Document RLBG9VeG4KG8wr770EMKqeka

HA 7 ^^* M arch 20, 1957 H alogen D erivatives of D ibenzo-P-dioxin 1409 ( k>ncd abnve was added dropwue to a 300-ml. ether solution with that of tbe sample of the trimer obtained by the hy of phenyllithium , which had been made from 110 [. (0.70 drolysis of pbcnylbromosilane. inule) of bromobenxene >n*l u excess of litbhnr metal. A fter re during far ooc boar) this reaction mirtine poured, onto cracked Ice d dilate sulfuric acid to destroy th e exces nhenyllthium. The ether was then removed by evaporation, leaving a white solid, which was collected and d ried. This soli was placed hi a SoahVt extractor and ex tracted far ooc boar with 20--40* petroleum ether to dis A**I. Calcd. for C*HOSi: C. 59.0; H, 4.95. Found: C, 59.9; H, 5.20. Cfeavag of rnw-DkhsayM Migrano by Baoxytmagnaaf Chloride.--A 23-f. (0.10 mole) remple of ryw-d^heayldtsilaxaoe in 25 ml. of ether was added dropwim to a 300ml. ether sotutiaa of benxyhnagneshun chloride, which bad solve tbe methyttripbenybDaae (derived from the metbyl- been made from 63 r . (0-50 mole) of benzyl chkrida and 13 pbenylailaDe). Tbe yield at this compound was 7.0 f. g. (0-5 g. atom) of magnesium turnings. Tha reaetka (0.03 mole), m .p. 65-68*.* The remaining solid was ex started immediately and rcflnxkg of the solvent resultsd. tra c te d with toluene for 13 hoars to give 33-0 g. (0.10 mole) The reaetka mixture was held a t tha reflux temperatmu for of trtm nhenyhilaoc (derived from pheaykOane), m.p. 232- ooe hour, then hydrolysed and worked up in tha usual are- 233*." ncr. Tbe ether was thrilled ctf and a 19f. mixtare of Cl aavaga af jym-Di^haoyidiaftaxaaa by I t h r i s u p o h a pbesyisflane and toloene distilled a t 130*, Waving a raridne Brom ida.--A 46-g. (0-20 mote) sample of ij w dipbenyldi- which was distilled later. Tha mi l t m s of pbea r faBaua and ailoxane ia SO ml. of ether was added dropwwe to a 200-tnl. tolneac was treated with phrnyUrthhmi, which had baan ohitioa af ethyhaagnesknm bromide, which had been made made from 94 g. (0JO mole) of brrsnnbruiraa and an as from 70 g. (0.50 mole) of ethyl bromide sad 12 p (0JO f. cesa of lithium metal. The yield of tctxapbcsyUaaa was ato m ) of -~r-- ^ttb tamings. The reaction m ature was 7.0 g. (0-03 mole), m.p. 233-233*. Tba readaal Book held a t the r o a r tmxxperatsrc for one hoa r , then hydrolysed was distDrd under vacuum, giving a 34-g. u litm a of 1,3- an d worked up as du a fc c J in the above experiment. Tbe dipbenykthane and benzylpbeayktlaae, which dhtiflvd pbcnybilaae -and ethyipfceayirihme obtained were am - at 106-160* (0.43 mm.). This mixture was treated with v erted to tetmpfaenybdmne and ethyferipbenybilaae, re an ether sohttka of phenytUthhzm, which had beta made spectively. The yield of tetranheayUlane was 24.0 g. from 63 f . (0.40jnole) of bromobesuene and sa f u r a of (0-073 mole)* m .p. 233-233*"; that of triphenyletfaybihne lithium metal. Tbe reaction mixture was hydrolysed and ras 7 JO g. (0-034 malm}, m.p. 73-73*.