Chromium oxidation, well known and widely explored in organic chemistry since the very beginning of this science, is a topic of current interest for the organic chemist as evidenced by the continuous development of new techni­ ques and procedures reported in the literature. Chromium oxidation is a simple process which can be easily performed in the laboratory and scaled up in industry as well. Although almost every oxidizable organic functional group may undergo chromium oxidation, the most important fields of appli­ cation are the oxidation of alcohols, allylic and benzylic oxidation, oxidative degradation and oxidation of some organometallic compounds. A high degree of selectivity is often possible by choosing the most suitable reagent among those several ones now available. This book takes account of the various functional groups that undergo oxidation and the entire literature up to 1982. It has been written in the hope to help the synthetic organic chemist in his experimental work. For this purpose a number of tables comprising yields and references have been included; detailed descriptions of typical procedures are meant to show the experimental conditions and the scope of the reactions. We wish to thank Dr. Mario Orena for his valuable scientific and technical assistence and Prof. Bruno Camerino, who read the entire manuscript and corrected many of the errors. Bologna, February 1984 Gianfranco Cainelli Giuliana Cardillo Table of Contents I. Introduction . . . . . . . . . . .

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I. Introduction.- 1. The Oxidation States of Chromium.- 2. The Chemistry of Chromium(VI).- 3. Chromium(VI) as Oxidant in Organic Chemistry.- References of Chapter I.- II. Oxidation of Carbon-Hydrogen Bonds.- A. Oxidation of Alkanes.- 1. Oxidation of Alkanes With Chromic Acid in Acetic Acid.- 2. Oxidation of Alkanes With Chromic Acid inAqueous Sulphuric Acid.- 3. Oxidation of Alkanes With Chromyl Chloride.- 4. Mechanism of Oxidation of Alkanes.- B. Oxidation of Arylalkanes (Benzylie Oxidation).- 1. Oxidation of Arylalkanes With Chromic Acid in an Acidic medium.- 2. Oxidation of Arylalkanes With Aqueous Sodium Dichromate.- 3. Oxidation of Arylalkanes With Chromyl Chloride (Etard Reaction).- 4. Mechanism of Benzylic Oxidation.- C. Allylic Oxidation.- 1. Allylic Oxidation of Olefins With Chromium(VI) in Acetic Acid and Acetic Anhydride.- 2. Allylic Oxidation With Chromium Trioxide-Heterocyclic Bases Addition Compounds.- 3. Allylic Oxidation With Tert-butyl-chrornate.- 4. Mechanism of Allylic Oxidation.- References of Chapter II.- III. Oxidation of Carbon-Carbon Double Bonds.- A. Oxidation of Alkenes.- 1. Oxidation of Alkenes With Chromium Trioxide in Acetic Anhydride or Acetic Acid.- 2. Oxidation of Alkenes With Chromic Acid in Aqueous Sulphuric Acid.- 3. Mechanism of Alkene Oxidation With Chromic Acid.- 4. Oxidation of Alkenes With Chromyl Chloride.- 5. Mechanism of Alkene Oxidation With Chromyl Chloride.- 6. Oxidation of Alkenes With Silver Chromate-Iodine.- B. Oxidation of Enol-Derivatives 901. Oxidation of Enol-Ethers With Pyridinium Chlorochromate.- 2. Oxidation of O-Silylated Enolates With Chromyl Chloride.- C. Ring Oxidation of Aromatic Compounds.- 1. Oxidation of Polynuclear Arenes With Chromium(VI) Under Acidic Conditions.- 2. Oxidation of Phenols and Aromatic Amines With Chromium(VI) Under Acidic Conditions.- 3. Oxidation of Phenols With Chromyl Chloride.- 4. Oxidation of Hydroquinone Silyl Ethers With Pyridinium Chlorochromate.- 5. Oxidation of Ortho-Allylphenols With Tetraalkylammonium Dichrornate.- 6. Oxidation of Some Aromatic Heterocyclic Compounds With Chromium(VI).