The Role of Elimination Processes in the Reaction of ...

The Role of Elimination Processes in the Reaction of Substituted Ureas and Thioureas with Chlorides of Mono- and Bifunctional Acids Thomas D. Smith*, Peter G. Jones, and Reinhard Schmutzler** Institut für Anorganische und Analytische Chemie der Technischen Universität, Hagenring 30, D-W-3300 Braunschweig Dedicated to Prof. Josef Grobe on the occasion o f his 60 th birthday Z. N aturforsch. 47b, 526-532 (1992); received August 29, 1991 Reactive Halides, Substituted Ureas, Elimination Reactions, X-Ray The reaction of phthaloyl chloride 2 with 1,3-dimethylurea 1 in dichloromethane at room temperature leads to the form ation of N ,N -l,l'-phthaloyl-bis(l,3-dim ethylurea) 3 whereas in refluxing solvent N-methyl-phthalimide 4 is the principal product. The reaction of 1,3bis(trimethylsilyl)-1,3-dimethylurea 5 separately with phthaloyl- 2, 4-nitrobenzoyl- 6, and 5-chlorothiophene-2-carbonyl chloride 9 results in the formation of 1,3-phthaloyl-1,3-di methylurea 7, 1,3-bis(4-nitrobenzoyl)- 1,3-dimethylurea 8, and N ,N-bis(5-chlorothiophene-2-carbonyl)-N-methylamine 12, respectively. The reaction of N,N-bis(trimethylsilyl)acetamide II with 9 furnished N,N-bis(5-chlorothiophene-2-carbonyl)-acetamide 13, while the reaction of 13 with 1,3-dimethylthiourea 10 afforded 1.3-dimethyl-1,3bis(5-chlorothiophene-2-carbonyl)thiourea 14. The structures of 3 and 12 were confirmed by low tem perature X-ray crystallography. Both display crystallographic twofold symmetry.

The products obtained from the reaction of 1,3dim ethylurea with phosphorus pentachloride [ 1 ], oxalyl chloride [2] and acetyl chloride [3] have been characterized previously. The present study de scribes the reactions of the bis(trimethyl)silylated 1,3-dimethylurea 5 with phthaloyl chloride 2, 4-nitrobenzoyl chloride 6 and 5-chloro-thiophene carbonyl chloride 9 taking advantage of the leaving group properties o f the silyl group. In teresting com parisons may be made with the sul phur-containing analogues of oxygen-containing com pounds [41; the reaction o f 9 with 1,3-dim ethylthiourea 10, whose silyl derivative cannot be prepared, has been studied. The reaction of phthaloyl chloride 2 with 1,3dim ethylurea 1 was studied first. A solution of 1 and 2 in methylene chloride was allowed to stand at room tem perature for one week. After filtration and removal of solvent, the product was recrystal lized from m ethanol, and characterized by an X-ray crystallographic study as N-phthaloylbis( 1,3-dimethylurea) 3 (Fig. 1, Table I).

*

On study leave from the Chemistry Department, Monash University, Clayton, Victoria, Australia 3168. ** Reprint requests to Prof. R. Schmutzler. Verlag der Z eitschrift für N atu rfo rsch u n g . D -W -7400 T übingen 0 9 3 2 -0 7 7 6 /9 2 /0 4 0 0 -0 5 2 6 /$ 01.00/0

Fig. 1. The molecule o f com pound 3 in the crystal, show ing the numbering scheme of the asymmetric unit. Ellip soids represent the 50% probability level; H atom radii are arbitrary.

The molecule displays crystallographic twofold symmetry; the twofold axis 0,>’, 1/4 bisects the bonds C ( l) - C ( l') and C (3)-C (3'). The side chain exhibits an extended conform ation, with torsion angles C ( 2 ) - C ( l) - C ( 4 ) - N ( l) 60°, C ( l) - C ( 4 ) N ( l) - C ( 6 ) -161°, C (4 )- N (l)-C (6 ) -N (2 ) 1°, N (l)-C (6 )-N (2 )-C (7 ) 179°. The packing dia gram of 3 is shown in Fig. 2; it involves layers of phenyl rings parallel to the xy plane.