* Tbe ttqnid m a s k worked up ia tbe usual manner. The ether was evaporated, ing a fter tbe separation of the phenyWkae and ethyipbenyl- and the residual liquid dw*Bed under reduced premura to silane was distated under reduced pressore, giving 12.0 g. of remora tbe 1,2-dipnenylethane. Tbe residua waa treated erode j y s-diethyldJLiltr nyhlh flnrerw, (C*H*SiHC*H*)jO, d*t- with 20-40* petroleum ether, which earned benxyferiphenyl- tilling a t 140-200* (0-06 mm.). The crede prodoct was re sQaae to precipitate. This compound was recryitaCbed distilled a t 107* (0.03 mm.) to obtain a sample for inaiyds twice from 95% ethanol; yield 16 g. (0-04 mole), a .p . 96- ar>d physical properties. The infrared spectrum of the 97*." compound was ideatimi with th at" of an in thentic sample CUavaga at ryv-D ffhiniU hD aT in by UtUam Ahad- of l ym diethyhUphf nyMaakganc, "d 1.523. sum Hydride.--A4.0-g. (0ju3 mole) sampfeof t rm dkheayi- Amml. Calcd. for C^HnOS,: C, 672; H, 7.75; mol. dbiloxane wax added dropwise to 2.0 g. (0.7 mole) of lithium w t-, 286. Pound: C, 67.0; H, 7.90; mol. wt., 283. alummum hydride to 250 ml. at ether. Slight rvflmliiy of Claovag* of fvs-Piphi)fi1iaflnTsna by PhanytmagD*Iwtq Bromida.--A 23-g. (0.10 moie) sample of ijm diphenyldmkxxaoe in 20 ml. of ether was added dr opwise to a 200-ml. ether solution of pbenytmagnrsinm bromide, which had been made from 63 g. (0.40 mole) of bromobenrene and 4-8 g. (0.40 g. atom) of magnesium turnings. The reaction mix ture was held a t tbe reflnx temperature for ooe hour, then hydrolyzed and worked op in tbe usual way. Tbe ether was removed, and the residual lionid fractionated. A tbe solvent resulted, and a henry white predpitatt farmed. Tbe reaction mixture was allowed to stand for two hours and then it waa poured onto a mixture of cracked k a and dilute hydrochloric add. Tbe etber layer was separated, wubed first with dibit* hydrochloric i d and then with water, and dried over Drierite. Tbe etber waa dist3td atf sod the product (2.1 g., 50%) distilled at 119* (740J mm.). Tbe prodnet waa identified as pbenybikne fay ha point and infrared spectrum.** 3.0-g. (0.03 mole) fraetioa composed of pbenylsilue dis Acknowledgments.--Analyses were by Miss J . tilled a t 118-120*. This compound was identified by its infrared spectrum*4 and its boiKng point. Tbe residual liquid was distilled under reduced premure, erring 11.7 g. Dickey of tbe Indiana U niversity M kroanalytacal Laboratory. This paper is based upon work per (0.064 mole) of dtphcnybEane, which distilled at 60* (0.6 formed under contract N onr-90802 NR 356-321 m m .). Tbe dipbcnylsUane was identified by ha infrared spectrum .1* A fraetioa consisting of 5.0 g. (0.014 mole) af (Office of Naval Research). 2.4.6-triphenylcyelotrTtiloxane, (C*H*SiHO)i. distilled at (18) C. Hue* u l C. Rim t , Tan Joesal, 74, 1IN (IMS). 168* (0.02 mm.), a"u I -566; calcd. mol. wt. 366, found 352. The infrared spectrum of this compound was identical Bloomington, I ndiana N O T iC P T h .s w . \ -------------------- * * p r o t e c t e d b y Cc a0 Pr yJ r " g p fI, [CosTxiBunoM ntOM ths Cubiocal LABOEAToar of Iowa Stats Collxgs] H alo g en D eriv ativ es of D ib en zo -p -d io iin B y H enry G ilman and J oseph J . D ietrich RacirvzoO croax* 15, 1956 P u get preparations for 2^hioro- (II). 2.7-dichloro- (III). 2.7-dibromo- (VI) and 2.3.7.8-tetrabrr>moMdibetiio.-dioxia .