (C-2), 73.21 (C-5), 52.92 (NC(CH3)3), 48.06 (4-C), 27.45 (CH2CH3), 27.11 (NC(CH3)3), 8.55 (CH2CH3).

3-(tert-Butyl)-5-(chloromethyl)oxazolidin-2-one (4b). Colorless liquid. bp: 80 °C/2 mmHg. IR (neat): 1743.33 cm−1. HRMS: (EI+, 70 eV) Calculated (n class="Chemical">C8H14ClNO2) 191.0713 (M+) Found: 191.0714. 1H-NMR: (270 MHz, CDCl3) δ 4.64–4.55 (m, 1H, 5-H), 3.74 (dd, J = 8.8, 8.8 Hz, 1H, 4HH), 3.65 (dd, J = 5.9, 6.4 Hz, 2H, CH2Cl), 3.52 (dd, J = 5.9, 8.8 Hz, 1H, 4HH), 1.40 (s, 9H, NC(CH3)3). 13C-NMR: (67.5 MHz, CDCl3) δ 155.62 (C-2), 70.09 (C-5), 53.52 (NC(CH3)3), 46.00 (CH2Cl), 44.70 (C-4), 27.16 (NC(CH3)3).

3-(tert-Butyl)-5-(phenoxymethyl)oxazolidin-2-one (4c). Colorless liquid. bp: 140 °C/2 mmHg. IR (neat): 1727.91 cm−1. HRMS: (EI+, 70 eV) Calculated (n class="Chemical">C9H17NO2) 249.1365 (M+) Found: 249.1371. 1H-NMR: (270 MHz, CDCl3) δ 7.10 (m, 5H, Ph), 4.72 (m, 1H, 5-H), 4.10 (d, J = 2.9 Hz, 2H, OCH2), 3.76 (dd, J = 8.8, 8.8 Hz, 1H, 4HH), 3.59 (dd, J = 5.9, 8.8 Hz, 1H, 4HH), 1.40 (s, 9H, NC(CH3)3). 13C-NMR: (67.5 MHz, CDCl3) δ 158.09 (C-2), 156.24, 129.53, 121.45, 114.14, 69.57 (OCH2), 67.97 (C-5), 53.45 (NC(CH3)3), 45.55 (4-C), 27.36 (NC(CH3)3).

3-(tert-Butyl)-5-(methoxymethyl)oxazolidin-2-one (4d). Colorless liquid. bp: 75 °C/0.07 mmHg. IR (neat): 1743.33 cm−1. HRMS: (EI+, 70 eV) Calculated (n class="Chemical">C9H17NO3) 187.1208 (M+) Found: 187.1212. 1H-NMR: (270 MHz, CDCl3) δ 4.51 (m, 1H, 5-H), 3.64 (dd, J = 8.3, 8.8 Hz, 1H, 4HH), 3.52 (dd, J = 4.9 Hz, 2H, CH2O), 3.43 (dd, J = 6.4, 8.3 Hz, 1H, 4HH), 3.40 (s, 3H, OCH3), 1.38 (s, 9H, NC(CH3)3). 13C-NMR: (67.5 MHz, CDCl3) δ 156.30 (C-2), 72.66 (OCH2), 70.38 (C-5), 59.92 (OCH3), 53.13 (NC(CH3)3), 45.14 (4-C), 27.14 (NC(CH3)3).

3-Butyl-5-ethyloxazolidin-2-one (4e). Colorless liquid. bp: 85 °C/2 mmHg. IR (neat): 1751.05 cm−1. HRMS: (EI+, 70 eV) Calculated (n class="Chemical">C9H17NO2) 171.1259 (M+) Found: 171.1257. 1H-NMR: (270 MHz, CDCl3) δ 4.72 (m, 1H, 5-H), 3.59 (dd, J = 8.3, 8.3 Hz, 1H, 4HH), 3.25 (m, 2H, NCH2), 3.14 (dd, J = 6.8, 8.3 Hz, 1H, 4HH), 1.83–1.64 (m, 2H, NCH2CH2), 1.53 (dt, J = 7.3, 7.3 Hz, 2H, CH2CH3), 1.34 (tq, J = 7.3, 7.3 Hz, 2H, NCH2CH2CH2), 1.00 (t, J = 7.3 Hz, 3H, CH2CH3), 0.94 (t, J = 7.3 Hz, 3H, NCH2CH2CH2CH3). 13C-NMR: (67.5 MHz, CDCl3) δ 157.81 (C-2), 74.18 (C-5), 49.06 (C-4), 43.39 (NCH2), 29.02 (NCH2CH2), 27.70 (CH2CH3), 19.46 (NCH2CH2CH2), 13.34 (NCH2CH2CH2CH3), 8.39 (CH2CH3).

5-Ethyl-3-phenyloxazolidin-2-one (4f). Colorless liquid. The NMR data of n class="Chemical">1H and 13C agreed with the previous report [77]. 1H-NMR: (270 MHz, CDCl3) δ 7.56–7.10 (m, 5H, Ph), 4.59 (ddt, J = 6.4, 7.3, 8.3 Hz, 1H, 5-H), 4.08 (dd, J = 8.3, 8.8 Hz, 1H, 4HH), 3.66 (dd, J = 7.3, 8.8 Hz, 1H, 4HH), 1.96–1.71 (dq, J = 6.4, 7.3 Hz, 2H, CH2CH3), 1.07 (t, J = 7.3 Hz, 3H, CH2CH3). 13C-NMR: (67.5 MHz, CDCl3) δ 154.88 (C-2), 138.29, 128.91, 123.79, 118.06, 74.05 (C-5), 49.94 (C-4), 27.88 (CH2CH3), 8.62 (CH2CH3).

5-Ethyl-N,3-diphenyloxazolidin-2-imine (5). Colorless liquid. The NMR data of n class="Chemical">1H and 13C agreed with the previous report [56]. 1H-NMR: (270 MHz, CDCl3) δ 8.23–6.60 (m, 10H, Ph × 2), 4.70–4.15 (m, 1H, 5-H), 3.92 (t, J = 8.1 Hz, 4-HH), 3.52 (dd, J = 6.8, 8.1 Hz, 1H, 4HH), 1.95–1.35 (m, 2H, CH2CH3), 0.97 (t, J = 6.8 Hz, 3H, CH2CH3). 13C-NMR: (67.5 MHz, CDCl3) δ 148.79, 148.05, 140.44, 139.34, 129.03, 124.03, 123.30, 122.82, 119.34, 76.16 (C-5), 50.74 (C-4), 27.44 (CH2CH3), 8.78 (CH2CH3).

4.4. Observation of Tin-Indium System by 119Sn NMR

To a two-neck 10-mL reaction vessel, InCl3 (1.0 mmol) and n class="Chemical">Bu2SnI2 (1.0 mmol) were added in MeCN-d3 (1 mL) and stirred at room temperature for several minutes. After transferring of the reaction mixture into an NMR test tube and addition of tetramethyl stannane as an internal standard, 119Sn NMR was recorded.

5. Conclusions

A novel type of indium-tin species n class="Chemical">Bu2SnI+[InCl3I]− was revealed to be effective for the catalytic annulation of epoxides. In the reaction with carbon dioxide, the fixation of CO2 proceeded well even at room temperature. In the reaction with isocyanates, novel types of 2-oxazolidiones were obtained in good yields.