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and SF5Cl2 are known, efforts to prepare alkyl- and arylsulfur pentafluorides have been unsuccessful. 1b,3 The only alkyl- or arylsulfur trifluoride known is 2,4-dinitrophenylsulfur trifluoride, prepared by Chamberlain and Kharasch4 by the reaction of fluorine with the corresponding disulfide in anhydrous hydrogen fluoride solution. We have found that phenylsulfur trifluoride is obtained in 30 to 60c& yield by the exothermic reaction of silver difluoride with a solution of phenyl disulfide in a "Freon" solvent, 1,1,2-trichloro-1,2,2trifluoroethane. Phenylsulfur trifluoride is a color(CIHBS)? f 6AgFs +ZCJ-IjSFa 6AgF less liquid, b.p. 60' ( 5 mm.), that is hydrolyzed rapidly by water to benzenesulfinic acid and slowly attacks "Pyrex" glass. Anal. Calcd. for C6H5F3S: F, 34.3;S, 19.3. Found: F, 33.5;S, 19.9. Phenylsulfur trifluoride fluorinates carbonyl compounds : for example, benzaldehyde is converted to benzal fluoride (80y0)by being heated with phenylsulfur trifluoride for 3 minutes a t 100°.5 SFbOFIb
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Vol. 82
other substituents. Thus, we have determined that the sulfur pentafluoride group is strongly electron-withdrawing and is meta-directing to electrophilic substitution. A detailed report of the method of synthesis and chemistry of the arylsulfur trifluorides and pentafluorides, as well as quantitative measurements on the inductive and resonance effects of the sulfur pentafluoride group, will be published i n the near future. IVe are indebted to Drs. B. C . LlcKusick and T. L. Cairns for helpful discussions and suggestions during the course of the work CONTRIBUTION 1-0 634 FROM THECENTRAL RESEARCH DEPARTMEST ~VILLIAMA. SHEPPARD EXPERIMENTAL STATION E. I. DU PONT DE SEMOCRS A N D COMPANY WILMISGTOS, DEL. RECEIVED JULY18, 1960 THE SYNTHESIS OF PHENYLATED AZIRIDINONES'
Sir:
This communication describes the preparation of a new class of cyclic amides, a-lactams, previously 0 0 postulated as an intermediate in the sodamideII ll pronioted conversion of a-chloro-a-phenylacetaniCaHsSF3 f CsHsCH +CeHsSF CtjHjCHF? lide (Ia) into a-anilinophenylacetamide' (11). Substituted arylsulfur trifluorides, XC6H4SF3, where Ia(XE","," 247-250 mp (4.19); ; :A: (cm.-l) 3306, X = NO2 or CH3, are prepared in a similar manner. 3150,1667) was caused to react with sodium hyWhen phenylsulfur trifluoride is heated gradu- dride in a manner described2 (this time with a ally to 130' with silver difluoride in a reactor made complete exclusion of oxygen from the reacting of copper or Teflon [polytetrafluoroethylene], system), giving two compounds : (1) 2,5-diketophenylsulfur pentafluoride is obtained in about 10% 1,3,4,6,-tetraphenylpiperazine( 12y0 yield), and yield. Phenylsulfur pentafluoride is a colorless (2)1,3-diphenyl-2-aziridinone, IIIa, (78-8S7cyield) C~HBSFB 2AgF2 --+ CeHsSFj + 2AgF as colorless crystals, (sintering a t 1 1 5 O ) melting liquid, b.p. 149", n Z 51.4290, ~ that is comparable a t 145-150' (dec.) (XE",","243-247 mp (4.02); in thermal and hydrolytic stability to benzotri- Xz?2'3 (cm.-') 1720, 1704, 1689; anal. found for CllHllON: C, 79.9: H , 5.6; Tu', 6.4; mol. wt., fluoride. 212 (ebullioscopic, benzene) . 3 Alkaline hydrolysis Anal. Calcd. for C6H5F5S: C, 35.3;H , 2.47; of I I I a was slow even a t 78", consuming approxiF, 46.5; S, 15.7. Found: C, 35.5; H , 2.74; mately 0.4 equivalent of alkali on being refluxed F,46.7;S,15.G. with 0.1 N ethanolic potassium hydroxide during The n.m.r. (fluorine and proton), infrared and six hours. However, ammonolysis of IIIa by ultraviolet spectra are consistent with the struc- means of sodamide in liquid ammonia provided ture C6H5SF6. The compound is hydrolyzed I1 as the only isolable product. slowly to benzenesulfonyl fluoride by heating a t A-aH 100' with 