Organocatalyzed conjugate addition of carbonyl compounds to nitrodienes/nitroenynes and synthetic applications
The purpose of this study is to point out the synthetic utility of a new class of Michael acceptors (nitrodienes and nitroenynes). The highly enantioselective organocatalytic Michael addition of carbonyl compounds to these functionalized nitroolefins has been carried out in the presence of (S)-diphenylprolinol silyl ether to achieve some interesting building blocks in high selectivities. The adducts thus obtained can be easily converted by taking advantage of the corresponding unsaturated carbon-carbon bond. In presence of the double bond, metathesis or electrophilic activation could be carried out whereas in the presence of the triple bond electrophilic acti-vation could be conducted. We thus focused on a gold-catalyzed cyclization of the bis-homopropargylic alcohol to afford the corresponding substituted tetrahydrofuran. Then, we also demonstrated that organic and gold catalysts were compatible in a one-pot process. Indeed, we developed a one-pot enantioselective organocatalytic Michael addition to a nitroenyne followed by a gold-catalyzed acetalization/cyclization to achieve tetrahydrofuranyl ethers in high diastereoand enantioselectivities with excellent yields.
Enantioselective one-pot organocatalytic michael addition/goldcatalyzed tandem acetalization/cyclization
Au-rganocatalytic reaction: A one-pot process consisting of a Michael addition to a nitroenyne and a subsequent acetalization/ cyclization is reported (see scheme; TMS=trimethylsilyl), which results in the formation of nitro-substituted tetrahydrofuranyl ethers with high diastereo- and enantioselectivities. Organocatalysis and gold catalysis are compatible and complementary in a one-pot process
Belot, Sebastien,Vogt, Kim A.,Besnard, Celine,Krause, Norbert,Alexakis, Alexandre
supporting information; experimental part
p. 8923 - 8926
(2010/03/03)
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