United States Patent Office

Patented Dec. 23, 1947 2432,991 UNITED STATES PATENT OFFICE ACYLATION OF THOPHENE Howard D. Hartough, Pitman, and John J. Sar della, Woodbury, N. J., assigners to Socony Wacuum Oil Company, incorporated, a corpo ration of New York No Drawing. Application January 8, 1946, Seria No. 642.13 12 Claims, (C. 260-329) 2 This invention relates to a catalytic acylation in carbon disulfide to a suspension of aluminum process for thiophenes and, more particularly, is chloride in the same solvent. If, however, a car directed to a method for acylating thiophene and oon disulfide solution of the acid chloride was its derivatives in the presence of glauconite as a added to a suspension of thiophene and alumi catalyst. r nun chloride, much tar was formed and a low The acylation of thiophene. and thiophene de yield of ketone resulted. The acylation of thio rivatives has previously been carried out employ phene has, accordingly, been an exceedingly dif ing Organic acid anhydrides, acyl halides, and fictly reaction to carry out, the usual acylation acyl nitriles as acylating agents and in the pres catalysts causing excessive resinification of the eace of various catalysts, including aluminun thiophene reactant. The resinification usually chloride, stannic chloride, titanium tetrachloride, occurs before acylation can be effected, and if phosphorus pentoxide and 2-chloronercurithio 'the expected reaction product is formed, it is phene. Other methodis of inaking acylated thio generally only in relatively Small amounts. phene include the dry distillation of calcium It has now been discovered that acylated thio salts of thiophene carboxylic acids and the action s phenes may be obtained in an efficient manner of nitriles on thienyiragnesium iodide. by reacting thiophene or thiophene derivatives Of these processes, the catalytic methods en with an acylating agent in the presence of a Small ploying Friedel-Crafts type catalyst, such as alus amount of glauconite. It has been found that by inum chloride, stannic chloride, titanium tetra using glauconite as a catalyst, the above-men chloride and the like, have been used most ex tioned difficulties encountered in the acylation of tensively. These catalysts, although applicable thiophene have largely been overcome. Thus, by with considerable Success in the acylation of aro employing a catalyst of glauconite, the undue re ratic hydrocarbons, are only moderately Success sinification and formation of addition complexes fu where thiophene is involved. This appears formerly encountered in the catalytic acylation to be due to the relative instability of the thio ES of thiophene have been substantially eliminated, phene ring; the Friedel-Crafts catalyst, for exam the products resulting being almost entirely acyl pe aluminum chloride, attacking the sulfur and thiophenes having one or more side chains corre causing many undesirable secondary reactions sponding to that of the acylating agent, it has with concomitantly low yields of acy thiophenes, been found, in accordance with this invention, Furthermore, compounds such as aluminum chlo that glauconite effects the acylation of thiophene ride form addition complexes with the carbonyl smoothly and specifically in contrast to the more group of the resulting ketone, Substantially de conventional catalysts employed heretofore, giv creasing the yield of desired product and requir ing a substantial yield of desired ketone without ing a considerable excess of aluminum chloride accompanying formation of complex addition over the theoretical amount required for the products and resinification. The acylation of acylation process. Thus, when aluminum chlo thiophenes using glauconite as a catalyst, more ride is used as the condensing agent, the mole over, can be carried out in a direct manner with ratio of catalyst to acyl chloride or acyl nitrile out a detailed observance of experimental con is at least one and, in the case of acid anhydrides, ditions, such as is a necessary precaution to be at least two. Likewise, other Friedel-Crafts cat 40 taken when aluminum chloride is employed as alysts, such as stannic chloride, must be used in catalyst. molecular quantities with respect to the acyl hal It is, accordingly, an object of the present in ide being employed in the acylation of thiophene. vention to provide an efficient process for Syn This is probably due to the fact that acyl halides thesizing acylated thiophenes. Another obiect is form comparatively stable molecular complexes 5 to provide a process for catalytically acylating with aluminum chloride and stannic chloride, thereby diminishing their catalytic effect. thiophene and its derivatives. A still further ob Moreover, the use of aluminum chloride in the ject is to afford a process for catalytically acyl acylation of thiophene entails strict observance ating thiophene in a relatively simple and direct of detail in experimental observations. Thus, it 50 manner which can be easily carried out by using is known that thiophene and aluminum chloride an