Vol. 75
E. EARLROYALS AND KENTC. RRANNOCK
2050
[CONTRIBUTION FROM THE DEPARTMENT O F CHEMISTRY O F EMORY UNIVERSITY]
Hydroxymethylene Ketones. I. The Preparation of P-Ketodimethylacetals and Methoxymethylene Ketones BY E. EARLROYALS AND KENTC. BRANNOCK RECEIVED OCTOBER 29, 1952 Sodium hydroxymethylene ketones of the type, R-CO-CH=CHONa, give good yields of ,+ketodimethylacetals on treatment with methanolic hydrogen chloride. The sodium salts of hydroxymethyleneacetophenone and hydroxymethylenecyclohexanone give methoxymethylene ketones on similar treatment. Sodium salts of the type R-CO-CR’=CHONa give mixtures of B-ketodimethylacetals and methoxymethylene ketones. Evidence is presented that the Claisen condensation of methyl formate with methyl ethyl ketone and methyl n-?ropyl ketone occurs a t both the methyl and methylene units of the ketones. &Ketodimethylacetals and methoxymethylene ketones are readily cleaved by aqueous alkali.
&Ketoacetals constitute a class of compounds which should be valuable as intermediates in organic synthesis. The most frequently applied method for preparing @-ketoacetalsis that of Nellesl according to which a chlorovinyl ketone is treated with an alcohol and the stoichiometric amount of alkali 0
/I
RC-CH=CHCI
+ 2 R’OH + Ka0H --+
have prepared the dimethylacetal of hydroxymethyleneacetone in 4570 yield by the addition of sodium hydroxymethyleneacetone to a mixture of methanol and concentrated sulfuric acid. More recently, RichmondLohas described the preparation of hydroxymethyleneacetone diethylacetal in 47.5% yield by a method analogous to that of Sugasawa. We have prepared 0-ketodimethylacetals from Letones in good yields by the sequence of reactions
0
II H RC-CHQC(OR’)~
+ XaCl + H i 0
Price and Pappalardo2 and Nesmeyanov3 have prepared a number of 0-ketoacetals by the Nelles procedure. Ruzicka and his co-workers4 reported the preparation of three 0-ketoacetals in the alicyclic series by treatment of the appropriate hydroxymethylene ketone with ethyl orthoformate. Shantz5 has reported the preparation of the acetal of hydroxymethylene-p-ionone by treatment of the hydroxymethylene ketone with ethanol and calcium chloride. Theimer and Rittera prepared the cyclic 2-methyl-2,4-pentanediol acetal of acetoacetaldehyde (or hydroxymethyleneacetone) by the Oppenauer oxidation of the corresponding acetal of acetaldol. After developing the method of preparation of @-keto acetals described below, it came to OUT attention that Sugasawa’ had prepared the diethylacetal derived from hydroxymethyleneacetone in 35% yield by the treatment of the sodium salt of hydroxymethyleneacetone with ethanolic hydrogen chloride, a method essentially the same as ours. In fact, Sugasawa* had much earlier reported the preparation of ethyl P,@-diethoxypropionate in 60y0 yield by an analogous procedure, i.e., by treatment of the sodium salt of ethyl hydroxymethyleneacetate with ethanolic hydrogen chloride. Hata and co-workersg (1) Johannes Nelles, U. S. Patent 2,091,373 (1937). (2) Charles C. Price and Joseph A. Pappalardo. THISJOURNAL, 72, 2613 (1950). (3) A. N. Nesmeyanov, N. K. Kochetkov and M. I. Rybinskaya, Izvesl. Nauk. Akad. S.S.S.R., O f d e l . Khim. N a u k , 395 (1951) [C.A , , 46, 3007 (1952)). (4) L. Ruzicka, C. F. Seidel, H. Schinz and M. Pfeiffer, Helu. Chim. Acta, 31, 422 (1948). (6) Edgar M. Shantz. THIS JOURNAL, 68, 2553 (1946). (6) Ernst Theodore Theimer and John J. Ritter, Abstracts, Organic Division, 110th Meeting. American Chemical Society, Chicago, I11 , Sept.. 1946. (7) S. Sugasawa, Yoshio Ban and R . Mochizuki, J . Pharm. SOC. Japan, 69, 82 (1949); 6.Sugasawa. Japanese Patent 177,821 (1949). ( 8 ) S . Sugasawa, J. Pharm. SOC. Japan, No. 545, 551 (1927) [C. A , , 21, 3601 (1927)l. (9) Junji Hata, Shun-ichi Yamada, Jun-ichi Iwao, Nobuyuki Kato. Norio Sugimoto and Rynji Inoge, ibid., 69, 477 (1949).
0
/I
R-C-CHI
0
I1 + H-C-OCHa
+ NaOCH3 +
0
!I
R-C-CH=CH-ONa
+ 2CH30H
(1)
0
I/
RC-CH=CH-OSa 0
/I
+ ZCHJOH + HC1+
R-C-CH2-CH(OCHa)2
+ NaCl + H20
(2)
The experimental procedure is convenient in that isolation of the intermediate sodium salt is not necessary, and the sequence of reactions may be run in a single reaction vessel. The products obtained are shown in Table I. Hydroxymethylene ketones of the type R-COCH=CHOH, ;.e., those which arose from the condensation of a methyl ketone with methyl formate a t the methyl group of the ketone, gave good yields of P-ketodimethylacetals on treatment with methanolic hydrogen chloride. Hydroxymethyleneacetophenone and hydroxymethylenecyclohexanone gave methoxymethylene ketones rather than @-ketoacetals. Hydroxymethylenediethyl ketone, which is derived from a symmetrical ketone through condensation a t a methylene group, gave a sharply boiling fraction of the &ketoacetal, while the methoxymethylene ketone was obtained by rapid distillation of the still residue after the P-ketoacetal had been removed. Our results indicate that the unsymmetrical methyl ethyl and methyl n-propyl ketones give products arising from condensation with methyl formate a t both methyl and methylene groups under our experimental conditions. l1 Frac(10) Henry J. Richmond, U. S. Patent 2,570,713 (1951). (11) Erich Benary, Ber., 59, 2198 (1926), presented evidence that the condensation of methyl ethyl ketone with ethyl formate occurs a t both the methyl and methylene positions. At the same time Benary could detect only one isomer from the condensation of methyl n-propyl ketone with ethyl formate,
