Patented Mar. 5, 1946 2,395,800 UNITED STATES PATENT OFFICE METHOD FOR THE PREPARATION OF 1,3-DIKETONES Albert B. Boese, Jr., Pittsburgh, Pa., and Frank G. Young, Jr., Charleston, W. Va., assignors to Carbide and Carbon Chemicals Corporation, a corporation of New York No Drawing. Application May 26, 1944, Serial No. 537,532 7 Claims. (C. 260-586) This invention relates to the synthesis of beta acetophenone, C6HsCOCH3; tolyl methyl ketones, diketones by the rearrangement of enol-esters CH3C5H4COCH3; benzyl methyl ketone, isomeric therewith, as in the conversion of iso propenyl acetate, CH3COOC(CH3):CH2, to ace In addition to the acetic acid ester of the enol tyl acetone, CH3COCH2COCH3. The invention is based on my 'discovery that form of the ketones there may be used the enol an acyl ester of the enolic form of a ketone may esters of such acids as: propionic acid, be caused to undergo rearrangement by heating C2HsCOOH - it to an elevated temperature. Such enol-esters butyric acids, C3H7COOH, pentanoic acids, are characterized by the presence therein of the () group-RCO. O'C:C= and in the resulting iso meric change the acyl group, RCO-, migrates hexanoic acids, CsPI11COOH, heptanoic acids, from the enolic oxygen atom to the second ethyl C6H3COOH, octanoic acids, CH15COOH, non enic carbon atom to form a diketone in which anoic acids, C8H17COOH, decanoic acids, two carbonyl groups are attached to the same C9H19COOH carbon atom. Diketones of the type having car bonyl groups attached to the same carbon atom benzoic acid, C6HsCOOH, toluic acids, are commonly referred to as 1,3-diketones or CH3C6H4COOH ... beta-diketones. phenyl acetic acid, C6H5CH2COOH, phenyl propi My discovery seems to be of general applica 20 onic acids, C6H5C2H4COOH, phenylbutyric acids, bility to the acyl enol-esters of ketones. Enol C6H5C3H8COOH, dimethyl benzoic acids, esters which may be isomerized to the corre sponding 1,3-diketone include the acetic acid esters of the enol form of such ketones as: ace hexahydrobenzoic acid, C6H11COOH, hexahydro 25 toluic acids, CH3CshioCOOH. tone, CH3COCH3; methyl ethyl ketone, The reaction which takes place may be illus trated by the following general equation: methyl propyl ketones, CH3COC3H7; methylbutyl R2 ketones, CH3COC4H9; methyl pentyl ketones, R1CR o CH3COC5H11; methylhexyl ketones, CH3COCs-13; 30 methylheptyl ketones, CH3COC7H15; methyl octyl loco R- R&R! ketones, CH3COCs17; methyl nonyl ketones, k bo CH3COCoH19; methyl decyl ketones, k CH3COC10H1 in which R1 and R4 may be hydrogen, aliphatic 35 or aromatic; R2 and R3 may be aliphatic or aro diethyl ketone, CahsCOC2H5; ethylpropyl ketones, matic or R1 and R taken together may be part of CahsCOC3H7; ethyl butyl ketones, CahsCOC4H9; a cycloaliphatic ring. By the term aliphatic it ethyl pentyl ketones, C2H5COC5H11; ethyl hexyl is meant to include cycloaliphatic. ketones, CaHsCOCshi3; ethyl heptyl ketones, The conversion of an enol-ester to the isomeric CHsCOC7H15; dipropyl ketones, C3H7COC3H7; 40 beta-diketone may be carried out by heating the propyl butyl ketones, C3H7COC4H9; propyl pentyl starting material to an elevated temperature in ketones, C3H7COC5H11; propyl hexyl ketones, a suitable reactor. If desired, the enol-ester may C3H7COCsI13; dibutyl ketones, C4H9COC4H9; bu be refluxed in a ketene lamp over a heated metal tyl pentyl ketones, C4H9COC5H11; dipentyl ke filament. For commercial production of the tones, CsI11COCs11; methyl cyclohexyl ketone, 45 beta-diketones, the conversion may be effected CH3COCs11; ethyl cyclohexyl ketone, by passing the vapors of the enol-ester through a heated tube which is fitted with a vaporizer, C2H5OOC6H11 preheater and condenser. The tube may be con propyl cyclohexyl ketones, C3H7COCsI11; cyclo 50 structed of chrome iron, nichrome, stainless steel, hexyl acetone, CsP11CH2COCH3; cyclohexanone, silica or other material which is resistant to the .CsH10O; methyl cyclohexanones, CH3CshipO; ethyl corrosive action of the diketone produced. On cyclohexanones, Ca?sCsHoO; propyl cyclohexa a single pass of the enol-ester through the Con nones, C3HaC6HoO; butyl cyclohexanones, verter, yields of diketone of from 20 to 60 per C4,ECHO cent may be obtained in efficiencies as high as