inexpensive, easily obtainable catalyst. A react vigorously in carbon disulfide suspension, very important object is to provide a process ca It has been reported that a moderately good pable of reacting thiophene or its derivatives with yield of phenylthienyl ketone is obtained by add an acylating agent in the presence of an efficient ing a solution of benzoyl chloride and thiophene 55 catalyst without undue formation of addition 2,482,991 3 complexes between the catalyst and thiophene or Thiophene or derivatives of thiophene having between the catalyst and acylating agent. one or more substituent groups, such as halogen, These and other objects which will be recog alkyl, aryl, or alkoxy groups attached to the thio nized by those skilled in the art are attained in phene ring, may be acylated in accordance with . accordance with the present invention, wherein this invention. The 2- and 5-positions in the thiophene or its derivatives are acylated by reac thiophene ring, being adjacent to the sulfur atom, tion with organic carboxylic acid anhydrides or are generally much more reactive than the 3- and acyl halides in the presence of glauconite as a 4-positions and, in acylating thiophene, the en catalyst. tering acyl group will preferably attach itself to Glauconite, also referred to as greensand, is 10 the carbon atom adjacent to the sulfur. When the well known to the art as a water softener wherein 2-position of the thiophene ring is already occupied it plays the role of an ion exchanger. It is a by a substituent group or atom, the entering acyl naturally occurring deposit found in various lo group will preferably attach itself to the 5-posi calities. Its exact composition, of course, will be tion. When the 3-position is occupied, the acyl dependent upon the area in which it is found. 15 substituent will enter for the most part at the 2 In general, the oxides of aluminum, silicon, iron, position. However, in some instances, a small potassium and magnesium will comprise the portion of the 3,5-product may be obtained. larger portion of the composition of glauconite Thiophene derivatives having substituents of a employed in the process of the present invention. highly negative character, such as carbonyl, The use of sands containing major amounts of 20 ester, nitro and cyano groups, and no activating the alkaline earth metals such as calcium should substituent, such as a hydroxy or alkoxy group, be avoided, since samples containing relatively do not acylate readily. These groups, commonly large quantities of calcium have been found to referred to as meta-directing, possess a highly have little catalytic effect in promoting the acyl electronegative character which tends to inhibit ation of thiophene. The composition of glau 25 the acylation reaction. conite may generally be defined as follows: The acylation of thiophene or its derivatives is carried out, in accordance with the process of this Per cent invention, by employing substantially equimolar - composition quantities of thiophene and acylating agent. An SiO2 ---------------------------- 40.00 to 53.61 30 excess of either of the reactants, as will be shown Alao.3 --------------------------- 6.62 to 13.00 hereinafter, does not appear to appreciably affect FeaC3 --------------------------- 15.16 to 23.43 the yield of acylated thiophene. The upper limit Fe0 ---------------------------- 1.32 to 10.17 of temperature at which the process is carried out MgO --------------------------- 0.95 to 2.97 will be dependent upon the boiling point of the re Cao ---------------------------- 0.57 to 1.97 35 actants at the specific pressure of the reaction. Na2O --------------------------- 0.42 to 2.6 In general, temperatures between about 80° C. K2O ---------------------------- 3.49 to 9.54 and about 150° C. and pressures between atmos HoO ---------------------------- 4.93 to 10.32 pheric and about six atmospheres have been It may be used in accordance with the present found satisfactory for effecting the acylation re invention upon mere drying to remove adhering 40 action. The effect of increased pressure, theo surface water or may be activated by acid treat retically, is toward increased reaction but, from ment and heating at an elevated temperature. a practical standpoint, this is not a very great A catalyst which had been activated by the latter effect with reactions such as those involved here treatment was found to give a higher yield of in, which go readily at normal pressures. The acylated thiophene. Glauconite is employed in temperature to be employed will depend on the the process of this invention in a finely divided time of reaction and the nature of the acylating form and in amounts between about 4 and about agent used. Ordinarily, a pressure sufficient to 25 per cent, based on the weight of the reactants. maintain the reactants in the liquid phase is emi The acylating agents to be used herein may be ployed and this is more or less dependent upon 50 the particular temperature involved.

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