(VTTP tlrofli dlbcniA-jb-dioxui (1) are reported. The 1-bromo-dibcnzo-p-dioxin (IV) ana th e -iodo-dibcnxo-p-diaxM ( l A) X* obtained by Inolrecx raemoSZ II, IV, VT.'VIII and IX are new compounds. Structure proofs for these ami JJ-dU brwno-dibenxo-p-dioxin (VII) are included along with a brief theoretical dbcum kn dealing with VI, VII and VIII. Brief instructkoas are given for the preparation of 2-bromo-dibenzo-^-<Uoxin (V) and of VII. I Is formed from Inexpensive achlorophcnol in low yield.' Studies on the orientation of entering groups on preparation of a number of halogen derivatives and tbe dibenzo-p-dioxin (I) nucleus have led to the confirmation of their structures. 1440 H enry G ilman and J ossth J. D ittrich Vol. 70 1 * * 41 Flc. 1. I. X,. X*. X*. X. X* - H II. Xj - Cl; X*. X*. X* Rad X* - H III. X * .X -a ;X t. X ^ X t - H IV. X, B r ;X i,X i,X ,X i- H V. X - B r ;X i,X ,X * X - H VI, X*. X* - Br; Xj. X*. X* - H VII. X h X * -B r:X i.X * .X -H VIII. Xfc X*. X4. X* " Br: X* --H IX . X* - I ; X |. Xfc X * X* - H X . X*. X - N H ,; X t.X 1 .X 4 - H X I. X . - N H ,: X t.X 4. X 4.X 1 - H X II. X ,. X* - COOCH,; X,. Xi. X, - H rh eae co n sist of th e 2-cbloro-dibenzo-^-dioxm (II). T ^ -5 IcE Io ro ^ b m ro -^-d k m n (III), 1-bromo-di- enxo-p-diaxm (TV), 2-bromo-dibenxo--dkran (V), ^7-^brrraK H dibenzo-^-dioxin (VI). 2*&-dibromo-di- >enzo-^-dioKzn (V ID . 2& 7,8-tetiR hrnft-dihi*o-f- tiozin (VI I I ) wkI th e a -w iw i6 g m )^ 4 k a in - i x r ' O nly" 2^-dicfaloro-dibenxo-^-diaxin, 2-bro- odibenzo-^-dioxin u d an niTiaiirnrd dibromo- libenzo-^-diozin have been reported in the Hteru- basis of infrared spectra comparisons. Both com u re to d ate. 2,7-D K hio^dhxnzo-^-dioain was pounds gave the same infrared spectra which >btained from ^7-djamjuo-dibenio-ft-diqxm (X) would only be true if the second bromine atom ia a S andm eyer reaction.1 Later, TuKa and BaD- were in the 7-position. The ooeitioci occupied by arge1 p rep ared th e aarne compound by ring demur the bromine atoms in the tetrabromo-dibcnzo-fr- if Is 2,4-dicnlo o ttteri in rophenoL A Sandmeyer reactioa was th e preparation of 2-bromo-dibenzo-p- * cUonn must be non 01 a nurtu Z&7.S, tmce re oi z-prom hanative brom o-. ^./-<iibromo> inaand linrin from 2-amino-dibenxo*-dHmn. (XI).* The 2^ -d ih rom o-d ib en zn -0~ ftin Tin r a v e op h r o n e tM ra . le n tificatio n of th e tmaarigned dibrocno com lJll>lu6 derivativeea_s__sho^_w__n_i_n_Fig.27 o u n d 4 w as accompHsbed in the course of these A Handmeyer reaction carried out on 2-amino to d ie s . dibenzo - p - dioxin gave 2 - i o d o - d i b e n z o d i o x i n . D irect chlorination of dibenxo-p-dioxin in glacial Attempts to make the compound directly by a c e tic acid a t room temperature gave 2-chloro- method developed for the iodination of a closely re ibenzo-p-dioxin and a small amount of 2,7-di- lated compound in thl Laboratory failed.* hloro-dibenzo-p-diazm . A ttem pt! to increase the I t has been found th a t 2^-dibroniodibenzo-^- id d o f th e 2,7-compound fay use of ultraviolet dioxin can be made in 22% yield whereas 2,7- g h t an d elevated temperatures were only partially dibromo-<fibenxo-p-dioxin can be formed in only 7% uccessful. 