2896 stretching), 3055 (cyclopropyl C-H stretching), 1073, 1040, 1005, 833 cm-l; nmr (100 MHz, CHClr) T 8.84 (m, 2 H, cyclopropyl protons), 8.52 (doublet of triplets, 1 H, J = 14 Hz, 2 Hz, methylene proton), 8.44 (m, 1 H), 7.90 (doublet of doublets, 1 H, J = 14 Hz, 7 Hz, methylene proton), 7.84 (broad singlet, 1 H, bridgehead proton), 7.68 (broad singlet, 2 H, bridgehead protons), 6.74 (s, 4 H , --SCH2CH2S-),5.88 (doublet of doublets, 1 H, J = 7.0 Hz, 3.5 Hz, CHOH). Anal. Calcd for CIIHIIOS~:C, 58.37; H, 6.23. Found: C, 58.74; H , 6.07. Preparation of exo-8-Brosyloxydeltacyclan-5-oneEthanedithiol Ketal (exo-19b). p-Bromobenzenesulfonyl chloride (15.0 g, 0.056 mol) was added in small portions over 1 hr to a stirred solution of 11 .O g (0.049 mol) of exo-thioketal alcohol exo-19a in 200 ml of dry pyridine. A temperature of 0-7" was maintained during the addition. The mixture was stirred for 1 hr at room temperature, allowed to stand in a refrigerator for 8 days, and worked up as described for brosylate 14. Upon recrystallization from a 70: 30 pentane-ether mixture, 18.0 g (0.040 mol, 82% yield) of crystalline brosylate was obtained: mp 119-121 '; nmr (100 MHz, CHClr) T 8.82 (t, 2 H, J = 6 Hz, cyclopropyl protons at (2-2, C-3), 8.38 (t, 1 H, cyclopropyl proton), 8.28 (doublet of triplets, 1 H , J = 14 Hz, 2 Hz, methylene proton), 7.89 (doublet of doublets, 1 H, J = 14 Hz, 7 Hz, methylene proton), 7.84 (broad singlet, 1 H, bridgehead proton), 7.64 (broad singlet, 1 H, bridgehead proton), 7.48 (broad singlet, 1 H, bridgehead proton), 6.76 (broad singlet, 4 H , -SCHICH,S-), 5.20 (doublet of doublets, 1 H, J = 6.8 Hz, 2.3 Hz, -CHOBs). A n d . Calcd for CI7H17O3S3Br:C, 45.83; H, 3.84. Found: C, 45.97; H, 3.95. Preparation of endo-8-Acetoxydeltacyclan8-one Ethanedithiol Ketal. To 19.0 g (0.043 mol) of exo-thioketal brosylate exo-19b was added 21.0 g (0.074 mol) of tetra-n-butylammonium acetate in 50 ml of dry benzene. The flask was tightly sealed, and the contents were heated to 60" for 16 hr and worked up as described for endo acetate 15, giving 10.5 g (0.039 mol, 89% yield) of endo-thioketal acetate as a waxy solid: mp 65-66" (vpc collected); ir (neat) 3055 (cyclopropyl C-H stretching), 1724 (C=O), 1361, 1245, 1125, 1031 cm-1; nmr (60 MHz, CC1J T 8.3-8.8 (m, 4 H), 8.17 (d, 1 H , J = 14 Hz, methylene proton), 8.05 (s, 3 H, -OCOCH& 7.85 (m, 1 H , bridgehead proton), 7.68 (broad singlet, 1 H, bridgehead proton),
7.44 (broad singlet, 1 H, bridgehead proton), 6.80 (s, 4 H, -SCH2CHIS-), 4.93 (doublet of triplets, 1 H , J = 9.8 Hz, 3.4 Hz, -CHOAc). Anal. Calcd for C 1 3 H l ~ 0 ~ SC,~ :58.17; H, 6.02. Found: C, 58.13; H, 5.78. Preparation of endo-8-Hydroxydeltacycland-one Ethanedithiol Ketal (endo-19a). endo-Thioketal acetate (13.0 g, 0.048 mol) in 50 ml of ether was added to a rapidly stirred solution of 2.5 g (0.066 mol) of lithium aluminum hydride in 150 ml of ether. The mixture was stirred at room temperature for 12 hr and worked up as described for alcohol 12, giving 9.5 g (0.042 mol, 88% yield) of waxy solid endo-thioketal alcohol: mp 9C93"; nmr (100 MHz, CHCL) T 8.8-8.35 (m, 4 H), 7.8-8.2 (m, 2 H), 7.72 (broad singlet, 1 H, bridgehead proton), 7.52 (m, 1 H , bridgehead proton), 7.04 (s, 1 H, -CHOH), 