2 2,895,800 80 to 95 per cent. If desired, the converter may be packed with an inert material although ex cent. There was also recovered 40 grams of un cellent results are obtainable in the absence of a changed alpha-acetoxy styrene for a conversion packing material. The conversion appears to be efficiency of 80.1 per cent. brought about primarily by a thermal reaction Eacample 3 since such basic or acidic materials as were tried CH3(CH2)3CH(C2H5) COCH2COCH3 for catalytic activity had a definite deleterious 2-ethyl hexanoyl acetone (5-ethyl nonanedione-2,4) effect on the yield. With the exception of a small Isopropenyl 2-ethyl hexanoate was converted amount of tarry material, no by-products or side to 2-ethyl hexanoyl acetone at a temperature of reaction products of significance are formed, and .0 500 C., using an apparatus and procedure sim the main reaction product may be separated from ilar to that described in Example 2. On distilla unchanged starting material by ordinary proce tion of the condensate obtained from a three dures for recovery or purification, as by distilla hour run during which 150 grams of enol-ester tion at a suitable pressure or the like. were passed through the converter, there was ob In general, the useful conversion temperatures 5 tained 92.4 grams of 2-ethyl hexanoyl acetone lie in the range from 300° to 700° C., but the most distilling at 90° C. at an absolute pressure of 5 satisfactory results are obtainable at a tempera millimeters of mercury. 2-ethyl hexanoyl ace ture of about 500 to 600° C. which is preferred. tone was found to be a colorless liquid having the With decrease in temperatures below 500° C., the following properties: D 20/20,09060; N0, 1,4600. yield falls off rapidly while at temperatures sub 20 The single pass yield was 61.6 per cent. The re stantially above 500 C., the loss of the acylated covery of unchanged starting material was 32.1 ketone by decomposition becomes excessive. grams per cent for an efficiency of 78.3 per cent. Enol-esters which are the starting materials Eacample 4 for carrying out my process may be obtained in various ways, for instance, by ester interchange, CH using an enol-ester such as isopropenyl acetate as 25 off, Yoo the acylating agent for reaction with the ketone. bH, &H coch, This latter method is no part of the present in Y cf. - vention but is described and claimed in copend ortho-acetyl cyclohexanone ing applications of Quattlebaum and Noffsinger 30 Acetoxycyclohexene made by the reaction of filled on or about June 6, 1944, Serials Nos. ketene" with cyclohexanone was converted to 539,024 and 539,025. - ortho-acetylcyclohexanone at a temperature of The present invention may be further illus 500° C., using a silica tube packed with cerami trated by the following examples: cally bonded, fused aluminum oxide. Except for Ecample 1 35 the packing, the apparatus and procedure Were substantially as described in Example 2. Over a CH3COCH2COCH period of five hours 574 grams of acetoxycyclo Acetyl acetone hexene were passed through the converter tube. Isopropenyl acetate was passed through a The resulting condensate which was distilled heated chrome iron tube, having an inside diam 40 under reduced pressure yielded 272 grams of eter of one inch, at a uniform rate of about 225 ortho-acetyl cyclohexanone, distilling at 80° grams per hour for a period of four hours. The 80.5° C. at an absolute pressure of 5 millimeters apparatus included a vaporizer and a preheater of mercury, and 248 grams of unchanged start for the isopropenyl acetate and an efficient con ing material. The single pass yield was 43 per denser for collecting the conversion products at 43 cent and the efficiency was as 82 per cent. the outlet of the tube. Over a distance of 21 The foregoing results were obtained after the inches of its length the converter tube was main packed converter had been inservice for a period tained at a temperature of 500° C. by electrical of time and a thin coating of carbon had been heating. The vaporizer and preheater were deposited on the aluminum oxide packing. It maintained attemperatures of 180° C. and 300° C. 50 was observed that until the thin deposition of respectively. , carbon had formed, some decomposition of ma On distillation of the condensate from the terial to lower boiling substances took place, with four-hour run there was obtained 407 grams of acetyl acetone distilling at 69-70° C. at an abso a resultant lower yield. lute pressure of 100 millimeters of mercury, and Eacample 5 427 grams of recovered isopropenyl acetate. 