Aspects of Homogeneous Catalysis

1. INTRODUCTION Although quite spectacular results have been obtained in the last few decades in the field of homogeneous transition metal catalyzed transformations of olefins and alkynes [1], reactions which could lead to heterocycles have been partly neglected. An obvious reason for this is that substrates containing heteroatoms such as N, 0 or S could coordinate the metal and suppress the catalytic activity. Nevertheless, some interesting early examples of transition-metal-catalyzed syntheses of heterocyclic compounds have been reported and these have been reviewed by C. W. Bird [2] . More recently the incorporation of CO , which enables esters and lactones 2 to be synthesized from olefinic starting materials, has begun to attract attention (see, for example, ref. [3]). The dominant role of palladium as the catalyst for the formation of O-containing heterocycles has been suggested to be associated with the relatively low strength of the Pd-O bond. Among the first examples of a nitrogen-containing heterocycle to be formed by homogeneous catalysis is the triazine shown in Equation 1 which is the product of the trimerization of benzonitrile in the presence of iron penta carbonyl or Raney­ nickel [4] .

Inhalt

of Volume 5.- Telomerization of Dienes by Homogeneous Transition Metal Catalysts.- 1. Introduction.- 2. Telomerization of Butadiene.- 3. Telomerization of Isoprene.- 4. Telomerization of Further 1,3-Dienes.- 5. Telomerization of 1,2-Dienes.- 6. Cotelomerizations.- 7. Acknowledgement.- 8. References.- The Cobalt-Catalyzed Synthesis of Pyridine and Its Derivatives.- 1. Introduction.- 2. Survey of the Organocobalt Catalysts.- 3. The Application of the Cobalt-Catalyzed Pyridine Synthesis.- 4. Experimental Details.- 5. Mechanistic Considerations.- 6. Experimental Optimization of the Catalytic Turnover Number.- 7. Synthesis of the Catalysts.- 8. Related Reactions.- 9. Acknowledgement.- 10. Glossary of Abbreviations.- 11. References.- Homogeneous Catalysis Using Iodide-Promoted Rhodium Catalysts.- 1. Introduction.- 2. Rhodium Iodocarbonyls.- 3. Catalysis of the Water Gas Shift Reaction.- 4. Alcohol Carbonylation.- 5. Carbonylation of Esters and Ethers.- 6. Reductive Carbonylation of Esters and Ethers.- 7. Hydrocarboxylation of Olefins.- 8. Hydrocarboxylation of Formaldehyde.- 9. Hydrogenolysis Reactions.- 10. Homologation of Carboxylic Acids.- 11. Heterogenisation of the Rh/I Catalyst.- 12. Conclusions.- 13. References.- Recent Developments in the Homogeneous Catalysis of the Water-Gas Shift Reaction.- 1. Introduction.- 2. Background.- 3. Chemistry of the WGSR Catalytic Cycles.- 4. Catalysis of the WGSR under Basic Conditions.- 5. Catalysis of the WGSR under Acidic or Neutral Conditions.- 6. References.- Homologation of Alcohols, Acids and Their Derivatives by CO + H2.- 1. Introduction.- 2. Homologation of Alcohols.- 3. Carbonylation and Homologation of Ethers.- 4. Homologation of Aldehydes.- 5. Homologation of Carboxylic Acids.- 6. Homologation of Carboxylic Acid Esters.- 7. Homologation Reactions with Heterogeneous Catalysts.- 8. Homologation Reactions with CO and H2O.- 9. Reaction Mechanism.- 10. Concluding Remarks.- 11. Addendum.- 12. Glossary of Abbreviations.- 13. References.