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T h. D. Sm ith et al. ■S u b stitu ted U reas and T hioureas

527

C (l)-C (2 ) C ( l) -C (li) C (3)-C (3 i) C(4)—0(1) C (6 )-N (l) C(6)—0(2)

138.9(2) 139.9(2) 138.5(3) 122.3(2) 143.0(2) 122.3(2)

C (l)-C (4 ) C (2)-C (3) C (4 )-N (l) C (5 )-N (l) C (6)-N (2) C (7)-N (2)

150.1(2) 139.1(2) 137.7(2) 147.0(2) 133.3(2) 145.2(2)

C ( 2 ) -C (l) —C(4) C (4 ) -C (l) —C (li) C (2 )-C (3 )-C (3 i) C ( l) - C ( 4 ) - 0 ( 1 ) N (l)-C (6 )-N (2 ) N (2 )-C (6 )-0 (2 ) C (4 )-N (l)-C (6 ) C (6 )-N (2 )-C (7 )

121.2(1) 118.2(1) 120.3(1) 118.2(1) 117.2(1) 124.3(1) 124.7(1) 121.2(1)

C (2 )-C (l)- C (li) C (l)-C (2 )- -C(3) C (l)-C (4 )- 'N (l) N( 1)—C(4)- 0(1) N (l)-C (6 )--0(2 ) C (4 )-N (l)--C(5) C (5 )-N (l)--C(6)

120.0(1) 119.7(1) 117.9(1) 123.8(1) 118.5(1) 120.5(1) 114.6(1)

Table 1. Bond lengths (pm) and angles (°) for com pound 3.

Symmetry operator (i): - x , y , 0 .5 -z .

Fig. 2. Stereographic packing diagram of com pound 3, viewed approximately parallel to the z axis. Radii are arbi trary; H atom s omitted for clarity.

The layers are linked by weak hydrogen bond ing from the N(2)H group to the carbonyl oxygen [N (2 )-0 (2 )3 2 2 pm]. The principal product obtained from the reac tion of 2 with 1,3-dimethylurea in refluxing acetonitrile is N-m ethylphthalim ide 4, which was also the main product obtained when triethylamine was added to the reaction mixture. Phthaloyl chloride 2, reacts smoothly with 1,3bis(trimethylsilyl)- 1,3-dimethylurea 5 in refluxing methylene chloride to form l,3-phthaloyl-l,3-dimethylurea 7. O ther cyclic derivatives of 1,3-di-


I

0

528

Th. D. Sm ith et al. - S ubstituted U re a s an d T h io u rea s

methylurea have been described [5-8], U nder sim ilar conditions, the reaction of 4-nitrobenzoyl chloride 6 with 5 was shown to lead to the form a tion of l,3-bis(4-nitrobenzoyl)-l,3-dim ethylurea 8 . 0

II

C-CI

,ch3

C-Ns c=o

C-CI

I

ch3

'c=o r

-n ; ‘ ch3

C 'N( II ch3

0

J

0

-2RCI

0

-2RCI

7 '

ch

The conform ation of the central moiety is spe cified by the torsion angles C (3 )- C ( 4 )-C (5 )- N -31°, C(4)- C(5)- N - C(5‘) -3 3 °. The m olecular dimensions (see Table II) of the thiophene ring in 12 are similar to those found in thiophene-3,4-trithioanhydride [9] and 2,5-bis-N-chlorothioim ino3,4-dicyanothiophene [10]. However, it is clear from comparisons of the relevant bond lengths and bond angles that the molecular shape o f the

3

o 2n

2 0 2N o 2n

6 R = ( CH3 )3 Si

The reaction o f 5-chlorothiophene-2-carbonyl chloride 9 with 5 in refluxing methylene chloride leads to the form ation of N,N-bis(5-chlorothiophene-2-carbonyl)-N-methylamine 12, which was also characterized by X-ray methods. The mole cule of 12 (Fig. 3) possesses crystallographic two fold symmetry, with the atom s N and C( 6 ) lying on the twofold axis \ / 2 , y , \ / 4 (the packing diagram, Fig. 4, makes clear the alignment o f the molecules with the N - M e bonds parallel to the b axis).