2-Chloro-dibenro-p-dioxin was also yield using forced cooditiona. These results can Trmed when a Sandmeyer reactioa was run ou be explained satisfactorily fay consideration of Fig. -am ino-dibenzo-p-dioxin. 3. M etal& tioa of dibenzo-p-dioxin with pbenyl- th iu m followed by addition to a bromine-ether fix tu re produced a mooobrcmo compound difler- ig from 2-hcomo-dibenzo-p-diazxn and m ust there- >re be 1-bromo-dibenso-p-diozxn, the only other ossible isomer. W ith the constitution of 2-bromo-dibenzo-p- ioxin known, the structure proofs of the two diromo-dibenzo-p-diarin derivatives were tmder- iken. 2,8-Dibrocno-dibenzo^-diaxifi, being the u ie r to obtain, was converted to the di-Grignard, irbonated and finally treated with thiouyf cfaJode followed by absolute methyl alcohol to give le dimethyl ester of 2r8-dibenzo-p-dioxin-dicaroxylic acid (XII), a known compound.* The ther dibrorno-dibenzo-p-dioxm was thus considred to be 2,7-dibrOTDO-dibenxo-p-dioxiii on the (1) S. U*e, M . Ciam. Sac. 1. 177 (1M1). (3) M. Jail* Md i t . BaBWi . Bait. Mr. d im . France, MO (ISU). (1) r i w d i h t M t 7S0.CJ7 ( J m * 1*. IS M ), In Fig. 3(a), the oxonhtm ion form ed in the interipfriiatr stage received no assistance from the bro mine atom in the 2-poitioa. However, in Fig. 8(b), the oxotuum ion is para to the wwh`1 hfnm tnf atom and can therefore receive a certain am ount of reso nance stabihration. The evidence for a qtrinoidtype intermediate is enhanced fay ^ formatiou of 2,3,73 tetrabromo - d i b e n z o d i o x i n , where the third and fourth entering bromine atoms, despite steric hindrance, enter ortke to the bromine, al- tbcugh a completely unhindered position ortko to the oxygen is available. r o S-Um h i n t m . 7 7 Ja lj I I . I N I) . (V M 1. Biarm. Sac. Japan. M. 0 (IMfl). C6) R. GOm *. O. I r m , W. >r*tar Md W. J o v m a l , H , 2471 (1 U 4 ) M ar ch 20, 1957 H aIOGEM D eMYATTV* O r DtEKXO-f-DIOXIK 1441 Experim ectaT Dib>Hxo-^>-diori (I).--Udag the n e t bod developed b r Toemta* but n b * tita tin | i liWs igfirai J for a-brumophcacl. it to pousible to obtain field* r u d u from 10-90% win* th is inexpensive starting malarial. Under the oonditiaaa usd w ith th- equipment mad befew, h h u bees found that increasing tiic aixe o/ the preparation apparently decrease tbc yield. "Chloropfaenol (410 f .16 m ofe). 0 x. (1A note) of an h y d ro u s potassium carbonate end 34 f . of copper powder w ere heated for 6 h r. in an ofl-bath at 170-180*. The tarry m ixture was further with aqnsous potssshmi hy d roxide, allowed to cool and feaBy ertractsd with ether. W a ih in i th e ether layer with cenonrtrated potsfe nm hy droxide dispelled the dark color. The ether was evapo r a te d , th e reaidoe. rlhnnlvart In bnanene and chromatographed on alum ina. Beat re--He were d i n h s l by evaperatioo of th e effluent and leery st afflas tfan of the residue from hot e th an o l to white plates or mcedks, m.p. 190-193* (reported (Y).--Several 0.05- to 0.1- mok preparations were carried out using potassium bromide-- bruoate hi refltixbg acetic arid as the brocnlnating agent. The crude prodoct was purified by vacuum distillation and a feaJ rsaystiU bat too from ethanol-water, m.p. 93-94.5". Ykids of 40% were obtained consistently. Earlier workers* prepared this compound by direct brominatiou in carboo dhulflde reporting a melting point of 90-92* but making no mention ci o a t t s t m Yield. 