Imanishi, Tamotsu

Iwata, Shingo

Okano, Masaya

Sugimoto, Toyonari

Tanimoto, Shigeo

Kyoto University Research Information Repository

Title Interchange Reactions of Diphenyl Acetals and AlkylDialkylaminomethyl Ethers with ThiolsAuthor(s)Tanimoto, Shigeo; Iwata, Shingo; Imanishi, Tamotsu;Sugimoto, Toyonari; Okano, MasayaCitationBulletin of the Institute for Chemical Research, KyotoUniversity (1979), 57(3): 235-239Issue Date1979-08-31URL http://hdl.handle.net/2433/76836RightType Departmental Bulletin PaperTextversionpublisherKyoto UniversityBull. Inst. Chem.  Res.; Kyoto Univ., Vol. 57, No. 3, 1979      Interchange Reactions of Diphenyl Acetals and      Alkyl Dialkylaminomethyl Ethers with Thiols     Shigeo TANIMOTO,* Shingo IWATA, Tamotsu IMANISHI,Toyonari SUGIMOTO,                           and Masaya OKANO                              Received October 26, 1978     Sulfur-for-oxygen i terchange in diphenyl acetals, which may be generally applicable to the  preparation of mercaptals of aldehydes other than formaldehyde, has been studied. The related  interchange in the case of alkyl dialkylaminomethyl ethers has also been demonstrated. A possible  explanation for the reaction of diphenyl acetals has been given.    KEY WORDS : Sulfur-for-oxygen interchange / Mercaptals / Aryl dialkyl-   aminomethyl sulfides /    Some interchange reactions of carboxylic esters') with alcohols and of thiol esters2) with alcohols were demonstrated long ago. The related interchanges in the cases of orthoesters3) and acetals4) have also been known for a long time. Moreover, it has been shown that oxygen-for-sulfur interchanges in orthothioformates2,5) and mer-captoles2,6) can be readily carried out in the presence of a catalyst such as ZnC12, furnishing an alternative means of preparation of orthoformates and acetals. The reported preparation of 2-ethoxy-1,3-dithiolane from ethyl orthoformate and 1,2-ethanedithiol with the liberation of ethyl alcohol is a kind of sulfur-for-oxygen inter-change.7) Shostakovskii and co-workers have reported the formation of acetaldehyde mercaptals in the interchange reaction of 2-methyl-1,3-dioxolane with thiophenol or aliphatic thiols.8,9) Recently, in the presence ofp-toluenesulfonic acid the interchange reaction indicated below was achieved using dichloromethane as solvent with which methyl alcohol forms an azeotropic mixture.10) R p-CH3C6H4SO3H/CH2Cl2 <Q>--OH+CH2(OCH3)2---------------- R 0 OCH2OCH3+CH3OH R=H, m-CHO, p-CHO    We now report sulfur-for-oxygen interchanges in diphenyl acetals of acetaldehyde and of benzaldehyde under mild conditions, which may be generally applicable to the preparation of mercaptals of aldehydes other than formaldehyde. Thus, in the * gA , 4- , * a )Z, RITE '.a : Laboratory of Petroleum Chemistry, Institute   for Chemical Research, Kyoto University, Uji, Kyoto. ( 235 )                S. TANIMOTO, S.  