6.76 (s, 4 H, -SCHICH~S-), 5.60 (doublet of triplets, 1 H, J = 9.5 Hz, 3.5 Hz, -CHOH). A n d . Calcd for CllH,iOS~r: C, 58.37; H, 6.23. Found: C, 58.11; H, 6.12. Preparation of endo-8-Brosyloxydeltacycland-one Ethanedithiol Ketal (endo-19b). To a stirred solution of 8.0 g (0.034 mol) of endo-thioketal alcohol endo-l9a in 120 ml of pyridine was added 11.O g (0.043 mol) of p-bromobenzenesulfonyl chloride over 1 hour while the temperature was maintained at 0-7". The solution was stirred an additional 0.5 hr at room temperature and then allowed to stand in a refrigerator for 10 days. The reaction was worked up as described for brosylate 14. Recrystallization of the brosylate from a 70:30 pentane-ether mixture gave 14.0 g (0.031 mol, 91 yield) of product: mp 127.5-129"; nmr (100 MHz, CHC13) T 8.58 (m, 2 H), 8.42 (m, 2 H), 7.8-8.4 (m, 2 H), 7.66 (broad singlet, 1 H, bridgehead proton), 7.52 (m, 1 H , bridgehead proton), 6.80 (d, 4 H, -SCH2CH2S-), 5.03 (doublet of triplets, 1 H, J = 9.4 Hz, 3.6 Hz, -CHOBs). A n d . Calcd for CI7HnSsOdBr: C, 45.83; H, 3.84. Found: C, 45.84; H , 3.92. Kinetic Measurements. The acetolysis conditions and analytical methods were similar to those employed in our initial study.Ib
Acknowledgment. The authors gratefully acknowledge the generous support of this work by the National Science Foundation.
Polyfunctional Catalysis. IV. Oxy Acid Catalysis of the Mutarotation of Tetramethyl-D-glucose in Benzene Peter R. Rony*' and Robert 0. Neff
Contribution from the Central Research Department, Monsanto Company, St. Louis, Missouri 63166. Received October 24, 1972 Abstract: An experimental study of the mutarotation of 2,3,4,6-tetramethyl-~-glucose (TMG) in benzene has been kl')[catalyst]{[TMG] - [TMG],}, where performed. The rate law for all of the catalysts studied is rate = (kl [TMG], is the concentration of a-tetramethylglucose at equilibrium. The activation parameters, relative to the catalyst-substrate complex, are: (1) diphenyl phosphate, AH* = 14.1 kcal/mol and AS* = -10.8 gibbslmol a t a standard state of 1 mol/l. a t 25'; (2) benzenephosphinic acid, AH* = 14.9 kcal/mol and AS* = -8.8 gibbs/ mol; (3) trichloroacetic acid, AH* = 14.1 kcal/mol and AS* = -15.4 gibbsjmol; (4) benzoic acid, AH* = 13.2 kcal/mol and A S * = -21.4 gibbsjmol; (5) 2-pyridone, AH* = 13.2 kcal/mol and A S * = -22.7 gibbs/mol; (6) pyrazole, AH* = 13.2 kcal/mol and AS* = -30.2 gibbs/mol; (7) 2-aminopyridine, AH* = 13.2 kcal/mol and AS* = -24.6 gibbs/mol; and (8) picric acid, AH* = 12.7 kcal/mol and A S * = -28.4 gibbs/mol. BrOnsted plots of catalytic activity 6s. pKEg0suggest that strong oxy acids act as tautomeric catalysts for the mutarotation of tetramethylglucose in nonpolar solvents.
+
I
n a previous paper, we proposed that the catalysis of chemical reactions by tautomeric molecules was a
(1) Address correspondence to this author at the Department of Chemical Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Va. 24061.
Journal qf the American Chemical Society j 95:9 / May 2, 1973
general phenomenon.2 We called this type of catalysis tautomeric catalysis, defined a tautomeric catalyst as "a molecule t h a t repeatedly cycles between two or more (2) P. R. Rony, J . Amer. Chem. Soc., 91, 6090 (1969).