1,7-Oftrrsn dOi msn f fitorlji (VI).--In 100 ml. of gla de! acetic add were dissolved 4.6 g. (0.025 mole) of dlbcnsos-dtoxto and 12A f . (0X8 mole) of broenbe and the result ing soiatiou atirrtd and refluxed for 6A hr. Dilution with aqueous andbin bisulfite and filtration gave 11 g. of crude material mehbtg over the range 110-1*. Five reaystalflaattoua of this material from glacial acetic odd yielded OX g. (7%) of white needles, m.p. 174-176*. Anal. Caicd. for CnH,OiBr,; Br. 46.76. Found: Br, 46.91. 46.73. m .p . 110*). lA -Pfeom c dft--ro ) dirrrin (VII).--T hb compound f-Chloco-dfti m in I iirrin (II).--Chlorine gas was slowly was prepared in 22% yidd using the theoretical amount of bubbled in to a stirred solution of 4A f . (0X26 mok) of dj- pnfisinm hromldt-h rcu nte hi refluxing acetic acid. The bcnxo-^-dlaxto in 126 ml. of gladal acetic add over a period crude material was purified by repeated m r ystallbattoc of 2 b r . a t room temperature. A t that time, a yellow color from ethanol to a constant mrittog point of 149A-151*. w as evident in the dear solution. Aqweous sodium I t bad bees prepared previously by direct brombutton of bisulfite was used to dilute the reaction n h t a i t and destroy rUVnsn / dioxin to nit robenroe at room temperature with th e excess chlorine. Filtration p n 6 g. of erode material ^reported netting range of 145-180* and to unspecified over th e range 66-86*. Vaemon f e S h d a n of this produced 2.4 g . of material, h p . 3-94* (025 ms>.). Five The dimethyl ester obtained via tbc Grignard reagent and rearyetaffim tioos Cram ethanol-water yielded 1 g. (18%) of subsequent carboastion and estcrificmtb n of th b dllrom o w h ite needles, m .p. 87-60*. A 0X6 mole preparation ran melted at 168-171*. A point of 167 a t 76* did not resalt in a higher yidd. reportetF earlier far the dimethyl ester of 2A~di- A n a l. Caicd. lor G uB iO id: CX 16A4. Found: a . nrnm i add. 16.81. 16X6. 2J7A-Tstitt r owm-mhw o p fibrin (VHI).--A aohittoo I / / P i. h h s s d ft-- / dtorrto (HI).--An identical pro cedure was employed lor th b reaction a s h tb t preceding experim ent except for irradiation of the l u i with ultra violet light for 4 A hr. giving a owdc yidd of 5A g., m ritiar over th e range 66-106*. Two nerystafliatiaws from methyl u i m l a s d n final rraystaStostton from petroleum ether (b .p . 00-70*) produced 0.9 g. (1% ) of white needles, m.p. 201-203* (reported*-1m .p. 907*. 1-902*). of 9A g. (0X6 mole) of dlbesm-F-dtoxm, 64 g. (0.4 mole) ofbrocnke and 900 oil. of gladal acetic add was stirred and refluxed far 6 far. Ditottoa with aqueous bisulfite foQowod flltratton produced 18-2 g. of crude material rnrhiny over the range 397-3*. Due to the fauohablUty of this material hi all common solvents, only a small porttoo was purified by three recrystaUarnttoas from hot pyridine to yidd a white, granular product, m.p. 334-336*. T h b --we reaction gave only a trace of product when nm Anal. Caicd. for CaHjOiBr: Br, 62X0. Found: Br, a t room ternpar store to the abarwee of ahraviolet light. A 63.49, 62A4. Pyrcx flask was ased ho all of the preparatkau. I n 11 11n dTissss > f e r i s (IV).