IWATA, T. IMANISHI, T. SUGIMOTO, and M. OKANO presence of a catalytic amount of p-toluenesulfonic acid the following reactions take place. p-CH3C6H4SO3H/ether CH3CH(0C6H5)2+RSH -----------------------> CH3CH(SR)2 R=n-C4H9, C6H5 p-CH3C6H4SO3H/ether C6H5CH(OC6H5)2+RSH-----------------—> C6H5CH(SR)2 R=n-C4H9, C6H5, p—CIC6H4    Though more evidence has to be collected to clarify the detailed scheme of the reactions, from the type of catalyst employed it seems reasonable to propose a stepwise substitution mechanism in analogy with that postulated for the acid-catalyzed inter-change reaction of ethyl orthothioformate with an alcohol.2) H+ + C6H5OCH(R)0C6H5 C6H5O(H)CH(R)OC6H5                                              R'SH —> C6H5OH C+H(R)0C6H5 ------> R'S CH(R)OC6H5 H+    slowfast H+, R'SH RS'CH(R)0C6H5 ---------— R'SCH(R)SR'                                    R=CH3, C6H5; R'=n—C4H9, C6H5    When diphenoxymethane was allowed to react with either thiophenol or p-chloro-thiophenol under the same conditions, it was recovered in high yield and no formal-dehyde mercaptal could be isolated from the reaction mixture. The same was true for the reaction of bis(p-chlorophenoxy)methane with thiophenol orp-chlorothiophenol.    In these formaldehyde acetals, 2p-2p u-bond resonance between the phenyl group and the oxygen would operate against the formation of the protonated intermediate. While, such resonance in acetaldehyde diphenyl acetal or benzaldehyde diphenyl acetal, because of a greater twist of the phenyl groups, would be hindered and would thus permit the easy formation of protonated intermediate in assisting in the rate—               Table I. Interchange Reaction of Diphenyl Acetals with ThiolsRuna) Diphenylacetal ThiolReactionProduct")Yield")                time (hr)(%)   1CH3CH(OC6H5)2 n-C4H9SH 4 CH3CH(S-n-C4H9)2d)89   2CH3C1-1(0C6H5)2C6H5SH 8 CH3CH(SC6H5)2e)95   3C6H5CH(OC6H5)2 n-C4H9SH 2 C6H5CH(S-n-C4H9)2I) 97  4C6H5CH(OC6H5)2 C6H5SH 2 C6H5CH(SC6H5)2g)96   5C6H5CH(OC6H5)2 p-C1C6H4SH 2 C6HsCH(S-<O j-C1)2h) 65   a) All runs were conducted in boiling ether. b) All spectral data (NMR and IR) of the isolated products were consistent with the assigned structures. c) Yield of isolated, pure product. d) Bp 82-84°C/1 mmHg (lit,") 92°C/2 mmHg). e) Bp 159-163°C/1 mmHg (lit,12) 166-171°C/1.2 mmHg). f) Bp 147-151°C/1 mmHg (lit,13) 133-135°C/0.3 mmHg). g) Mp 51-52°C (from ethyl alcohol) (lit,u) 49.5-51°C). h) Mp 59-61°C (from ethyl alcohol) (lit,14) 60-61°C). (236)                              Some Interchange Reactions    Table II. Interchange Reaction of Diethylaminomethyl Methyl Ether with Aromatic Thiols   Runa) Aromatic thiolReaction Productb)Yieldc) (%)        time (hr)°   1C6H5SH5C6H5SCH2N(C2H5)281    2 p-CH3C6H4SH8p-CH3C6H4SCH2N(C2H5)280     3 nz-CH3C6H4SH8nz-CH3C6H4SCH2N(C2H5)2 67    4 o-CH3C6H4SH9o-CH3C6H4SCH2N(C2H5)284    5 p-C1C6H4SH8p-C1C6H4SCH2N(C2H5)258    6C6H5CH2SH8C6H5CH2SCH2N(C2H5)20 67    a) All runs were conducted in boiling dichloromethane. b) The first five products were identified by direct comparison with samples synthesized according to ref. 16; the remainder is a new compound. c) Yield of isolated, pure product. d) Bp 149-151°C/17 mmHg. Found: C, 68.58; H, 9.42%. Calcd for C12H19NS: C, 68.84; H, 9.15%. NMR(CC14) S 0.97 (t, 6H), 2.55 (q, 4H), 3.68 (s, 2H), 3.95 (s, 2H), 7.03-7.38 (m, aromatic 5H). determing unimolecular decomposition to phenol and a resonance-stabilized carbonium ion.    