R\ ,N-

R

Piperidino- Piperidino- Piperidino- Dimethyl-

aniino- Dimethyl-

amino-

94 84.5 87 80

100

155-157 ca. 148

247-248 247-248 220-221 223-224

221-223 S 1 87.5 1 110-111

Whereas the aminophenols ( I ) are in the benzenoid form, spectroscopic results indicate that the acylation products have the tautomeric quinonemethide structure (3a). Accord- ing to the results of Gompper et al.[31 quinonemethides with w,w-hetero-substituents are relatively stable. It is possible that hydrogen bridges contribute further to the stabilization of (3.). Heating the acylation products (3.) above their melting points causes intramolecular removal of alcohol and forma- tion of 1,3-oxazetidin-2-ones ( 4 ) , X = 0, and 1,3-thiazetidin- 2-ones (4), X = S , whose structures are proved by elemental analysis, molecular-weight determination, and 1H-NMR and UV spectra. In contrast to the behavior of the bis(dialky1amino)phenols ( I ) , reaction of the less activated phloroglucinol dimethyl ether with (2), X = 0, R' = CzH5, causes exclusive 0-

The rapid polymerization of (2) is responsible for the low yields of adducts. For instance, with acetylene only 3 % of isoxazole was obtained but 20 % of isoxazole-3-aldoxinie (the adduct of dimeric fulminic acid) "1. We converted mercuric fulminate into pure crystalline formo- hydroximoyl iodide ( I ) in 60 % yield with HI/KI without the detour through thesodium salt [31.Thefulminicacidis liberated by adding one equivalent of triethyiaminedropwiseand slowly to an ice-cooled, stirred solution of (1) in an excess of the dipolarophile (sometimes after dilution with ether). The low stationary concentration of (2) provides optimal conditions for the formation of 2-isoxazolines or isoxazoles from olefinic or acetylenic dipolarophiles, respectively.

Methyl acrylate gives a 90 % yield of methyl 2-isoxazoline- 5-carboxylate (3), which is purified by high-vacuum distilla- tion (b.p. 70-8O0C/0.O01 mm) [NMR (CDCl3): z = 2.72 (H-3,t), J34 = 1.7 Hz; T = 6.67 (H-4,q). J45 = 9.1 Hz; z = 5.00 (H-5, t); T = 6.20 (OCH3,s)l. An excess of triethylamine

H d N \ O

(3)

NC OH N ( c H ), I 1 75%H2S04 H02C\

H..W..COzCH, - HzC-C-COzCH, 7 ,c = c, H COzH I

H H H

( 4 )

acylation with formation of the urethane (5), which, when heated above the melting point, also loses alcohol and gives the benzoxazine derivative (6).

t C z H 5 0 - C O - N = C = 0 - CH30 OCH,

Other phenols also react similarly to yield benzoxazines (6).

Received: March 23rd, 1967 [Z 477 IE] German version: Angew. Chem. 79, 474 (1967)

[*] Doz. Dr. F. Effenberger and Dr. R. Niess Institut fur organische Chemie der Technischen Hochschule Azenbergstr. 14 7 Stuttgart-N (Germany)

[l] We thank the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie for support of this work. [2] F, Effenberger and R. Niess, Angew. Chem. 1961, in press; Angew. Chem. internat. Edit. 1967, in press. [3] R. Gompper, R . R . Schmidt, and E. Kutter, Liebigs Ann. Chem. 684, 37 (1965); R . Gompper and E. Kutter, Chem. Ber. 98, 1365 (1965); R . Gompper and R. R . Schmidt, ibid. 98, 1385 (1965).

