ABSTRACT
I. Introduction .............................................................................................................................706 II.General Survey .......................................................................................................................706 III.Coupling via Radical Cations ................................................................................................. 707
A.Mechanism and Favorable Solvents ................................................................................ 707 B.Aromatic Compounds ..................................................................................................... 708
1. Hydrocarbons.......................................................................................................... 708 2.Phenols.................................................................................................................... 710 3.Aryl Ethers ............................................................................................................. 714 4.Aryl Amines ........................................................................................................... 714
C.Heterocycles .................................................................................................................... 716 D. Olešns ............................................................................................................................. 718
1.General ................................................................................................................... 718 2.Aryl Olešns ............................................................................................................ 718 3.Dienes..................................................................................................................... 720 4.Enols and Enol Ethers............................................................................................. 720 5. Enamines ................................................................................................................ 721 6.Alkenes with Alkyl Substituents ............................................................................ 725 7.Alkynes ................................................................................................................... 726 8.Alkanes ................................................................................................................... 726
E.Intramolecular Coupling ................................................................................................. 726 1. Aromatic Compounds ............................................................................................. 726 2.Olešns..................................................................................................................... 734
F.Anodically Induced Cycloadditions ................................................................................ 740 1.[2 + 2] Cycloadditions ............................................................................................. 740 2.[4 + 2] Cycloadditions ............................................................................................. 742
IV. Coupling via Radicals ............................................................................................................. 747 A.General Comments ......................................................................................................... 747 B.Anodic Decarboxylation of Carboxylates as Radical Source ......................................... 748
1.Experimental Procedure ......................................................................................... 748 2.Homocoupling ........................................................................................................ 749 3. Heterocoupling ....................................................................................................... 752 4.Diastereoselective Coupling ................................................................................... 754 5. Addition of Radicals from Anodic Decarboxylation of Carboxylic Acids to Olešns ....756 6.Oxidation to Carbocations ...................................................................................... 761
C.Anions from CH-Acids as Radical Source ..................................................................... 761 1. Coupling ................................................................................................................. 761 2.Addition .................................................................................................................. 762
V.Outlook ................................................................................................................................... 765 References ...................................................................................................................................... 766
For the synthesis of organic molecules, two types of reaction are used: carbon-carbon bond-formingreactionsandfunctionalgroupinterconversions.Theformerassembleslargermoleculesfrom smallerunits;thelatterintroducesfunctionalgroupsintoamoleculeorconvertsfunctionalgroups thatarepresentinthemolecule.Thelargenumberofcarbon-carbonbond-formingreactionscan be summarized in four groups:
1.Polar reactions between an activated acceptor and a donor or vice versa 2.Radical coupling and addition reactions 3.Pericyclic reactions, especially cycloadditions 4.Transition metal catalyzed and organocatalyzed reactions
Electrochemistrycancontributetothesesynthetictransformations,especiallytopolarreactions, toradicalreactions,andpartiallytocycloadditions.Thereactiveintermediatesbeinginvolved, namely,radicalions,cations,andradicals,canbegeneratedattheelectrodesimply,inlargevariety, cheap,andwithreducedproductionofwaste.Thereareseveralbooksandreviewsthatdealwith the topic: organic electrosynthesis [1]. It should be added that organic electrosynthesis is in good accordwithmanyrulesofgreenchemistry[2].Theselectivityinorganicelectrosynthesishasbeen improvedinthelastdecadebynewdevelopmentsinŽowcells,microreactors,andreactionconditions (see Chapters 7 through 9) [1b,3].
