Crystal and molecular structure of 3-ethyl-4-hydroxy-l,2,3(4H)-benzotriazine and 6-chloro-4-hydroxy-3-methyl-4-phenyl-1,2,3-benzotriazine'

KWONG KHEE L A I A N D CARL H. SCHWALBE Department of Pharmacy, University of Aston in Birmingham, Go.st(l Green. Birminghatn B47ET, England

KEITH VAUGHAN' A N D RONALD J . LAFRANCE Department of Chemistry, Saint Mary's University, Halifnx, N.S., Cnnada B3H 3C3

AND

CLIVE D. WHISTON Deportment of Physical Sciences, The Polytechnic, Wolverhatnpton, WVI ILY, England

Received January 4, 1984'

KWONG KHEE LAI, CARL H. SCHWALBE, KEITH VAUGHAN, RONALD J. LAFRANCE, and CLIVE D. WHISTON. Can. J . Chem. 63, 581 (1985).

The crystal structures of the title compounds have been determined from X-ray data collected on a four-circle diffractometer and refined by the full-matrix least-squares method. The forper compound crystallizes in the orthorhombic system, space group Pbcn, with a = 14.346(8), b = 7.239(1), c = 17.276(2) A, and has been refined to a conventional R factor of 0.043 for 890 observed reflections. Corresponding results for the latter compound are monoclinic, P 2 , / n , a = 12.222(4), b = 7.482(2), c = 14.170(8) A, P = 94.06(4)', R = 0.060 for 2128 observed data. The triazine rings of both compounds exhibit short N(I)-N(2) bonds and tetrahedral geometry at C(4); however, the ring is puckered in the first compound but flat in the second. Molecules in both crystals are linked by O(4)-H...N(l) hydrogen bonds.

KWONG KHEE LAI, CARL H. SCHWALBE, KEITH VAUGHAN, RONALD J. LAFRANCE et CLIVE D. WHISTON. Can. J . Chem. 63, 581 (1985).

Faisant appel ii des donnCes de rayons-x obtenues i I'aide d'un diffractornetre a quatre cercles et affintes par la mCthode des moindres carrts (matrice complete), on a dCterminC les structures cristallines des composCs mentionnCs dans le titre. Le premier compost cristallise dans le systtme orthorhombique, groupe d'espace Pbcn, avec a = 14,346(8), b = 7,239(1), c = 17,276(2) A et on a affint sa structure jusqu'a un facteur R de 0,043 pour 890 rkflexions observtes. Les [Csultats correspondants pour le dernier composC sont: monoclinique, P2,/n, a = 12,222(4), b = 7,482(2), c = 14,170(8) A, P = 94,06(4)", R = 0,060 pour 2 128 rtflexions observees. Les cycles triazines des deux composts sont caracteristes par des liaisons N(I)-N(2) qui sont courtes et une gComCtrie tCtratdrique en C(4); toutefois, alors que le cycle du premier compose est plisst, celui du deuxitme est plan. Dans chacun des cristaux, les molCcules sont rell&es par des liaisons hydrogtnes O(4)-H .-eN(1).

[Traduit par le journal]

Intrtiduction This paper describes the X-ray crystal structure determi-

nation of 3-ethyl-4-hydroxy- lj2,3(4H)-benzotriazine (1) and 6-chloro-4-hydroxy-3-methyl-4-phenyl-1,2,3-benzotriazine (2).

Interest in the chemistry of the Chydroxy-l,2,3-triazines was stimulated by the study of Fong and Vaughan (1) in which the diazonium salt (3) from o-aminoacetophenone was coupled with an excess of aqueous methylamine. The initial coupling product, the monomethyltriazene (4), could not be isolated due to the facility of the cyclodehydration of 4 to give the novel methylenetriazine (6). The i~termediate 4-hydroxy-l,2,3-ben- zotriazine (5), itself a novel heterocyclic structure, could not be isolated from this reaction. An alternative route to 6. via - -

the reaction of methyl magnesium bromide with 3-methyl- 40x0- l,2,3(4H)-benzotriazine, likewise proceeds directly without isolation of 5 (2).

Stable 4-hydroxytriazines should be available from anal- ogous reactions with diazonium salts in which the o-acyl group is lacking the a-hydrogen necessary for the dehydration step 5 4 6. Indeed it has now been shown (3) that coupling the diazonium salt from o-aminobenzaldehyde (7a) or o- aminobenzophenone (7b) with alkylamines leads to stable

'Contribution from the Joint Crystallography Unit, Universities of Aston and Birmingham.

'To whom all correspondence should be addressed. 'Revision received August 21, 1984.

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LA1 ET AL.

TABLE 2. Coordinates and equivalent isotropic temperature factors ( X lo4) for non-hydrogen atoms of 2 with esd in

parentheses

FIG. I. The molecule of 3-ethyl-4-hydroxy-l,2,3(4H)-benzotri- azine projected onto its least-squares plane, showing the numbering scheme. Nitrogen atoms are stippled and oxygen atoms hatched.