1,3-Dipolar Cycloadditions of Fulminic Acid

By R. Huisgen and M. Christ l [*]

Quilico et al. [ 1 ~ 1 described cycloadditions of fulminic acid (2), which was liberated from sodium fulminate by 20 P: sulfuric acid or from formohydroximoyl iodide (1) by a base.

converts (3) quantitatively into methyl 3-cyano-2-hydroxy- propionate (4) [NMR (CDC13): T = 5.48 (H-2, t), J 2 3 =

5.5 Hz; z = 6.12 (OCH3, s); z = 6.37 (OH, s, broad); T = 7.12 (H-3, d): IR (film), 2248 (C s N ) , 3400 cm-1 (OH)].

Methyl crotonate and (2) afford the adducts (5) and (6) in the proportions 62:38 (yield 36 %) and the 2: l adducts (7) and (8) in the proportions 45:55 (31 % yield). Thus cyclo- addition of (2) to give (5) and (6) is in competition with dimerization of (2) to hydroxyiminoacetonitrile oxide which combines with the dipolarophile to give (7) and (8). Benzo- nitrile oxide and methyl crotonate provide (9) and (10) in the proportions 34:66[41.

H COzCH3 H3C 0 : C O H

H i'H3

IS), R = H (7), R = -CH=NOH

(6 ) , R = H (S ) , R = -CH=NOH

( 9 ) J R = C6H5 ( lo ) , R = CsH5

NC OH

The adducts (5) and (6) can be separated by thin-layer chromatography (with benzene on silica gel PF254 + 366). NMR spectra indicate the structures. Ring opening of (5) to give ( I I ) , catalysed by triethylamine, occurs even in the cold. NMR spectrum of (11) (CDC13): z = 5.74 (H-2, d), J 2 3 =

3.5 Hz; z = 6.81 (H-3, octuplet); z = 8.67 (4-CH3, d), J34 =

7.3 Hz; T = 6.11 (OCH3,s); T = 6.28 (OH, s, broad). IR (film) : 2270 (C =N), 3400 cm-1 (OH). The 2: 1 adducts (7) and (8), which distil only at 12O-15O0C (bath)/0.001 mm, were analysed in admixture by NMR spectroscopy.

Methyl cinnamate affords analogously 1 : 1 (23 % yield) and 2: 1 adducts (33 % yield). The 1 : 1 adducts contain the 4- and

456 Angew. Chem. internat. Edit. 1 Vol. 6 (1967) No. 5

5-carboxylic esters in the proportions 76:24 (70:30 on addition of benzonitrile oxide to cinnamic ester [41). By virtue of the angular strain of its double bond, norbornene reacts with (2) to give 76 % of the adduct (12), b.p. 65-75 "C/ 0.001 mm [NMR (CDC13): T = 3.08 (H-3, d), J33a = 1 Hz; T = 6.85 (H-3a, q), J3a7a = 8.2 Hz; z = 5.61 (H-7a, d). The absence of coupling of H-3a and H-7a with the bridge- head hydrogen proves the exo-addition. Triethylamine converts (12) into the nitrile (13) [m.p. 35-38 'C; I R : 2270 (C-N), 3450 cm-1 (OH)] in 93 % yield, but only after boiling for 12 h.

Cyclopentene and (2) give (14) in 8 % yield (b.p. 95-110°C (bath)/lO mm). The adduct (15) of cyclooctatetraene, also isolated in 8 % yield, is derived from the bicyclo[4.2.0]- octadiene skeleton, as is shown by the ratio of vinyl-H to

tert1ary-5-Phenyl-2-isoxazoline (16) (b.p. 90-100 "C/O.OOl mm) is formed in 70 % yield by cycloaddition of (2) to styrene. Its N M R spectrum (CDCl3) proves the structure: T = 2.91 (H-3, to J34 -= 1.7 Hz; the CH2 group on C-4 provides the expected 16-line signal (Jgem = -17.6 Hz). Ring opening to give the hydroxynitrile occurs only in boiling triethylamine.

The norbornadiene adduct (17), which is isolated by distilla- tion (b.p. 60-65 "Cj0.001 mm) in 41 % yield and whose structure is proved by NMR and I R spectra, undergoes a retro-Diels-Alder reaction at 140-160 "C, which leads to cyclopentadiene and isoxazole (90 % yield). N M R spec- trum of (18) (CDC13): T = 1.66 (H-3, d), T = 3.59 (H-4, t), and T = 1.49 (H-5, d) with J34 = J 4 5 = 1.5 Hz.

H&

H R H COzCH, H3C02C H

Reaction of (2) with phenylacetylene gives a 51 % yield of 5-phenylisoxazole (19). NMR (CDC13): z = 1.72 (H-3, d) and T = 3.52 (H-4, d) with J34 = 1.9 Hz.

