80
Anthelmintic Quaternary Salts.
111.
Benzothiazoliuin Salts
The synthesis and anthelmintic activity of a number of berizothiazoliiim salts analogoiis to the dye thioflavin
T are described. The stritctitral requirements for activity include a 2-phenyl srtbst>itntentwith n basic group i n the para posit,ion, and a %alkyl group no larger than et,hyl (preferably methyl). The isomeric salts in which t'he site of qnaternization is the exocyclic nitrogen, as well as the unquaternized benzothiazoles, are devoid of act,ivity. The benaothiaaole nucleiis may be srihstituted with alkyl, alkoxy, or methj-Ithio groups, bitt not witah halogen. The most active compounds are of interest because they provide both Iitng and liver protection to swine by inhibiting the migration of Ascaris S I O L V Z larvae in swine. Thioflavin xiid two nnnlogs also shotyed activity against gastrointestinal nematodes in sheep.
'l'he berizothiazoliuni dye, thioflavin T i ( l ) , h:t< cH1*,q-J-RcH{l-
3
-
I
.(I-
CII 1
rccwitly been shown to have anthelmintic properties.' The dye has also been claimed t o have antibacterial ii~tivity3and growth-inhibitory activity on fungi of the
ride at elevated temperatures to give the p i d u c t :t< the chloride salt. this niethod was not :idaptahlc to the preparation of analogs, recourse I\ a i had to t h e synthetic niethods for berizothinzoliuni salts illu5a11 o-aminobenzenethiol trattd belo\\ . IIImethod i. condensed uith an aldehyde or an acid chloride t o J ield a 2-substituted benzothiazole \i hich i.: thcti quaternized. In method J3, the product i. obtained directly from the condensation of mi o-nlkylnniitiobenzenethiol with an acid c~liloridc.
*. 3
K \ = /
*x-
4
candida group.4 Its pruperties :is :I fluorescent staiiiiiig acid-base indicator,fiaud photooxidation sensitizer' have been investigated. Thioflavin is of considerable interest as a i l anthelmintic: because it is highly effective in protecting swine from liver and lung damage caused hy the larvae of ilscaris suum, whereas earlier antiascaris agents were eff ective only against the :idult stages. This paper is concerned with structure-activity relationships ztnzong benzothinzoliuni salts related to thioflavin. Chemistry.--Thioflavin T \vas originally prepared'" by condensing sulfur with p-toluidine to form dehydrothiotoluidine followed by treatment wit'h methyl chlo(1) Basic yellow 1 (Colour Index S o . 49008): (a) A. G. Green, Ber.. 22, !I68 (1889): (b) N.T. Bogert and I T - . S. Taylor, Collect. Czech. Chem. Commun., 3 , 480 (1931). (2) (a) American Cyanamid Co., Netherlands Patent 6,501, 092 (Sept 8. 196.5); I t ) ) h b b o t t Laiioraturies, U. S . Patent Application AL56,869/65: Patent 3,3:iti,329 (.lug 16, 1967). i t . ) I)ow Chemical Co., U ( 3 ) U.J. Alartin, An.J . Pharm., 119,432 (1947). ( 4 ) F. Aliyazaua. E i w i Stiikrnaliu t l o i o i . u , 74, ; 3 4 l (1!256): Clirrn. . 4 b s l r . , 61,8277 (19.77). ( 5 ) 1'. S. Vasanr, ( ' . 1'. .I. (:ulling. : ~ m l I I . 1:. 'Taylor, .tm. ./. I',cthd., 35. 718 (1959). ( 6 ) 0 . LV. TCollina and T. I,. stevens, . I i ( d . Client., 34, 1633 (1962). t i ) G. Oster, .I. S. Bellin, It. IV. liiniball. and 31. E. Sclirader, .I. A m i . . Chtm SOC.,81,30Y5 (1959).
