Homogeneous catalysis of the decomposition of dimethyl diazomalonate in alcohols

摘要

1976 2483Homogeneous Catalysis of the Decomposition of Dimethyl Diazomalonatein AlcoholsBy Roberto Pellicciari and Pietro Cogolli, lstituto di Chimica Farmaceutica e Tossicologica delt'Universit3,Decomposition of dimethyl diazomalonate in alcohols catalysed by trimethyl phosphite-copper(1) iodide leads todimethyl alkoxymalonates.Perugia, ItalyWE have previously1 reported the synthesis of diethylethoxymalonate by decomposition of diethyl diazo-malonate in the presence of the homogeneous trimethylphosphite-copper( I) iodide catalyst in ethanol. Sincediazomalonic esters are now readily accessible viathe diazo transfer reaction: this procedure could beusefully employed for the introduction of an etherfunction into malonic esters under mild, neutral con-ditions.Alkoxy-esters of the general structureRO*C(CO,R'), are otherwise not readily ac~essible.~We have carried out this reaction in a number ofrepresentative alcohols, following the procedure previ-ously described,l i.e. dropwise addition of dimethyldiazomalonate (1) to a stirred solution of the catalyst inthe alcohol. Once the evolution of nitrogen had ceased,the excess of alcohol was evaporated off and the oilyresidue analysed by g.1.c. The results are summarizedin Table 1.Only the decomposition of the diazo-ester (1) inmethanol gave the corresponding dimethyl alkoxy-malonate (2a) in high yield. With the other alcohols,the major products were those arising from either partialor complete ester interchange. We were thus unable toisolate the pure alkoxyrnalonates (2b-d) from therespective reaction mixtures. These products, how-ever, were obtained pure by a reverse transesterification,achieved by refluxing the crude product in an excess ofmethanol in the presence of a catalytic amount oftoluene-9-sulphonic acid.Analytical and n.m.r. dataR. Pellicciari and P. Cogolli, Synthesis, 1975, 269.31. Regitz, Angew. Chem. Intemzat. Edn., 1967, 6, 733.( a ) W. Wislicenus and 3'1. Munzesheimer, Chem. B e y . , 1898,31, 553; ( b ) J . Prideand 1C. T. Williams, J . Chew. Soc., 1933, 1627;(cj J. Vida, C. M. Samour, M. H. O'Dea, T. S. Wang, and J. F.Reinhard, J . Medicill. Chew., 1974, 17, 1 .for the dimethyl alkoxymalonates (2a-f) are given inTable 2.Dimethyl malonate (5) was another, unexpected by-product of the reaction of the diazo-ester (1) withTABLE 1C02MeR0c02Me + C02Me P(OMc13 c u l 4- ROHN2 =I= C0,Me(1 1 ( 2 )C02R 3- C02Me C0,Me C02 R4- RO( 3 ) (4 1 (5)ReactionYields (yo) time temp.- R (2)a ; Me SO (77)c ; Pm 11 (00)d; Pri 23 (45)ce ; But 30 (23)f ; PhCH, 43 (40)The figures referg.1.c. analysis of theb; Et - (65);(3) (4) (4 '(h) ("C) '15 5014 55 8 16 6020 34 13 42 10025 18 30 7010 8 24 7617 10 22 100to Droduct distribution determined byoilf residue from the reaction mixture.Obtained by fractional distillation at reduced pressure of theoily residue from the reaction mixture. C Obtained by frac-tional distillation a t reduced pressure of the oily residue from thetransesterification reaction.d Obtained by silica gel columnchromatography (eluant 90 : 10 hexane-diethyl ether) of theoily residue from the transesterification reaction.alcohols. Hydrogen abstraction from the solvent hasbeen observed in the benzophenone-sensitized photo-lysis * and in the diethyl peroxodicarbonate-promoted* (a) A. P. Padwa and R. Layton, ?'ptr.ahcd!on Letters, 1965,( b ) S. Julia, H, Ledon, and G. Linstrumentelle, Compt. 