STUDIES OF SOMEd-l,3,4-0XADIAZOLINES -OXADIAZOLINONES

Transcription

1 STUDIES OF SOMEd-l,3,4-0XADIAZOLINES AND -OXADIAZOLINONES

2 THE SYNTHESIS AND THERMAL DECOMPOSITION OF OXADIAZOLINES AND 5,5-DIPHENYL-2-(ARYLIMINO)-~-l,3,4 5,5-DIALKYL-~-l,3,4- OXADIAZOLIN-2-0NES by AUDREY M. CAMERON, B.A. A Thesis Submitted to the Faculty of Graduate Studies in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy McMaster University ~ Cameron 1973 A.udrey 1"1..

3 DOCTOR OF PHILOSOPHY (1972) (Chemistry) McMASTER UNIVERSITY Hamilton, Ontario TITLE: AUTHOR: SUPERVISOR: NUMBER OF PAGES: The Synthesis and Thermal Decom~osition of 5,5-Diphenyl-2-(Arylimino)-~-1,3,4 Oxadiazolines and 5,5-Dialkyl-L\3-l,3,4 Oxadiazolin-2-ones Audrey M. Cameron, B.A. (Saskatchewan) Dr. J. Warkentin 120, x SCOPE AND CONTENTS: The thermal decomposition of 2-(arylimino)-5,5 diphenyl-~3-l,3,4-oxadiazolines,prepared by the oxidation of benzophenone 4-arylsemicarbazones by lead tetra-acetate, was studied. A possible mechanism of the decomposition is discussed in the light of a correlation between the rate constants and substituent constants. The configuration of N,5,5-trisubstituted-2-imino-~3-l,3,4-oxadiazolines was determined. Several new compounds, 5,5-dialkyl ~3-l,3,4-oxadiazolin-2-ones,were prepared by hydrolysis of 5,5-dialkyl-2-(methylimino)-~3-l,3,4- oxadiazolines. A literature survey of the oxidative cyclization of nitrogen-containing carbonyl derivatives, and of the thermal decomposition of cyclic azo compounds is presented. ii

4 Acknowledgements The author is very grateful to Dr. J. Warkentin for his knowledgeable guidance and assistance in this work. His encouragement, as well as the stimulating atmosphere he created about the work, were invaluable. The author also expresses her thanks to fellow graduate students for helpful discussions, material aid, and a spirit of cooperation. The determination of an X-ray crystal structure by Drs. A. Prakash and C. Calvo is greatly appreciated. The author would also like to thank Mrs. C. G. Kauffmann for her skill in typing this thesis. The financial assistance of the National Research Council of Canada during the years 1966 to 1970 is gratefully acknowledged. iii

5 Index Page Scope and Contents Acknowledgements List of figures List of Tables ii iii viii x GENERAL INTRODUCTION 1 HISTORICAL INTRODUCTION General 4 4 I. Oxidative Cyclization of Carbonyl Derivatives 5 II. A. By lead tetra-acetate B. By oxidizing agents other than lead tetra-acetate Thermal Decomposition of Cyclic Azo Compounds - Mechanistic Studies EXPERIMENTAL Introduction I. Synthesis A. B. General Preparation o~ 5,5-dimethyl-2 (arylimino)-~-1, 3,4-oxadiazolines (1) Preparation of ~,5-Dimethyl-2 (phenylimino)-~-1,3,4 oxadiazoline (2) Preparation of 5,5-dimethyl-2 [(~-methoxyphenyl)imino-~3 1,3,4-oxadiazoline iv 35