L'-,~mitiol,enzciretliiol. (2) \\ w e 1)rel)arod by
:t
i,:wivty
of' routcb, tlic (*lioicebeing (let ermined ~ J the Y :iv:dability of startirig materid, (Sclienie 1). Exaniplez of c~,icli
UJUte iire desrribcd iii 1hc &q"imctital Sertion. 'rhc :ri~iirioberizenethiol~ crc c*oiivertctl in thwe st c y ' to :i-nlkyl- (or :traIkyI-) I)etizothli~zolirie-L'-thioiie~(5). Sew compounds of thiy type which nerc prcp:ircd in this program iire libted in Table I. .Ul;aline hydroly of 5 vieldcd the 2-dkylamiiioiol. 3, which wcrc required for t h e direct i f benzotliiazoliurii salts by method B. Thc previou4y uiireportcd 2-(p-dinietliylaniiii~p}ienyl)-3-metliylbe~tzot hiazole W;IS prepared by roilderisi ng zinc. L'-ntizino-l-tolyIn~ercaptide (obtained froni 4-c.hloro-3-1~itrotol~i~tie~ with p-dimethy1aminobenz:ddehyde. Other neiv benzothiazoles which n ere prepared as intermediate< in method X are listed in T:tble 11. The ~-~j~-diethylaniiriopIieoyl) analog 7 w a ~prepared in the usual ivxy by reaction of p-diethylaniinot)erizaldehydc wit11 /~-aiiiiiiobeiizei~et~iiol.The 'L-(wcarho-iy:ilkyl) clwiv,rt ivc.. S : i t i d 9 w ' r v prei):iretl by t IIV ro:iction o f tIicwl)o\plic~:wid itnhydrid(xi \I itli o-:tiiiitiohcnzericthiol, : t i i d thcl S.S-diiiiethylxtiiide:, 10-13 i \ - ( ~ r ( ~ ohtailled by twating the c.,irboxylic acids IT itli dirnetliyluniirie at 200".
ANTHELMINTIC BESZOTHIAZOLIUN SALTS
January 1969
31
SCHEME I
R
3
5
TABLE I &ALKYL-
(.ISD
-ARALKYL-) BENZOTHIAZOLINE-2-THIONES
difficulties were encountered with method A because, as in the case of thioflavin itself, both possible isomers 1 and 6 were formed on alkylation. The relative yields
R R
R'
CI13 6-C1 CH3 5-CH3 CH3 6-CzHb CH3 6-OCzH6 CZHS 6-CH3 n-CsH? 6-CH3 n-C4H9 H n-CaH9 6-CH3 CsHsCHz 6-CH3 O - C H ~ C ~ H ~ C H6-CH3 Z P - C H ~ C ~ H ~ C H6-CH3 Z 1-Sap ht hylmethyl 6-CH3 2-Methyl-lnaphthylmethyl 6-CII3 All compounds analyzed
Mp,
O C
130-131 188.5-189.5 74-75 133-134 108-109 103-104 53 96-97 154 85-87 88-89
Yield, %
57 79 51 96 55 22 30 72 93 43 62
Formula'
csHac1NS~ CsHgrjSz CloHiiNSz CioHiiNOSz CioHiiNSz CiiHiaNSz CiiHisNSz CizHi6NSz CisHiaNS2 CisHisNSz C16HijNSz
I
c
H
3
~
~
-~
(
C *
H
x-
6
of the two isomers depended on the reaction conditions? Under mild conditions the anilinium isomer 6 predominated, but when temperature and reaction time were increased, the benzothiazolium isomer 1 was formed 204-206 30 CZOII17~S2 preferentially. I n some cases it was possible to convert correctly for C, H, N, S. the anilinium isomer to the benzothiazolium isomer in good yield by refluxing in hexanol. The isomers could TABLE I1 be readily distinguished by their uv spectra. The 2-SUBSTITUTED BENZOTHIAZOLES benzothiazolium isomers had maxima a t 413420 mp, as contrasted with maxima a t 300-313 mp for the anilinium isomers. The benzothiazolium isomers usuR g R ally crystallized with water of hydration and formed Yield, stable insoluble complexes with phenols, particularly LIP, o c % Formula' NO. R resorcinol. I n the case of 31 (Table V), the isomers 7 p-CsHaNEtz 125-126 30 Ci7HisNsS 3.5 C I Z H ~ ~ N O Z S were separated most conveniently by the addition of 8 (CHz)dCOOH 133-134 resorcinol in aqueous solution to precipitate the benzo72-73 48 CiaHi5NOzS 9 (CH2)sCOOH 10 (CHz)zCOS(CH~)2192 (1.2 mm). 