55 These values correspond to a single pass yield of (CIs)(CH).C. ch, CB 15.3 per cent and an efficiency of 86.2 per cent. 7-ethyl nonanedione-2,4 Eacample 2 The enol-acetate of 5-ethylheptanone-2 made 60 by the reaction of ketene with the ketone, was CHCOCHCOCH converted to the isomeric diketone at a tempera Benzoyl acetone . . . ture of 500 C., using an unpacked silica tube as Alpha-acetoxystyrene which was obtained by the converter. The tube which had an inside reacting ketene with acetophenone was passed diameter of one inch was heated for 22 inches of through a heated silica tube at a uniform rate of 65 its length. The enol-ester was supplied to the about 55.3 grams per hour for period of three converter at a uniform rate of 130 milliliters per hours. The inside diameter of the tube was one hour. Otherwise the procedure was substantially inch and the temperature of the tube, over about as described in Example 2. Distillation of the 22 inches of its length, was maintained at approx condensate obtained from a three-hour run dura imately 500 G: On distillation of the condensate 70 ing which 290 grams of the enol-ester were passed obtained from the three-hour run, there was ob through the converter, yielded 63.2 grams of 7 tained 101 grams of benzoyl acetone, ethylnonanedione-2,4 distilling at 119 C., at an CeHsCOCH2COCH absolute pressure of 15 millimeters of mercury. The diketOne was found to have the following which represented a single pass yield of 60.8 per 75 properties: ID 20/20, 0.924; n. 20/D, 1,4508; Ma 2,895,800 3 calculated at 54.10, observed 54.12. The amount methylene carbon atom, -CH2-, which com of unchanged enol-ester recovered was 180.3 prises heating an aromatic acyl ester of the enol grams. The single pass yield was 22.2 per cent form of a ketone having a methyl group and an and the efficiency 60.5 per cent. aromatic group attached to the carbonyl group The invention is Susceptible of modification thereof to a temperature of about 300 to 700° C. within the scope of the appended claims. to cause said ester to rearrange to form a dike What is claimed is: tone having two aromatic acyl groups attached 1. A method of making a beta-diketone from to the same carbon atom by migration of the aro an enol-ester isomeric therewith which comprises matic acyl group of said ester from the enolic heating an acyl ester of the enolic form of a O oxygen atom to the methyl carbon atom of said ketone to a temperature of about 300 to 700° ketOne. to cause said acyl group of the acyl ester to mi 9. A method of making a beta-diketone in grate to form a diketone having two carbonyl which one of the carbonyl groups thereof is in a groups attached to the same aliphatic carbon cycloaliphatic ring, which comprises heating an 5 acyl ester of the enol form of a cycloaliphatic atom. ketone to a temperature of about 300 to 700° C. 2. A method of making a beta-diketone from to cause said ester to rearrange to form a dike an enol-ester isomeric therewith which comprises tone having the two carbonyl groups attached heating an acyl ester of the enolic form of a to the same carbon atom by migration of the acyl ketone to a temperature of about 500° C. to cause group of said ester from the enolic oxygen atom said acyl group of the acyl ester to migrate to 20. to a carbon atom adjacent the carbonyl group form a diketone having two carbonyl groups at of the ketOne. tached to the same aliphatic carbon atom. 10. A method of making an acyl acetone which 3. A method of making a beta-diketone from comprises heating