Intermolecular Dehydrative Coupling and Intramolecular Cyclization of Ruthenium Vinylidene Complexes Formed from Aromatic Propynes Containing Carbonyl Functionalities

Abstract

Ar emarkable intermolecular dehydrative coupling reaction with the formation of aC ÀCb ond was found for the vinylidenec omplex 2a,y ielding the dinuclear bisvinylidene complex 4a.C omplex 2a containing1 -hydroxyindan moiety wasf irst formed from the reactiono fo-propynyl benzaldehyde 1a with [Ru]-Cl ([Ru] = Cp(PPh 3 ) 2 Ru) by acyclization process. For analogousa ldehyde 1b containing an additional 1,3-dioxolane group on the aryl ring, similari ntermolecular coupling yields the dinuclear bisvinylidene complex 4b.H owever,t he fluoro group on the aryl ring in aldehyde 1c inhibits the coupling reaction, giving only the vinylidene complex 2c.F or the reactions of [Ru]-Cl in MeOH with compounds 1f, 1g and 1h,e ach with ak etone functionality, cyclization gives vinylidenec omplexes 2f,2 gand 2h,r e-spectively.H owever,n os imilari ntermolecular couplingw as observed, instead, the intramolecular dehydration yields 8f, 8g and 8h,r espectively.I nC DCl 3 ,c atalytic cyclization is observedf or the o-propynylphenyl ketone 1h with [Ru]-Cla t 50 8Cg iving the isochromene products 14 h.F urthermore, treatment of the o-propynylaryl a,b-unsaturatedk etones 1k-m and 1n with [Ru]-Cl in MeOH affords the corresponding vinylidene complexes 10 k-m and 11 n each with 1-benzosuberonem oiety in the presence of NH 4 PF 6 .T hese intramolecular cyclization products weref ormed by the addition of Cb onto the terminal carbon of the alkenem oiety.A ll these reactionp roducts were characterized by spectroscopic methods. In addition, structures of complexes 4a,a nd 10 l were confirmed by single crystal X-ray diffraction analysis.Scheme2.Reactions of two o-propynylaryl aldehydes.Scheme3.Proposed mechanism for the formation of 2a and subsequent transformation to 4a.Scheme4.Reactions of 1d and 1e with [Ru]-Cl.Scheme5.Reactions of o-propynylaryl ketone with no a,b-unsaturated olefin.Scheme6.Formation of isochromene 14 h andproposed mechanism.

DFT calculations bring insight to internal alkyne-to-vinylidene transformations at rhodium PNP- and PONOP-pincer complexes

“…This process can lead to the coordination of alkynes to a metal centre to give h 2 -alkyne complexes, which are stable enough to be characterised experimentally [11][12][13][14][15][16][17] or can act as transient intermediates that undergo C-R (R ¼ C 6 H 5 , Ar 0 and H) bond cleavage and migration of the R group to yield TMvinylidene complexes. [18][19][20][21][22][23][24][25][26][27][28][29][30][31] Such reactivity can be feasibly modulated by factors such as changing the nature of alkynes or the transition metal.…”