61 C~Hi7N50sS thiazolium chloride-resorcinol complex. I n general, method B was the preferred method for picrate 151-152 86 C13HisNzoS 11 (CHz)aCOX(CH3)z 67-68 the compounds in Table IV because the products were 84 CiaHiBNzOS 12 (CI-IZ)~CON(CH~)Z 4445 obtained without contamination by the anilinium 60 CijHzoNzOS 13 (CHz)sCOX(CHa)z 58-60 isomers. Boiling point. * All compounds analyzed correctly for C, A number of miscellaneous benzothiazolium salts are H, N, S. listed in Table V. 2-(3-Pyridylvinyl) benzothiazole dimethiodide (35) and the 2-(4methoxystyryl) derivative All of the benzothiazolium salts listed in Table I11 36 were prepared by reaction of 2,3-dimethylbenzowere prepared by treating arid chlorides with S-alkylthiazolium iodide with 3-pyridinecarboxaldehyde methaminobenzenethiols (method €3). Both methods A and iodide and p-anisaldehyde, respectively. The other B were used to prepare the p-dimethylaminophenylbenzothiazolium salts listed in Table IV. However, (8) D. L. Garmaise a n d G. Y. Pari;, Chem. I n d . (London), 1645 (1967). 0
222-223
71
CisHisNSz
J
)
J
32
ii '
\
11
I
*-,
ti-( 'I .i-( ' I I,
1 ii
I
('11,
ti-VIl,, !t!l
I7 1s
I!, 20
January 1969
ANTHELAfIiXTIC
TABLE
v:
33
BENZOTHIAZOLIUM SALTS
LIISCELLANEOUS ?,-SUBSTITUTED 3-~~ETHYLBENZOTHIAZOLIUMSALTS
GLR AIL
It
?io,
oc
20’2-204 dec 4-l)iethylamiiiopheii~l~ 180-181 3-Dimethylaminophenyl 203-204 2-Fury1 206 2-Thien yl 226-228 3-Pyridylviiiyl (methiodide) 234-235 4-1Iethosystyi yl 1.57-158 2-(N,S-IXmethylcai barnoy1)ethyl 186-187 3-(N,N-lIime th!lcarbamoyl)-n-prol-’yl 167 4-(N,N-l)irnethylcar bamoy1)-n-butyl 5-(K>K-IArnethylcnrharnoyl)-~~-~~eiityl87-89 40 Chloride salt, resorciiiol complex.
31 32 33 34 3.5 36 37 38 3!)
I \ = /
CHJ
*Br-
CHj
‘OH-
-
CH, OCHj 42
uv absorption, ,A,( 416 mp) of thioflavin. The 2methoxyberizothiazolirie was volorless and had, , ,A 310 mp in ligroin, but its solution in NeOH gradually turned 416 nip. (2-Ethoxy-2-phenyl-3yellow arid had, , ,A methylbenzothiazoline has been reportedg to have Amax 30s mp.) Compound 42 was only very slightly soluble in water and formed a stable aqueous suspensiori under neutral conditions. I t could be obtained more conveniently by treating thioflavin bromide with S a O N e in MeOH. Treatment of thioflavin bromide with hot aqueous alkali gave a solution of the sodium salt of the thiol 43, which was converted to the disulfide 44 and was also alkylated and acylated to give the derivatives 45a-d. 1-
‘A
hlethod
A B B B
53 62 52 40 S3
60 95 89 ‘33 93
A A A
’4
in mice and six gastrointestinal nematodes in lambs, and for prophylactic activity against Ascayis suum in mice and swine. The results are summarized in Table VI. Compounds which showed activity were all closely related to thioflavin (1) in that they had a a-(p-dialkylaminophenyl) substituent and were quaternized on the heterocyclic nitrogen atom. Sone of the benzothiazoles was active. The ariilinium isomer (6) of thioflavin, the 3-dimethylamino analog 32, the berizothiazoline 42, the ring-opened derivatives 44 and 45, and all the compounds in Tables I11 and V (except for the p diethylamino analog 31) were inactive. The 6-methyl group was not critical for good activity; replacement by hydrogen, ethyl, butyl, methoxyl, ethoxyl , and methylthio gave compounds which were very active against -4.suum. I n their prophylactic action against A . suum in swine, these compounds eliminated lung pathology as effectively as thioflavin itself, but only the 6-ethyl analog was as active as thioflavin in preventing the development of liver lesions. Replacement of the &methyl by 6-chloro gave an inactive product. Less latitude was possible in replacing the 3-methyl substituent. The 3-ethyl analogs 22 and 23 showed some activity against N . clubius and A . suum in mice, but the introduction of groups larger than ethyl (25-30) resulted in complete loss of activity. The basic substituent on the 4 position of the phenyl group was essential, as evidenced by the total inactivity
3q@N,HJ.2
41
CH
Yield,
c H J a i , C O e N ( C H J -
43
It(.