2897
tautomeric states during the course of catalyzing a chemical reaction,” and advanced suggestions concerning the potential scope of such catalysis. In this paper, we wish to consider whether oxy acids (I), where M = C, P, S, As, etc., can function as -M
H0 \OH
I
tautomeric catalysts. Hofer and Brenner have observed that such acids (where M = C, P, or S) are effective catalysts for the rearrangement of N-acyl-N’-acyl-aaminoacylhydrazines in a variety of solvents, including ethers, esters, weak tertiary amines, and N,N’-dialkylamides. Swain and Brown,4 Kergomard and Renard,j and others have already shown that benzoic acid and other carboxylic acids act as bifunctional catalysts for (TMthe mutarotation of 2,3,4,6-tetramethyl-~-glucose G) in benzeneu2v6 Based on these observations, we have previously suggested that oxy acids can indeed function as tautomeric catalysts. 2,6 We report experiments designed to determine whether or not strong oxy acids can function as tautomeric catalysts in the mutarotation reaction. We have focused our attention upon the activation parameters in benzene and the change in catalytic activity as a function of solvent, and report data for catalysis by benzoic acid (11), trichloroacetic acid (111), trifluoroacetic acid (IV), benzenephosphonic acid (V), benzenephosphinic acid (VI), diphenyl phosphate (VII), benzenesulfinic acid (VIII), toluenesulfonic acid (IX), benzenearsenic acid (X), sulfuric acid (XI), perchloric acid (XII), picric acid (XIII), hydrochloric acid, and the bisulfate (XIV), dihydrogen phosphate (XV), and dihydrogen arsenate (XVI) ions. H0
CeH& ‘OH
CC1,C /p \OH
Iv
w
VI
VIII
Experimental Section Materials. The source and purification procedures for 2,3,4,6tetramethyl-D-glucose (TMG), benzene, ether, methanol, 2-pyridone, benzoic acid, pyrazole, n-butylamine, trichloroacetic acid, 1.4diazabicyclo[2.2.2]octane (Dabco), and tetra-n-butylammonium hydroxide titrant solution are described elsewhere.23638 The purification procedures for the following Eastman reagents are given in parentheses after each compound : anhydrous and Spectrograde acetonitrile (Eastman X488 and 13102, respectively; used directly without further purification), trifluoroacetic acid (used directly without further purification), benzenephosphinic acid (recrystallized once from benzene), and benzenesulfinic acid (sodium salt neutralized, extracted with ether from aqueous solution, recrystallized once from ether, and used immediately). Other compounds include 2-aminopyridine (Baker, used directly without further purification), diphenyl phosphate (Aldrich, recrystallized from heptane), picric acid (Baker and Adamson, recrystallized from acetone-ether or from benzene), 4-toluenesulfonic acid monohydrate (Fisher, water in excess of the monohydrate azeotroped with benzene), dimethylacetamide (Fisher, used directly without further purification), and arsenic pentoxide (Fisher, used directly without further purification). Gaseous hydrochloric acid (Matheson) was bubbled directly into acetonitrile at 0”. A portion of the acid solution was diluted with water and titrated to a phenolphthalein end point t o determine the acid concentration. Source of Phenol. Reagent phenol (Mallinckrodt) was vacuum sublimed at 26” in an attempt to remove the 0.15% H3P02 preservative. As can be seen from Table I, this purification procedure Table I. Mutarotation of 2,3,4,6-Tetramethyl-~-glucose in Various Solvents
CF3C
m
II
model reaction for three reasons: (1) the reaction exhibits rigorous pseudo-first-order kinetics and is easy t o study, (2) considerable data on the catalysis of the mutarotation reaction by tautomeric molecules already exist, and (3) strong acids are not neutralized by the tetramethylglucose. The aminolysis of 4-nitrophenyl acetate2 was eliminated as a model reaction because of the formation of ion pairs between the attacking amine and the catalytic acid.’ There also exists some question concerning what fraction of the aminolysis catalytic activity of 2-pyridone is a consequence of its hydrogen bonding ability.7b
V
IX OH
Solvent Benzene Acetonitrile Ether 0.25 M dimethylacetamide-benzene 6 % methanol-benzene 0.25 M phenol-benzene
k,,: 10-6 sec-1 0.65