100yO sulfuric acid. m- and p-nitro- RiR?ClCCOPI" CsH 5 + -H2, -iSaCl phenylsulfur pentafluorides are also prepared (1530% yield) by heating the corresponding disulfide with silver difluoride, first in the "Freon" solvent, CCl2FCC1F2,and then a t 130" in a copper reactor I' with fittings of "Teflon." Anilines substituted C by a sulfur pentafluoride group in the meta- or para-position are prepared by catalytic hydrogenaR1\ccY-CsHi tion of the corresponding nitro derivatives, and react in the manner typical of anilines; thus, they can be acylated or diazotized. The above series of arylsulfur trifluorides and a-Chloro-a,or-diphenyla~etanilide~ (Ib, m.p. &(io, pentafluorides are unique in providing key com- AElH: 245 mp (4.24)) was brought to reaction pounds necessary for determination of the properM a y otherwise be termed or-lactams or azacyclopropanonrs. ties of the SF3and SFs groups in comparisons with t h e(1) above systematic name, illustrating a carbonyl containing deriva-
+
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( 2 ) H. L. Roberts and N. H. R a y , J . Chem. SOL..665 (1960). ( 3 ) H. J. Emeleus and H . G. Heal, ibid. 112G (1946). (4) D. L. Chamberlain a n d N. Kharasch, THIS J O U R N A I . , 7 7 , 1041
(1955). ( 5 ) T h e use of SA for fluorination of carbonyl compounds is described b y w. R. Hasek, w. C. Smith and V. A . Engelhardt, ibid., 82, 543 (1960).
tive of aziridine (otherwise termed ethyleneirnine) is t o be preferred. See Patterson and Capell "The Ring Index," Reinhold Publishing Corp., New York, N. Y., 1940. (2) S Sarel a n d A. Greenberger, J . Oug. Chem., 23,330 (1958). (3) Measurements were t a k e n with a Gallenkamp semimicro ehuliometer, No. 7665K. (4) H. Klinger, A f z n . , 389, 253 (1912).
Sept. 5 , 1960
COMMUNICATIONS TO THE EDITOR
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with sodium hydride in a fashion described here, uent, such as methyl ; iinsubstituted benzoyl affording IIIb (857'( yield) as colorless crystals isothiocyanate has up to now resisted cyclization, although @-naphthoyl isothiocyanate reacts sucm.p. 202'; A%": 255 mp (4.02); ; : A: (cm.-') 3419, 1736, 1720, (anal. found for C20H160N: cessfully. Within this apparent limitation, the C, 84.3; H , 5.8; N, 4.86; mol. wt., 290 (ebullio- reaction provides a direct route for the synthesis showed no identity with of compounds heretofore available only with scopic, b e n ~ e n e ) ~ )IIIb . difficulty or not a t all. The cyclization of benzoyl a sample of 2,5-diketo-1,3,3,4,6,6-hexaphenylpiperazine (IV), m.p. 224'; A:".", 250-255 mp isothiocyanates appears to be selective when two (4.10); : : :A (cm.-') 3226, 1727, 1659 (anal. ortho-positions are open, for m-toluyl isothiocyanate C, 84.4; H , 5.5), prepared yielded only 3-methylphthalic acid, resulting from found for C40H3002N2: as d e s ~ r i b e d . ~I I I b readily dissolved in cold cyclization in the vicinal position. concd. sulphuric acid (scarlet-red coloration) co-KCS giving on dilution with water an immediate l,SOCI, precipitate of colorless a-anilino-a,a-diphenyl2, PbiSCN acetic acid, m.p. 174-177' (reported6 m.p. 174.5') ; ; :A: (cm.-l) 3419, 3367, 1733 (anal. found for CzoH170.N: N , 4.4).7 The physical and chemical evidence presented here clearly suggest that the azacyclopropanone, in analogy with cyclopropenone system,8 has presumably a remarkable resonance stabilization to set off its internal strain. The observed low reactivity of (111) toward nucleophilic reagents seems to be parallel to that of CH; C H3 substituted 2-azetidinones (P-lactanis) with alkalies. Preliminary experiments indicate that the reAcknowledgment.