-+ P
H
J
a
-i
H
e
44
C H J a g C OO N-( C H J &a,
b,
R = CH,
R = CH2C6H5
R = COC,H, d, S = COC,H,C1,-3,4 e,
Biological Results.-The compounds were tested for therapeutic activity against Nematospiroicles dubius (9) J. M e t a p e r , H. Larlv6, R. Dennllauler, R Baralle, and c. Gaurat, Bull. S O L .Chzm. Frtu’ce, 2868 (1964).
of the isosteric 4-methoxy and 4-isopropyl analogs. However, the methyl substituents on the 4-amino group be replaced by ethyl, as in 31, mhich Was very active on A . suum in both mice and swine.
34
IL
NO.
14 1.5
CIIi
CHT 16 CH3
. .... . I . .*iiiiiiiill >wine"----- Liver lesions, Laryae in lunen. :; redn ('i, redn
1
('I I I
h7 .ill
I1
2.i I.io
I
!I,>
lJ.3 h ~ i o : i t c
C1 1 1
I
( 'I ('I
1
r
1
I
r
1 I 1 ('1 1
100 IO0
II
1.iO
I1
I1
.iO 100
a Each of three mice which had been infected with 30 ,Y. clubiiis larvae severs1 n w k s earlier WLY administered a dose of 15--50nig; kg orally. A similar dose was administered on the following day. On the seventh day the niive were sacrificed and the teat compounds were graded on the basis of the number of worms remaining in the intestiiie: 5 = total or near total elimination, 1 = moderate reduction, 0 = no activity. The compounds were tested on sheep which had been experimentally infected with six species of gastrointestinal nematodes: Haemonchus contortus, Cooperia cztrticei, Trichostrongylus colubri'ormis, Trichostrongyl l i s axei, Ostertagia circumcincta, and il'ematodirus spathiger. The compounds were administered in two equal doses on consecutive days, and the reduction of the worm burden was estimated after determination of the egg count per gram of feces. The activity recorded is the average of the activity against the six helminths tested: 5 = total or iiear total elimination of the n-orm burden, 1 = moderate reduction, 0 = no activity. c -4dose of 10 mg/kg was administered orally to each of three mice, followed by the administration of an infection of 100,000 embryonated Ascaris swum eggs. A second dose of 10 mgjkg was administ,ered4 hr later. Xft,er 8 days the mice were sacrificed and the extent of lung lesions was determined by gross examination of the lungs for the number and size of hemorrhagic area3 due to the migration of the Ascaris larvae. The table lists the percentage reduction in lung lesions of the treated animals as compared with the unmedicated controls. d The test compounds were administered at a level of 0.01 yo in feed for a period of 10 days to two pigs in concrete-floored pens. h i infection of 100,000 embryonakd Ascaris s u u m eggs was administered 3 days after the start of the inclusion of the test compound in the feed. The animals were sacrificed after 10 days. The percentage reduction in liver lesions due to migrating Ascaris larvae in treated animals as compared with controls was determined by counting the sniall white scar6 ("milk spots") found on the surface of the liver. The procedure uied to determine the number of larvae in the lungs of the pigs was based on the method described onsin, 1062). e ~ - - ( 4 - l ~ i e t h y l : t i n i i i o i ) ~ i e i i ~ l ) - ~ ~ - n i e ~ h y l b e n z ochlothi~~~oli~~m for mice by D. K. Ilass (Ph.D. Thesis, TTniver+ityof ride-resorcinol complex.
Thioflavin was also very active against the gastrointestinal nematodes of sheep a t 2.5 mg/kg. Two close arialogs (14 and 17) were also classified as being very active, but a t the relatively high dosage of 150 mg/kg. In general, the compounds were significantly less active against the sheep nematodes than against A . suum. A number of the most active compounds were tested as the pamoate and Y-hydrosy-X-naphthoate salts ab 1 ~ 1 as 1 the halide salts. The less soluble salts were les.; toxic to mice on oral administration, but showed no significant difference in anthelinintic potency.