The attempted interchange reactions of several diaryl mercaptals such as formal-dehyde diaryl mercaptals, acetaldehyde diaryl mercaptals or benzaldehyde diaryl mercaptals with phenols were futile under the same conditions, supporting the concept that sulfur is considerably less basic than oxygen. It may be said that the cleavage of the carbon-sulfur bond in diaryl mercaptals would generally be more difficult than that of the carbon-oxygen bond in diaryl acetals. However, there is an example in-volving such a carbon-sulfur bond cleavage, i.e., in the presence of HC1 benzaldehyde diphenyl mercaptal interchanged with a large excess of ethanethiol in poor yield.11) On the other hand, it has been shown that the Lewis acid-catalyzed oxygen-for-sulfur interchange in aliphatic mercaptoles proceeds smoothly, and that it is an equilibrium reaction and can be shifted to give the desired acetals by removal of the produced low— boiling aliphatic thiols.2)    The results of sulfur-for-oxygen interchange in diphenyl acetals of acetaldehyde and of benzaldehyde are given in Table I.    Sulfur-for-oxygen interchange reaction of several alkyl dialkylaminomethyl ethers with higher aliphatic thiols such as 1-octanethiol or 1-decanethiols has previously been observed,15) where the reaction was carried out in absence of any catalyst. We have      Table III. Reaction of Dimethyl(methylene)ammonium Chloride with Aromatic Thiols Runa) Aromatic thiolReactionProductYieldb)(%)        time (hr)°   1C6H5SH20C6H5SCH2N(CH3)2664    2 p-CH3C6H4SH 24 p-CH3C6H4SCH2N(CH3)2d)70    a) Both runs were conducted in dimethylformamide at room temperature. b) Yield of isolated, pure product. c) Bp 118-120°C/16 mmHg. Found: C, 64.30; H, 7.64%. Calcd for C9H13NS: C, 64.62; H, 7.83%. NMR (CC14) S 2.27 (s, 6H), 4.35 (s, 2H), 7.00-7.53 (in, aromatic 5H). d) Bp 79--81°C/1 mmHg. Found: C, 66.27; H, 8.05 °o. Calcd for C10H15NS: C, 66.25; H, 8.34%. NMR (CC14) S 2.21 (s, 6H), 2.27 (s, 3H), 4.31 (s, 2H), 6.84-7.42 (m, aromatic 4H). ( 237 )                S. TANIMOTO, S. IWATA, T.  IMANISHI, T. SUGIMOTO, and M. OKANO now found that in the presence ofp-toluenesulfonic acid several aromatic thiols behave like the higher aliphatic thiols, furnishing an alternative means of preparation of aryl dialkylaminomethyl sulfides.16) For instance, the results in the case of diethylamino-methyl methyl ether are gathered in Table II. p-CH3C6H4SO3H/ CH2C12 CH30 CH2N (C2H5) 2 +RSH-------------------> RSCH2N(C2H5)2 R=CsH5, p-CH3C6H4, m-CH3C6H4,                                      o-CH3C6H4, p-C1C6H4, C6H5CH2   This kind of compounds are also derived from dialkyl(methylene) ammonium chlorides.17) Two examples from dimethyl(methylene)ammonium chloride are given in Table III.                            EXPERIMENTAL    Illustrative examples of the reactions will be given below.    Reaction of Benzaldehyde Diphenyl Acetal with Thiophenol. To a solution containing 2.76 g (10 mmol) of benzaldehyde diphenyl acetal and 2.2 g (20 mmol) of thiophenol in 40 ml of ether is added 0.17 g (1 mmol) of p-toluenesulfonic acid and the resulting mixture is refluxed for 2 hr. The mixture is cooled, washed repeatedly with dilute aqueous NaOH, then with water, dried (MgSO4) and the solvent is removed to afford a crystalline solid. The crude product is recrystallized from ethyl alcohol.    