Aldimines, ruthenium-catalyzed

Scheme 17 Ruthenium-catalyzed direct arylation of aldimine 42...

Jun and coworkers used a related approach for a ruthenium-catalyzed arylahon of aldimines [31]. Here, a pyridyl-subshtuent allowed for the selective arylahon employing arylboronates. Methyl vinyl ketone (61) as additive led to high isolated yields of the corresponding ketones (Scheme 9.22). 

The ruthenium-catalyzed [3 + 2] cycloaddition of ethynylcyclopropanes, bearing two carboxy groups at the homopropargylic position, with aldehydes and aldimines was developed for the synthesis of the corresponding 2-ethynyltetrahydrofurans in high to excellent yields. The ruthenium aUenylidene complexes serve as reactive intermediates (13AGE1758). 

Nishibayashi and Sakata recently described the Ru-catalyzed [3+2] cycloaddition of ethynylcyclopropanes bearing two carboxy groups at the homopropargyUc position with aldehydes and aldimines to afford 2-ethynyltetrahydrofurans and pyrrolidines (Scheme 52) [179]. The proposed mechanism requires the formation of the ruthenium allenylidene species II by isomerization of the initially formed vinylidene I. Nucleophilic attack of species II to the aldehyde or aldimine, which are activated by BF3-OEt2, would afford allenylidene III. Final nucleophilic attack on the Cy by the oxygen or nitrogen followed by tautomerization of the vinylidene... 

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