Experimental Section1(' 3-Substituted Benzothiazoline-2-thiones (Table I). From Arylthioureas. 6-Ethyl-3-methylbenzothiazoline-2-thione.--pEthylphenylthiourea (75 g, 0.4 mole) fprepared in 45% yield from p-ethylaniline hydrochloride and ICCSS) was dissolw(I (BT.5 g, 0.5 mole) wits n d d d in chlorobenzene (250 ml) and SOLCIA (10) Melting points uerp taken on a Thomas-€hovel ,ipParatua and are corrected.
dropwise a t 7 0 " . The mixture was stirred a t TO" for 2 hr and then cooled and filtered t,o yield 2-amino-6-ethylbenzothiazole hydrochloride, mp 213-214'. An aqueous solution of the hydroc>hloridewas basified with SH,OII to give the free base, m p C, I I , N, I13--ll6" (from EtOII), iri 64% yield. Anal. (C!I€Il0N2S)
S. B solution of the 2'-amino derivative (40 g, 0.22 mole) in 50(?, aqueoiia KOH solution was refluxed for 6 hr. The solution was cooled and treated with CS?(22.8 g, 0.3 mole). After refluxing for 6 hr, the aolution was cooled and neutralized with ArOH to give 6-ethylbenzuthiazoline-%-thione, mp 138-139" (from CHCl~-petroleum ether (bp 60--90°)),yield 23 g (535%). Anal. (CsHgNSz) C, 13, N, S. Me1 (10 ml) was added to a solution of 6-ethylbenzothiazoline-2-thione (22.4 g, 0.11 mole) in 12 KaOH (65 ml) and the mixture was stirred for 2 hr. The int mediate S-methyl derivative was separated by extraction w1 CC14 and the evaporated extract was re:trranged t.o the Y-inethyl derivative by heating a t 200' fur 1 hr with AIeI (10 ml) and a crystal of I?. The cooled reaction mixture was extracted with 350 ml of concentrated HC1, and the insoluble residue was crystalfloni EtOH to give the prodiirt,, nip 74-75", yield 11.8 g )repwatioii \\-its b a s d on the gellerd proced11l.cb oore and Waight.11
melting jioint (11) C. G. Moore and E. S. Waight, J . C h e m Soc., 4 2 3 i (193%).
January 1969
ANTHELMINTIC BESZOTHIAZOLIUM SALTS
From Chloronitrobenzenes. 3,5-Dimethylbenzothiazoline-2thione.4-Chloro-3-nitrotoluene (171.6 g, 1.0 mole) was refluxed with NaZS.H*O (648 g, 2.7 moles) in 1600 ml of HzO for 24 hr. The solution was cooled and CSZ (70 ml) was added dropwise. The mixture was heated on the steam bath for 1 hr and was then cooled and acidified with AcOH to give crude 5-methylbenzothiazoline2-thione, mp 170-175'. Recrystallization from EtOH raised the melting point to 179-BO", yield 57.6 g (32%). Anal. (CsH7NSz) C, H, N. Treatment of 5-methylbenzothiazoline-2-thione (52 g) dissolved in 250 ml of 1.6 iV aqueous NaOH with Me1 (31 ml) gave 2-methylthio-5-methylbenz&hiazole, mp 54-55', yield E% g (91%). Anal. (CgHgNS2) C, H. N. The 2-methylthio derivative (46 g) was rearranged as described above to the 3-methyl-2-thio isomer, mp 188.5-189.5", in 797, yield. 3-Methyl-6-ethoxybenzothiazoline-2-thione.-~~ezSO~(80 ml) was added a t 40" to a solution of the commercially available 6ethoxybenzothiazoline-2-thione (140 g, 0.66 mole) and XaOH (105 ml of 5oyo XaOH) in 650 ml of HzO. The reaction mixture was heated a t 70" for 1hr and then cooled giving the crude 2-methylthio-6-ethox> benzothiazole, mu 39-42". Recrvstallization from dilute EtOH raised the melting point to 46-47', yield 60%. A n d . ICioHiiXOS2) C. H. N. , .. .~ The 2-methylth:;~derivative (58.8 g) was added to Me1 (57 g ) and a crystal of 1 2 . The Me1 was slowly removed by distillation and the temperature of the residue was raised to 210". After 30 min at that temperature the reaction mixture was cooled and extracted with 200 ml of concentrated HCI. The insoluble residue was crystallized from CHCI,-petroleum ether to give the pure product, mp 133-134', in 96% yield. Substituted benzothiazoles (Table 11). 