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Synthesis and Reactions of Triphenylphosphine-O- Benzophenonimine and Derivatives

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Synthesis and Reactions of Triphenylphosphine-O- Benzophenonimine and Derivatives INIS-SD-123 SYNTHESIS AND REACTIONS OF TRIPHENYLPHOSPHINE-O- BENZOPHENONIMINE AND DERIVATIVES SD0000044 A Thesis submitted by Manahil Babiker Elamin (B. Sc. Science) For the M. Sc. Degree in Chemistry Department of Chemistry Faculty of Science University of Khartoum Sudan August 1999 31/ 39 "Chem\stry creates \ts subject. Th\s creatwe abWvty, s\m\\ar to that o\ arts, essent\a\\v d\st\ngu\shes chemistry among the natura\ sc\ence" MarceWn Berthe\ot"one o\ the great organ\c chem\sts o^ the \ast centurv" "Chemvstrv has strongty creatwe potent\a\. \t can creates substance and mater\a\ never dreamt o\ before" . Ba\d\N\n "one o\ the great organic cherrnsts o^ the th\s century" Dedication To the Memory of my dear friend Omima Ghorashi To my parents and all whom I Jove Acknowledgements All praise is due to "ALLA". I would like to express my deep indebtedness to my supervisor Dr. Farouk Eltayeb for his keen guidance, assistance and continuous encouragement especially pleasant by his fatherly advice and persistent interest and patience made it possible to develop and improve this thesis. Thanks and deepest gratitude to Dr. Osman Ibrahim, the head Department of Chemistry for his helps. Thanks and appreciation due to Mr. Ali M. Shareif for his helps. Also my thanks to Mr. Magdi A/ Eldaiem, Rashid Moghi Eldin, Ashraf Mahmoud(Department of Botany), Ismael Elkhalifa, Mohammed Agbash (Department of Physics). My deepest gratitude is also extended to all my friends and colleagues for their good help. (i) Abstract o-Aminobenzophenone and its para and meta isomers were prepared using Friedl-Craft benzoylation. Their azides were also prepared via their diazonium salts. The azide of o-aminobenzophenone in its reduced form (o-benzylaniline) and its cyclic gketal were synthesised. All azides thus formed were reacted separately with triphenylphosphine to give the corresponding phopsphinimines, the Wittig reagents nitrogen analoug. The reactivity of the phosphorous-nitrogen bond. (P"=N)inthe different phosphoranes were studied by two types of reactions. (1) The Wittig type of reaction using benzaldehyde and its nitro derivatives with each of the above prepared phosphinimines. While triphenylphosphin-m-benzophenonimine (ii) and the triphenylphosphine benzophenonimine ethylene acetal (v) and it's reduced form triphenylphosphine-o-benzylphenylimine (iv) react giving the corresponding schiffis bases. However, the ortho (i) and the para (iii) isomers failed to react. This lack of reactivity is presumably due to their great stability which came about through the extensive resonance that reduced the nucleophilicity of the nitrogen nucleophile (2) The phosphinimines each was irradiated using Hanovia medium pressure UV lamp. Also the ortho and para isomers were not affected while others reacted giving the corresponding azo-compound and triphenylphosphine. They were separated and detected by chromatography. o N=PPh3 PPh3 N=PPh3 (0 (n) (iii) (iv) (v) R—N = N —R (vi) R = f O •N=PPh3 PPh3 N=PPh3 (0 (iii) (iv) (v) R—N = ' N —R (vi) R = C (V) List of Contents Title Page Acknowledgements i Abstract (English) ii Abstract (Arabic) iv Contents vi Chapter One : 1. Introduction 1 1.1 Wittig Reaction , 3 1-1.1 Phosphorous ylids 5 1.1.2 Preparation of Alkylidene