Fig. 3. The molecule of com pound 12 in the crystal, showing the numbering scheme o f the asymmetric unit. Radii are arbitrary.

Fig. 4. Stereographic packing diagram of com pound 12, viewed parallel to the z axis. Radii are arbitrary; H atom s omitted for clarity.


T h. D. Sm ith et al. ■S u b stitu ted U reas and T hioureas

529

S - C ( l) C l- C ( l) N —C(5) C (l)-C (2 ) C (3)-C (4)

171.1(2) 171.4(2) 139.8(2) 135.2(2) 136.5(2)

S-C (4) 0 -C (5 ) N -C (6) C(2)-C (3) C(4)-C (5)

171.6(2) 121.5(2) 146.3(3) 140.4(3) 146.9(2)

C ( l) - S - C ( 4 ) C ( 5 )-N -C (5 i) S -C (1 )-C 1 C l- C ( l) - C ( 2 ) C (2 )-C (3 )-C (4 ) S -C (4 )-C (5 ) 0 -C (5 )-N N -C (5 )-C (4 )

90.7(1) 124.7(2) 119.8(1) 126.9(1) 113.4(1) 118.8(1) 121.4(2) 116.5(1)

C (5 )-N -C (6 ) C (6 )-N -C (5 i) S -C (l) - C ( 2 ) C (l)-C (2 )-C (3 ) S -C (4 )-C (3 ) C (3)-C (4) —C(5) 0 - C ( 5 )- C ( 4 )

117.7(1) 117.7(1) 113.2(1) 111.4(2) 111,4( 1) 129.6(1) 122.0(1)

Table II. Bond lengths (pm) and angles (°) for com pound 12.

Symmetry operator (i): l —x, y, 0 .5 -: 0

thiophene ring is influenced by its substituent groups; in particular, the C (l)-S -C (4 ) angle of 90.7° in 12 increases to 91.3° in the thiophene an hydride [9] and 94.5° in the dicyanothiophene [10], while the bond lengths S ( l) - C ( l) and C (l)-C (2 ) increase from 171.2, 135.2 pm respectively in 12 to 177.5, 143.9 pm [9] and 173.1, 137.8 pm [10]. The form ation o f 12, which is structurally relat ed to 4, may involve an intermediate similar in structure to 7 but forming 2 on elimination of methyl isocyanate. It is o f interest to note that the loss o f methyl isocyanate is involved in the mass spectrometric fragm entation pattern of 7, 8 , and 12. The substituent in the 5-position of the thio phene ring exerts an electronic influence similar to that experienced on para-substitution in the ben zene ring [11], O ther studies have shown that there is no conjugation between the thiophene ring and substituent carbonyl groups [ 12 ] and that different proximity effects exist in thiophene and benzene derivatives [13]. The present investigation high lights the ease o f methyl isocyanate removal from the bridging 1,3-dimethylurea group by the 5-chlorothiophene carbonyl, in contrast to the 4-nitrobenzoyl groups. The silyl leaving group properties o f N,N-bis(trimethylsilyl)-acetamide 11 allow the formation of N,N-bis(5-chlorothiophene-2-carbonyl)-acetamide 13 in the reaction of 11 with 9 in methylene chloride. The mass spectral fragmentation pattern o f 13 shows the profound changes in the break down of the bridging group compared with that of 1 2 , as a result o f the insertion of the carbonyl group into its structure. The reaction o f 1,3-dimethylthiourea 10 with 9 was investigated to establish the effect on the sta-