6 Page (3) Preparation of 5,5-dimethy1 2-(~-to1y1imino)-~3-1,3,4 oxadiazo1ine (4) Preparation of 5,5-dimethy1 2~<E-ch1oropheny1)iminoJ ~3-1,3,4-oxadiazo1ine (5) Preparation of 5,5-dimethy1 2-[ (~-nitropheny1)iminoj ~-1,3,4-oxadiazo1ine (6) Preparation of 5,5-dimethy1 2-[(~-bromopheny1)iminoJ ~3-1,3,4-oxadiazo1ine c. Preparation of 5,5-diphenyl-2-(substituted imino)-a3-1,3,4-oxadiazo1ines 43 (1) (2) ( 5) (6) Preparation of 5,5-dipheny1 2-(~-anisy1imino)-~-1,3,4 oxadiazo1ine Preparation of 5,5-dipheny1 2-(pheny1imino)-~-1,3,4 oxadiazo1ine Preparation of 5,5-dipheny1 2-(~-to1y1imino)-~~1,3,4 oxadiazo1ine Preparation of 5,5-dipheny1 2[(~-ch1oropheny1)iminoJ ~3-1,3,4-oxadiazo1ine Preparation of 5,5-dipheny1 2-(methy1imino)-A3-1,3,4 oxadiazo1ine Attempted preparation of 5,5 diphenyl-2~(~-nitropheny1)iminoj A3_1,3,4-oxadiazo1ine v

7 Page D. Preparation of 5,5-dialkyl-2-(alkylimino)-~3-1,3,4-oxadiazolinesand 5,5-dia1kyl-~3-1,3,4-oxadiazo1inones 50 (1) (2) Preparation of 5,5-dimethy1 2-(phenethy1imino)-~3-1,3,4 oxadiazo1ine Preparation of 5,5-dimethyl 2-(methy1imino)-b.3-1,3,4-oxadiazoline and 5,5-dimethyl-A3 1,3,4-oxadiazo1inone Preparation of 5-ethyl-5-methy1 2-(methy1imino)-~3-1,3,4-oxadiazoline and 5-ethyl-5-methy1-b.3-1,3,4 oxadiazo1inone Oxidative cyclization of acetone semicarbazone Oxidative cyc1ization of benzophenone semicarbazone E. Alternative means of oxidative cyc1ization of 4-substituted ketone semicarbazones 57 (1) Oxidative cyclization of benzophenone 4-pheny1semicarbazone using active manganese dioxide 57 (2) Attempted oxidative cyc1ization of acetone 4-pheny1semicarbazone 58 (3) Oxidative cyclization of acetone 4-pheny1semicarbazone by an oxygen/basic alumina system 59 F. Attempted isomerization of some ~3-1,3,4-oxadiazolines 60 vi

8 II. Thermal Decomposition Studies of Some 1~-1,3,4-0xadiazolinesand Oxadi~zolinones Page 62 A. Thermal decomposition of 2-(arylimino)- 5,5-dimethyl-~3_l,3,4-oxadiazolines 62 B. Thermal decomposition of ~(arylimino) S,S-diphenyl-~3-l,3,4-oxadiazoline C. Thermal decomposition of S,5-dimethyl ~3-l,3,4-oxadiazolinone, and of S-ethyl- 5-methyl-~3_l,3,4-oxadiazolinone 68 RESULTS AND DISCUSSION 69 I. Preparation and Stereochemistry of 2-Imino-~3-l,3,4-oxadiazolines 69 II. Preparation and Thermolysis of ~-1,3,4 Oxadiazolin-2-ones III. IV. StJMlvIARY Thermolysis of S,S-Dimethyl-2-(arylimino) 6 3-l,3,4-oxadiazolines Thermolysis of S,5-Diphenyl-2-(arylimino) ~3-l,3,4-oxadiazolines BIBLIOGRAPHY 115 vii

