Catalytic Methods for Carbon-Carbon Bond Formation

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DESCRIPTION (provided by applicant): Several new gold(I) catalyzed carbon-carbon formatting reactions are proposed. In general, these reactions involve activation of alkynes or allenes by coordination to cationic gold(I) complexes. Both monomeric gold(I) complexes and gold(I) clusters are employed as catalysts and show distinct reactivities. Gold(I) catalyzes the intramolecular addition of beta-dicarbonyl compounds to alkynes and allenes. Additions to alkynes can be employed to produce either exo-methylene cyclopentanes or -hexanes or to prepare cyclopentenes through a 5-endo-dig carbocyclizations. Use of other enolate equivalents, such as silyl enol ethers and enamines is also proposed. Catalytic enantioselective versions of these reactions, using a dual palladium-silver catalysts system, will also be examined. Additionally, the use of simple olefins as intramolecular nucleophiles towards gold(I)-alkyne complexes results in the isomerization of 1,5-enynes to bicyclo[3.1.0]hexenes. The reaction motif can also be used in conjunction with a ring expansion to rapidly generate complex carbocyclic frameworks. Development of catalyst systems for a range of rearrangement reaction is also described. For example, a mild catalytic Saucy-Marbet rearrangement is detailed. Application of this rearrangement to the synthesis of enantioenriched allenyl silanes and stannanes is proposed. The reaction is believed to proceed by coordination of gold(I) to an alkyne. Application of this mode of activation to other sigmatropic rearrangements, such as the Cope and Overman rearrangements, is also proposed. Additionally, gold(I) catalyzed Nazarov-like cyclization of vinyl allenes and the pinacol rearrangements of propargylic alcohols are described. A key component of this proposal will be the application of new reaction methodology to the construction of complex natural products. Two classes of bioactive natural product are targeted: (I) the lycopodium alkaloids(II), illustrated by a sieboldine A synthesis; (II) and the pinguisane sesquiterpenes, exemplified by bisacutifolone A. This proposal integrates method development and total synthesis to advance the field of organic synthesis and its application to the preparation of bioactive molecules.