5-(2-Benzothiazolyl)n-pentanoic Acid @).-The procedure used was a modification of the method described by Babichev and Derkachlz for lower homologs. o-Aminobenzenethiol (42 g, 0.33 mole) in C6H6 (150 ml) was added dropwise to a solution of the anhydride13of adipic acid (42 g, 0.33 mole) in C& (150 ml) a t room temperature, and the solution was refluxed for 1.5 hr. The cooled solution was extracted with 10% NaOH and the alkaline extract was acidified to give the product, mp 133-134" (from dilute MeOH), yield 27 g (35%). 6-(2-Benzothiazolyl)-n-hexanoicAcid (I)).-Pimelic acid was refluxed in an excess of ACZOfor 3 hr, and the excess Act0 was removed under reduced pressure. The residue of pimelic anhydride14 was treated with o-aminobenzenethiol as described above to give the product, mp 72-73", in 487, yield. 2- (3-N,N-Dimethylcarbamylpropyl jbenzothiazole (I 1).-4-(2Beiizothiazoly1)butyric acid12 (25 g, 0.1 mole) was heated a t 200" while Me2SH was bubbled through the melt for 2 hr. The mixture was extracted with C6H6, and the CaH6 solution was washed with 5% KzC03. Concentration of the solution gave the product, mp 67-68", in 86% yield (from petroleum ether). The other N,N-dimethylamides listed in Table I1 were prepared by the same method, which is based on the procedure described by McMillan and King.15 2-(p-Dimethylaminophenyl)-5-methyIbenzothiazole.-A mixture of 4-chloro-3-nitrotoluene (171.6 g, 1.0 mole) and NazS,HzO (648 g, 2.7 moles) in Hz0 (1600 ml) was refluxed, with stirring, for 20 hr. The mixture was filtered, and to the clear filtrate was added H202 (160 ml of 30yc solution) a t 50-55' during 2 hr. The precipitated 2,2'-diamin0-4,4'-dimethyldiphenyl disulfide was filtered and recrystallized from LTeOH, giving 75 g (547,), mp 68-70. The disulfide was added to EtOH (300 ml) and 7% HCl (750 mlj and the solution was heated to boiling. Zn powder (19.8 g, 0.3 g-atom) was added in portions until a clear solution resulted. The excess Zn was filtered, and KaOBc was added to the filtrate to precipitate zinc 2-amino-4tolylmercaptide, yield 57 g. p-Dimethylaminobenzaldehyde (48.5 g, 0.34 mole) was added to a suspension of the zinc mercaptide (57 g, 0.17 mole) in AcOH (1.5 1.) and the mixture was heated on the steam bath for 30 min. The solution was filtered and diluted with HZO t o give the product, mp 182-184" (from hIezCO), yield 42 g (467,). A n d . (CI6IIl6NZS) Cj H, N, S. 2-Aryl-3-alkylbenzothiazolium Iodides (Table 111). 2 - ( p ~~~~
~
(12)
.
35
Chlorophenyl)-3-methylbenzothiazoliumIodide (Method B).-A solution of p-chlorobenzoyl chloride (17.5 g, 0.1 mole) in (40. ml) was added dropwise to a stirred solution of 2-methylaminobenzenethiol (13.9 g, 0.1 mo1e)l6 in C6H6 (70 ml) a t 20". The mixture was stirred for 1 hr and 150 ml of H20 was added. The aqueous layer was separated and treated with K I (30 g ) giving the product, mp 224-225' (from MeOH), yield 24.7 g (64%). 2-p-Anisyl-3-n-propylbenzothiazolium Iodide.-3-n-Propylben~othiazoline-2-thione'~(19.5 g, 0.09 mole) was refluxed for 20 hr in EtOH (2 1.) containing 95 g (1.7 moles) of KOH. The mixture was filtered and the filtrate was concentrated. The residue was dissolved in H 2 0 (800 ml), neutralized to p H 7 , and extracted with CHC13 (200 mlj. The CHCla extract was dried and evaporated, giving 2-n-propylaminobenzenethiol as a yellow oil which was used without further purification. The thiol was condensed with panisoyl chloride as previously described for method B to give the product, mp 192-193", in 487, yield. 2-p-Anisyl-3-allylbenzothiazolium Iodide.