9 List of Figures Fig. 1. Plot of Absorption Peak Height -1 ( 2263 cm ) Page versus Molarity of ~-Chlorophenyl Isocyanate in Bromobenzene. Fig. 2. 5,5-Dimethyl-2-(~-bromophenYl)-~- 1,3,4-oxadiazoline. 75 Fig. 3. Total Rate of Decomposition of 5,5 Dimethyl-2-(phenylimino)-~-1,3,4- oxadiazoline at C in Bromobenzene. 93 Fig. 4. Rate of Benzophenone Production in the Decomposition of 5,5-Diphenyl-2-(~-tolylimino) ~-1,3,4-oxadiazolinein Chlorobenzene at 99 Fig. 5. Rate of Isocyanate Production in the Decomposition of 5,5-Diphenyl-2 (~-tolylimino)-~3-1,3,4-oxadiazolinein Chlorobenzene at 85 C. 100 viii

10 Pig. 6. Fig. 7. Correlation of Rates of Aryl Isocyanate Formation by the Hammett Equation Using Hammett Substituent Constants (~). Correlation of Rates of Benzophenone Production by the Hammett Equation Using Haoonett Substituent Constants (8). Page ix

11 List of Tables Page Table I. Table II. Table III. Table IV. Table V. Decomposition of S,S-Dimethyl-2 (Phenylimino)-~-1,3,4-0xadiazoline at lsooc in Bromobenzene. 94 Kinetics of Benzophenone Production in the Decomposition of S,S-Diphenyl 2-(~-Tolylimino)-~3-1,3,4-0xadiazoline at 8S O C in Chlorobenzene. 97 Kinetics of Isocyanate Production in the Decomposition of S,S-Diphenyl 2-(~-Tolylimino)-A3-l,3,4-0xadiazoline at 8S o C in Chlorobenzene. 98 Correlation of Rates of Isocyanate Formation from S,S-Diphenyl-2 (Arylimino)-A3-l,3,4-0xadiazolines by the Hammett Relation. 101 Correlation of Rates of Benzophenone Formation from S,S-Diphenyl-2 (Arylimino)-~3-l,3,4-0xadiazolines by the Hammett Relation. 102 x

12 GENERAL INTRODUCTION West and Warkentin reported that the oxidative cyclization of 4-substituted semicarbazones gave 2-(substituted imino)-~-1,3a~xadiazolines(1). The thermolysis of these heterocycles proceeded by two parallel o R l R 2 C=NNHCNHR 3 first-order pathways. From the variation in the ratio of the two modes of decomposition with the substituents R l and R 2, the authors were able to reach some conclusions about the nature of the transition states involved. ---~~ R l R 2 C=O + N 2 + R 3 &:C ~ R l R 2 C=i N + R 3 NCO f R l R 2 C: + N 2 1

13 2 One of the objectives of this study was to gain a better insight into the mechanism of decomposition by studying the effects of changing the exocyclic substituents (R 3 ) on rates and products of the thermolysis of 5,5-diphenyl-2-(arylimino)-A 3 -l,3,4- oxadiazolines. A second objective was to determine the stereochemistry (E or Z) of the oxadiazolines that had been synthesized. E A new series of compounds, 5,5-dialkyl-~-1,3,4- oxadiazolin-2-ones, were discovered to be byproducts from the lead tetra-acetate oxidation of alkanone 4- alkylsemicarbazon~s. The thermolysis of these compounds was also investigated.

14 3 The use of agents other than lead tetra-acetate for the oxidative cyclization of 4-substituted semicarbazones was studied.

15 HISTORICAL INTRODUCTION General This introduction will examine first the scope and applicability of the oxidative cyclization of nitrogencontaining derivatives of carbonyl compounds. Although the use of such a cyclization was restricted in this study to the oxidation of 4-substituted semicarbazones, the background of this preparative method encompasses many other carbonyl derivatives. Indeed, this reaction, employing lead tetraacetate, manganese dioxide, ferric chloride, as well as other oxidizing agents, has been a valuable synthetic route to many heterocyclic compounds. Reviews of this field may be found in the literature (lb, Ie). The second part of this introduction will examine the kinetic results previously obtained from the thermolysis of some 2-(phenylimino)-5,5-diaryl-~-1,3,4-oxadiazolinesUa). In addition, descriptions of the various modes of azo decompo sition to be found in the literature are included. 4

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