--A OXfrvnok preparation of pben y llith iu a was added to a eolatinn of 0X6 mole of dibemxo-^-dioxm in anhydrooe cth o 'wader an atoxwpbere of d ry , oxygen-free nitrogen. Dne to the ease of di-metaJatiao, > r excess of m r t i h t h l f ea t wes avoided. EH-mefahflon did n o t occwr whew metkyfflthlnm was nacd, bat the yield of m ooo-m etsbted prodoct was sigoiflesntiy lower. A 0 .06-mole preparetioe of phcayffthhun was added to OX g. (0.06 mole) of dibenso^-dtozto b 60 ml. of ether refluxed with stirring for 6 far. The m olting mixture was added to a stored m ature of 10 g. (0X6 m okl of faromnw in 160 m l. of ether a t ice-bath tem poatore over a period of 18 m in. I t was allowed to warm to roam temperature, stirred for 3 h r. and then washed with aaneons sortiam bisulfite. T he ether layer, after drying over anhydrous aodiun sulfate, was evaporated and the residue vacnaa dbrftkd at 181- 7 I*4* ifkman / finris (IX).--Nhrosybulfaric ad d eras made by dbsolvtog 0A g. (0X15 mole) of sodfam nitrite to 8 ml. cf concentrated mtfnric add and then slowly warming it to 70*. TUs was cooled to 15* in an toe-bath and 2 g. (0X1 m ok) of wmbodfecnao-p-dtoxto to 26 ml. of gtoda! acetic add wss added slowly with rigorous storing* After addition, it was rtkred 16 mto. before being added rapidly to a cold solution of 2A g. (0X16 mole) of potassium iodide to dilute mlhtric add. The now brown m ature was heated to botttog to destroy the complex, diluted and filtered. Remndafiizatfau of the crude material from ethanol-water (Korn A) gave 1 g. of product, a .p . 92-94A*. Two more reeryitaltixattoas from ethanol-water (Narit A) resulted in 0.4 g. of fine, white needles, m.p. 95-97*. Anal. Cakd. far CuHiOil: 1,40.96. Found: 1,40.64, 40.40. 136* (0.1 mm.) to give 1A g. of crwde prodoct. Two n - Acknowledgment--Tbc authors ere indebted to crystallastioeu from methyl airohol m alted in I g. (8%) at R . McCord of the Institute of Atomic Research, white needles, m.p. 104-106*. Ames, lo s t, for infrared spectra. A nal. Caicd. far CuHfOiBr: Br, .4 0 . Found: Br, 2SA1. 29X2. A jc ks, I o w a CT) AH () M. T iw Ju. / . rtn-m . Aw. Jpf*m. St, (I ?). trow C. R. Seeaden, 'T W AroU n N Xrm eid *w l C o., t w i n s . IM S, p . z H lK lT G tU A K AND J OOMTS J . DlTUlCH Vol. 70 ,Br, X. X*. X* X* - H , - Cl; X*. X*. X* and X* - H *. X, - Cl; X*. X*. X, - H - Br; X* X* X* X* - H U - Br; Xu Xfc X* X. - H * X* - Br; X,. X* X. - K . Xk Xi. X X*. XB4.Xr :.X-i . Xi.X4Br: X* - H H X, - I; XuXfc X*.X, - H XjuX , -- NH; Xi. X i. Xi - H X, - NHi: X i . X t . X t . X i - K X b X t - GOOCH*; Xi, X*. X* --H ponaist of th e 2-chloto-dibrnro-^-d>cxm (II), lloro-dibenzo~-dioxzn (III), 1-bromo-dis-Hwrrm (TV), 2-beouio-dbenio--dkmn (V), rotno-dibenro-^-dioxin (VI), 2^-dibrotna-di' B i^ VBr. /Br VI BrN ,Br \ sBr, Br, VII id,Br >-dioxin (V II), 2,8,73`tetrabgocno^Kbenyo^r (V III) and th e a-o<k>-mbenro-p-<lKMnn jjg ty l^ ^ k A ik to -d ib r n to ^ S a x x a , 2-bct>- aizo -^ d io ziii to d u unasagncd dibtomoD-/>-dioxin have been reported in theK tera- B r/ VIII Fif. 2. 