- References of Chapter III.- IV. Oxidation of Alcohols.- A. Oxidation of Alcohols by Chromium(VI) Under Acidic Conditions.- 1. Oxidation of Alcohols With Chromic Acid in Aqueous Sulfuric Acid.- 2. Oxidation of Alcohols With Chromic Acid in Acetic Acid or Aqueous Acetic Acid.- 3. Oxidation of Alcohols With Chromic Acid in Aqueous Sulfuric Acid and Acetone (Jones'Reagent).- 4. Oxidation of Alcohols With Chromic Acid in Dimethylformamide or Dimethylsulphoxide Containing Sulphuric Acid.- 5. Oxidation of Alcohols With Chromic Acid in Two-phase systems.- B. Oxidation of Alcohols With Compounds of Chromium(VI) and Heterocyclic Bases.- 1. Oxidation of Alcohols With Chromium Trioxide-(Pyridine)2 Complex.- 2. Oxidation of Alcohols With Pyridinium Dichromate.- 3. Oxidation of Alcohols With Pyridinium Chlorochromate (PCC).- 4. Oxidation of Alcohols With Pyridinium Fluorochromate.- 5. Oxidation of Alcohols With Chromium Trioxide-3,5-Dimethylpyrazole Complex.- 6. Oxidation of Alcohols With 2,2?-Bipyridinium Chlorochromate.- 7. Oxidation of Benzylic and Ally lic Alcohols With 4-(Dimethylamino)pyridinium Chlorochromate (DMAP . HCrO3Cl).- 8. Oxidation of Alcohols With Chromium(V) Reagents.- C. Oxidation of Alcohols With Chromium(VI) Under Neutral Conditions.- 1. Oxidation of Alcohols With Di-tert-butylchromate (TBC).- 2. Oxidation of Alcohols With Chromium Trioxide in Hexamethylphosphoramide.- 3. Oxidation of Alcohols With Tetraalkylammonium Chromates in Apolar Solvents.- D. Oxidation of Alcohols With Supported Chromium(VI) Reagents.- 1. Oxidation of Alcohols With Chromium(VI) Reagents Supported on Organic Polymers.- 2. Oxidation of Alcohols With Chromium(VI) Reagents Adsorbed or Dispersed on Inorganic Support.- E. Mechanism of Oxidation of Alcohols.- F. Effect of the Structure and Stereochemistry of Secondary Alcohols on the Rate of Oxidation.- References of Chapter IV.- V. Oxidation of Aldehydes and Ketones.- A. Oxidation of Aldehydes.- 1. Oxidation of Aldehydes With Chromic Acid Under Acidic Conditions.- 2. Oxidation of Aldehydes With Pyridinium Chlorochromate and Pyridinium Dichrornate.- 3. Oxidation of Aldehydes With Chromium(V) Reagents.- 4. Mechanism of Aldehyde Oxidation.- B. Oxidation of Ketones.- 1. Oxidation of Ketones With Chromic Acid Under Acidic Conditions.- 2. Mechanism of Ketone Oxidation.- References of Chapter V.- VI. Oxidation of Carbon-Metal Bonds.- A. Oxidation of Organoboron Compounds.- 1. Oxidation of Organoboranes With Chromic Acid Under Acidic Conditions.- 2. Oxidation of Organoboranes With Pyridinium Chlorochromate.- 3. Oxidation of Trialkylborates With Pyridinium Chlorochromate.- 4. Oxidation of 1,1- and 1,2-diorganoboranes With Chromium Trioxide-(Pyridine)2.- B. Oxidation of Organotin Compounds.- 1. Oxidation of Organotin Compounds With Chromium Trioxide-(Pyridine)2 and Pyridinium Chlorochromate.- References of Chapter VI.- VII. Oxidation of Halides, Ethers, Acetals, Sulphides, and Some Nitrogen Containing Compounds.- A. Oxidation of Alkyl Halides.- B. Oxidation of Ethers.- C. Oxidation of Acetals.- D. Oxidation of Sulphides.- E. Oxidation of Alkyl Aryl Amines.- F. Oxidation of Oximes.- G. Oxidation of Hydroxylamine.- References of Chapter VII.- VIII. Some Remarks on Selectivity and Synthetic Use of Chromium (VI) Oxidation.- A. Oxidation of Carbon-Hydrogen Bond.- 1. Alkanes.- 2. Arylalkanes.- 3. Allylic Oxidation.- B. Oxidation of Carbon-Carbon Double Bonds.- 1. Oxidation of Alkenes.- 2. Oxidation of Enol Derivatives.- C. Ring Oxidation of Aromatic Compounds.- D. Oxidation of Alcohols.- E. Oxidation of Aldehydes and Ketones.- F. Oxidation of Carbon-Metal Bonds.