Methyl propiolate adds fulminic acid in both directions. A 84: 16 mixture of (20), m.p. 47-50 "C [51, and (21) is obtained in 50 % yield. NMR spectrum of (20) (CDCl3) : z = 1.47 and 2.93 (H-3 and H-4, d) with J34 = 1.8 Hz, T = 5.98 (OCH3,s). N M R spectrum of (21) (CDC13): T = 1.30 (H-3, s ) , T = 0.85 (H-5, s), and T = 6.09 (OCH3, s). Benzonitrile oxide reacts with methylpropiolate, giving the 5- and the 4-carboxylic ester in the ratio 72: 28 [41.

These cycloadditions are incompatible with the classical carboxime formula but agree with the formonitrile oxide structure of fulminic acid, thus supporting a recent assign- ment [61 based on IR spectroscopy.

Received; March ZOth, 1967 [Z 478 IE] German version: Angew. Chem. 79, 471 (1967)

[*I Prof. R. Huisgen and Dipl.-Chem. M. Christ1 Institut fur Organische Chemie der Universitgt Karlstr. 23 8 Munchen 2 (Germany)

[l] A. Quilico and G. Stagno d'Alcontres, Gazz. chim. ital. 79, 654, 703 (1949).

[2] G. Stagno d'Alcontres and G. Fenech, Gazz. chim. ital. 82, 175 (1952). [3] A. Quilico and L. Panizzi, Gazz. chim. ital. 72, 155 (1942). [4] R. Sustmann, Dissertation, Universitat Munchen, 1965. [S] Synthesis by another method: A. Quilico and L. Punizzi, Gazz. chim. ital. 72, 458 (1942); M.p. 49-50°C. [6] W. Beck and K. Feldl, Angew. Chem. 78, 746 (1966); Angew. Chem. internat. Edit. 5, 525 (1966).

1,3-Cycloadditions of Nitrones to Methylenephosphoranes

By J. Wulff and R . Huisgen [*I

It has recently been shown that methylenephosphoranes are dipolarophiles and combine with nitrile oxides to give five- membered cycloadducts [1,21. We have chosen azomethine oxides (nitrones) for further investigations since they represent a class of 1,3-dipoles that contain no double bond in their sextet structure [31.

(a). R = R' = H ( b ) , R = R' = D (C), R = C6H5, R' = €I (d), R = R' = CH,

If one equivalent each of C,N-diphenylnitrone ( I ) and methylenetriphenylphosphorane (2u) are mixed in ether at 20 "C, the colorless, crystalline 1,2,5-oxazaphosphole deriva- tive (3u) precipitates in 93 % yield (decomp. 136-137 "C); C, H, and N analyses and osmometric determination of the molecular weight give correct values for (3a) as well as for the other new compounds prepared. N M R spectrum (CDC13) of (3.) : H-4 and H-4' as octuplets at T = 6.36 and 6.93 with J44, = -16.3, J34 = 8.5, J45 = 12.0, J34, = 7.0, and J4'5 =

12.4 Hz. The similarity of the couplings of H-3 (J35 = 8.1 Hz) leads to a quadruplet at T = 5.30. The 31P signal at +58.6 ppm (CDC13, 85 % phosphoric acid as external standard) indicates quinquecovalent phosphorus; if the phosphonium zwitterion (4) were present instead of the isomeric (3n), then a large negative chemical shift would be observed [41. The IH-NMR spectrum could be interpreted only by comparison with that of the 4,4-dideuterio compound (3b). The compound (2b) is obtained from (trideuteriomethy1)- triphenylphosphonium bromide by reaction with sodamide in benzene [51 without D-exchange. N M R spectrum (CDCI3) of (3b) : H-3 as broad doublet at T = 5.32 with J35 = 8.1 Hz.

(6)

Hydrolysis of (3u) in dioxane water (5 : 1 v/v) at 100 "C give (1,2-diphenylethyl)diphenylphosphine oxide (5) (yield 81 :4 identified by comparison with an authentic specimen 161. Tht N-phenylhydroxylamine that is also expected can be isolated

Angew. Chem. internat. Edit. / Vol. 6 (1967) J No. 5 457