3,658,828 United States Patent Office Patented Apr. 25, 1972 2 3,658,828 R R UNSYMMETRICAL DIALKYL THAZOLE / SULFENAMIDES T-S -N-ce John Joseph D'Amico, Akron, Ohio, assignor to R3 Monsanto Company, St. Louis, Mo. 5 wherein T is benzothiazolyl or substituted benzothiazolyl, No Drawing. Filed Nov. 19, 1969, Ser. No. 878,243 where the substituents are chloro, bromo, fluoro, iodo, ni Int, C. C07d 91/44 tro or lower alkoxy, R is tertiary-alkyl of 4-12 carbon U.S. C. 260-306.6A 5 Claims atoms, R2 and R3 are alkyl of 1-8 carbon atoms or to gether with the carbon atom to which they are attached O form cycloalkyl of 5-8 carbon atoms. ABSTRACT OF THE DISCLOSURE Examples of tertiary-alkyl radicals suitable for the prac Unsymmetrical dialkyl thiazole sulfenamides of the tice of this invention are tertiary-butyl, tertiary-amyl, formula tertiary-hexyl, tertiary-octyl, tertiary-nonyl, tertiary-decyl and tertiary-dodecyl. A tertiary-alkyl radical has its first 5 carbon atom linked to three other carbon atoms. The aliphatic groups from which R2 and R can be Selected include alkyl groups containing from 1-8 car bon atoms having straight or branched chains, for ex wherein T is benzothiazolyl or substituted benzothiazolyl, ample, methyl, ethyl, propyl, isopropyl, butyl, secondary where the substituents are chloro, bromo, fluoro, iodo, 20 butyl, amyl, hexyl and octyl. Cyclopentyl, cyclohexyl and nitro or lower alkoxy, R is tertiary-alkyl of 4-12 carbon cyclooctyl are examples of radicals when R2 and R3 to atoms, R2 and R3 are alkyl of 1-8 carbon atoms or to gether with the carbon to which they are attached form gether with the carbon atom to which they are attached cycloalkyl. form cycloalkyl of 5-8 carbon atoms are delayed-action Compounds of this invention may be produced by the 25 oxidative condensation of the appropriate secondary accelerators. amine with a thiazole mercaptain or disulfide. Amines used in the preparation of these compounds are known. For This invention relates to new thiazole sulfenamides. example, N-isopropyl-tertiary-butyl amine is reported in More particularly, it relates to unsymmetrical thiazole Angew. Chem. vol. 72, 1001. N-tertiary-butyl cyclohexyl sulfenamide accelerators having a tertiary-alkyl radical 30 amine is reported in J. Org. Chem. vol. 29, 2240. Other and a secondary-alkyl or cycloalkyl radical attached to amines needed to practice the invention can be made by the sulfenamide nitrogen. known methods. BACKGROUND OF THE INVENTION DESCRIPTION OF PREFERREED 35 EMBODIMENTS The N,N-dialkyl thiazolesulfenamides were among the Example 1 first thiazolesulfenamide accelerators discovered but gen eral commercial acceptance lagged behind that of mono The preparation of N-tert-butyl-N-isopropyl-2-benzo alkyl and cycloalkyl analogues. Some of them are liquids thiazolesulfenamide is as follows: 341.6 milliliters of a whereas solids are preferred because of easier purification, 40 sodium hypochlorite solution containing 0.75 mole (16.4 longer shelf life and greater convenience in mixing with grams NaOCl/100 ml.) of sodium hypochlorite is added dropwise at 45-50° C. over a period of one and one-half rubber. Thiazolesulfenamides possess delayed action, a hours to a slurry containing 84.6 grams (0.5 mole) of 2 property which is valuable because of the processing safe mercaptobenzothiazole and 86.4 grams (0.75 mole) N ty it imparts. One theory of delayed action relates in tert-butyl-N-isopropyl amine in 500 milliliters of isopropyl creasing delayed action to increasing steric hindrance but 45 increasing steric hindrance of dialkyl amines increases alcohol. To this reaction mixture 100 milliliters of hot difficulty of forming the sulfenamide. water is added which results in formation of two liquid Processing safety is a property which has great eco layers. This mixture is cooled to 30° C. and then added nomic importance because in its absence rubber stocks oft in one portion to 3000 grams of ice water containing 10 times partially vulcanize before they can be shaped into 50 grams sodium sulfite. The resulting mixture is stirred at useful articles. Fortunately, when styrene butadiene co 0-10 C. for one hour. The product is collected by filtra polymer rubber became a commercial reality the delayed tion and is washed with cold water until neutral and air action thiazolesulfenamide accelerators had already been dried at 25-30 C. 103 grams of a solid representing a discovered and were available for use. The higher tem yield of 74% is recovered. The product recrystallized peratures generated in the processing of styrene butadiene from heptane melts at 69-70° C. Analysis of the prod copolymer rubber intensified the prevulcanization of 55 uct gives nitrogen 9.91% and sulfur 22.72% compared scorch problem. However, even higher processing temper with 9.99% N and 22.87% S calculated for C4H2NS2. atures came into use and more scorchy carbon blacks were Example 2 introduced so that improved delayed-action accelerators have been continually needed. N-tert. -butyl- N - cyclohexyl - 2 - benzothiazolesul 60 fenamide is prepared in a similar manner except one mole of N - tert. - butylcyclohexylamine is used in place of SUMMARY OF THE INVENTION N-tert-butyl-N-isopropyl amine. 