'B r basis of infrared spectra comparisons. Both com p Hat^. 2,7-Dkhloro-dibeuxo-^-dkxm w ti pounds gave the same infrared spectra which H ` from 7-diamiDCKiibenzo-^-diasin (X) would only be true if the second bromine atom undm eyer reactioa.1 Later, ToHa and Bail- were in the 7-position. The positions occupied by prepared th e Mine compound 07ring closure the bromine atoms in toe tetrabromo-chbenxo-^- dicnloropbenoL A Sandmeyer r a d ia n was dtonn must be ,5,7,8, since exhaustive bromina- ed in th e preparatioa of 2-hronuMBbenzo-^- tiaa ot a nurture of ^-promo-. ^.7-<^bromo- and < from 2-amiiK>-djbenxo-p-<lkcdn (XI).* The 2,8-dibrotDO-dibenxo-^-diorin gave only one tetj-a- ic atio a of th e mvassigpcd cHbrwno com- Ur>iu5 derivative as shown in Fig. 27 . * w as aooompHsbed in the course of these A Sandmeyer reaction carried out on 2-amino- i. dlbesuo -p - dkm n gave 2 -iodo-dibenzo-p-dioxin. x t chlorination of dibenzo-^-dioxin in gladal Attempts to make the compound directly by a a d d a t zoom temperature gave 2-chloro- method developed for the iodination of a closely re o-p-dicm n and a small amount of 2,7-di- lated compound in this Laboratory failed.* Khbenzo-p-dkmn. A ttem pts to inaease the I t has been found th a t 23"<iihromo*<iibenzo-p^ pf th e 2,7-cocnpound by use of ultraviolet dioxin can be made in 22% yield whereas 2,7- n d d e ra te d tem peratures were only partially dibromo-dibenzo-^-dioxin can be formed in only 7% sful. 2-ChIocr>-dibesixo--<haxin was also yield using forced conditions. These results can 1 when a Sandmeyer reaction was run ou be explained satisfactorily by consideration of Fig. lo-dibenzo-p-dkndn. 3. alatinn of dibenxo-/Hliaxin with pbenyl- n followed by addition to a bromine-ether Br re produced a mooobrcmo compound difTer- rm 2-bronx>-dibenzo-p-dkmn and must there- l-brocno-dibenzo-p-dioxin, the only other le isomer. h th e constitution of 2-bromo-dibenzo-p- known, th e structure proofs of the two di- >-dibeszo-p-dioxin derivatives were under- 2,8-IXbromo-dibeazo--dkmn, being the to obtain, was converted to the di-Grignard, lated and finally treated with thiocyl chJooOowed by absolute methyl alcohol to give im etbyl ester of 2,8-dibenzo-p-dioxin-dicar- c ad d (X II), a known compound.* The dibronw ^benzo-p-dkm n was thus consd- to be 2,7-dibrcmo--dibenro-p-dioxin on the Um , M . C tn . S*. S t, IT7 (1M 1). 'J ^ U w d M . B d D w n . Bmtl. m t. M m . F rtm a. *40 ( 1 U J ) . n d ) T+Umt jS 9 ,t 17 ( / I I , 1M6). mim r*!n< m .rr atr si. imbi. Toh. /. fM m . S t. M , 06 In Ftg. 3(a), the oxochzm ion forzncd in the inter mediate stage received no assistance from th e bro mine atom in the 2-position. However, in Fig. 3(b), the oxomum ion is para to the h n min* atom and can therefore receive a certain am ount of reso nance stabilization. The evidence for a qmnoid- type intermediate is enhanced by th e formation of 2,3,7,8- tetrabroroo - dibenzo - p - dioxin, where the third and fourth bromine atoms, despite stenc hindrance, enter ortho to the bromine, al though a completely unhindered position ortho to the oxygen is available. 4 W.(8 ) IT. C l l a , O. f c , a . W . I f * m JovftMAi., M , 24T3 ( l t M ) .