Enantiopure Acetals of α-Alkynyl Carbonyl Compounds: Organoaluminum-Mediated 1,2-Shift of Cobalt-Complexed Alkynyl Group with Concomitant Capture by a Nucleophile

Taya, Kimiko; Nagasawa, Tetsuya; Suzuki, Keisuke

doi:10.1055/s-1997-776

Cited by 13 publications

(1 citation statement)

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“…The β,γ -epoxy-α-trimethylsiloxy alkyne complexes (41) also rearrange, to give α-trimethylsiloxy carbenium ions, which lose the formal Me 3 Si + to give homopropargylic ketones containing an additional hydroxy function, or are reduced in situ to give the diol. Finally, the β-mesyloxy propargyl acetal complexes rearrange to give α,α-dialkoxy carbenium ions, which may be trapped by hydride, alkyl, or alkynyl nucleophiles to give the corresponding ketals [77]. In each of these cases, when the original leaving group is on a chiral centre, the migration occurs with complete inversion of stereochemistry at this migration terminus.…”

Section: Migrationsmentioning

confidence: 99%

Chemistry of Propargyldicobalt Cations Recent Developments in the Nicholas and Related Reactions

Green

2001

COC

146

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Abstract:The chemistry of propargyldicobalt cations, also known as the Nicholas reaction, is reviewed, with a focus on the developments since 1995. Advances in the understanding of the fundamental properties, such as structure, stability, and reactivity, of both the hexacarbonyl complexes and those bearing other ligands are discussed. All reactions involving propargyl cation dicobalt complexes are covered, including those stemming from ionization of propargylic leaving groups and those created by electrophilic addition to enyne complexes. Migration reactions involving either initiation or termination by propargyl cation complexes are included, as are the generation and reactions of propargyldicobalt radicals. Cyclization reactions employing these cations have received much attention, in cases with the alkynedicobalt unit located in both exocyclic and endocyclic positions, and these reports are described. Particular attention is paid to preparation of medium ring cycloalkyne complexes and their heterocyclic analogues. In addition, there is discussion of the progress in the in selectivity of these reactions, especially in terms of introduction of asymmetry at the propargylic site. Finally, recent applications of Nicholas reaction chemistry in the synthesis of natural products and related compounds are reported.

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Section: Migrationsmentioning

confidence: 99%