,

CH3

2Cl i j sL C. 0 / 9

'ci

N

N

R

R

1

CH3

I

^ 3

^

0N _ \ *C

C*

Q

-2RCI -CH 3 NCO

* • 5

£ Cl■

Cl

12 c h 3v ^

^ ^CH 3 -2HCI

H

H

ch3

I

\ CH3 C >. , r -2 R C l\ N' R 11

00

10

N "°

CHj ' n^ I 0=C

x „ ' ch3 1 c *=0

•C$l c >ci

ci

1

ci

5

13 R =(CH 3 )3 Si

14 bility of the urea bridging group with respect to eli m ination reactions of replacing the oxygen atom by sulphur. The product obtained from this facile reaction was 1,3-dimethyl-l,3-bis(5-chlorothiophene-2-carbonyl)thiourea 14 whose mass spectral fragm entation pattern illustrates the enhanced sta bility of the thiourea bridging group. Experimental The solvents were freshly distilled and dried be fore use. The chemicals used were available com mercially. 1,3-Dimethylthiourea was dried over phosphorus pentoxide. 1,3-Bis(trimethylsilyl)-1,3dim ethylurea was synthesized by the literature method [14], 5-Chlorothiophene-2-carbonyl chlo ride was kindly made available by Dr. M eidert of Hoechst AG. Elemental analyses were performed by the N ational Analytical L aboratory, Mel-


Th. D. Sm ith et al. • S ubstituted U reas an d T h io u reas

530

bourne. The melting points are uncorrected. Mass spectra were obtained using an AEI M S 9 spec trometer. N .N -l J'-P hthaloyl-bis( 1,3-dimethylurea) 3

A solution containing 1,3-dimethylurea 1 (8.80 g, 0 .10 mol) and phthaloyl chloride 2 ( 10 .1 g, 0.05 mol) in methylene chloride (20 ml) was al lowed to stand at room tem perature (20 °C) for one week. The solid m aterial (5.86 g) that sep arated was filtered off. Methylene chloride was re moved, leaving a crystalline product that was washed with toluene (50 ml) and oven dried (120 C). Recrystallization from hot m ethanol (50 ml) gave (3) (4.28 g, 28.3%), m .p. 162-163 °C.

was removed, giving a crude solid product, which was recrystallized from a hot mixture o f m ethanol (50 ml) and methylene chloride (50 ml). A solution of the recrystallized product in methylene chloride (50 ml) was treated with activated charcoal for 30 min, after which the charcoal was removed by fil tration. Most o f the methylene chloride was re moved and the product recrystallized again from methanol/methylene chloride to give 8 (3.15 g, 81.6%), m .p. 182-183 °C. MS: m /e (% ) 386 (0.3) [M]+, 329 (1.25) [M -C H 3NCO]+; 301 (1.2) [M -C H 3N C O -C O ]+; 150 (100) [ M -C H 3N C O C O -C 6H 4(NO,)(NCH3)]+; 104 (24) [M -C H 3N C O C 0 - C 6H 4(N 0 2)(N C H 3) - N 0 2]+. C 17H I4N , 0 7 (386.28)

Calcd C 52.86 Found C 52.77

C I4H isN 40 4 (306.32)


H 5.92 H 5.91

N 18.29, N 18.31.

A solution o f 1 (4.40 g, 0.05 mol) and 2 (10.2 g, 0.05 mol) in acetonitrile (50 ml) was refluxed for 6 h. After removal o f acetonitrile at diminished pressure the crude product ( 10.0 g) was taken up in hot m ethanol (50 ml), which on cooling gave needle-like crystals o f 4 (5.33 g, 66.2%), m .p. 133-134 °C. C9H 7N 0 2 (161.16)

H 4.38 H 4.35

N 8.69, N 8.63.