F IG . 2. The molecule of 6-chloro-4-hydroxy-3-methyl-4-phenyl- 1,2,3-benzotriazine in projection onto its least-squares plane. Nitro- gen atoms are stippled and oxygen atoms hatched.

regarded as I-aryl-3,3-dialkyltriazenes, one of whose 3-alkyl groups has been tied back to the ring. Bond distances (Table 3) and bond angles (Table 4) can be compared with those in a series of open-chain triazenes: I-p-tolyl-3-methyltriazene ( 6 ) , I -(4-carbethoxypheny1)-3-hydroxymethyl-3-thy t r z e e (7) , 2-(3,3-dimethyl- I-triazeno)phenyl- l -carboxamide (8), and two independent tautomers of 5-(3,3-dimethyl-1-triazeny1)imida- zole-4-carboxamide (9) and its hydrochloride (10). The title compounds may also be regarded as reduced forms of 1,2,3- benzotriazin-4(3H)-ones (henceforth abbreviated triazinones), for which crystal structure determinations exist on 1,2,3-ben- zotriazin-4(3H)-one (I I), 3-hydroxy-l,2,3-benzotriazin-4(3H)- one (12), and 0,O-dimethyl-S-(4-0x0- I ,2,3-benzotriazin-3-yl) methyl phosphorodithioate (1 3).

The N(I)-N(2) bond remains-very strong acrossothis entire series of compoun!s: 1.268(3) A in 1, 1.263(3) A in 2, an average of 1.281 A over the indep~ndent molecules of the triazenes, and an average of 1.255 A in the triazinones. Th; N(2)-N(3) bond is affected little by ring closure: 1.333(3) A in 1, 1.316(3) A in 2, and 1.325 in the triazenes. However, introduction of conjugation at C(4)oconsiderably weakens this bond; for N(2)-N(3) is 1.385 A in the triazinones. The "natural" bond angles averaging 1 12. 1" at N(1) and 1 13.8" at N(2) in the unrestrained triazenes are increased by ring closure to 120.0(2)" and 119.3(2)" at N(1) and 120.3(2)" and 122.3(2)" at N(2) in 1 and 2 respectively. Oxidation at C(4) has little

Atom x y z u,,,

"Equivalent isotropic temperature Factors are calculated from anisotropic thermal parameters by the equation U,,, = (113) ( U , , + UI? + U>> + 2Ull cos p).

TABLE 3. Bond distances (A) for non-hydrogen atoms with esd in parentheses

Distance

Bond 1 2

effect on these angles: they are 120.3" at N(1) and 1 18.6" at N(2) in the triazinones.

In both 1 and 2 carbon atom C(4) shows the expected tet- rahedral geometry. In the relatively uncrowded 1 the OH group is able to avoid both the 3-ethyl substituent and the fused ring by increasing the 0-C(4)-N(3) and 0-C(4)-C(4A) an- gles above tetrahedral values to 1 11.3(2)" and 113.4(3)". The requirement to accommodate a phenyl group in 2 and the dim-

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CAN. J . CHEM. VOL. 63. 1985

TABLE 4. Bond angles (deg) for non-hydrogen atoms with esd in parentheses

Angle

Bonds 1 2

TABLE 5. Selected torsion angles (deg)

Angle

Bonds 1 2

inution of the 3-substituent to methyl allow the OH group to move closer to N(3): 0-C(4)-N(3) is 109.7(2)" while O-C(4)-C(4A), Ph-C(4)-N(3), and Ph-C(4)-C(4A) are 1 12.6(2)", 108.8(2)", and 1 1 1.2(2)", respectively. In 1 the single bond C(4)-C(!A) is only 1.475(4) A long; in 2 this increases to 1.507(3) A.

Torsion angles (Table 5) show that the degree of planarity is quite different in these two molecules. In the triazine ring of 1 there are deviations from pure cis geometry of 22" about N(2)-N(3) and 35" about N(3)-C(4). In 2 these alterations are only 2". Apparently the unconjugated triazine ring in these systems is flexible. In 1 it distorts, allowing the C(31)...0(4) contact to reach 3.025(4) A. The distortion is not simply a

FIG. 3. Packing of molecules of 3-ethyl-4-hydroxy-l.2,3(4H)- benzotriazine in the unit cell viewed down b with hydrogen atoms omitted for clarity.

FIG. 4. Packing of molecules of 6-chloro-4-hydroxy-3-methyl-4- phenyl-l,2,3-benzotriazine in the unit cell viewed down b. The O(4)-H...N(I) hydrogen bonds are shown by dashed lines. All hydrogen atoms have been omitted for clarity.

twisting of bonds N(2)-N(3) and N(3)-C(4); some pyr- amidalization of N(3) is also involved since the deviation of N(3) from the plane o! N(2), C(4), and C(31), the atoms bonded to it, is 0.164(4) A. However, in 2 the 3-substituent is sandwiched between the 4-hydroxyl and 4-phenyl moieties at C(3 1) O(4) p d C(3 1 ) C(1') contact distances of 2.870(4) and 3.022(4) A. Apparently there is no energy gain from dis- torting the ring since one contact would be relieved only at the expense of the other. The deviation of N(3) from the plane of the atoms bonded to it is only 0.015(4) A in 2.

As expected, the OH group in each molecule acts as a proton donor in an intermolecular hydrogen bond. Of the various proton acceptors available, N(I) plays this role in both mole- cules. The OH ... N distance an! 0-H ... N angle are 2.842(4) A and 169" in 1, 2.778(3) A and 180" in 2. Although these hydrogen bonds are similar in 1 and 2, the mode of association is quite different (Figs. 3 and 4). Molecules of 1 dimerize about a center of symmetry with the heterocyclic rings resembling two treads of? staircase and the N(1)-..N(I)' contact being only 3.139(3) A. The hydroxyl group of each molecule is turned back over its own ring so that it can associate with N(I) of the other ring. In 2 the hydrogen-bonded contact is generated by the action of a screw axis, thereby producing

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LAI ET AL. 585

chains of molecules. The presence of centers of symmetry within the unit cells of both 1 and 2 guarantees that the popu- lations of these chiral molecules are equal.

Acknowledgement The financial assistance (to K.V.) of the Natural Sciences

and Engineering Research Council of Canada is gratefully acknowledged.

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