phosphoranes 6 1.1.3 The Characteristic Feature of Wittig Reaction 9 1.1.4 The Mechanism of Wittig Reaction 11 1.1.5 The Stereochemistry of Resulting Olefin 13 1.1.6 The Reactions of Alkylidenephosphoranes with various functional Groups 20 1.2 Iminophosphoranes 20 1.2.1 The Structure of iminophosphoranes 23 1.2.2 Reaction of Iminophosphoranes 37 1.2.3 Photochemical Reactions of Iminophosphoranes 33 Chapter Two : Experimental Details 35 Chapter Two : Page 2. Experimental Details 35 Extremely Dry "or super dry" Ethyl Alcohol 35 Purification of Benzene 35 Purification of Nitrogen gas 35 Preparation of Sodium Ethoxide 36 Preparation of 2,4-Dinitrobenzaldehyde 37 Preparation of o-Aminobenzophenone (62) 39 Preparation of o-benzophenone Azide 39 Preparation of Triphenylphosphine-o-benzophenonimine (63)... 39 Reactions of Triphenylphosphine-o-benzophenonimine with : Benzaldehyde 40 p-Nitrobenzaldehyde 40 2,4-Dinitrobenzaldehyde 40 Irradiation of Triphenylphosphine-6-benzophenonimine 40 Preparation of p-Benzophenone Azide 41 Preparation of Triphenylphosphine-p-benzophnonimine (64) .... 41 Reactions of Tripheny Iphosphine-p-benzophenonimine with : Benzaldehyde 41 P-Nitrobenzaldehyde 41 2,4-Dinitrobenzaldehyde 42 Irradiation of Triphenylphosphine-p-benzophenonimine 42 Preparation of o-Benzylaniline 42 Preparation of o-phenylbenzyle Azide 42 Preparation of Tripheny Iphospine-o-phenylbenzylimine (65) ... 43 Reactions of Triphenylphosphine-o-phenylbenzylimine with : Benzaldehyde \.... 43 p-Nitrobenzaldehyde 43 2,4-Dinitrobenzaldehyde 44 Irradiation of Triphenylphosphine-O-phenylbenzylimine 44 Preparation of o-Aminobenzophenone ethylene acetal (66) 45 Preparation of Triphenylphosphonium-o-benzophenone ethylene acetal bromide (67) ; 45 Preparation of Triphenylphosphine-o-benzophenonimine ethylene acetal (68) 46 Reaction of Triphenylphosphine-o-benzophenonimine ethylene acetal with : Benzaldehyde 46 p-Nitrobenzaldehyde 46 2,4-Dinitrobenzaldehyde 46 Irradiation of Triphenylphosphine-o-benzophenonimine ethylene acetal :.. 47 Preparation of m-Nitrobenzophenone Method 1 (69) 47 Preparation of m-nitrobenzoylchloride 48 Preparation of m-Nitrobenzophenone Method 2 (70) 48 Preparation of m-Aminobenzophenone Method 1 (71) 49 Preparation of m-Aminobenzophenone Method 2 (72) 49 Preparation of m-Benzophenone Azide 49 Preparation of Triphenylphosphine-m-benzophenonimine (73) 50 Reactions of Triphenylphosphine-m-benzophenonimine with : Benzaldehyde 50 p-Nitrobenzaldehyde 50 2,4-Dinitrobenzaldehyde 50 Irradiation of Triphenylphosphine-m-benzophenonimine ... v 51 Chapter Three : ~ Page 3. Results and Discussion 52 3.1 Reaction of Triphenylphosphine-o-benzophenonimine 52 3.1.1 The photolysis of Triphenylphosphine-o-benzophenonimine .. 53 3.2 Reaction of Triphenylphosphine-p-benzophenonimine :.. 55 3.2.1 The Photolysis of Triphenylphosphine-p-benzophenonimine... 57 3.3 The Reaction of Triphenylphosphine-o-benzylphenylimine 57 3.3.1 The Photolysis of Triphenylphosphine-o-benzylphenylimine.. 60 3.4 Reaction of Triphenylphosphine-o-benzophenonoimine ethylene acetal 62 3.4.1 The photolysis of Triphenylphosphine-o-benzophenonimine ethylene acetal 64 3.5 Attempted synthesis of m-Nitrobenzophenone 65 3.5.1 Nitration of Benzophenone 65 3.5.2 Friedle Craft Acylation 65 3.6 Attempted synthesis of m-Aminobenzophenone 66 3.6.1 Reduction of m-Nitrobenzo by Stanous Chloride 66 3.6.2 Reduction of m-Nitrobenzophenone by Catalytic Hydrogenation 67 3.7 Reaction of Triphenylphosphine-m-benzophenonimine 67 3.7.1 The Photolysis of