1.3-Phthaloyl-1,3-dimethylurea 7

A solution o f 5 (2.34 g, 0.01 mol) and 2 (2.03 g, mol) in methylene chloride (20 ml) was re fluxed for 30 min. After removal o f m ost of the methylene chloride a solid product separeted. Re crystallization of the crude product from hot tol uene (20 ml) gave 7 (1.64 g, 75.2%), m .p. 9 5 -9 6 °C. MS: m /e (% ) 218 (2.4) [M +]; 190 (0.5) [M -C O ]+; 161 (90) [M -C H 3N C O ]+; 133 (28) [ M - C O - C H 3N C O ]+; 104 (100) [M -C H 3N C O C H 3NCO]+; 76 (64) [M -C H 3N C O ~ C H 3- N C O C O j+. 0.01

C ,,H I0N ,O 3 (218.20)


H 4.62 H 4.60

N 12.84, N 12.81.

1.3-B is( 4-nitrobenzoyl)-l,3-dim ethylurea 8

A solution of 5 (2.23 g, 0.01 mol) and 6 (3.90 g, mol) in methylene chloride (20 ml) was re fluxed for 30 min. M ost o f the methylene chloride

0.02

N 14.50, N 14.41.

N,N-Bis(5-chloro-thiophene-2-carbonyl)N-methylamine 12

N-M ethylphthalim ide 4


H 3.65 H 3.60

A solution of 5 (2.32 g, 0.01 mol) and 9 (3.28 g, mol) in methylene chloride (20 ml) was refluxed for 30 min. After removal of m ost of the methylene chloride under reduced pressure, a crude product (3.35 g) was obtained, which was washed with cold methanol (50 ml) and oven dried (80 °C), then recrystallized from hot m ethanol (50 ml). The recrystallized product was dissolved in methylene chloride (25 ml) and the solution treated with activated charcoal for 20 min. After filtration the product was recovered by removal of methylene chloride. A final recrystallization from hot methanol (20 ml) gave 12 (1.48 g, 46.7%), m .p. 125-126 °C. MS: m /e (% ) 319(7) [M -l]+; 284 (4.8) [M -C1]+; 262 (3.3) [M -C H 3NCO]+; 227 (2.5) [M ~ C l-C H 3N C O ]+; 199 (1.6) [ M - C l- C H 3N C O -C O ]+; 145 (100) [M -C H 3N C 0 - C 4H,SC1]+; 117(12) [M -C H 3N C O -C 4H 2S C l-C O ]+.

0.02

C u H 7CU NO,S, (320.21)

Calcd C 41.26 H2.20 N4.37 S 20.03 C l22.14, Found C41.13 H2.26 N4.32 S 19.91 C122.29. N ,N -bis( 5-chIorothiophene-2-carbonyl) -acetamide

13 A solution of 11 (4.06 g, 0.02 mol) and 9 (6.56 g, 0.04 mol) was refluxed in methylene chloride for 3 h. After cooling, the solution was treated with activated charcoal (2 g), filtered and the methylene chloride removed. The solid product was washed with acetonitrile (50 ml) and recrystallized twice from hot toluene (2 x 20 ml) to give 13 (2.40 g,


531

T h. D. Sm ith et al. ■Substituted U reas and T hioureas

34.5%), m. p. 188- 189 °C. MS: m/e (%) 347 (0.03) [M -l]+; 306 (122) [M -C H 3CN]+; 203 (13) [M -C 4H,SCl(CO) + H]+; 162 (59) [M -C H 3C N -C 4H,Cl(CO) + H]+; 145 (100) [M -C 4H 2S C l(C O )-C H 3NCO]+. C ,7H 7CI iN 0 3S i (348.21)

Calcd C 41.39 H2.03 N4.02 S 18.42 C120.36, F ound C41.16 H1.97 N4.09 S 18.31 C120.49. 1,3-Dimethyl-l ,3-bis( 5-chlorothiophene-2-carbonyl)thiourea 14

