Chiral discrimination at the η3-allyl units of rhodium(I) η3-cyclo-octenyl complexes containing chiral bidentate phosphanes

Formation of 18e− and 16e− Acyl(η3-cyclooctenyl)rhodium(III) Complexes in the Reaction of Cationic (Cycloocta-1,5-diene)rhodium(I) Compounds with 2-(Diphenylphosphino)benzaldehyde

“…In the 13 C{ 1 H}-NMR spectrum, C(2) appears as a d at 113.6 ppm, and the magnetically inequivalent C(1) and C(3) at 90.1 and 80.2 ppm, respectively, show dds due to coupling to Rh and to the corresponding trans-positioned P-atom. The coupling constants for both C-atoms are identical and are similar to those reported for the rhodium(I) complex, [Rh(h 3 -C 8 H 13 ){(À)diop}] [13]. The assignments are confirmed by 2D-13 C, 1 H correlation.…”

“…[Rh(cod) 2 ]ClO 4 (cod cycloocta-1,5-diene) reacted with pCHO to undergo the oxidative addition of one pCHO with (1,2,3-h)cyclooct-2-en-1-yl (h 3 -C 8 H 13 ) formation, and the coordination of a second pCHO molecule as (phosphino-kP)aldehyde-kO(s-coordination) chelate to give the 18e À acyl(allyl)rhodium(III) species [Rh(h 3 -C 8 H 13 )(pCO)(pCHO)]ClO 4 (see 1). Complex 1 reacted with [Rh(cod)(PR 3 ) 2 ]ClO 4 (R aryl) derivatives 3 ± 6 to give stable pentacoordinated 16e À acyl[(1,2,3-h)-cyclooct-2-en-1-yl]rhodium(III) species [Rh(h 3 -C 8 H 13 )(pCO)(PR 3 )]ClO 4 7 ± 10.…”

“…90 and 80 ppm, respectively, agree with a trans-position of these C-atoms with respect to the P-atoms. The d(C) 21.8(s) of C(6) is characteristic for the h 3 -cyclooctenyl ligand adopting a boat-like conformation [8b] [13].…”

Regioconvergent and Enantioselective Rhodium‐Catalyzed Hydroamination of Internal and Terminal Alkynes: A Highly Flexible Access to Chiral Pyrazoles

“…Second, a regioselective approach might be aggravated by virtue of competing π‐benzyl, or π‐allyl systems being adjacent in case of unsaturated substituents connected to the alkyne ( A II in Scheme ). Third, coincidently, the last effect might also decrease the enantioselectivity, since this selectivity is engendered by coordination of the rhodium–ligand species with the π‐allyl system ( A I in Scheme ) . Thus, we anticipated that there might be an opportunity to control the N‐selectivity as well as the enantio‐ and regioselectivities of the obtained products by using our previously established Rh/JoSPOPhos system ,,…”

“…Third, coincidently, the last effectm ight also decrease the enantioselectivity, since this selectivity is engendered by coordination of the rhodiumligand speciesw ith the p-allyl system (A I in Scheme2). [20] Thus, we anticipated that there might be an opportunity to control the N-selectivity as well as the enantio-a nd regioselectivities of the obtained products by using our previously established Rh/JoSPOPhos system. [11d,k,l] Following on from our prior investigations, [11l] initial reactivity assays werec onducted using 1-phenyl-1-propyne and soliciting 4-bromopyrazole as af easible pyrazole.…”