Triphenylphosphine-m-benzophenonimine 68 4. Conclusion * 70 References 71 (viii) CHAPTER ONE t. Introduction Ylids are important class of compounds in which an atom from group V or VI of the periodic table bearing a positive charge, is connected to a carbon atom carrying an unshared pair of electrons-represented by the general formula : © © ^;c—x The term "ylid" was first coined in the German language by Wittig in 1944. It was derived by use of the ending -yl to imply an open valence (i.e.. a methyl) and the ending -id to emply anionicity (i.e., cetylid) both on a carbon atom. The special characteristic of ylids that make them worthly of study in their own right is the unique stabilization afforded the carbanions by the presence of the adjacent 'onium 'atom group. Thus, many ylids have been isolated as crystalline, stable substances where as normal carbonion are seldom isolable and are very reactive toward atmospheric components. Ylids undergo two basic types of reactions, those in which only the carbanion is involved mechanistically and those in which both carbanion and the heteroatom portion are involved. The former group consists basically of those reactions which any carbanion, regardless of structure would undergo. The presence of the heteroatom portion of the ylid usually is reflected only in its effect to the nucleophilicity exhibited by the carbanion. The usefulness of ylids in this type of reaction, is due mainly to their availability in a wide variety of structural environments. Since carbanion reactions inevitably are these which permit the formation of a new carbon-carbons bonds. The availability of almost any carbanion without worry of isomeric possibilities has been a boon to synthetic organic chemisty. The most interesting reactions of ylids are the second group which involve both the carbanion and the heteroatom portion. The Wittig reaction (1) falls into this category and the discovery of this and related reactions incited the burst of activity in the field of ylid chemistry during the last decades studies of the mechanism of these reactions and of the physical properties of ylid have evoked interest in, and provided a substrate for the study of valence shell expansion by elements of the? second and lower periods. There are three main types, phosphorous, nitrogen and sulphur ylids although aresnic, selenium, etc ylids are also known. Because of P^-d^ bonding, two canonical forms can be written for phosphorous and sulphur ylids, but for nitrogen ylids there is only one. Once again, because of the resonance, phosphorous ylids are much more stable than the nitrogen ylids. Inspite of their resonance, sulphur ylids also have a low stability R P - CR «—•R Pe- CQ-R , R S- 3 2 3 2 2 2 K2 Phosophorus ylids Sulphur ylids K3 "^ 2 Nitrogen ylid In almost all compounds which have P^-d^ bonds, the central atom is connected to four atoms or to three atoms and an unshared pair of electron, to give tetrahedral structure. The P^-d^ bond, therefore; does not change the geometry of the molecule, in contrast to the normal n bond which changes an atom from tetrahedral to trigonal. 1.1 The Wittig Reaction The Wittig reaction is named after professor George Wittig of the University of Heidelberge. The reaction involving a condensation of alkylidenephosphorane (R - alkyl, aryl) and carbonyl compound, followed by eliminatin of phosphine oxide from the intermediate betaine to give the olefin1 (1). ! 2 3 4 2 3 4 R3P = CR R + R R CO • R3P®- CR*R .
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