A solution of 1,3-dimethylthiourea 10 (5.20 g, 0.05 mol) and 9 (16.40 g, 0.1 mol) in methylene chloride (50 ml) was allowed to stand at room tem perature for 3 h. The solid product (13.81 g) that separated during this time was isolated by filtra tion and recrystallized from hot acetonitrile (150 ml) to give 14 (8.0 g, 42.5%); m .p. 130131 °C. MS: m/e (% ) 392 (0.26) [M -l]+; 336 (0.41) [M -C H 3NCO + H]+; 248 (64) [M -C 4H ?SCl(CO) + H]+; 213 (100) [M -C 4H,SCl(CO) + H -C 1]+, 145 (67) [M -C 4H 2SCl(CO• N C H 3•CS •N C H 3)]+. C I3H l0Cl2N 2S3 (393.32)

Calcd C 39.70 H2.56 N7.12 S24.46 Cl 18.03, Found C 39.58 H2.51 N7.06 S 24.28 Cl 18.11.

wR 0.049. 100 param eters; 5 2.1; max. A /a 0.001; max. A q 0.2 x 10“ 6 e p m '3. Final atomic coordi nates are presented in Table III. Table III. Atom coordinates (x 104) and equivalent iso tropic tem perature factors (pm 2) for compound 3. Atom C (l) C(2) C(3) C(4) C(5) C(6) C(7) N (l) N(2) 0(1) 0(2)

.Y 397.6(7) 789.5(8) 390.8(8) 833.7(7) 1073.0(9) 1876.6(7) 2665.0(9) 1264.9(6) 2044.9(7) 819.1(6) 2222.6(6)

y 3783(2) 5253(2) 6721(2) 2191(2) 2420(2) 555(2) -1372(2) 1751(1) - 163(2) 1403(1) 284(1)

z

u eq

2804(1) 3122(1) 2816(1) 2921(1) 5254(1) 4321(1) 3438(1) 4099(1) 3308(1) 1955(1) 5414(1)

209(4) 252(4) 276(5) 218(4) 312(5) 216(4) 296(5) 225(4) 252(4) 309(3) 309(4)

X-ray crystal structure determination of compound 12 C rystal data: C n H 7Cl2N 0 2S2, M r = 320.2, monoclinic, C2/c, a = 973.6(3), b - 1595.2(5), c = 867.0(3) pm, ß = 98.59(3)°, U = 1.3315 nm 3, Z = 4, D x = 1.597 Mg n r 3, F(000) = 648, 2(M oK a) = 71.069 pm , p = 0.78 m m ’ 1, T = -7 0 °C. D ata collection and reduction, structure solution and refinement: A colourless block 0.7x0.35x0.4 mm was used. Other details as for 3, with the fol

X-ray crystal structure determination of compound 3 C rystal data: C 14H 18N 40 4, M r = 306.3, m ono clinic, C2/c, a = 1748.9(5), b = 818.4(2), c = 1082.2(3) pm, ß = 102.88(2)°, U = 1.5099 nm 3, Z = 4, D x = 1.348 M g m '3, / ’(OOO) = 648, i(M o K a ) = 71.069 pm, n = 0.09 m m "1, T = -9 5 °C. D ata collection and reduction: A colourless p ar allelepiped 0.5 x 0.4 x 0.4 mm was mounted on a glass fibre and transferred to the cold gas stream of the diffractom eter (Siemens R 3 with LT-2 low tem perature attachment). O f 2163 intensities regis tered with m onochrom ated M oK a radiation (2 #max 55°), 1740 were unique ( Rml 0.017) and 1409 > 4 a(F) considered observed. Cell constants were refined from setting angles of 48 reflections in the 2 0 range 20-25°. Structure solution and refinement: (Program sys tem “Siemens SHELXTL PLU S”). The structure was solved by routine direct methods and subject ed to anisotropic full-matrix least-squares refine ment on F. H atoms were included using a riding model. The weighting scheme was w" 1 = o \F ) + gF1, with g 0.0002; the final R was 0.040, with

