Chemistry Building, Room 400
Organic Seminar

Tetrasubstituted alkenes are a difficult functional group in organic synthesis to synthesize. The desire for stereoselective synthesis of tetrasubstituted alkenes has grown as well. Alkene synthesis can be divided into five categories of reactivity: Wittig-type, elimination, metathesis, additions across alkynes, and miscellaneous.  These reactions have a specific stereoselectivity that is seen in most cases. New methods for tetrasubstituted olefin synthesis have been developed. These stereoselective reactions developed either go with or against normal reactivity seen.  The two classifications of reactions that are going to be discussed are miscellaneous reactions and additions across alkynes reactions. Classification of miscellaneous reactions is discussed extensively.  The creation of a vinyl cation from a copper-catalyzed carboarylation of an alkyne to then be trapped by a nucleophile forming the E-alkene stereospecifically.1 Another method uses the cross coupling of diazo-compounds with a copper catalyst to create the Z-tetrasubstituted alkene.2 The creation of a tetrasubstituted alkene from a beta-keto-ester using a phosphonate gives both E and Z isomers is also looked at.3 Additions across alkynes will also be discussed. The creation of a vinyl bromide from addition across an alkyne using zinc powder yields E-selectivity.4   A three-component domino reaction with an alkyne and Grignard reagent, followed by addition of aryl halide yields excellent Z-isomer selectivity.5 An application of additions across alkynes is also presented in the synthesis of isodomoic acid G and H.6



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