Reaction of Diethylaminomethyl Methyl Ether with Thiophenol. To a solution containing 23.4 g (0.2 mol) of diethylaminomethyl methyl ether and 11.0 g (0.1 mol) of thiophenol in 120 ml of dichloromethane is added 0.26 g (1.5 mmol) of p-toluenesulfonic acid and the resulting mixture is refluxed for 5 hr. The mixture is poured into twice its volume of ether, and the ether solution is washed repeatedly with dilute aqueous NaOH, then with water, dried (MgSO4) and evaporating the solvents gives a light yellow oil which is distilled.    Reaction of Dimethyl(methylene)ammonium Chloride with Thiophenol. A solution containing 6.0 g (64 mmol) of dimethyl(methylene)ammonium chloride and 7.0 g (64 mmol) of thiophenol in 100 ml of dimethylformamide is allowed to stir for 20 hr at room temperature. The mixture is poured into a large quantity of cold brine, made basic with K2CO3, and then extracted with several portions of ether. The ether solution is washed with water, dried (Na2SO4) and evaporating the solvent gives a light yellow oil which is distilled.                            REFERENCES (1) P. R. Fehlandt and H. Adkins, J. Am. Chem. Soc., 57, 193 (1935); G. B. Hatch and H. Adkins,       ibid., 59, 1694 (1937). (2) W. E. Mochel, C. L. Agre, and W. E. Hanford, ibid., 70, 2268 (1948). (3) H. Hunter, J. Chem. Soc., 1389 (1924); H. W. Post and E. R. Erickson, J. Am. Chem. Soc., 55,      3851 (1933); B. Helferich and W. Reimann, Ber., 80, 163 (1947). (4) H. W. Post, J. Am. Chem. Soc., 55, 4176 (1933). ( 238 )                            Some Interchange Reactions  (5) W. E. Hanford and W. E. Mochel, U. S. 2,229,651 [Chem. Abstr., 35, 2904 (1941) I. ( 6) W. E. Mochel, U. S. 2,229,665[ibid., 35, 2905 (1941) ]. (7) S. Tanimoto, T. Miyake, and M. Okano, Bull. Inst. Chem. Res., Kyoto Univ., 55, 276 (1977). (8) M. F. Shostakovskii, V. M. Vlasov, and A. A. Nikiforov, Chem. Abstr., 61, 5550 (1964). (9) M. F. Shostakovskii, A. S. Atavin, B. A. Trofimov, A. V. Gusarov, and G. A. Gladkova, ibid.,    61, 15969 (1964). (10) J. P. Yardley and H. Fletcher, III, Synthesis, 244 (1976). (11) M. M. Campos and H. Hauptmann, J. Am. Chem. Soc., 74, 2962 (1952). (12) A. Froling and J. F. Arens, Rec. Tray. Chim., 81, 1009 (1962). (13) F. Bessette, J. Brault, and J. M. Lalancette, Can. J. Chem., 43, 307 (1965). (14) J. Degani, M. Tiecco, and A. Tundo, Chem. Abstr., 58, 13830 (1963). (15) R. A. Lapina and K. G. Mizuch, ibid., 49, 13241 (1955). (16) The syntheses of a series of aryl dialkylaminomethyl sulfides by the condensation of formaldehyde     and secondary amines with aromatic thiols have first been studied by Grillot and co-workers:     G. F. Grillot, H. R. Felton, B. R. Garrett, H. Greenberg, R. Green, R. Clementi, and M.     Moskowitz, J. Am. Chem. Soc., 76, 3969 (1954). (17) H. Boehme and K. Hartke, Ber., 96, 604 (1963). • (239)

Interchange Reactions of Diphenyl Acetals and Alkyl Dialkylaminomethyl Ethers with Thiols

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Interchange Reactions of Diphenyl Acetals and Alkyl Dialkylaminomethyl Ethers with Thiols

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