lowing differences: 3170 reflections, 1531 unique (R mt 0.019), 1315 observed. The H atom s o f the methyl group at C( 6 ) are disordered over two posi tions. An extinction correction of the form Fcorr = F/[\ + x F 2/sin 2 #]-0 25 was applied; x refined to 4.6(6) x 10~6. 84 param eters, R 0.032, wR 0.042, g 0.00015, S' 2.1, max. A /a 0.002; max. Aq 0.24x 10~6 e p m -3. Final atom ic coordinates are presented in Table IV. Table IV. Atom coordinates ( x 104) and equivalent iso tropic tem perature factors (pm 2) for compound 12. Atom

.V

y

z

u eq

S Cl O N C (l) C(2) C(3) C(4) C(5) C(6)

4921.3(5) 3347.4(7) 5704(2) 5000 3546(2) 2695(2) 3173(2) 4368(2) 5109(2) 5000

1793.3(3) 228.2(4) 3623(1) 3707(1) 1150(1) 1462(1) 2237(1) 2499(1) 3300(1) 4625(2)

5422.0(5) 5742(1) 5125(2) 2500 4785(2) 3543(2) 3073(2) 3968(2) 3941(2) 2500

462(2) 802(3) 594(5) 401(6) 451(6) 443(5) 383(5) 335(4) 382(5) 604(11)


T h. D. Sm ith et al. • S ubstituted U reas an d T h io u reas

532

Further details of the structure determ inations (H atom coordinates, structure factors, tem pera ture factors) have been deposited at the Fachinfor m ationszentrum Karlsruhe, Gesellschaft für Wis senschaftlich-technische Inform ation mbFI, D-7514 Eggenstein-Leopoldshafen 2, Federal Re public of Germany. Any request for this m aterial

[1] H. Ulrich and A. A. R. Sayigh, J. Org. Chem. 30, 2779(1965). [2] H. Ulrich and A. A. R. Sayigh, J. Org. Chem. 30, 2781 (1965). [3] M. Yu. Demitrichenko, V. I. Donskikh, V. G. Rozinov, V. V. Rybkina, and L. M. Sergienko, Zh. Obshch. Khim. 55, 1881 (1985). [4] C. J. Broan, A. R. Butler, D. Reed, and I. H. Sadler, J. Chem. Soc. Perkin Trans. II 1989, 731. [5] F. B. Slezak, H. Bluestone, T. A. Magee, and J. H. Wotiz, J. Org. Chem. 27, 2181 (1962). [6] J. Nematollahi and R. Ketcham, J. Org. Chem. 28, 2378(1963). [7] A. R. Butler and I. Hussain, J. Chem. Soc. Perkin Trans. II 1981,302.

should quote a full literature citation and the refer ence num ber CSD 5581 1. We are grateful to BASF AG, BAYER AG, and HOECHST AG for generous supplies of chemicals used in this research, and to Fonds der Chem i schen Industrie for financial support.

[8] A. R. Butler, I. Hussain, and K. M. Peet, J. Chem. Soc. Perkin Trans. II 1981, 320. [9] S. Yoneda, K. Ozaki, K. Yanagi, and M. Minobe, J. Chem. Soc. Chem. Commun. 1986, 19. [10] F. Wudl and E. T. Zellers, J. Am. Chem. Soc. 102, 4283(1980). [11] S. Alunni, S. Clementi, C. Ebert, P. Linda, G. Musum arra. M. Sjöström, and S. Wold, J. Chem. Soc. Perkin Trans. II 1985, 485. [12] R. N oto, L. Lam artina, C. Arnone, and D. Spinelli, J. Chem. Soc. Perkin Trans. II 1987, 689. [13] R. N oto, L. Lamartina, C. Arnone, and D. Spinelli, J. Chem. Soc. Perkin Trans. II 1988, 887. [14] H. W. Roesky and J. Lucas, Inorg. Synth. 24, 120 (1986).