-H. L. is indebted to Abrahm action also occurs with heterocyclic analogs, such and Herbert Sive Memorial Research Fellowship, as 3-thenoyl isothiocyanate, and with P,y-unsatuJohannesburg, South Africa, for financial aid. rated aliphatic acids such as cyclohexene-1-acetic ( 5 ) H . Klinger a n d Xickell, A n n . , 390,367 (1912). acid. Examples of the closely related cyclization ( 8 ) W. Schlenk, J. A. Apyenrodt, A. Michael and A. Thal, B e y . , of P-arylethyl isocyanates have previously been 47,484 (1914). r e p ~ r t e d ,although ~ its utilization in an ortho(7) BY contrast ( I V ) was sparingly soluble in concd. sulfuric acid carboxylation procedure was not undertaken. (brown coloration), giving unchanged s t a r t i n g material upon dilution with water. acyl isocyanates would presumably behave simi( 8 ) R . Breslow, R . Haynie a n d J. Mirra, THISJOURNAL, 81, 217 larly, but we have not as yet investigated them, (1959). owing to the greater difficulties in preparing and (9) S. A. Ballard and D. S. Melstrom in Elderfield's "Heterocyclic handling them compared to the sulfur analogs. Compounds," Vol. I , John Wiley & Sons, Inc., New York, N. Y . , 1950, p p . 107-110. The intermediate monothioimides, which can be isolated in moderate yields, constitute a class DEPARTMEKT O F PHARMACEUTICAL CHEMISTRY THEHEBREW UNIVERSITY SHALOM SAREL of compound of which only one example (monoSCHOOL OF PHARMACY HAIMLEADER thiophthalimide4) has heretofore been reported, JERUSALEM, ISRAEL and to which no preparatively satisfactory general RECEIVED JULY 14, 1960 route has been available. Aill the monothiophthalimides we have prepared are red substances, SPECIFIC ortho-CARBOXYLATION OF AROMATIC while the monothiohomophthalimides are yellow ACIDS AND ARALKYLAMINES : MONOTHIOIMIDES (thioamides are usually colorless or straw-colored). AND THIOLACTAMS Lithium aluminum hydride reduces both thioSir: imides and thiolactams with removal of sulfur, We wish to report a simple reaction for convert- giving tetrahydroisoquinolines. The potentialities ing benzoic acids to phthalic acids, arylacetic acids for the synthesis of these and other classes of heteroto homophthalic acids, and P-arylethylamines to cyclic compounds from the thioimide intermediates o-carboxy-0-arylethylamines.The acids are con- are obvious. Treatment of m-toluyl chloride with lead thioverted through their chlorides by reaction with lead thiocyanate to acyl isothiocyanates, which are cyanate gave m-toluyl isothiocyanate, a colorless, cyclized to monothio-phthalimides or -homophthal- unstable liquid, b.p. 78'(0.85 mm.) (N-m-toluylimides by treatment with aluminum chloride in "-phenylthiourea, m.p. 113'). (Since acyl isocarbon disulfide for periods of several hours to thiocyanates are in most cases unstable to shortseveral days. P-Arylethyl isothiocyanates, pre- term storage, most of those prepared in this work pared from amines and carbon disulfide,2 are simi- have been converted by reaction with aniline t o larly cyclized to thiolactams. Hydrolysis of the N-acyl-?J '-phenylthioureas for analysis and charcyclized products then gives the acids corresponding acterization) . 5 Refluxing a mixture of m-toluyl to carboxylation of the starting materials. The (3) L. M . M o h u n t a and J. S. R a y , J . Chem. SOC.,1263 (1934); cyclization of benzoyl isothiocyanates appears to R . H . F. Manske a n d R . Robinson, ibid.,240 (1927). (4) J . C . Porter, R . Robinson a n d M . Wyler, ibid 620 (1941); require the presence of an activating meta-substit~
(1) A. E Dixon and J. Taylor, J . Chem. SOL.,93, 684 (1908). (2) W R. Vauphan, M. V. Anderson, H. S. Blanchard a n d D. I. IvlcCane. J . Org. Chem., 20, 819 (1955); M L. Moore a n d F . S. Crossley, Org Synlheses, Coll. Vol. 111, 599 (1955).
H. D. K. Drew a n d D. B. Kelly, ibid., 625 (1941). ( 5 ) Satisfactory analyses have been obtained for all new compounds reported here, with t h e noted exception of some of t h e less stable acyl isothiocyanates, all of which, however, showed infrared absorption a t 1960 cm. -1.