an acyl ester of the enolic an enol-ester isomeric therewith which comprises form of acetone to a temperature of about 300 heating the acyl ester of a ketone to a tempera 25 to 700 C. to cause said ester to rearrange to form ture of about 300 to 700° C. in the vapor phase an acyl acetone isomeric therewith by migration to cause Said acyl group of the acyl ester to mi Of the acyl group from the enolic oxygen atom grate to form a diketone having two carbonyl to a carbon atom. groups attached to the same aliphatic carbon 11. A method of making an acyl acetone which aton. 30 comprises heating an aliphatic acyl ester of the 4. A method of making a beta-diketone from enolic form of acetone to a temperature of about an enol-ester isomeric therewith which comprises 300 to 700° C. to cause said ester to rearrange heating an acyl ester of the enolic form of a to form an aliphatic acyl acetone isomeric there ketone to a temperature of about 300 to 700° C. with by migration of the aliphatic acyl group to form a diketone having two carbonyl groups from the enolic oxygen atom to a carbon atom. attached to the same aliphatic carbon atom, said 12. A method of making an acyl acetophenone acyl group containing not more than twelve car which includes heating an acyl ester of the enolic bon atoms. 5. A method of making a beta-diketone from form of acetophenone to a temperature of about an enol-ester isomeric therewith which comprises 40 300' to 700° C. to cause said ester to rearrange to heating an acyl ester of the enolic form of a form an acyl acetophenone isomeric therewith by ketone which ketone contains not more than migration of the acyl group to the beta carbon twelve carbon atoms to a temperature of 300° to atom of the side chain of acetophenone. 700° C. to cause the acyl group to migrate to 13. A method of making an aliphatic acyl form a diketone having the two carbonyl groups 45 acetophenone which includes heating an aliphatic attached to the same aliphatic carbon atom. acyl ester of the enolic form of acetophenone to 6. A method of making a beta-diketone con a temperature of about 300 to 700° C. to cause taining two acyl groups attached to the same Said ester to rearrange to form an aliphatic acyl methylene carbon atom, -CH2-, which com acetophenone isomeric therewith by migration of prises heating an acyl ester of the enol form of 50 the aliphatic acyl group from the enolic oxygen a ketone having a methyl group CH3, attached atom to the beta carbon atom of the side chain to the carbonyl group thereof to a temperature of acetophenone. of about 300 to 700° C. to cause said ester to 14. A method of making acetyl acetone which rearrange to form a diketone having two acyl comprises heating isopropenyl acetate to a tem groups attached to the same carbon atom by mi 55 perature of about 500 to 600° C. to cause it to gration of the acyl group of said ester from the rearrange by migration of the acetyl group to a enolic oxygen atom to the methyl carbon atom carbon atom. of Said ketone, 15. A method of making acetyl acetone which 7. A method of making a beta-diketone con comprises heating isopropenyl acetate to a tem taining two aliphatic acyl groups attached to the 60 perature of about 300° to 700° C. to cause it to re same methylene carbony atom, -CH2-, which arrange by migration of the acetyl group to a comprises heating an aliphatic acyl ester of the carbon atom. enol form of an aliphatic ketone having a methyl 16. A method of making acetyl acetone which group, CH3-, attached to the carbonyl group comprises heating isopropenyl acetate in the va thereof to a temperature of about 300° to 700° C. 65 por phase at a temperature of about 500 C. to to cause said ester to rearrange to form a dike cause it to rearrange by migration of the acetyl tone by migration of the acyl radical of said ester group to a carbon atom, from the enol oxygen atom to the methyl group 17. As a new chemical compound 5-ethyl of said ketone. ' - nonanedione-2,4, 8. A method of making a beta-diketone having 70 ALBERT B. BOESE, Jr. two aromatic acyl groups attached to the same FRANK G. YOUNG, Jr.