Transhalogenation of mucohalic acids by grignard reagents

摘要

2470 J.C.S. Perkin ITranshalogenation of Mucohalic Acids by Grignard ReagentsBy Emanuel BeSka and Pave1 RapoS,' Research Institute of Agrochemical Technology, 81 0 04 Bratislava,CzechoslovakiaThe reaction of alkylmagnesium halides with mucohalic acids (2.3-dihalogenomalealdehydic acids) in aproticsolvents results in an exchange between the 2-halogen of the mucohalic acid and the halogen of the Grignardreagent. The mechanism is discussed.THE reaction of alkylmagnesium halides with mucohalicacids is reported 1$ to lead to 5-alkyl-3,4-dihalogeno-furan-Z(5H)-ones. We now describe another mode ofreaction of mucohalic acids with Grignard reagents,involving exchange between the a-halogen atom of theformer and the halogen of the latter; this takes placeprovided that the Grignard reagent is added to themucohalic acid (i.e.inverse addition), and the halogenof the Grignard reagent is a stronger nucleophile thanthat attached to the a-position of the mucohalic acidused.Transhalogenations of various compounds by Grignardreagents are Nevertheless, the present re-action is not a direct halogen-halogen exchange. TheH. Sirnoilis, E. Marben, and E. Merrnod, Ber., 1905, 38, 3983.E. J, Vinogradova and M. M. Shemyakin, Zhuv. obshcheiKhim., 1946, 16, 709.first step is a reaction with active hydrogen, i.e. neutraliz-ation of the mucohalic acid with the Grignard reagent,leading to the halogenomagnesium salt. The nextstage is the nucleophilic substitution of the a-halogenof the mucohalic acid by the halogen of the halogeno-magnesium salt according to the Scheme.This mechan-ism was confirmed by studying the rate of reaction ofthe acid (1) with methylmagnesium iodide to give theacid (4).In the present reaction only the a-halogen of themucohalic acids is substituted. This was confirmed bythe reactions of the acids (2) and (3) with methyl-magnesium iodide : both gave the same compound ( 5 ) .The i.r. and n.m.r. spectra of the acids (4) and (5)J. Thessing, S. Klussendorf, P. Ballach, and H. Mayer,N. S. Popov, Zhur. obshchei Khim., 1940, 10, 1141.Ckem. Bey., 1955, 88, 12951976 2472confirm their lactol structure, as known for the otheririucohalic acids (1)-(3) .5-7E SPE RIME NTAL1.r. spectra wcre determined with a double beam UR-10Zeiss spectrophotometcr, u .v.spectra with a UnicamSI' 8000 instrument, and 1i.m.r. spectra with a TeslaBS 487 spectrometer (80 MHz) with tetraniethylsilane asinternal standard. M.p.s were determined with a Reichertmicroscope.5-ChEovo-Z-iodoinaTeal~~eJ~ydic Acid (4) .-A 500,; solutionof methylmagnesiuni iodide (42.0 g) in ether was addeddropwisc to a stirred solution of the acid (1) (42.0 g) insodium-dried ether (150 1x1) under reflux during 2 11.After it further 3 h heating the mixture was set aside for3 clays, and thoroughly decomposed with dilute sulphuricacid. The organic phase w-as separated, washed withaqueous sodium hydrogen sulphite and with water, dried,and evaporated. The residue was crystallized frombenzene to yield the acid (4) (28.0 g, 43.0%), m.p.156-157 "C (Found: C, 18.5; H, 0.8; C1, 13.7; I, 48.5.C,H,ClIO, requires C, 18.45; H, 0.8; C1, 13.6; I, 48.77;);vIIIRX. (CHCI,) 1 615 (C=C), 1 578 and 1 798 (GO), and3 100--3 400 cm-l (OH); (MeOH) 205 and 248 nni( E 5 130 and 6 400); 6 [(CD,),SO] 8.37 (1 H, s, OH) andli.13 (1 H, s, CH). From the benzene mother liquor 3,4-dichloro-5-methylfurnn-2( 5 H ) - 0 n e , ~ b.y. 93 "C and 10 minHg(16.2 g), N~~~ 1.503 0, was obtained.:3-Uro,no-2-iodozri~lZeaZdehydic Acid (5) .-(i) X lo? solu-tion o i niethylniagnesiuni iodide (16.6 g) in ether wasadded dropwise during 1.5 h to the acid (2) (24.5 g) in drycther (150 ml). The temperature was maintained a t 30 "C._After 2 days, isolation as described for the acid (4) gave theE. Kuh and R. L. Sheparcl, ,I. -4nzo. CJieiii. Soc., 1953, 75,1397.acid (5) (8.1 g, 26.6%), m.p. 143-144 "C (from benzene)(Found: C, 15.9; H, 0.65; Br, 26.65; I, 42.3. C,lH2BrI0,requires C, 15.7; H, 0.7; Br, 26.2; I, 41.6%); vnlau. (CHCI,)1604 (CZC), 1770, 1790 (C=O), and 3 050-3 450 6m-lI1x ' YO=CH C02MgX201 21 2( 1 ) X=X=CL, Y = I ( L )( 2 ) X=X=Br, Y = I ( 5 1( 3 1 X1=Br, X = C \ , 2 Y = I 1 5 )R = a l k y lSCHEME(OH); A,,, (MeOH) 206 and 252 nm (E 4 400 and 4 200);6 [(CD,),SO] 8.37 (1 H, s, OH) and 6.08 (1 I-I, s, CH).(ii) The acid (5) was similarly obtained (31.3%) from theacid (3) (21.3 g) with ethylniagnesium iodide (18.0 g);n1.p. 143-144 "C (from benzene) (Found: C, 15.5; H, 0.6;Br, 26.6; I, 41.4%).[6/502 Received, 15th Mavch, 19761Y . Hachihama, T. Shono, and S. Ikeda, J . 0 1 g . Chrm., 1964,Dong Han Kim and D. N. Harpp, CJic~z. I d . , 1966, 153.I), 1371