120 grams (73% yield) It has now been discovered that highly sterically hin of a solid are recovered; recrystallized from heptane the dered thiazolesulfenamides containing one tertiary-alkyl product melts at 93-94 C. Analysis gives 8.79% N and and one secondary-alkyl or cycloalkyl on the amide nitro 65 19.82% S compared to 8.74% N and 20.00% S calcu gen form in good yields from the corresponding highly lated for CH4NS2. sterically hindered secondary amines. In spite of the lack of symmetry, the products are stable solids at ordinary Example 3 temperatures and possess special delayed-action accelerat N-tert-butyl-N-cyclohexyl - 5 - chloro-2-benzothiazole ing properties. The compounds of this invention may be 70 sulfenamide is prepared by the procedure of Example 2 represented by the formula: except 5-chloro-2-mercaptobenzothiazole is used in place 3,658,828 3 4 of the mercaptobenzothiazole. 66 grams (75% yield) of the new accelerators. The effect on processing safety of the sulfenamide are recovered. The product recrystallized substituents in the benzothiazole portion of the molecule from ethyl acetate melts at 165-166 C. Analysis gives is demonstrated. 7.88% N and 18.02% S compared to 7.89% N and 18.07% S calculated for CHCINS TABLE R CaCat O. 123-live2 5. Stock.------------ I K Example 4 Masterbatch--- 66. O 66.0 66. N-tert-butyl - N - cyclohexyl-6-ethoxy-2-benzothiazole- NESNyclohexybenzodiazolesulten.Sieki.I.ilt.0ile ----- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ''0.5 '' '' sulfenamide is prepared in a like manner by using 6- 10 is li:iii, - - - - Vu - - - - - - - - - - - - - - - - ethoxy-2-mercaptobenzothiazole. 57 grams (63% yield) Nittingelohexylchlorobenzoli. 0.5 -------- of a solid which melts at 106°-107 C. after recrystalliza- NSEE,yclohexy 6-ethoxy-benzothia- 0.5 tion from alcohol is obtained. Analysis of the product Mooney scorch at 35°C. (...I.I.I. 25.333i 25.3 gives 7.52% N and 17.59% S compared to 7.68% N and 17.59% S calculated for C9HNOS2. 15 As further examples of the processing safety of the The new compounds can be used as accelerators in the compounds of the invention, vulcanizable compositions vulcanization of natural and synthetic sulfur-vulcanizable are compounded comprising the following stocks: rubbers. The special properties of the new delayed-action sulfenamides in rubber stocks compounded in styrene bu- MASTERBATCH tadiene rubber and in blends of styrene butadiene rubber 20 Ingredients: Parts with polybutadiene rubber are shown below. Oil extended SBR ----------------------- 137.5 The amount of accelerator used depends on a number Carbon black (ISAF) ------------------- 650 of factors uch as process conditions, type of elastomer, Stearic acid ---------------------------- 1. use of the vulcanized product, other components in the Zinc oxide ----------------------------- 3.0 recipe and other variable to which the compounder must 25 Hydrocarbon softener -------------------- 1.5 address himself. The amount is, however, usually within aara the range of 0.1 to 5 parts by weight, and more often Total ------------------------------- 208.0 within the range of 0.3 to 2 parts by weight per 100 parts by weight of rubber. The preferred usage generally falls TABLE within the range of 0.5 and 1.5 parts by Weight 30 Stock------------------------------------------- L N accelerator. Masterbatch------------------------------------ 208.0 2.08.0 208.) acceleratingA styrene-butadiene activity of themasterbatch new compounds. is used Theto testmaster- the SEE---Niopsigianzothiazofeifetide. 83...'...' 1.8 8 batch is prepared by milling the following ingredients: Neihuyl-N-isopropyl-2-benzothiazolesalien:Ell06- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 1.2 - - - - - - MASTERBATCH 35 N-tert-butyl-N-cyclohexyl-2-benzothiazole-Encycloney-benzoate. - - 1.2- - Mooney Scorch at 135C. (ts)------------------- 36, O 42.5 44.5 Parts by weight Styrene-butadiene rubber --------------------- 100.0 MASTERBATCH Carbon Black (HAF) ---------------------- 52.2 40 Ingredients: Parts Stearic acid -------------------------------- 2.0 Styrene-butadiene rubber ---------------- 68.75 Zinc oxide -------------------------------- - 4.0 Cis-4-polybutadiene rubber -------------- 50.0 Hydrocarbon Softener -----------------------