2167;rend., 1971, 272, 18982484TABLE 2Analytical and spectral data aJ.C.S. Perkin IB.p. ("C)76 [1.5]78 [0.7]80 [0.2]52 [0.06]90 [1.0]112 [0.08]Compd. [mmHg] WC14)( 2 4(2b)(2c)(2d)(2e)(2f)3.41 (3 H, s), 3.74 (6 H, s), 4.31 (1 H, s)1.25 (3 H, s), 3.50 (2 H, q), 3.67 (6 H, s), 4.30 (1 H, S)0.90 (3 H, t), 1.57 (2 H, m), 3.43 (2 H, t), 3.67 (6 H, s),1.17 (6 H, d), 3.70 (6 H, s), 3.80 (1 H, m), 4.33 ( 1 H, s)1.22 (9 H, s), 3.45 (3 H, s), 3.75 (3 H, s), 4.50 ( 1 H, s)3.67 (6 H, s), 4.22 (1 H, s), 4.40 (2 H, s ) , 7.23 (5 H, s)4.30 (1 H, s)decomposition of diazocarbonyl compounds, but this isthe first example of this process in a catalysed decom-position reaction. Wolff rearrangement products, oft enformed by photolysis of diazocarbonyl compounds,6were not observed in the present case.EXPERIMENTALG.1.c. analyses were carried out with a Fractovap G 1(Carlo Erba) chromatograph (6 f t column packed withCarbowax 20 M).Yields determined by g.1.c. were notcorrected for thermal conductivities. N.m.r.spectra wererecorded with a JEOL INM-C-60 HL spectrometer forsolutions in carbon tetrachloride (internal tetramethyl-silane as standard).Dimethyl diazomalonate was prepared by treatment ofa solution of dimethyl malonate and tosyl azide withtriethylamine.2 The trimethyl phosphite-copper (I) iodidecomplex was prepared as described.' Reagent gradealcohols were employed. Column chromatography wasperformed with Merck silica gel (0.063-0.200 mm).L. Horner and H. Schwarz, Annulen, 1971, 747, 1.W. Kirmse, ' Carbene Chemistry,' 2nd edn., AcademicPress, New York, 1971, pp. 475 et seq.Found (:6)r----7C H44.2 6.147.55 6.6550.4 7.150.2 7.3652.85 7.9660.2 5.76Required (%)t--7Formula C HC6H1,05 44.45 6.2C,Hl,O, 47.7 6.85C8H1405 50.5 7.4C8H,,05 50.5 7.4C,H160, 52.95 7.9C,,H,,O, 60.5 5.9Reactions of Divnetltyl Diazomalonate with Alcohols.-To asolution of trimethyl phosphite-copper(1) iodide catalyst(0.6 mmol) in a large excess of the alcohol, a solution ofdimethyl diazomalonate in the same alcohol was addedfrom a dropping funnel at 5 drops per min, with stirring, atthe temperature indicated in Table 1.The mixture wasthen maintained at constant temperature until evolution ofnitrogen ceased, and filtered. The excess of alcohol wasremoved by use of a water aspirator and the oily residuewas further purified (see Table 1).Transesteri~cation.-In a typical procedure, the oilyresidue (1.8 g) obtained by removal of the excess of alcoholfrom the product of the reaction of diethyl diazomalonate(1) with ethyl alcohol was refluxed a t 65 "C for 6 h inmethyl alcohol (50 ml) in the presence of toluene-p-sulphonicacid (0.1 g), The excess of methyl alcohol was thenevaporated off (water pump) and the oily residue furtherpurified by distillation at reduced pressure. Furtherexperimental details are given in Tables 1 and 2.[6/790 Received, 2 3 ~ d Afi~il, 197617 B. W. Peace, F. Carman, and D. S. Wulfman, Synthesis,1973, 658