-3-Allylbenzothiazoline-2-thione11 (33 g, 0.16 mole) was added to a refluxing solution of KOH (45 g, 0.8 mole) in EtOH (350 ml). The mixture was allowed to reflux overnight (17 hr) with vigorous stirring. Most of the EtOH was then distilled and the residue was treated with 300 ml of H20. The aqueous solution was carefully neutralized with concentrated HCl (cooling) and extracted with three 100-ml portions of CHC13. The CHC13 extract was dried and concentrated under reduced pressure at 40'! giving 2-allylaminobenzenethiol as a dark red oil. The crude thiol was treated with panisoyl chloride to give the product, mp 153-155', in 307, yield. 2-(p-Dimethylaminophenyl)-3-alkylbenzothiazoliumSalts (Table IV). 2-(p-Dimethylaminophenyl)-3,6-dimethylbenzothiazolium Chloride (1) and p-(6-Methyl-2-benzothiazolyl)phenyltrimethylammonium Chloride (6) (Method A).-2-(p-Dimethylaminophenyl)-6-methylbenzothiazole1~ (20 g, 0.075 mole) was heated with Me1 (30 ml) in a pressure bottle a t 90-95" for 4 hr. Since the chloride salt was desired for evaluation purposes, the crude methiodide (30.6 g) was added t o Amberlite IRA-400 (chloride form, 250 ml) suspended in 1500 ml of MeOH and the suspension was boiled for 30 min. Concentration of the methanolic solution gave the mixture of chloride salts (23.4 g, yield quantitative), mp 203-204.5'. The crude product, which gave two main spots on tlc (HOAc-HzO-EtOAc, 65:12:23 on silica gel G), was fractionated by extraction with CHCl,. The CHC13&oluble fraction consisted of 6, mp 205", Amax 313 mp. Anal. (CI~HI~ClN231 C, H, C1, N, S. The CHC18-soluble fraciion was concentrated and crystallized from HzO, giving the benzothiazolium chloride as the dihydrate, 413 mp. The product was identical with mp 212' dec, =A, that prepared by method B. Both isomers dequaternized on melting and reverted to the starting benzothiazole, mp 204.5205'. 2-(p-Dimethylaminophenyl)-3-methylbenzothiazolium Chloride (Method B).-p-Dimethylaminobenzoyl chloride (29 g, 0.16 mole) was dissolved in 100 ml of CeHe, and the solution was added to 2methylaminobenzenethiol16 (22 g, 0.16 mole) in C6H6 (30 ml). The reaction mixture was allowed to stand overnight and the product was filtered (chloride salt), mp 179-180' dec, yield 45.5 g (95%). The chloride (1 g) dissolved in HzO was treated with excess aqueous NaI, giving the iodide salt, mp 223-224", lit.lb mp 223-224". 2-(p-Diethylaminophenyl)-3-methylbenzothiazoliumChlorideResorcinol Complex (31).-2-(p-Diethylaminophenyl)benzothiazole (7)(20.0 g) was heated with Me1 (24 ml) a t 100" for 2.5 hr in a pressure bottle. The product was crystallized from hIeOH-Et20 giving 30.0 g (quantitative) of crude product, The uv spectrum indicated the presence of both mp 183-185'. the benzothiazolium isomer (420 mp) and the anilinium isomer (300 mp). The mixture of iodides (12.8 g, 0.03 mole) was stirred in 280 ml of Amberlite IRA400 (Cl- form) at room temperature for 1 hr. The resin was removed by filtration and the filtrate was concentrated to give 8.9 g (quantitative) of the product as a mixture of chloride salts. Resorcinol (3.3 g) was added to a solution of the mixture of chlorides (8.9 g ) in 500 ml of €IiO cztusing the precipitation of
F. S. Bal)icllev and N. Ya. Ilerkacll. Ckr. Khim. Zh., 7.2 208 (108G);
Chem. Abstr., 51, 373 (1957). (13) J. W. Hill, J . Amer. Chem. Soc., 52, 4110 (1930). (14) J. W. Hill and W. H. Carothers, ibid., 66, 5023 (1933). 15) F. H. hIcMillan and J. A. King, i b i d . , 73, 3165 (1951).
(16) A. I. Iiiprianov and Z. N. Pazenko, Zh. Obshch. Rhim., 19, 1523 (1949); Chem. Abstr., 44, 3488 (1950). (17) F. P. Reed, A. Robertson, and W. A. Sexton, J . Chem. Soc., 473 (1939).
